RISC-V: wrong fixup code generated for vararg calls with fixed FP args

This is a follow-up to 2076a3bb.

Integer registers were wrongly reserved for fixed FP arguments,
causing variadic FP arguments to end up in the wrong integer registers.

Added regression test in test/regression/varargs2.c

riscV/Asmexpand.ml

@@ -72,27 +72,33 @@ let rec fixup_variadic_call fixed ri rf tyl =
     | (Tint | Tany32) :: tyl ->
         fixup_variadic_call (fixed - 1) (ri + 1) rf tyl
     | Tsingle :: tyl ->
-        if fixed <= 0 then begin
+        if fixed > 0 then
+          fixup_variadic_call (fixed - 1) ri (rf + 1) tyl
+        else begin
           let rs = float_param_regs.(rf)
           and rd = int_param_regs.(ri) in
-          emit (Pfmvxs(rd, rs))
-        end;
-        fixup_variadic_call (fixed - 1) (ri + 1) (rf + 1) tyl
+          emit (Pfmvxs(rd, rs));
+          fixup_variadic_call (fixed - 1) (ri + 1) (rf + 1) tyl
+        end
     | Tlong :: tyl ->
         let ri' = if Archi.ptr64 then ri + 1 else align ri 2 + 2 in
         fixup_variadic_call (fixed - 1) ri' rf tyl
     | (Tfloat | Tany64) :: tyl ->
         if Archi.ptr64 then begin
-          if fixed <= 0 then begin
+          if fixed > 0 then
+            fixup_variadic_call (fixed - 1) ri (rf + 1) tyl
+          else begin
             let rs = float_param_regs.(rf)
             and rd = int_param_regs.(ri) in
-            emit (Pfmvxd(rd, rs))
-          end;
-          fixup_variadic_call (fixed - 1) (ri + 1) (rf + 1) tyl
+            emit (Pfmvxd(rd, rs));
+            fixup_variadic_call (fixed - 1) (ri + 1) (rf + 1) tyl
+          end
         end else begin
           let ri = align ri 2 in
           if ri < 8 then begin
-            if fixed <= 0 then begin
+            if fixed > 0 then
+              fixup_variadic_call (fixed - 1) ri (rf + 1) tyl
+            else begin
               let rs = float_param_regs.(rf)
               and rd1 = int_param_regs.(ri)
               and rd2 = int_param_regs.(ri + 1) in
@@ -100,9 +106,9 @@ let rec fixup_variadic_call fixed ri rf tyl =
               emit (Pfsd(rs, X2, Ofsimm _0));
               emit (Plw(rd1, X2, Ofsimm _0));
               emit (Plw(rd2, X2, Ofsimm _4));
-              emit (Paddiw(X2, X X2, _16))
-            end;
-            fixup_variadic_call (fixed - 1) (ri + 2) (rf + 1) tyl
+              emit (Paddiw(X2, X X2, _16));
+              fixup_variadic_call (fixed - 1) (ri + 2) (rf + 1) tyl
+            end
           end
         end
         

test/regression/Results/varargs2

@@ -10,4 +10,5 @@ Twice: -1 1.23
 With va_copy: -1 1.23
 With va_copy: -1 1.23
 With extra args: x & Hello, world! & 42 & 123456789012345 & 3.141592654 & 2.718281746
+With extra FP args: 123456789012345 & 3.141592654 & 2.718281746
 va_list compatibility: x & Hello, world! & 42 & 123456789012345 & 3.141592654 & 2.718281746

test/regression/varargs2.c

@@ -104,6 +104,17 @@ void miniprintf_extra(int i1, int i2, int i3, int i4,
   va_end(va);
 }
 
+/* Add a few dummy FP arguments to test passing of variadic FP arguments
+   in integer registers (mostly relevant for RISC-V) */
+
+void miniprintf_float(double f1, double f2, const char * fmt, ...)
+{
+  va_list va;
+  va_start(va, fmt);
+  minivprintf(fmt, va);
+  va_end(va);
+}
+
 /* Test va_list compatibility with the C library */
 
 void printf_compat(const char * fmt, ...)
@@ -143,6 +154,11 @@ int main()
                    123456789012345LL,
                    3.141592654,
                    2.71828182);
+  miniprintf_float(0.0, 1.0,
+                   "With extra FP args: %l & %e & %f\n",
+                   123456789012345LL,
+                   3.141592654,
+                   2.71828182);
   printf_compat("va_list compatibility: %c & %s & %d & %lld & %.10g & %.10g\n",
                 'x',
                 "Hello, world!",