Changelog 66 KB
Newer Older
Xavier Leroy's avatar
Xavier Leroy committed
1
2
3
Release 3.8, 2020-11-16
=======================

Xavier Leroy's avatar
Xavier Leroy committed
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
New features:
- Support `_Static_assert` from ISO C11.
- Support `__builtin_constant_p` from GCC and Clang.
- New port: x86 64 bits Windows with the Cygwin 64 environment.
  (configure with target `x86_64-cygwin`).
- The following built-in functions are now available for all ports:
  `__builtin_sqrt`, `__builtin_fabsf`, and all variants of
  `__builtin_clz` and `__builtin_ctz`.
- Added `__builtin_fmin` and `__builtin_fmax` for AArch64.

Removed features:
- The x86 32 bits port is no longer supported under macOS.

Compiler internals:
- Simpler translation of CompCert C casts used for their effects but
  not for their values.
- Known builtins whose results are unused are eliminated earlier.
- Improved error reporting for `++` and `--` applied to pointers to
  incomplete types.
- Improved error reporting for redefinitions and implicit definitions
  of built-in functions.
- Added formal semantics for some PowerPC built-ins.

The clightgen tool:
- New `-canonical-idents` mode, selected by default, to change the way
  C identifiers are encoded as CompCert idents (positive numbers).
  In `-canonical-idents` mode, a fixed one-to-one encoding is used
  so that the same identifier occurring in different compilation units
  encodes to the same number.
- The `-short-idents` flag restores the previous encoding where
  C identifiers are consecutively numbered in order of appearance,
  causing the same identifier to have different numbers in different
  compilation units.
- Removed the automatic translation of annotation builtins to Coq
  logical assertions, which was never used and possibly confusing.

Coq and OCaml development:
Xavier Leroy's avatar
Xavier Leroy committed
41
- Compatibility with Coq 8.12.1, 8.12.0, 8.11.2, 8.11.1.
Xavier Leroy's avatar
Xavier Leroy committed
42
43
44
45
46
47
48
49
50
51
- Can use already-installed Flocq and MenhirLib libraries instead of their
  local copies (options `-use-external-Flocq` and `-use-external-MenhirLib`
  to the `configure` script).
- Automatically build to OCaml bytecode on platforms where OCaml
  native-code compilation is not available.
- Install the `compcert.config` summary of configuration choices
  in the same directory as the Coq development.
- Updated the list of dual-licensed source files.


Xavier Leroy's avatar
Xavier Leroy committed
52
53
54
Release 3.7, 2020-03-31
=======================

Xavier Leroy's avatar
Xavier Leroy committed
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
ISO C conformance:
- Functions declared `extern` then implemented `inline` remain `extern`
- The type of a wide char constant is `wchar_t`, not `int`
- Support vertical tabs and treat them as whitespace
- Define the semantics of `free(NULL)`

Bug fixing:
- Take sign into account for conversions from 32-bit integers to 64-bit pointers
- PowerPC: more precise determination of small data accesses
- AArch64: when addressing global variables, check for correct alignment
- PowerPC, ARM: double rounding error in int64->float32 conversions

ABI conformance:
- x86, AArch64: re-normalize values of small integer types returned by
  function calls
- PowerPC: `float` arguments passed on stack are passed in 64-bit format
- RISC-V: use the new ELF psABI instead of the old ABI from ISA 2.1

Usability and diagnostics:
- Unknown builtin functions trigger a specific error message
- Improved error messages

Coq formalization:
- Revised modeling of the PowerPC/EREF `isel` instruction
- Weaker `ec_readonly` condition over external calls
  (permissions can be dropped on read-only locations)

Coq and OCaml development:
- Compatibility with Coq version 8.10.1, 8.10.2, 8.11.0
- Compatibility with OCaml 4.10 and up
- Compatibility with Menhir 20200123 and up
- Coq versions prior to 8.8.0 are no longer supported
- OCaml versions prior to 4.05.0 are no longer supported

Xavier Leroy's avatar
Xavier Leroy committed
89

90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
Release 3.6, 2019-09-17
=======================

New features and optimizations:
- New port targeting the AArch64 architecture: ARMv8 in 64-bit mode.
- New optimization: if-conversion.  Some `if`/`else` statements
  and `a ? b : c` conditional expressions are compiled to branchless
  conditional move instructions, when supported by the target processor
- New optimization flag: `-Obranchless`, to favor the generation of
  branchless instruction sequences, even if probably slower than branches.
- Built-in functions can now be given a formal semantics within
  CompCert, instead of being treated as I/O interactions.
  Currently, `__builtin_fsqrt` and `__builtin_bswap*` have semantics.
- Extend constant propagation and CSE optimizations to built-in
  functions that have known semantics.
- New "polymorphic" built-in function: `__builtin_sel(a,b,c)`.
  Similar to `a ? b : c` but `b` and `c` are always evaluated,
  and a branchless conditional move instruction is produced if possible.
- x86 64 bits: faster, branchless instruction sequences are produced
  for conversions between `double` and `unsigned int`.
- `__builtin_bswap64` is now available for all platforms.

Usability and diagnostics:
- Improved the DWARF debug information generated in -g mode.
- Added options -fcommon and -fno-common to control the generation
  of "common" declarations for uninitialized global.
- Check for reserved keywords `_Complex` and `_Imaginary`.
- Reject function declarations with multiple `void` parameters.
- Define macros `__COMPCERT_MAJOR__`, `__COMPCERT_MINOR__`, and
  `__COMPCERT_VERSION__` with CompCert's version number. (#284)
- Prepend `$(DESTDIR)` to the installation target. (#169)
- Extended inline asm: print register names according to the
  types of the corresponding arguments (e.g. for x86_64,
  `%eax` if int and `%rax` if long).

Bug fixing:
- Introduce distinct scopes for iteration and selection statements,
  as required by ISO C99.
- Handle dependencies in sequences of declarations
  (e.g. `int * x, sz = sizeof(x);`).  (#267)
- Corrected the check for overflow in integer literals.
- On x86, __builtin_fma was producing wrong code in some cases.
- `float` arguments to `__builtin_annot` and `__builtin_ais_annot`
  were uselessly promoted to type `double`.

Coq formalization and development:
- Improved C parser based on Menhir version 20190626:
  fewer run-time checks, faster validation, no axioms. (#276)
- Compatibility with Coq versions 8.9.1 and 8.10.0.
- Compatibility with OCaml versions 4.08.0 and 4.08.1.
- Updated to Flocq version 3.1.
- Revised the construction of NaN payloads in processor descriptions
  so as to accommodate FMA.
- Removed some definitions and lemmas from lib/Coqlib.v, using Coq's
  standard library instead.

The clightgen tool:
- Fix normalization of Clight `switch` statements. (#285)
- Add more tracing options: `-dprepro`, `-dall`. (#298)
- Fix the output of `-dclight`. (#314)


152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
Release 3.5, 2019-02-27
=======================

Bug fixing:
- Modeling error in PowerPC ISA: how register 0 is interpreted when
  used as base register for indexed load/stores.  The code generated
  by CompCert was correct, but was proved correct against the wrong
  specification.
- Modeling error in x86 ISA: how flag ZF is set by floating-point
  comparisons.  Here as well, the code generated by CompCert was
  correct, but was proved correct against the wrong specification.
- Revised handling of attributes so that they behave more like in
  GCC and Clang.  CompCert now distinguishes between attributes that
  attach to names (variables, fields, typedefs, structs and unions)
  and attributes that attach to objects (variables).  In particular,
  the `aligned(N)` attribute now attaches to names, while the `_Alignas(N)`
   modifier still attaches to objects.  This fixes issue 256.
- Issue with NULL as argument to a variadic function on 64-bit platforms
  (issue 265)
- Macro __bool_true_false_are_defined was missing from <stdbool.h> (issue 266)

Coq development:
- Can now be entirely rechecked using coqchk
  (contributed by Vincent Laporte)
- Support Coq version 8.9.0
- Avoid using "refine mode" when defining Instance
  (contributed by Maxime Dénès)
179
- Do not support Menhir versions more recent than 20181113, because
180
181
182
183
184
185
186
  they will introduce an incompatibility with this CompCert release.

New feature:
- PowerPC port: add __builtin_isel (conditional move) at types int64, uint64,
  and _Bool.


