Ping^2: PR target/45074: Check targets of multi-word operations

Richard Sandiford rdsandiford@googlemail.com
Wed Jun 1 19:50:00 GMT 2011


Bernd Schmidt <bernds@codesourcery.com> writes:
> On 05/31/2011 07:51 PM, Richard Sandiford wrote:
>> Ping for:
>> 
>>     http://gcc.gnu.org/ml/gcc-patches/2011-04/msg01327.html
>> 
>> It fixes the expansion of multiword operations in cases where the
>> suggested target is a hard register and where CANNOT_CHANGE_MODE_CLASS
>> forbids word-mode subparts.
>
> Can you call the new function valid_multiword_target_p? In a sense, we
> already know it's a multiword target, so the function name is a bit
> unfortunate.

Yeah, that's better.

> I see two copies of this code
>
>  	  /* If TARGET is the same as one of the operands, the REG_EQUAL note
>  	     won't be accurate, so use a new target.  */
> -	  if (target == 0 || target == op0 || target == op1)
>
> in expand_binop, and you seem to be changing only one? Also, there's
>
>       xtarget = gen_reg_rtx (mode);
>
>       if (target == 0 || !REG_P (target))
>         target = xtarget;
>
>       /* Indicate for flow that the entire target reg is being set.  */
>       if (REG_P (target))
>         emit_clobber (xtarget);

Good catch.

> Ok with these changes (or if there's a good reason not to touch the ones
> you left out).

Thanks.  Here's what I installed after retesting on x86_64-linux-gnu.

Richard


gcc/
	PR target/45074
	* optabs.h (valid_multiword_target_p): Declare.
	* expmed.c (extract_bit_field_1): Check valid_multiword_target_p when
	doing multi-word operations.
	* optabs.c (expand_binop): Likewise.
	(expand_doubleword_bswap): Likewise.
	(expand_absneg_bit): Likewise.
	(expand_unop): Likewise.
	(expand_copysign_bit): Likewise.
	(multiword_target_p): New function.

gcc/testsuite/
	PR target/45074
	* gcc.target/mips/pr45074.c: New test.

Index: gcc/optabs.h
===================================================================
--- gcc/optabs.h	2011-06-01 18:53:46.000000000 +0100
+++ gcc/optabs.h	2011-06-01 18:54:09.000000000 +0100
@@ -1059,6 +1059,8 @@ create_integer_operand (struct expand_op
   create_expand_operand (op, EXPAND_INTEGER, GEN_INT (intval), VOIDmode, false);
 }
 
+extern bool valid_multiword_target_p (rtx);
+
 extern bool maybe_legitimize_operands (enum insn_code icode,
 				       unsigned int opno, unsigned int nops,
 				       struct expand_operand *ops);
Index: gcc/expmed.c
===================================================================
--- gcc/expmed.c	2011-06-01 18:53:46.000000000 +0100
+++ gcc/expmed.c	2011-06-01 18:54:09.000000000 +0100
@@ -1341,7 +1341,7 @@ extract_bit_field_1 (rtx str_rtx, unsign
       unsigned int nwords = (bitsize + (BITS_PER_WORD - 1)) / BITS_PER_WORD;
       unsigned int i;
 
-      if (target == 0 || !REG_P (target))
+      if (target == 0 || !REG_P (target) || !valid_multiword_target_p (target))
 	target = gen_reg_rtx (mode);
 
       /* Indicate for flow that the entire target reg is being set.  */
Index: gcc/optabs.c
===================================================================
--- gcc/optabs.c	2011-06-01 18:53:46.000000000 +0100
+++ gcc/optabs.c	2011-06-01 18:57:38.000000000 +0100
@@ -1537,7 +1537,10 @@ expand_binop (enum machine_mode mode, op
 
       /* If TARGET is the same as one of the operands, the REG_EQUAL note
 	 won't be accurate, so use a new target.  */
-      if (target == 0 || target == op0 || target == op1)
+      if (target == 0
+	  || target == op0
+	  || target == op1
+	  || !valid_multiword_target_p (target))
 	target = gen_reg_rtx (mode);
 
       start_sequence ();
@@ -1605,7 +1608,10 @@ expand_binop (enum machine_mode mode, op
 
