[RS6000] Correct powerpc sysv stack argument accounting

ppc32 starts using the stack for integer arg passing when we run out
of integer arg passing registers.  Similarly, we start using the stack
for floating point args when we run out of floating point registers.
The decision on where an integer arg goes does not depend on number of
floating point args, nor does the decision on where a floating point
arg goes depend on number of integer args.  Alignment of stack args
also simply depends on number of stack args.

This patch untangles the horrible mess we had, with intarg_count being
wrongly used to count both integer args and stack words.

	* src/powerpc/ffi_sysv.c (ffi_prep_cif_sysv_core): Count fprs,
	gprs, and stack words separately.
	(ffi_prep_args_SYSV): Similarly.

From-SVN: r228307

2 files changed, 104 insertions, 109 deletions

diff --git a/libffi/ChangeLog b/libffi/ChangeLog
index 19a6433f..c7ade43 100644
--- a/libffi/ChangeLog
+++ b/libffi/ChangeLog
@@ -1,3 +1,9 @@
+2015-10-01  Alan Modra  <amodra@gmail.com>
+
+	* src/powerpc/ffi_sysv.c (ffi_prep_cif_sysv_core): Count fprs,
+	gprs, and stack words separately.
+	(ffi_prep_args_SYSV): Similarly.
+
 2015-05-13  Michael Haubenwallner  <michael.haubenwallner@ssi-schaefer.com>
 
 	* Makefile.in: Regenerated with automake-1.11.6.
diff --git a/libffi/src/powerpc/ffi_sysv.c b/libffi/src/powerpc/ffi_sysv.c
index 646c340..4078e75 100644
--- a/libffi/src/powerpc/ffi_sysv.c
+++ b/libffi/src/powerpc/ffi_sysv.c
@@ -93,7 +93,7 @@ ffi_prep_cif_sysv_core (ffi_cif *cif)
 {
   ffi_type **ptr;
   unsigned bytes;
-  unsigned i, fparg_count = 0, intarg_count = 0;
+  unsigned i, fpr_count = 0, gpr_count = 0, stack_count = 0;
   unsigned flags = cif->flags;
   unsigned struct_copy_size = 0;
   unsigned type = cif->rtype->type;
@@ -155,7 +155,7 @@ ffi_prep_cif_sysv_core (ffi_cif *cif)
 	  flags |= FLAG_RETURNS_SMST;
 	  break;
 	}
-      intarg_count++;
+      gpr_count++;
       flags |= FLAG_RETVAL_REFERENCE;
       /* Fall through.  */
     case FFI_TYPE_VOID:
@@ -182,24 +182,41 @@ ffi_prep_cif_sysv_core (ffi_cif *cif)
 	{
 #if FFI_TYPE_LONGDOUBLE != FFI_TYPE_DOUBLE
 	case FFI_TYPE_LONGDOUBLE:
-	  fparg_count++;
-	  /* Fall thru */
+	  if (fpr_count >= NUM_FPR_ARG_REGISTERS - 1)
+	    {
+	      fpr_count = NUM_FPR_ARG_REGISTERS;
+	      /* 8-byte align long doubles.  */
+	      stack_count += stack_count & 1;
+	      stack_count += 4;
+	    }
+	  else
+	    fpr_count += 2;
+#ifdef __NO_FPRS__
+	  return FFI_BAD_ABI;
 #endif
+	  break;
+#endif
+
 	case FFI_TYPE_DOUBLE:
-	  fparg_count++;
-	  /* If this FP arg is going on the stack, it must be
-	     8-byte-aligned.  */
-	  if (fparg_count > NUM_FPR_ARG_REGISTERS
-	      && intarg_count >= NUM_GPR_ARG_REGISTERS
-	      && intarg_count % 2 != 0)
-	    intarg_count++;
+	  if (fpr_count >= NUM_FPR_ARG_REGISTERS)
+	    {
+	      /* 8-byte align doubles.  */
+	      stack_count += stack_count & 1;
+	      stack_count += 2;
+	    }
+	  else
+	    fpr_count += 1;
 #ifdef __NO_FPRS__
 	  return FFI_BAD_ABI;
 #endif
 	  break;
 