Xavier Leroy's avatar
Xavier Leroy committed
187
Release 3.4, 2018-09-17
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
=======================

Bug fixing:
- Redefinition of a typedef in a different scope was wrongly rejected.
- Attach `_Alignas(N)` and `__attribute((aligned(N)))` to names
  instead of types, so that `_Alignas(16) int * p` means
  "16-aligned pointer to int", not "pointer to 16-aligned int".
- For packed structs, fix a discrepancy between the size and alignment
  computed during elaboration and those computed by the verified front-end
  after expansion.
- Honor qualified array types in function parameters: if a parameter is
  declared as e.g. `int t[const 4]`, it is now treated as `int * const t`
  in the function body, not `int * t` like before.
- Reject `__builtin_offsetof(struct s, f)` if `f` is a bit-field.
- Wrong parsing of attributes having multiple arguments such as
  `__attribute((packed(A,B,C)))`.
- If `__builtin_ais_annot` is followed immediately by a label (e.g. a
  loop head), add a nop instruction to separate the annotation from
  the label.
- Wrong parsing of the command-line options `-u <symbol>` and `-iquote`.
- PowerPC in hybrid 32/64 bit mode: reject %Q and %R register specifications
209
210
211
212
  in inline assembly code, since 64-bit integer arguments are not split
  in two registers.
- x86 64-bit mode: wrong expansion of __builtin_clzl and builtin_ctzl
  (issue #127).
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241

New checks for ISO C conformance:
- Removed support for `_Alignof(expr)`, which is not C11;
  only `_Alignof(ty)` is part of C11.
- Reject occurrences of `_Alignas` in places that are not allowed by C11,
  e.g. in `typedef`.  `__attribute((aligned(N)))` can be used instead.
- Reject occurrences of `restrict` in places that are not allowed by
  C99 and C11.
- Reject structs composed of a single flexible array `struct { ty []; }`.
- Check that qualified array types such as `int t[const 4]` occur only
  as function parameters, but nowhere else.
- In function definitions, reject function parameters that have no names.

New warnings:
- Warn for flexible array types `ty[]` in places where they do not make sense.
- Warn for inline (not static inline) functions that declare
  non-constant static variables.
- Optionally warn if the alignment of an object is reduced below its
  natural alignment because of a _Alignas qualifier or an aligned attribute,
  or a packed attribute.
- Warn for tentative static definitions with an incomplete type, e.g.
  `static int x[];`.
- The warning about uses of C11 features is now off by default.

Semantic preservation proof:
- Model the fact that external functions can destroy caller-save registers
  and Outgoing stack slots; adapt the proofs accordingly.

Coq and OCaml development:
242
- Support Coq versions 8.8.1 and 8.8.2.
Xavier Leroy's avatar
Xavier Leroy committed
243
- Support OCaml versions 4.7.0 and up.
244
245
246
247
248
249
250
251
- Support Menhir versions 20180530 and up.

Others:
- Improved error handling in "configure" script (issue #244)
- clightgen adds configuration information to the generated .v file (issue #226)



Xavier Leroy's avatar
Xavier Leroy committed
252
253
254
255
256
257
258
259
260
261
262
Release 3.3, 2018-05-30
=======================

New features:
- Introduced the __builtin_ais_annot built-in function to communicate
  source-level annotations to AbsInt's a3 tool suite via a special
  section in object and executable files.
- Improved C11 support: define the C11 conditional feature macros;
  define the max_align_t type in stddef.h.
- PowerPC 64-bit port: new built-in functions for 64-bit load-store with
  byte reversal and for 64-bit integer multiply high.
263
- x86 64 bits: add support for BSD.
Xavier Leroy's avatar
Xavier Leroy committed
264
265
266
267

Bug fixing:
- Wrong code generated for unions containing several bit fields.
- Internal compiler errors for some initializers for structs and
268
  unions containing bit-fields, and for anonymous members of unions.
Xavier Leroy's avatar
Xavier Leroy committed
269
270
271
272
- Missing error reporting for <integer> - <ptr> subtraction,
  causing an internal retyping error later during compilation.
- String literals are l-values.
- String literals have array types, not pointer types.
273
- Array sizes >= 2^32 were handled incorrectly on 64-bit platforms.
Xavier Leroy's avatar
Xavier Leroy committed
274
275
276
277
- Wrong code generated for global variables of size 2^31 bytes or more.
- struct and union arguments to annotation builtins must be passed by
  reference, regardless of the ABI calling conventions.
- "e1, e2" has pointer type if "e2" has array type.
278
- x86 64 bits: in "symbol + ofs" addressing modes, the offset "ofs"
Xavier Leroy's avatar
Xavier Leroy committed
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
  must be limited to [-2^24, 2^24) otherwise linking can fail.

New or improved diagnostics (errors and warnings):
- Warn for comparison of a pointer to a complete type and a pointer to
  an incomplete type.
- More checks on variables declared in "for" loops: not static, not
  extern, not function types.
- Reject empty declarations in K&R functions.
- Reject arrays of incomplete types.
- Reject duplicate 'case' or 'default' statements within a 'switch'.
- Reject 'case' and 'default' statements outside a 'switch'.
- Check that 'typedef' declares a name and doesn't contain '_Noreturn'.
- Function parameters are in the same scope as function local variables.
- More comprehensive constant-ness checks for initializers of global
  or static local variables.
- Make sure an enum cannot have the same tag as a struct or an union.
- More checks on where the 'auto' storage class can be used.
- Accept empty enum declaration after nonempty enum definition.
- Reject pointers to incomplete types in ptr - ptr subtraction.
- When defining a function, take attributes (_Noreturn, etc) from
  earlier declarations of the function into account.
- Better check for multiple definitions of functions or global variables.
- Reject illegal initializations of aggregates such as "char c[4] = 42;".
- Reject designated initializers where a member of a composite type is
  re-initialized after the composite has been initialized as a whole.
- Reject casts to struct/union types.
- Reject sizeof(e) where e designates a bit-field member of a struct or union.
- "e1, e2" is not a compile-time constant expression even if e1 and e2 are.
- "main" function must not be "inline"
- Warn for functions declared extern after having been defined.
- Warn for function declarations after function definitions when the
  declaration has more attributes than the definition.
- Warn for assignment of a volatile struct to a non-volatile struct.
- Warn for "main" function if declared _Noreturn.

Coq development:
- Added support for Coq versions 8.7.2 and 8.8.0.
- Rewrote "Implicit Arguments" and "Require" inside sections,
  these are obsolete in 8.8.0.
- Upgraded Flocq to version 2.6.1.
319
320
321
- Optionally install the .vo files for reuse by other projects
  (options -install-coqdev and -coqdevdir to configure script;
   automatically selected if option -clightgen is given).
Xavier Leroy's avatar
Xavier Leroy committed
322
323


Xavier Leroy's avatar
Xavier Leroy committed
324
325
326
Release 3.2, 2018-01-15
=======================

327
Code generation and optimization:
Xavier Leroy's avatar
Xavier Leroy committed
328
- Inline static functions that are called only once.
329
330
  Can be turned off by setting the "noinline" attribute on the function.
- More consistent detection and elimination of divisions by 1.
331
- ARM in Thumb mode: simpler instruction sequence for branch through jump table.
332
- ARM: support and use the "cmn" instruction.
333
334
335
- Issue #208: make value analysis of comparisons more conservative for
  dubious comparisons such as "(uintptr_t) &global == 0x1234" which are
  undefined behavior in CompCert.
336

337
338
Usability:
- Resurrected support for the Cygwin x86-32 port, which got lost at release 3.0.
339
340
341
342
- Support the "noinline" attribute on C function definitions.
- PowerPC port with Diab toolchain: support -t <target processor> option
  and pass it to the Diab tools.
- Clightgen tool: add -o option to specify output file.
343
344
- Pull request #192: improve the printing of Clight intermediate code
  so that it looks more like valid C source.  (Frédéric Besson)
345

346
Bug fixing:
347
- Issue #P25: make sure sizeof(long double) = sizeof(double) in all contexts.
348
- Issue #211: wrong scoping for C99 declarations within a "for" statement.
Xavier Leroy's avatar
Xavier Leroy committed
349

Xavier Leroy's avatar
Xavier Leroy committed
350
Coq and Caml development:
Xavier Leroy's avatar
Xavier Leroy committed
351
352
353
- Pull request #191: Support Coq version 8.7.0 and 8.7.1 in addition
  to Coq 8.6.1.  Coq 8.6 (.0) is no longer supported owing to an
  incompatibility with 8.7.0.
Xavier Leroy's avatar
Xavier Leroy committed
354
  (Sigurd Schneider)
355
356
357
- ARM code generator: refactoring of constant expansions and EABI fixups.
- Resynchronized the list of dual-licensed files given in file LICENSE
  and the copyright headers of the dual-licensed files.
Xavier Leroy's avatar
Xavier Leroy committed
358

359

360
361
362
Release 3.1, 2017-08-18
=======================

363
364
Major improvements:

365
- New port targeting the RISC-V architecture, in 32- and 64-bit modes.
366
367
368
369
370
371
372
373
374

- Improved support for PowerPC 64 processors: use 64-bit registers and
  instructions for 64-bit integer arithmetic.  Pointers remain 32 bits
  and the 32-bit ABI is still used.