 	case FFI_TYPE_FLOAT:
-	  fparg_count++;
+	  if (fpr_count >= NUM_FPR_ARG_REGISTERS)
+	    /* Yes, we don't follow the ABI, but neither does gcc.  */
+	    stack_count += 1;
+	  else
+	    fpr_count += 1;
 #ifdef __NO_FPRS__
 	  return FFI_BAD_ABI;
 #endif
@@ -208,11 +225,13 @@ ffi_prep_cif_sysv_core (ffi_cif *cif)
 	case FFI_TYPE_UINT128:
 	  /* A long double in FFI_LINUX_SOFT_FLOAT can use only a set
 	     of four consecutive gprs. If we do not have enough, we
-	     have to adjust the intarg_count value.  */
-	  if (intarg_count >= NUM_GPR_ARG_REGISTERS - 3
-	      && intarg_count < NUM_GPR_ARG_REGISTERS)
-	    intarg_count = NUM_GPR_ARG_REGISTERS;
-	  intarg_count += 4;
+	     have to adjust the gpr_count value.  */
+	  if (gpr_count >= NUM_GPR_ARG_REGISTERS - 3)
+	    gpr_count = NUM_GPR_ARG_REGISTERS;
+	  if (gpr_count >= NUM_GPR_ARG_REGISTERS)
+	    stack_count += 4;
+	  else
+	    gpr_count += 4;
 	  break;
 
 	case FFI_TYPE_UINT64:
@@ -225,10 +244,14 @@ ffi_prep_cif_sysv_core (ffi_cif *cif)
 	     Also, only certain register pairs can be used for
 	     passing long long int -- specifically (r3,r4), (r5,r6),
 	     (r7,r8), (r9,r10).  */
-	  if (intarg_count == NUM_GPR_ARG_REGISTERS-1
-	      || intarg_count % 2 != 0)
-	    intarg_count++;
-	  intarg_count += 2;
+	  gpr_count += gpr_count & 1;
+	  if (gpr_count >= NUM_GPR_ARG_REGISTERS)
+	    {
+	      stack_count += stack_count & 1;
+	      stack_count += 2;
+	    }
+	  else
+	    gpr_count += 2;
 	  break;
 
 	case FFI_TYPE_STRUCT:
@@ -249,7 +272,10 @@ ffi_prep_cif_sysv_core (ffi_cif *cif)
 	case FFI_TYPE_SINT8:
 	  /* Everything else is passed as a 4-byte word in a GPR, either
 	     the object itself or a pointer to it.  */
-	  intarg_count++;
+	  if (gpr_count >= NUM_GPR_ARG_REGISTERS)
+	    stack_count += 1;
+	  else
+	    gpr_count += 1;
 	  break;
 
 	default:
@@ -257,22 +283,19 @@ ffi_prep_cif_sysv_core (ffi_cif *cif)
 	}
     }
 
-  if (fparg_count != 0)
+  if (fpr_count != 0)
     flags |= FLAG_FP_ARGUMENTS;
-  if (intarg_count > 4)
+  if (gpr_count > 4)
     flags |= FLAG_4_GPR_ARGUMENTS;
   if (struct_copy_size != 0)
     flags |= FLAG_ARG_NEEDS_COPY;
 
   /* Space for the FPR registers, if needed.  */
-  if (fparg_count != 0)
+  if (fpr_count != 0)
     bytes += NUM_FPR_ARG_REGISTERS * sizeof (double);
 
   /* Stack space.  */
-  if (intarg_count > NUM_GPR_ARG_REGISTERS)
-    bytes += (intarg_count - NUM_GPR_ARG_REGISTERS) * sizeof (int);
-  if (fparg_count > NUM_FPR_ARG_REGISTERS)
-    bytes += (fparg_count - NUM_FPR_ARG_REGISTERS) * sizeof (double);
+  bytes += stack_count * sizeof (int);
 
   /* The stack space allocated needs to be a multiple of 16 bytes.  */
   bytes = (bytes + 15) & ~0xF;
@@ -367,13 +390,13 @@ ffi_prep_args_SYSV (extended_cif *ecif, unsigned *const stack)
   /* 'gpr_base' points at the space for gpr3, and grows upwards as
      we use GPR registers.  */
   valp gpr_base;
-  int intarg_count;
+  valp gpr_end;
 
 #ifndef __NO_FPRS__
   /* 'fpr_base' points at the space for fpr1, and grows upwards as
      we use FPR registers.  */
   valp fpr_base;
-  int fparg_count;
+  valp fpr_end;
 #endif
 