Code generation and optimization:

- Optimize leaf functions in the PowerPC back-end.
  (Avoid reloading the return address from the stack.)
375
- Avoid generating useless conditional branches for empty if/else statements.
376
- Earlier elimination of redundant `&*expr` and `*&expr` addressings.
377
- Improve utilization of addressing modes for volatile loads and stores.
378
379
380
381

Usability:

- Add options -finline / -fno-inline to control function inlining.
382
- Removed the compilation of '.cm' files written in Cminor concrete syntax.
383
384
385
- More precise warnings about missing function returns.
- clightgen: add option "-normalize" to avoid memory loads deep inside
  expressions.
386

387
Bug fixing:
388

389
- Issue #179: clightgen produces wrong output for "switch" statements.
390
- Issue #196: excessive proof times in .v files produced by clightgen.
391
392
- Do not generate code for functions with "inline" specifier that are
  neither static nor extern, as per ISO C99.
393
394
395
396
- Some line number information was missing for some goto labels and
  switch cases.
- Issue #P16: illegal PowerPC asm generated for unsigned division after
  constant propagation.
397
398
399
- Issue #P18: ARM addressing overflows caused by 1- underestimation of
  code size, causing mismanagement of constant pool, and 2- large stack
  frames where return address and back link are at offsets >= 4Kb.
400
401
402
403
- Pass -no-pie flag to the x86 linker when -pie is the default.

Coq and Caml development:

404
- Support Coq 8.6.1.
405
406
407
- Improve compatibility with Coq working version.
- Always generate .merlin and _CoqProject files.

408

Xavier Leroy's avatar
Xavier Leroy committed
409
410
411
412
413
414
Release 3.0.1, 2017-02-14
=========================

- Ported to Coq 8.6.


Xavier Leroy's avatar
Xavier Leroy committed
415
Release 3.0, 2017-02-10
Xavier Leroy's avatar
Xavier Leroy committed
416
=======================
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433

Major improvements:

- Added support for 64-bit target platforms, including pointers that
  are 64-bit wide, and the ability to use 64-bit integer registers and
  arithmetic operations.  This support does not replace but comes in
  addition to CompCert's original support for 32-bit target platforms,
  with 32-bit pointers and emulation of 64-bit integer arithmetic
  using pairs of 32-bit integers.  In terms of C data models, CompCert
  used to be restricted to the ILP32LL64 model; now it also supports
  I32LP64 and IL32LLP64.

- The x86 port of CompCert was extended to produce x86-64 bit code in
  addition to the original x86-32 bit (IA32) code.  (This is the first
  instantiation of the new support for 64-bit targets described
  above.) Support for x86-64 is currently available for Linux and MacOS X.
  (Run the configure script with 'x86_64-linux' or 'x86_64-macosx'.)
Xavier Leroy's avatar
Xavier Leroy committed
434
  This is an early port: several ABI incompatibilities remain.
435

Xavier Leroy's avatar
Xavier Leroy committed
436
437
438
439
440
441
442
443
444
445
446
447
Language features:

- Support for anonymous structures and unions as members of
  structures or unions.  (ISO C11, section 6.7.2.1, para 13 and 19.)
- New built-in functions for ARM and PowerPC:
  __builtin_ctz, __builtin_ctzl, __builtin_ctzll
  (count trailing zeros, 32 and 64 bits).

Usability:

- Added options -Wxxx and -Wno-xxx (for various values of "xxx")
  to control which warnings are emitted.
448
449
- Added options -Werror=xxx and -Wno-error=xxx (for various values of "xxx")
  to control which warnings are treated as errors.
Xavier Leroy's avatar
Xavier Leroy committed
450
451
452
- Support response files where additional command-line arguments can
  be passed (syntax: @file).
- Improved wording of warning and error messages.
453
454
455
456
457
- Improved handling of attributes, distinguishing attributes that apply
  to types from attributes that apply to names.  For example, in
    __attribute((aligned(8),section("foo"))) int * p;
  the "aligned" attribute is attached to type "int", while
  the "section" attribute is attached to name "p".
Xavier Leroy's avatar
Xavier Leroy committed
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479

Code generation:

- Support for ARM target processors in big-endian mode.
- Optimize 64-bit integer division by constants.

Bug fixing:

- Issue #155: on ARM, assembly errors caused by large jump tables for
  "switch" statements and overflow in accessing constant pools.
- Issue #151: large inductive definition causes a fatal error in
  32-bit versions of Coq.
- Issue #143: handle "%lf" printf() format in the reference interpreter
- Issue #138: struct declarations in K&R function parameters were ignored.
- Issues #110, #111, #113, #114, #115, #119, #120, #121, #122, #123, #124,
  #125, #126, #127, #128, #129, #130, #133, #138, #144: various cases
  of internal errors and failed assertions that should have been
  proper errors instead.
- For __builtin_memcpy_aligned, size and alignment arguments of 64-bit
  integer type were causing a fatal error on a 32-bit target.
- ARM and x86 ports: wrong register allocation for some calls to
  function pointers. 
480
481


482
Release 2.7.1, 2016-07-18
Xavier Leroy's avatar
Xavier Leroy committed
483
484
=========================

485
- Ported to Coq 8.5pl2.
Xavier Leroy's avatar
Xavier Leroy committed
486

487
488
489
490
Bug fixing:
- Fixed a compile-time assertion failure involving builtins
  taking a 64-bit integer parameter and given an unsigned 32-bit integer
  argument.
491
492
- Updates to the Cminor parser.

Xavier Leroy's avatar
Xavier Leroy committed
493

494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
Release 2.7, 2016-06-29
=======================

Major improvement:
- The proof of semantic preservation now accounts for separate compilation
  and linking, following the approach of Kang, Kim, Hur, Dreyer and
  Vafeiadis, "Lightweight verification of separate compilation", POPL 2016.
  Namely, the proof considers a set of C compilation units, separately
  compiled to assembly then linked, and shows that the resulting
  assembly program preserves the semantics of the C program that would
  be obtained by syntactic linking of the source C compilation units.

Language features:
- Parse the _Noreturn function attribute from ISO C11.
- New standard includes files: <iso646.h> and <stdnoreturn.h> from ISO C11.
- New built-in functions: __builtin_clzl, __builtin_clzll
  (count leading zeros, 32 and 64 bits) for ARM, IA32 and PowerPC;
  __builtin_ctz, __builtin_ctzl, __builtin_ctzll
  (count trailing zeros, 32 and 64 bits) for IA32.

Formal C semantics:
- The semantics of conversions from pointer types to _Bool
  is fully defined (again).

518
519
520
521
Usability:
- The generation of DWARF debugging information in "-g" mode is now
  supported for ARM and IA32 (in addition to PowerPC).

522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
Coq development:
- Revised the Stacking pass and its proof to make it more extensible
  later to e.g. 64-bit integer registers.
- Use register pairs in function calling conventions to control more
  precisely the splitting of 64-bit integer arguments and results
  into pairs of 32-bit quantities
- Revised the way register conventions are described in Machregs
  and Conventions.
- Simulation diagrams now live in Prop instead of Type.

OCaml development:
- Code cleanup to remove warnings, support "safe strings" mode,
  and be fully compatible with OCaml 4.02 and 4.03.
- Cminor parser: support for single-precision FP numbers and operators.

Bug fixing:
- Some declarations within C expressions were incorrectly ignored
  (e.g. "sizeof(enum e {A})").
- ARM in Thumb mode: incorrect "movs" instructions involving the stack
  pointer register were generated.


544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
Release 2.6, 2015-12-21
=======================

Usability:
- Generation of full DWARF v2 debugging information in "-g" mode,
  including function-local variables.  This is fully supported
  for the PowerPC target with GNU tools or Diab tools.  Support
  for IA32 and ARM is nearly there.
- Production of detailed explanations for syntax errors during parsing.
  (Exploiting recent work by F. Pottier on the Menhir parser generator.)
- PowerPC port: added many new builtin functions.

Code generation and optimization:
- Support for PowerPC 64-bits (pointers are still 32-bit wide)
  and Freescale's E5500 variant.
- More prudent alias analysis for operations over pointers that are
  formally undefined, such as bit masking.
- New pass: Debugvar, to associate debug information to local variables.

Coq development:
- Richer representation of arguments and results to builtin operations.
- As a consequence, annotation builtins no longer need special handling.
- Added EF_debug builtins to transport debugging information throughout
  the compiler back-end.
- Upgraded the Flocq library to version 2.5.0.

Bug fixing:
- Issue #71: incorrect initialization of an array of wchar_t
- Corrected the handling of bit-fields of type _Bool and width > 1
- Removed copy optimization when returning a struct from a function.
- Full parsing of unprototyped (K&R-style) function definitions.
  (Before, the parsing was incomplete and would reject some definitions.)

Miscellaneous:
- The cchecklink tool (for a posteriori validation of assembly
  and linking) was removed.  It is replaced by the Valex tool,
  available from AbsInt.
- Added a command-line option -conf <config file> to select
  a different "compcert.ini" configuration file.
- Removed the command-line options -fstruct-passing=<convention>
  and -fstruct-return=<convention>, more confusing than useful.
- Added a command-line option -fstruct-passing that activates
  ABI-conformant by-value passing of structs and unions as
  function arguments or results.  If this option is not set,
  passing a struct/union as function argument is now rejected.
- The -fstruct-return command-line option is deprecated and
  becomes a synonymous for -fstruct-passing.
591
592
- The return type of __builtin_clz() is "int", as documented,
  and not "unsigned int", as previously implemented.
593
594


Xavier Leroy's avatar
Xavier Leroy committed
595
Release 2.5, 2015-06-12
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
=======================

Language features:
- Extended inline assembly in the style of GCC.  (See section 6.5
  of the user's manual.)  The implementation is not as complete
  as that of GCC or Clang.  In particular, the only constraints
  supported over operands are "r" (register), "m" (memory), and
  "i" (integer immediate).