   /* 'copy_space' grows down as we put structures in it.  It should
@@ -405,11 +428,11 @@ ffi_prep_args_SYSV (extended_cif *ecif, unsigned *const stack)
   unsigned gprvalue;
 
   stacktop.c = (char *) stack + bytes;
-  gpr_base.u = stacktop.u - ASM_NEEDS_REGISTERS - NUM_GPR_ARG_REGISTERS;
-  intarg_count = 0;
+  gpr_end.u = stacktop.u - ASM_NEEDS_REGISTERS;
+  gpr_base.u = gpr_end.u - NUM_GPR_ARG_REGISTERS;
 #ifndef __NO_FPRS__
-  fpr_base.d = gpr_base.d - NUM_FPR_ARG_REGISTERS;
-  fparg_count = 0;
+  fpr_end.d = gpr_base.d;
+  fpr_base.d = fpr_end.d - NUM_FPR_ARG_REGISTERS;
   copy_space.c = ((flags & FLAG_FP_ARGUMENTS) ? fpr_base.c : gpr_base.c);
 #else
   copy_space.c = gpr_base.c;
@@ -425,10 +448,7 @@ ffi_prep_args_SYSV (extended_cif *ecif, unsigned *const stack)
 
   /* Deal with return values that are actually pass-by-reference.  */
   if (flags & FLAG_RETVAL_REFERENCE)
-    {
-      *gpr_base.u++ = (unsigned long) (char *) ecif->rvalue;
-      intarg_count++;
-    }
+    *gpr_base.u++ = (unsigned) (char *) ecif->rvalue;
 
   /* Now for the arguments.  */
   p_argv.v = ecif->avalue;
@@ -448,14 +468,11 @@ ffi_prep_args_SYSV (extended_cif *ecif, unsigned *const stack)
 	case FFI_TYPE_LONGDOUBLE:
 	  double_tmp = (*p_argv.d)[0];
 
-	  if (fparg_count >= NUM_FPR_ARG_REGISTERS - 1)
+	  if (fpr_base.d >= fpr_end.d - 1)
 	    {
-	      if (intarg_count >= NUM_GPR_ARG_REGISTERS
-		  && intarg_count % 2 != 0)
-		{
-		  intarg_count++;
-		  next_arg.u++;
-		}
+	      fpr_base.d = fpr_end.d;
+	      if (((next_arg.u - stack) & 1) != 0)
+		next_arg.u += 1;
 	      *next_arg.d = double_tmp;
 	      next_arg.u += 2;
 	      double_tmp = (*p_argv.d)[1];
@@ -468,42 +485,33 @@ ffi_prep_args_SYSV (extended_cif *ecif, unsigned *const stack)
 	      double_tmp = (*p_argv.d)[1];
 	      *fpr_base.d++ = double_tmp;
 	    }
-
-	  fparg_count += 2;
 	  FFI_ASSERT (flags & FLAG_FP_ARGUMENTS);
 	  break;
 # endif
 	case FFI_TYPE_DOUBLE:
 	  double_tmp = **p_argv.d;
 
-	  if (fparg_count >= NUM_FPR_ARG_REGISTERS)
+	  if (fpr_base.d >= fpr_end.d)
 	    {
-	      if (intarg_count >= NUM_GPR_ARG_REGISTERS
-		  && intarg_count % 2 != 0)
-		{
-		  intarg_count++;
-		  next_arg.u++;
-		}
+	      if (((next_arg.u - stack) & 1) != 0)
+		next_arg.u += 1;
 	      *next_arg.d = double_tmp;
 	      next_arg.u += 2;
 	    }
 	  else
 	    *fpr_base.d++ = double_tmp;
-	  fparg_count++;
 	  FFI_ASSERT (flags & FLAG_FP_ARGUMENTS);
 	  break;
 