Code generation and optimization:
- Revised translation of '||' and '&&' to Clight so as to
  produce well-typed Clight code.
- More prudent value analysis of uninitialized declarations of
 "const" global variables.
- Revised handling of "common" global declarations, fixes an issue
  with uninitialized declarations of "const" global variables.

Improvements in confidence:
- Formalized the typing rules for CompCert C in Coq and verified
  a type-checker, which is used to produce the type annotations
  in CompCert C ASTs, rather than trusting the types produced by
  the Elab pass.
- Coq proof of correctness for the Unusedglob pass (elimination
  of unreferenced static global definitions).  The Coq AST for
  compilation units now records which globals are static.
- More careful semantics of comparisons between a non-null pointer
  and the null pointer.  The comparison is undefined if the non-null
  pointer is out of bounds.

Usability:
- Generation of DWARF v2 debugging information in "-g" mode.
  The information describes C types, global variables, functions,
  but not yet function-local variables.  This is currently available
  only for the PowerPC/Diab target.
- Added command-line options to turn individual optimizations on or off,
  and a "-O0" option to turn them all off.
- Revised handling of arguments to __builtin_annot so that no code
  is generated for an argument that is a global variable or a local
  variable whose address is taken.
Xavier Leroy's avatar
Xavier Leroy committed
635
- In string and character literals, treat illegal escape sequences
636
  (e.g. "\%" or "\0") as an error instead of a warning.
637
638
- Warn if floating-point literals overflow or underflow when converted
  to FP numbers.
Xavier Leroy's avatar
Xavier Leroy committed
639
- In "-g -S" mode, annotate the generated .s file with comments
640
641
642
  containing the C source code.
- Recognize and accept more of GCC's alternate keywords, e.g. __signed,
  __volatile__, etc.
Xavier Leroy's avatar
Xavier Leroy committed
643
644
- cchecklink: added option "-files-from" to read .sdump file names
    from a file or from standard input.
645
646
647

ABI conformance:
- Improved ABI conformance for passing values of struct or union types
Xavier Leroy's avatar
Xavier Leroy committed
648
649
  as function arguments or results.  Full conformance is achieved on
  IA32/ELF, IA32/MacOSX, PowerPC/EABI, PowerPC/Linux, and ARM/EABI.
650
651
- Support the "va_arg" macro from <stdarg.h> in the case of arguments
  of struct or union types.
652

653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
Coq development:
- In the CompCert C and Clight ASTs, struct and union types are now
  represented by name instead of by structure.  A separate environment
  maps these names to struct/union definitions.  This avoids
  bad algorithmic complexity of operations over structural types.
- Introduce symbol environments (type Senv.t) as a restricted view on
  global environments (type Genv.t).
- Upgraded the Flocq library to version 2.4.0.

Bug fixing:
- Issue #4: exponential behaviors with deeply-nested struct types.
- Issue #6: mismatch on the definition of wchar_t
- Issue #10: definition of composite type missing from the environment.
- Issue #13: improved handling of wide string literals
- Issue #15: variable-argument functions are not eligible for inlining.
- Issue #19: support empty "switch" statements
- Issue #20: ABI incompatibility wrt struct passing on IA32.
- Issue #28: missing type decay in __builtin_memcpy_aligned applied to arrays.
- Issue #42: emit error if "static" definition follows non-"static" declaration.
- Issue #44: OSX assembler does not recognize ".global" directive.
- Protect against redefinition of the __i64_xxx helper library functions.
- Revised handling of nonstandard attributes in C type compatibility check.
Xavier Leroy's avatar
Xavier Leroy committed
675
676
677
678
679
- Emit an error on "preprocessing numbers" that are invalid numerical literals.
- Added missing check for static redefinition following a non-static
  declaration.
- Added missing check for redefinition of a typedef as an ordinary
  identifier within the same scope.
680
681
682
683
684

Miscellaneous:
- When preprocessing with gcc or clang, use "-std=c99" mode to force
  C99 conformance.
- Use a Makefile instead of ocamlbuild to compile the OCaml code.
685

686

xleroy's avatar
xleroy committed
687
688
Release 2.4, 2014-09-17
=======================
xleroy's avatar
xleroy committed
689
690
691
692
693
694

Language features:
- Support C99 compound literals  (ISO C99 section 6.5.2.5).
- Support "switch" statements over an argument of type "long long".

Code generation and optimization:
xleroy's avatar
Update    
xleroy committed
695
- Revised and improved support for single-precision floating-point
xleroy's avatar
xleroy committed
696
697
698
699
700
701
702
  arithmetic.  Earlier, all FP arithmetic was performed at double
  precision, with conversions to/from single precision as needed,
  in particular when loading/storing a single-precision FP number
  from/to memory.  Now, FP operations whose arguments are of type
  "float" are performed in single-precision, using the processor's
  single FP instructions.  Fewer conversions between double and
  single precision are generated.
xleroy's avatar
xleroy committed
703
704
- Value analysis and constant propagation: more precise treatment of
  comparisons against an integer constant.
xleroy's avatar
xleroy committed
705

xleroy's avatar
xleroy committed
706
707
708
709
Improvements in confidence:
- Full correctness proofs for the algorithms used in the runtime
  support library for conversions between 64-bit integers and
  floating-point numbers.
xleroy's avatar
xleroy committed
710

xleroy's avatar
xleroy committed
711
712
ARM port:
- Added support for Thumb2 instruction encoding (option -mthumb).
xleroy's avatar
xleroy committed
713
714
  Thumb2 is supported on ARMv7 and up, and produces more compact
  machine code.
xleroy's avatar
xleroy committed
715
716
717
- Exploit some VFPv3 instructions when available.
- Built-in function '__builtin_cntlz' (count leading zeros)
  renamed '__builtin_clz' for GCC / Clang compatibility.
xleroy's avatar
xleroy committed
718

xleroy's avatar
xleroy committed
719
720
PowerPC port:
- Refactored the expansion of built-in functions and
721
  pseudo-instructions so that it does not need to be re-done in
xleroy's avatar
xleroy committed
722
723
  cchecklink.
- Updated the cchecklink validator accordingly.
xleroy's avatar
Update    
xleroy committed
724
- More efficient code generated for volatile accesses to small data areas.
725
726
727
- Built-in function '__builtin_cntlz' (count leading zeros)
  renamed '__builtin_clz' for GCC / Clang compatibility.

xleroy's avatar
xleroy committed
728
729
IA32 port:
- Added built-in functions __builtin_clz and __builtin_ctz
730
731
  (count leading / trailing zeros).

xleroy's avatar
xleroy committed
732
733
734
735
736
737
738
739
740
741
Coq development:
- The memory model was extended with two new "chunks", Many32 and Many64,
  that enable storing any 32-bit value or 64-bit value using
  an abstract, not bit-based encoding, and reloading these values exactly.
  These new chunks are used to implement saving and restoring callee-save
  registers that can contain data of unknown types (e.g. float32 or float64)
  but known sizes.
- Refactored the library of FP arithmetic (lib/Floats.v) to support
  both 64- and 32-bit floats.

xleroy's avatar
xleroy committed
742
743
744
745

Release 2.3pl2, 2014-05-15
==========================

746
Usability:
747
748
749
750
751
- Re-added support for "__func__" identifier as per ISO C99.
- Re-added some popular GCC extensions to ISO C99:
     . alternate keywords __restrict, __inline__, etc, 
     . support for empty structs and unions
     . support '\e' escape in char and string literals, meaning ESC
752
753
754
755
756
- Do not assume that the preprocessor removed all comments.

Bug fixing:
- Fixed regression on initializers of the form  T x[N] = "literal";
  where T is a typedef for a character type.
757
758
759
- "asm" statements were causing syntax errors.
- Better handling of "extern" and "extern inline" function definitions.
- Internal error on some octal escape sequences in string literals.
xleroy's avatar
xleroy committed
760
761
762
- Parsing of "#pragma section" directives made more robust and
  with better error reporting.

763

xleroy's avatar
xleroy committed
764
765
766
Release 2.3, 2014-05-05
=======================
	
xleroy's avatar
xleroy committed
767
768
769
770
Language features:
- Support for C99 designated initializers. (ISO C99 section 6.7.8.)

Improvements in confidence:
771
772
773
774
775
776
- The parser is now formally verified against the ISO C99 grammar plus
  CompCert's extensions.  The verification proves that the parser
  recognizes exactly the language specified by the grammar, and that
  the grammar has no ambiguities.  For more details, see the paper
  "Validating LR(1) parsers" by Jacques-Henri Jourdan, François Pottier,
  and Xavier Leroy, ESOP 2012, http://dx.doi.org/10.1007/978-3-642-28869-2_20
xleroy's avatar
xleroy committed
777
778
779
780
781
782
783
784
785
786
787
788
- More theorems proved about float<->integer conversions.

Optimizations:
- Optimize "x != 0", "x == 0", "x != 1", and "x == 1" when x is known
  to be a boolean already, ranging over {0, 1, undef}.
- More systematic constant propagation in pass Selection, lightens
  the work of later RTL optimisations.
- IA32: recognize and use the "not" instruction.

Usability:
- Option "-timings" to print compilation times for various passes.
- Various tweaks in IRC graph coloring to reduce compilation time.
xleroy's avatar
xleroy committed
789
790
- IA32: add built-in functions for fused multiply-add
  (require a recent processor with FMA3 extensions).
xleroy's avatar
xleroy committed
791
792

Improvements in ABI conformance:
xleroy's avatar
xleroy committed
793
794
795
- New target platform: ARM with EABI "hard float" calling conventions
  (armhf in Debian's classification).
- IA32 and ARM: revised handling of "common" variables to conform with ABI.
xleroy's avatar
xleroy committed
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812

Bug fixing:
- In -fbitfields emulation: "a->f" was not properly rewritten if "a"
  had "array of structs" type instead of "pointer to struct".
- Moved analysis of single-precision floats from RTLtyping to Machtyping.
  (RTLtyping was incorrectly rejecting some functions involving
  single-precision floats.)  Simplified LTL semantics and Allocation
  pass accordingly.
- Assignment to a l-value of "volatile float" type could cause
  an internal error in RTLtyping/Machtyping.
- The case __builtin_fabs applied to integers was missing in the
  C semantics and in C#minor generation.
- Fixed some type annotations on CompCert C expressions.  These
  annotations were incorrect but not in a way that impacted code
  generation.


xleroy's avatar
xleroy committed
813
814
Release 2.2, 2014-02-24
=======================
xleroy's avatar
xleroy committed
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841

Major improvements:

- Two new static analyses are performed on the RTL intermediate form:
    . Value analysis, tracking constants, some integer range information,
      and pointer aliasing information.
    . Neededness analysis, generalizing liveness analysis to individual
      bits of integer values and to stack memory locations.

- Improved RTL optimizations, exploiting the results of these analyses:
    . Constant propagation can track constants across memory stores and loads.
    . Common subexpression elimination exploits nonaliasing information.
    . Dead code elimination can eliminate useless memory writes and 
      block copies, as well as integer operations that do not change
      the needed bits.
    . Redundant cast elimination is now performed globally (at
      function level) rather than locally on individual expressions.

- Experimental support for defining and calling variable-argument functions,
  including support for the <stdarg.h> interface.
  (Option -fvararg-calls, "on" by default.)

Language features:
- In "switch" statements, "default" cases can now appear anywhere, not
  just as the last case.
- Support for incomplete array as last field of a struct,
  as specified in ISO C 99.
842
843
- Support for declarations within 'for' loops, as specified in ISO C 99.
  (E.g. "for (int i = 0; i < 4; i++) ...")
844
845
- Revised semantics and implementation of _Alignas(N) attribute
  to better match those of GCC and Clang.
xleroy's avatar
xleroy committed
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
- Better tolerance for functions declared without prototypes
  (option -funprototyped, "on" by default).
- On PowerPC, support "far-data" sections
  (register-relative addressing with 32-bit offsets).

Improvements in ABI conformance:
- For x86/IA32, align struct fields of types "double" or "long long" to 4
  instead of 8, as prescribed by the x86 ELF ABI.
- For PowerPC and ARM, structs and unions returned as function results
  are now passed in integer registers if their sizes are small enough
  (<= 8 bytes for PowerPC, <= 4 bytes for ARM).

Usability:
- Revised parsing of command-line arguments to be closer to GCC and Clang.
  In particular, "ccomp -c foo.c -o obj/foo.o" now works as expected,
  instead of ignoring the "-o" option as in earlier CompCert versions.
xleroy's avatar
xleroy committed
862
863
- Recognize input files ending in .i and .p as C source files that
  must not be preprocessed.
xleroy's avatar
xleroy committed
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
- Warn for uses of the following GCC extensions to ISO C:
  zero-sized arrays, empty structs/unions, empty initializer braces.
- Option "-fno-fpu" to prevent the use of FP registers for some
  integer operations such as block copies.  (Replaces the previous
  "-fno-sse" option which was x86/IA32-specific, and extends it to
  PowerPC and ARM.)
- Option "-drtl" to record the RTL intermediate representation
  at every stage of optimization.  (Replaces "-dtailcall", "-dinlining",
  "-dconstprop", and "-dcse".)
- Add CompCert version number and command-line arguments as comments
  in the generated assembly files.

Other performance improvements:
- Recognize __builtin_fabs as a primitive unary operator instead of
  a built-in function, enabling more optimizations.
- PowerPC: shorter code generated for "&global_variable + expr".

Improvements in compilation times:
- More efficient implementation of Kildall's dataflow equation solver,
  reduces size of worklist and nomber of times a node is visited.
- Better OCaml GC settings significantly reduce compilation times
  for very large source functions.

Bug fixing:
888
889
890
891
- Fixed incorrect hypothesis on __builtin_write{16,32}_reversed.
- Fixed syntax error in __attribute__((__packed__)).
- Emit clean compile-time error for 'switch' over a value of 64-bit
  integer type (currently not supported).
892
893
- Recognize source files with .i or .p extension as C sources that
  should not be preprocessed.
894

xleroy's avatar
xleroy committed
895
896
897
898
899
Coq development:
- Removed propositional extensionality axiom (prop_ext).
- Suppressed the Mfloat64al32 memory_chunk, no longer needed.


xleroy's avatar
xleroy committed
900
901
Release 2.1, 2013-10-28
=======================
902

xleroy's avatar
xleroy committed
903
Language semantics:
xleroy's avatar
xleroy committed
904
905
- More precise modeling of not-a-numbers (NaNs) in floating-point
  arithmetic.
xleroy's avatar
xleroy committed
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
- The CompCert C language is now defined with reference to ISO C99
  instead of ISO C90 ("ANSI C") as before.  This affects mostly the
  wording of the reference manual.  However, the parsing of integer
  constants and character constants was revised to follow the ISO C99
  standard.

Language features:
- Support for _Alignas(N) attribute from ISO C 2011.
- Revised implementation of packed structs, taking advantage of _Alignas.
- Suppressed the pragma "packed", replaced by a struct-level attribute
  __packed__(params) or __attribute__(packed(params)).
- Fixed typing rules for __builtin_annot() to avoid casting arguments
  of small integer or FP types.

Performance improvements:
921
922
- Optimize integer divisions by positive constants, turning them into
  multiply-high and shifts.
923
924
925
- Optimize floating-point divisions by powers of 2, turning them
  into multiplications.
- Optimize "x * 2.0" and "2.0 * x" into "x + x".
xleroy's avatar
xleroy committed
926
927
928
929
- PowerPC: more efficient implementation of division on 64-bit integers.

Bug fixing:
- Fixed compile-time error when assigning a long long RHS to a bitfield.
930
931
- Avoid double rounding issues in conversion from 64-bit integers
  to single-precision floats.
xleroy's avatar
xleroy committed
932
933

Miscellaneous:
934
- Minor simplifications in the generic solvers for dataflow analysis.
935
- Small improvements in compilation times for the register allocation pass.
xleroy's avatar
xleroy committed
936
- MacOS X port updated to the latest XCode (version 5.0).
937

938

xleroy's avatar
xleroy committed
939
940
Release 2.0, 2013-06-21
=======================
xleroy's avatar
xleroy committed
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960

Major improvements:

- Support for C types "long long" and "unsigned long long", that is,
  64-bit integers.  Regarding arithmetic operations on 64-bit integers,
  . simple operations are expanded in-line and proved correct;
  . more complex operations (division, modulus, conversions to/from floats)
    call into library functions written in assembly, heavily tested
    but not yet proved correct.

- The register allocator was completely rewritten to use an "end-to-end"
  translation validation approach, using a validation algorithm
  described in the paper "Validating register allocation and spilling"
  by Silvain Rideau and Xavier Leroy, Compiler Construction 2010,
  http://dx.doi.org/10.1007/978-3-642-11970-5_13
  This validation-based approach enables better register allocation, esp:
  . live-range splitting is implemented
  . two-address operations are treated more efficiently
  . no need to reserve processor registers for spilling and reloading.
  The improvements in quality of generated code is significant for
961
  IA32 (because of its paucity of registers) but less so for ARM and PowerPC.
xleroy's avatar
xleroy committed
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979

- Preliminary support for debugging information.  The "-g" flag
  causes DWARF debugging information to be generated for line numbers
  and stack structure (Call Frame Information).  With a debugger like
  GDB, this makes it possible to step through the code, put breakpoints
  by line number, and print stack backtraces.  However, no information
  is generated yet for C type definitions nor for variables; therefore,
  it is not possible to print the values of variables.

Improvements in ABI conformance:
- For IA32 and ARM, function arguments of type "float"
  (single-precision FP) were incorrectly passed as "double".
- For PowerPC, fixed alignment of "double" and "long long" arguments
  passed on stack.