 	case FFI_TYPE_FLOAT:
 	  double_tmp = **p_argv.f;
-	  if (fparg_count >= NUM_FPR_ARG_REGISTERS)
+	  if (fpr_base.d >= fpr_end.d)
 	    {
 	      *next_arg.f = (float) double_tmp;
 	      next_arg.u += 1;
-	      intarg_count++;
 	    }
 	  else
 	    *fpr_base.d++ = double_tmp;
-	  fparg_count++;
 	  FFI_ASSERT (flags & FLAG_FP_ARGUMENTS);
 	  break;
 #endif /* have FPRs */
@@ -513,42 +521,34 @@ ffi_prep_args_SYSV (extended_cif *ecif, unsigned *const stack)
 	     is passed in four consecutive GPRs if available.  A maximum of 2
 	     long doubles can be passed in gprs.  If we do not have 4 GPRs
 	     left, the long double is passed on the stack, 4-byte aligned.  */
-	  {
-	    unsigned int int_tmp;
-	    unsigned int ii;
-	    if (intarg_count >= NUM_GPR_ARG_REGISTERS - 3)
-	      {
-		if (intarg_count < NUM_GPR_ARG_REGISTERS)
-		  intarg_count = NUM_GPR_ARG_REGISTERS;
-		for (ii = 0; ii < 4; ii++)
-		  {
-		    int_tmp = (*p_argv.ui)[ii];
-		    *next_arg.u++ = int_tmp;
-		  }
-	      }
-	    else
-	      {
-		for (ii = 0; ii < 4; ii++)
-		  {
-		    int_tmp = (*p_argv.ui)[ii];
-		    *gpr_base.u++ = int_tmp;
-		  }
-	      }
-	    intarg_count += 4;
-	    break;
-	  }
+	  if (gpr_base.u >= gpr_end.u - 3)
+	    {
+	      unsigned int ii;
+	      gpr_base.u = gpr_end.u;
+	      for (ii = 0; ii < 4; ii++)
+		{
+		  unsigned int int_tmp = (*p_argv.ui)[ii];
+		  *next_arg.u++ = int_tmp;
+		}
+	    }
+	  else
+	    {
+	      unsigned int ii;
+	      for (ii = 0; ii < 4; ii++)
+		{
+		  unsigned int int_tmp = (*p_argv.ui)[ii];
+		  *gpr_base.u++ = int_tmp;
+		}
+	    }
+	  break;
 
 	case FFI_TYPE_UINT64:
 	case FFI_TYPE_SINT64:
-	  if (intarg_count == NUM_GPR_ARG_REGISTERS-1)
-	    intarg_count++;
-	  if (intarg_count >= NUM_GPR_ARG_REGISTERS)
+	  if (gpr_base.u >= gpr_end.u - 1)
 	    {
-	      if (intarg_count % 2 != 0)
-		{
-		  intarg_count++;
-		  next_arg.u++;
-		}
+	      gpr_base.u = gpr_end.u;
+	      if (((next_arg.u - stack) & 1) != 0)
+		next_arg.u++;
 	      *next_arg.ll = **p_argv.ll;
 	      next_arg.u += 2;
 	    }
@@ -559,14 +559,10 @@ ffi_prep_args_SYSV (extended_cif *ecif, unsigned *const stack)
 		 (r5,r6), (r7,r8), (r9,r10).  If next arg is long long
 		 but not correct starting register of pair then skip
 		 until the proper starting register.  */
-	      if (intarg_count % 2 != 0)
-		{
-		  intarg_count ++;
-		  gpr_base.u++;
-		}
+	      if (((gpr_end.u - gpr_base.u) & 1) != 0)
+		gpr_base.u++;
 	      *gpr_base.ll++ = **p_argv.ll;
 	    }
-	  intarg_count += 2;
 	  break;
 
 	case FFI_TYPE_STRUCT:
@@ -601,29 +597,22 @@ ffi_prep_args_SYSV (extended_cif *ecif, unsigned *const stack)
 	  gprvalue = **p_argv.ui;
 
 	putgpr:
-	  if (intarg_count >= NUM_GPR_ARG_REGISTERS)
+	  if (gpr_base.u >= gpr_end.u)
 	    *next_arg.u++ = gprvalue;
 	  else
 	    *gpr_base.u++ = gprvalue;
-	  intarg_count++;
 	  break;
 	}
     }
 
   /* Check that we didn't overrun the stack...  */
   FFI_ASSERT (copy_space.c >= next_arg.c);
-  FFI_ASSERT (gpr_base.u <= stacktop.u - ASM_NEEDS_REGISTERS);
-  /* The assert below is testing that the number of integer arguments agrees
-     with the number found in ffi_prep_cif_machdep().  However, intarg_count
-     is incremented whenever we place an FP arg on the stack, so account for
-     that before our assert test.  */
+  FFI_ASSERT (gpr_base.u <= gpr_end.u);
 #ifndef __NO_FPRS__
-  if (fparg_count > NUM_FPR_ARG_REGISTERS)
-    intarg_count -= fparg_count - NUM_FPR_ARG_REGISTERS;
-  FFI_ASSERT (fpr_base.u
-	      <= stacktop.u - ASM_NEEDS_REGISTERS - NUM_GPR_ARG_REGISTERS);
+  FFI_ASSERT (fpr_base.u <= fpr_end.u);
 #endif
-  FFI_ASSERT (flags & FLAG_4_GPR_ARGUMENTS || intarg_count <= 4);
+  FFI_ASSERT (((flags & FLAG_4_GPR_ARGUMENTS) != 0)
+	      == (gpr_end.u - gpr_base.u < 4));
 }
 
 #define MIN_CACHE_LINE_SIZE 8