Improvements in code generation:
- More aggressive common subexpression elimination across some builtin
  function calls, esp. annotations.
980

xleroy's avatar
xleroy committed
981
982
983
Improvements in compiler usability:
- Option -fno-taillcalls to turn off tail-call elimination.
  (Some static analysis tools are confused by this optimization.)
984
985
986
987
- Reduced stack usage of the compiler by rewriting some key functions
  in tail-recursive style.
- Reduced memory requirements of constant propagation pass by forgetting
  compile-time approximations of dead variables.
988
- More careful elaboration of C struct and union types into CompCert C
989
  types, avoiding behaviors exponential in the nesting of structs.
990

xleroy's avatar
xleroy committed
991
992
993
994
995
996
997
998
999
1000
Bug fixing:
- Fixed parsing of labeled statements inside "switch" constructs,
  which were causing syntax errors.
- The "->" operator applied to an array type was causing a type error.
- Nested conditional expressions "a ? (b ? c : d) : e" were causing
  a compile-time error if "c", "d" and "e" had different types.

Coq development:
- Adapted the memory model to the needs of the VST project at Princeton:
  . Memory block identifiers are now of type "positive" instead of "Z"
1001
  . Strengthened invariants in the definition of memory injections
xleroy's avatar
xleroy committed
1002
1003
1004
1005
    and the specification of external calls.
- The LTL intermediate language is now a CFG of basic blocks.
- Suppressed the LTLin intermediate language, no longer used.

1006

xleroy's avatar
xleroy committed
1007
1008
Release 1.13, 2013-03-12
========================
1009

xleroy's avatar
xleroy committed
1010
Language semantics:
xleroy's avatar
xleroy committed
1011
1012
1013
- Comparisons involving pointers "one past" the end of a block are
  now defined.  (They used to be undefined behavior.)
  (Contributed by Robbert Krebbers).
xleroy's avatar
xleroy committed
1014
1015

Language features:
1016
1017
1018
- Arguments to __builtin_annot() that are compile-time constants
  are now replaced by their (integer or float) value in the annotation
  generated in the assembly file.
xleroy's avatar
xleroy committed
1019
1020

Improvements in performance:
1021
1022
- ARM and PowerPC ports: more efficient access to function parameters
  that are passed on the call stack.
1023
1024
- ARM port; slightly better code generated for some indirect memory
  accesses.
xleroy's avatar
xleroy committed
1025

xleroy's avatar
xleroy committed
1026
1027
1028
1029
1030
Bug fixing:
- Fixed a bug in the reference interpreter in -all mode causing some
  reductions to be incorrectly merged.
- Wrong parsing of hexadecimal floating-point literals 0xMMMMpEEE.

xleroy's avatar
xleroy committed
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
Improvements in usability:
- Better error and warning messages for declarations of variables
  of size >= 2^32 bits.
- Reference interpreter: more efficient exploration of states in -all mode.

Coq development:
- More efficient implementation of machine integers (module Integers)
  taking advantage of bitwise operations defined in ZArith in Coq 8.4.
- Revised handling of return addresses in the Mach language
  and the Stacking and Asmgen passes.
- A number of definitions that were opaque for no good reason are now
  properly transparent.
1043

1044

1045
1046
1047
1048
1049
1050
Release 1.12.1, 2013-01-29
==========================

Ported to Coq 8.4pl1.  Otherwise functionally identical to release 1.12.


xleroy's avatar
xleroy committed
1051
Release 1.12, 2013-01-11
1052
1053
========================

1054
1055
1056
1057
1058
Improvements in confidence:
- Floating-point literals are now parsed and converted to IEEE-754 binary
  FP numbers using a provably-correct conversion function implemented on
  top of the Flocq library.

1059
Language semantics:
1060
1061
1062
- Comparison between function pointers is now correctly defined
  in the semantics of CompCert C (it was previously undefined behavior,
  by mistake).
1063
1064
1065
- Bit-fields of 'enum' type are now treated as either unsigned or signed,
  whichever is able to represent all values of the enum.
  (Previously: always signed.)
1066
1067
1068
1069
1070
1071
1072
1073
- The "&&" and "||" operators are now primitive in CompCert C and are
  given explicit semantic rules, instead of being expressed in terms
  of "_ ? _ : _" as in previous CompCert releases.
- Added a "Ebuiltin" expression form (invocation of built-in function)
  to CompCert C, and a "Sbuiltin" statement form to Clight.
  Used it to simplify the encoding of annotations, memcpy, and volatile
  memory accesses.

1074
Performance improvements:
1075
- Better code generated for "&&" and "||" operators.
1076
1077
- More aggressive elimination of conditional branches during constant
  propagation, taking better advantage of inferred constants.
1078

xleroy's avatar
xleroy committed
1079
1080
1081
1082
1083
1084
1085
Language features:
- By popular demand, "asm" statements for inline assembly are now supported
  if the flag -finline-asm is set.  Use with extreme caution, as the
  semantic preservation proof assumes these statements have no effect
  on the processor state.

Internal simplifications and reorganization:
1086
1087
- Clight, Csharpminor, Cminor: suppressed the "Econdition" conditional
  expressions, no longer useful.
1088
1089
1090
- Clight: a single loop form, the three C loops are derived forms.
- Clight: volatile memory accesses are materialized as builtin operations.
- Clight: removed dependencies on CompCert C syntax and semantics.
xleroy's avatar
xleroy committed
1091
1092
1093
1094
- New pass SimplLocals over Clight that replaces local scalar variables
  whose address is never taken by temporary, nonadressable variables.
  (This used to be done in Cminorgen.)
- Csharpminor: simplified semantics.
1095
1096
- Cminor: suppressed the "Oboolval" and "Onotbool" operators,
  which can be expressed in terms of "Ocmpu" at no performance costs.
1097
1098
1099
- All languages: programs are now presented as a list of global definitions
  (of functions or variables) instead of two lists, one for functions
  and the other for variables.
1100

1101
Other changes:
1102
1103
1104
- For compatibility with other C compilers, output files are now generated
  in the current directory, by default; output file name can be controlled
  with the -o option, somewhat like with GCC.
xleroy's avatar
xleroy committed
1105
- Reference interpreter: better handling of volatile memory accesses.
1106
1107
- IA32/MacOS X: now supports referencing global variables defined in shared
  libraries; old hack for stdio is no longer needed.
1108
1109
- PowerPC/MacOS X: this port was removed, as recent version of MacOS X
  no longer support PowerPC.
1110

1111

xleroy's avatar
xleroy committed
1112
Release 1.11, 2012-07-13
xleroy's avatar
xleroy committed
1113
1114
1115
1116
1117
1118
========================

Improvements in confidence:
- Floating-point numbers and arithmetic operations, previously axiomatized,
  are now implemented and proved correct in Coq, using the Flocq library
  of S. Boldo and G. Melquiond.
1119

xleroy's avatar
xleroy committed
1120
Language semantics:
1121
1122
1123
1124
1125
1126
- In accordance with ISO C standards, the signed division min_int / -1
  and the signed remainder min_int % -1 (where min_int is the smallest
  representable signed integer) now have undefined semantics and are
  treated as "going wrong" behaviors.
  (Previously, they were defined with results min_int and 0 respectively,
  but this behavior requires unnatural code to be generated on IA32 and
1127
  PowerPC.)
1128

xleroy's avatar
xleroy committed
1129
1130
1131
1132
Performance improvements:
- Function inlining is now implemented.  The functions that are inlined
  are those declared "inline" in the C source, provided they are not
  recursive.
1133
- Constant propagation is now able to propagate the initial values of
xleroy's avatar
xleroy committed
1134
1135
1136
1137
  "const" global variables.
- Added option -ffloat-const-prop to control the propagation of
  floating-point constants; see user's manual for documentation.
- Common subexpression elimination can now eliminate memory loads
1138
  following a memory store at the same location.
xleroy's avatar
xleroy committed
1139
1140
1141
- ARM: make use of the "fcmpzd" and "fmdrr" instructions.

New tool:
1142
- The "cchecklink" tool performs a posteriori validation of the
xleroy's avatar
xleroy committed
1143
1144
1145
1146
1147
1148
1149
1150
  assembling and linking phases.  It is available for PowerPC-EABI
  only.  It takes as inputs an ELF-PowerPC executable as produced
  by the linker, as well as .sdump files (abstract assembly) as
  produced by "ccomp -sdump", and checks that the executable contains
  properly-assembled and linked code and data corresponding to those
  produced by CompCert.

Other changes:
xleroy's avatar
xleroy committed
1151
1152
- Elimination of "static" functions and "static" global variables that
  are not referenced in the generated code.
xleroy's avatar
xleroy committed
1153
1154
1155
1156
1157
- The memory model was enriched with "max" permissions in addition to
  "current" permissions, to better reason over "const" blocks and
  already-deallocated blocks.
- More efficient implementation of the memory model, resulting
  in faster interpretation of source files by "ccomp -interp".
xleroy's avatar
xleroy committed
1158
- Added option "-falign-functions" to control alignment of function code.
xleroy's avatar
xleroy committed
1159
1160


xleroy's avatar
MAJ doc    
xleroy committed
1161
Release 1.10, 2012-03-13
1162
1163
1164
1165
1166
1167
1168
1169
========================

Improvements in confidence:
- CompCert C now natively supports volatile types.  Its semantics fully
  specifies the meaning of volatile memory accesses.  The translation
  of volatile accesses to built-in function invocations is now proved correct.
- CompCert C now natively supports assignment between composite types
  (structs or unions), passing composite types by value as function
1170
  parameters, and other instances of using composites as r-values, with
1171
1172
  the exception of returning composites by value from a function.
  (The latter remains emulated, using the -fstruct-return option.)
1173
1174
- PowerPC: removed the -fmadd option, not semantically-preserving
  in the strict sense.
1175
1176
1177

Language features:
- Support for _Bool type from ISO C99.
1178
1179
- Support for _Alignof(ty) operator from ISO C 2011
  and __alignof__(ty), __alignof__(expr) from GCC.
1180
1181
1182
1183
1184
1185

Performance improvements:
- Improvements in instruction selection, especially for integer casts
  and their combinations with bitwise operations.
- Shorter, more efficient code generated for accessing volatile global
  variables.
1186
- Better code generated for the && and || operators.
1187
- More aggressive common subexpression elimination (CSE) of memory loads.
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
- Improved register allocation for invocations of built-ins,
  especially for annotations.
- In Cminor and down, make safe operators non-strict: they return Vundef
  instead of getting stuck.  This enables more optimizations.
- Cast optimization is no longer performed by a separate pass over
  RTL, but equivalent optimization is done during Cminor generation
  and during instruction selection.

Other improvements:
- PowerPC/EABI: uninitialized global variables now go in common (bss) section.
- PowerPC: work around limited excursion of conditional branch instructions.
1199
- PowerPC: added __builtin_fnmadd() and __builtin_fnmsub().
1200
1201
1202
- Reference interpreter: better printing of pointer values and locations.
- Added command-line options -Wp,<opt> -Wa,<opt> -Wl,<opt> to pass
  specific options to the preprocessor, assembler, or linker, respectively.
1203
- More complete Cminor parser and printer (contributed by Andrew Tolmach).
1204
1205


xleroy's avatar
Update    
xleroy committed
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
Release 1.9.1, 2011-11-28
=========================

Bug fixes:
- Initialization of a char array by a short string literal was wrongly rejected
- Incorrect handling of volatile arrays.
- IA32 code generator: make sure that min_int / -1 does not cause a
  machine trap.

Improvements:
- Added language option -flongdouble to treat "long double" like "double".
- The reference interpreter (ccomp -interp) now supports 2-argument main
  functions (int main(int, char **)).
- Improved but still very experimental emulation of packed structs
  (-fpacked-structs)
- Coq->Caml extraction: extract Coq pairs to Caml pairs and Coq
  characters to Caml "char" type.


1225
Release 1.9, 2011-08-22
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
=======================

- The reduction semantics of CompCert C was made executable and turned
  into a reference interpreter for CompCert C, enabling animation of
  the semantics.  (Thanks to Brian Campbell for suggesting this approach.)
  Usage is:  ccomp -interp [options] source.c
  Options include:
    -trace      to print a detailed trace of reduction steps
    -random     to randomize execution order
    -all        to explore all possible execution orders in parallel
1236

1237
1238
1239
1240
1241
1242
1243
1244
- Revised and strengthened the top-level statements of semantic preservation.
  In particular, we now show:
  . backward simulation for the whole compiler without assuming
    a deterministic external world;
  . if the source program goes wrong after performing some I/O,
    the compiled code performs at least these I/O before continuing
    with an arbitrary behavior.

xleroy's avatar
MAJ    
xleroy committed
1245
1246
- Fixed two omissions in the semantics of CompCert C
  (reported by Brian Campbell):
1247
1248
1249
1250
  . Functions calls through a function pointer had undefined semantics.
  . Conditional expressions "e1 ? e2 : e3" where e2 and e3 have different
    types were missing a cast to their common type.

1251
1252
1253
1254
1255
1256
1257
1258
- Support for "read-modify-write" operations over volatiles
  (such as e++ or --e or e |= 1 where e has volatile type)
  through a new presimplification (flag -fvolatile-rmw, "on" by default).

- New optimization pass: Redundant Reload Elimination, which fixes up
  inefficiencies introduced during the Reload pass.  On x86, it increases
  performance by up to 10%.  On PowerPC and ARM, the effect is negligible.

1259
1260
1261
1262
1263
1264
1265
1266
- Revised handling of annotation statements.  Now they come in two forms:
    1. __builtin_annot("format", x1, ..., xN)
       (arbitrarily many arguments; no code generated, even if some
        of the xi's were spilled; no return value)
    2. __builtin_annot_intval("format", x1)
       (one integer argument, reloaded in a register if needed,
        returned as result).

xleroy's avatar
Update    
xleroy committed
1267
- Related clean-ups in the handling of external functions and
xleroy's avatar
MAJ    
xleroy committed
1268
1269
  compiler built-ins.  In particular, __builtin_memcpy is now
  fully specified.
1270

1271
1272
1273
1274
- ARM code generator was ported to the new ABI (EABI in ARM parlance,
  armel in Debian parlance), using VFD instructions for floating-point.
  (Successfully tested on a Trimslice platform running Ubuntu 11.04.)

xleroy's avatar
MAJ    
xleroy committed
1275
1276
1277
1278
1279
1280
1281
1282
- IA32 code generator:
    . Added -fno-sse option to prevent generation of SSE instructions
      for memory copy operations.
    . More realistic modeling of the ST0 (top-of-FP-stack) register
      and of floating-point compare and branch.

- PowerPC code generator: more efficient instruction sequences generated
  for insertion in a bit field and for some comparisons against 0.
1283

xleroy's avatar
Update    
xleroy committed
1284

xleroy's avatar
xleroy committed
1285
1286
1287
Release 1.8.2, 2011-05-24
=========================

1288
- Support for "aligned" and "section" attributes on global variables, e.g.
1289
1290
    __attribute__((aligned(16))) int x;

1291
1292
- Experimental emulation of packed structs (flag -fpacked-structs).

1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
- Pointer comparisons now treated as unsigned comparisons (previously: signed).
  This fixes an issue with arrays straddling the 0x8000_0000 boundary.
  Consequently, the "ofs" part of pointer values "Vptr b ofs" is
  now treated as unsigned (previously: signed).

- Elimination of unreferenced labels now performed by a separate pass
  (backend/CleanupLabels.v) and proved correct.

- Stacking pass revised: supports more flexible layout of the stack
  frame; two-step proof (Stackingproof + Machabstr2concr) merged
  into one single proof (Stackingproof).

- The requirement that pointers be valid in pointer comparisons
  was pushed through all intermediate languages of the back-end
1307
  (previously: requirement present only up to Csharpminor).
1308

xleroy's avatar
xleroy committed
1309
1310
1311
1312
- Emulation of assignment between structs and between unions was
  simplified and made more efficient, thanks to a better implementation
  of __builtin_memcpy.

1313
1314
1315
1316
1317
1318
1319
- Improvements to the compiler driver:
    .  -E option now prints preprocessed result to standard output
       instead of saving it in a .i file
    .  support for .s (assembly) and .S (assembly to be preprocessed)
       input files


xleroy's avatar
xleroy committed
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
Release 1.8.1, 2011-03-14
=========================

- Adapted to Coq 8.3pl1.

- Reduced compilation times through several algorithmic improvements
  (contributed by A. Pilkiewicz).

- In the various semantics, allow float-to-int conversions to fail
  (if the float argument is outside the range of representable ints).

- Initialization of global C variables made more robust and proved correct.

- ABI conformance improved:
     . the "char" type is now signed for x86, remains unsigned for PowerPC and ARM
     . placement of bit-fields now follows SVR4 conventions (affects PowerPC)

- Bug fixes in the C pre-simplifier:
     . nontermination with some recursive struct types
     . issues with zero-width bit fields
     . elimination of struct assignments duplicating some volatile accesses


xleroy's avatar
xleroy committed
1343
1344
Release 1.8, 2010-09-21
=======================
xleroy's avatar
Update    
xleroy committed
1345

xleroy's avatar
Updated    
xleroy committed
1346
1347
- The input language to the proved part of the compiler is no longer
  Clight but CompCert C: a larger subset of the C language supporting
xleroy's avatar
xleroy committed
1348
1349
1350
1351
  in particular side-effects within expressions.  The transformations
  that pull side effects out of expressions and materialize implicit
  casts, formerly performed by untrusted Caml code, are now fully
  proved in Coq.
xleroy's avatar
Updated    
xleroy committed
1352
1353
1354

- New port targeting Intel/AMD x86 processors.  Generates 32-bit x86 code
  using SSE2 extensions for floating-point arithmetic.  Works under
xleroy's avatar
xleroy committed
1355
  Linux, MacOS X, and the Cygwin environment for Windows.
xleroy's avatar
Updated    
xleroy committed
1356
1357
1358
1359
1360
1361
  CompCert's compilation strategy is not a very good match for the
  x86 architecture, therefore the performance of the generated code
  is not as good as for the PowerPC port, but still usable.
  (About 75% of the performance of gcc -O1 for x86, compared with
   > 90% for PowerPC.)

xleroy's avatar
Update    
xleroy committed
1362
- More faithful semantics for volatile accesses:
1363
1364
1365
1366
1367
1368
  . volatile reads and writes from a volatile global variable are treated
    like input and output system calls (respectively), bypassing
    the memory model entirely;
  . volatile reads and writes from other locations are treated like
    regular loads and stores.

xleroy's avatar
Updated    
xleroy committed
1369
- Introduced __builtin_memcpy() and __builtin_memcpy_words(), use them
xleroy's avatar
Update    
xleroy committed
1370
1371
  instead of memcpy() to compile struct and union assignments.

xleroy's avatar
Updated    
xleroy committed
1372
1373
- Introduced __builtin_annotation() to transmit assertions from
  the source program all the way to the generated assembly code.
xleroy's avatar
Update    
xleroy committed
1374
1375
1376
1377
1378
1379
1380

- Elimination of some useless casts around "&", "|" and "^" bitwise operators.

- Produce fewer "moves" during RTL generation.  This speeds up the
  rest of compilation and slightly improves the result of register
  allocation when register pressure is high.

xleroy's avatar
Updated    
xleroy committed
1381
1382
1383
1384
1385
1386
- Improvements in register allocation:
  . Implemented a spilling heuristic during register allocation.
    This heuristic reduces significantly the amount of spill code
    generated when register pressure is high.
  . More coalescing between low-pressure and high-pressure variables.
  . Aggressive coalescing between pairs of spilled variables.
xleroy's avatar
Update    
xleroy committed
1387

xleroy's avatar
Updated    
xleroy committed
1388
- Fixed some bugs in the emulation of bit fields.
xleroy's avatar
Update    
xleroy committed
1389

xleroy's avatar
Update    
xleroy committed
1390

xleroy's avatar
xleroy committed
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
Release 1.7.1, 2010-04-13
=========================

Bug fixes in the new C pre-simplifier:
- Missing cast on return value for some functions
- Incorrect simplification of some uses of || and &&
- Nontermination in the presence of a bit field of size exactly 32 bits.
- Global initializers for structs containing bit fields.
- Wrong type in volatile reads from variables of type 'unsigned int'.

Small improvements to the PowerPC port:
- Added __builtin_trap() built-in function.
- Support for '#pragma reserve_register' (EABI)
- Less aggressive alignment of global variables.
- Generate '.type' and '.size' directives (EABI).


xleroy's avatar
xleroy committed
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
Release 1.7, 2010-03-31
=======================

- New implementation of the C type-checker, simplifier, and translation to
  Clight.  Compared with the previous CIL-based solution, the new
  implementation is more modular and supports more optional simplifications.

- More features of the C language are handled by expansion during
  translation to Clight:
    . assignment between structs and unions (option -fstruct-assign)
    . passing structs and union by value (option -fstruct-passing)
    . bit-fields in structs (option -fbitfields)

- The "volatile" modifier is now honored.  Volatile accesses are represented
  in Clight by calls to built-in functions, which are preserved throughout
  the compilation chain, then turned into processor loads and stores
  at the end.

- Generic support for C built-in functions.  These predefined external
  functions give access to special instructions of the processor.  See
  powerpc/CBuiltins.ml for the list of PowerPC built-in functions.

- The memory model now exposes the bit-level in-memory representation
  of integers and floats.  This strengthens the semantic preservation
  theorem: we now prove that C code that directly manipulates these
  bit-level representations (e.g. via a union between floats and integers)
  is correctly compiled.

- The memory model now supports fine-grained access control to individual
xleroy's avatar
Update    
xleroy committed
1437
  bytes of a memory block.  This feature is currently unused in the
xleroy's avatar
xleroy committed
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
  compiler proofs, but will facilitate connections with separation logics
  later.

- External functions are now allowed to read and modify memory.
  The semantic preservation proofs were strengthened accordingly.
  In particular, this enables the malloc() and free() C library functions
  to be modeled as external functions in a provably correct manner.

- Minor improvements in the handling of global environments and the
  construction of the initial memory state.

- Bug fixes in the handling of '#pragma section' and '#pragma set_section'.

- The C test suite was enriched and restructured.

xleroy's avatar
Update    
xleroy committed
1453

xleroy's avatar
xleroy committed
1454
Release 1.6, 2010-01-13
xleroy's avatar
xleroy committed
1455
1456
=======================

1457
1458
1459
1460
1461
- Support Clight initializers of the form "int * x = &y;".

- Fixed spurious compile-time error on Clight initializers of the form
  "const enum E x[2] = { E_1, E_2 };".

xleroy's avatar
xleroy committed
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
- Produce informative error message if a 'return' without argument
  occurs in a non-void function, or if a 'return' with an argument
  occurs in a void function.

- Preliminary support for '#pragma section' and '#pragma set_section'.

- Preliminary support for small data areas in PowerPC code generator.

- Back-end: added support for jump tables; used them to compile
  dense 'switch' statements.

1473
1474
1475
1476
- PowerPC code generator: force conversion to single precision before
  doing a "store single float" instruction.


xleroy's avatar
xleroy committed
1477
1478
Release 1.5, 2009-08-28
=======================
xleroy's avatar
xleroy committed
1479
1480
1481
1482
1483
1484
1485
1486

- Support for "goto" in the source language Clight.

- Added small-step semantics for Clight.

- Traces for diverging executions are now uniquely defined;
  tightened semantic preservation results accordingly.

xleroy's avatar
Update    
xleroy committed
1487
- Emulated assignments between structures
xleroy's avatar
xleroy committed
1488
1489
  (during the C to Clight initial translation).

xleroy's avatar
xleroy committed
1490
- Fixed spurious compile-time error on Clight statements of the form
xleroy's avatar
xleroy committed
1491
  "x = f(...);" where x is a global variable.
xleroy's avatar
xleroy committed
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510

- Fixed spurious compile-time error on Clight initializers where
  the initial value is the result of a floating-point computation
  (e.g. "double x = 3.14159 / 2;").

- Simplified the interface of the generic dataflow solver.

- Reduced running time and memory requirements for the constant propagation
  pass.

- Improved the implementation of George and Appel's graph coloring heuristic:
  runs faster, produces better results.

- Revised the implementation of branch tunneling.

- Improved modularization between processor-dependent and
  processor-independent parts.


xleroy's avatar
xleroy committed
1511
1512
1513
1514
1515
Release 1.4.1, 2009-06-05
=========================

- Adapted to Coq 8.2-1.  No changes in functionality.

xleroy's avatar
xleroy committed
1516
1517
Release 1.4, 2009-04-20
=======================
xleroy's avatar
Update    
xleroy committed
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530

- Modularized the processor dependencies in the back-end.

- Three target architectures are now supported:
       PowerPC / MacOS X       (most mature)
       PowerPC / EABI & Linux  (getting stable)
       ARM / Linux EABI        (still experimental)

- Added alignment constraints to the memory model.

- Clight: added support for conditional expressions (a ? b : c);
  removed support for array accesses a[i], now a derived form.

xleroy's avatar
xleroy committed
1531
1532
- C front-end: honor "static" modifiers on globals.

xleroy's avatar
xleroy committed
1533
1534
- New optimization over RTL: turning calls into tail calls when possible.

xleroy's avatar
Update    
xleroy committed
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
- Instruction selection pass: elimination of redundant casts following
  a memory load of a "small" memory quantity.

- Linearization pass: improved the linearization heuristic.

- Reloading pass: more economical use of temporaries.

- Back-end: removed "alloc heap" instruction; removed pointer validity
  checks in pointer comparisons.

xleroy's avatar
xleroy committed
1545

xleroy's avatar
xleroy committed
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
Release 1.3, 2008-08-11
=======================

- Added "goto" and labeled statements to Cminor.  Extended RTLgen and
    its proof accordingly.

- Introduced small-step transition semantics for Cminor; used it in
    proof of RTLgen pass; proved consistency of Cminor big-step semantics
    w.r.t. transition semantics.

- Revised division of labor between the Allocation pass and the Reload pass.
    The semantics of LTL and LTLin no longer need to anticipate the passing
    of arguments through the conventional locations.

- Cleaned up Stacking pass: the positions of the back link and of
    the return address in the stack frame are no longer hard-wired
    in the Mach semantics.

- Added operator to convert from float to unsigned int; used it in C front-end

- Added flag -fmadd to control recognition of fused multiply-add and -sub

- Semantics of pointer-pointer comparison in Clight was incomplete:
    pointers within different blocks can now be compared using == or !=

- Addition integer + pointer is now supported in Clight.

- Improved instruction selection for complex conditions involving || and &&.

- Improved translation of Cminor "switch" statements to RTL decision trees.

- Fixed error in C parser and simplifier related to "for" loops with
    complex expressions as condition.

- More benchmark programs in test/


xleroy's avatar
Update    
xleroy committed
1583
1584
Release 1.2, 2008-04-03
=======================
xleroy's avatar
xleroy committed
1585
1586

- First public release