 	  /* If TARGET is the same as one of the operands, the REG_EQUAL note
 	     won't be accurate, so use a new target.  */
-	  if (target == 0 || target == op0 || target == op1)
+	  if (target == 0
+	      || target == op0
+	      || target == op1
+	      || !valid_multiword_target_p (target))
 	    target = gen_reg_rtx (mode);
 
 	  start_sequence ();
@@ -1659,7 +1665,11 @@ expand_binop (enum machine_mode mode, op
 	 opportunities, and second because if target and op0 happen to be MEMs
 	 designating the same location, we would risk clobbering it too early
 	 in the code sequence we generate below.  */
-      if (target == 0 || target == op0 || target == op1 || ! REG_P (target))
+      if (target == 0
+	  || target == op0
+	  || target == op1
+	  || !REG_P (target)
+	  || !valid_multiword_target_p (target))
 	target = gen_reg_rtx (mode);
 
       start_sequence ();
@@ -1779,7 +1789,7 @@ expand_binop (enum machine_mode mode, op
 
       xtarget = gen_reg_rtx (mode);
 
-      if (target == 0 || !REG_P (target))
+      if (target == 0 || !REG_P (target) || !valid_multiword_target_p (target))
 	target = xtarget;
 
       /* Indicate for flow that the entire target reg is being set.  */
@@ -2481,7 +2491,7 @@ expand_doubleword_bswap (enum machine_mo
   t0 = expand_unop (word_mode, bswap_optab,
 		    operand_subword_force (op, 1, mode), NULL_RTX, true);
 
-  if (target == 0)
+  if (target == 0 || !valid_multiword_target_p (target))
     target = gen_reg_rtx (mode);
   if (REG_P (target))
     emit_clobber (target);
@@ -2724,7 +2734,9 @@ expand_absneg_bit (enum rtx_code code, e
   if (code == ABS)
     mask = double_int_not (mask);
 
-  if (target == 0 || target == op0)
+  if (target == 0
+      || target == op0
+      || (nwords > 1 && !valid_multiword_target_p (target)))
     target = gen_reg_rtx (mode);
 
   if (nwords > 1)
@@ -2915,7 +2927,7 @@ expand_unop (enum machine_mode mode, opt
       int i;
       rtx insns;
 
-      if (target == 0 || target == op0)
+      if (target == 0 || target == op0 || !valid_multiword_target_p (target))
 	target = gen_reg_rtx (mode);
 
       start_sequence ();
@@ -3386,7 +3398,10 @@ expand_copysign_bit (enum machine_mode m
 
   mask = double_int_setbit (double_int_zero, bitpos);
 
-  if (target == 0 || target == op0 || target == op1)
+  if (target == 0
+      || target == op0
+      || target == op1
+      || (nwords > 1 && !valid_multiword_target_p (target)))
     target = gen_reg_rtx (mode);
 
   if (nwords > 1)
@@ -7034,6 +7049,23 @@ insn_operand_matches (enum insn_code ico
 	      (operand, insn_data[(int) icode].operand[opno].mode)));
 }
 
+/* TARGET is a target of a multiword operation that we are going to
+   implement as a series of word-mode operations.  Return true if
+   TARGET is suitable for this purpose.  */
+
+bool
+valid_multiword_target_p (rtx target)
+{
+  enum machine_mode mode;
+  int i;
+
+  mode = GET_MODE (target);
+  for (i = 0; i < GET_MODE_SIZE (mode); i += UNITS_PER_WORD)
+    if (!validate_subreg (word_mode, mode, target, i))
+      return false;
+  return true;
+}
+
 /* Like maybe_legitimize_operand, but do not change the code of the
    current rtx value.  */
 
Index: gcc/testsuite/gcc.target/mips/pr45074.c
===================================================================
--- /dev/null	2011-06-01 19:41:05.354325326 +0100
+++ gcc/testsuite/gcc.target/mips/pr45074.c	2011-06-01 18:54:09.000000000 +0100
@@ -0,0 +1,8 @@
+/* { dg-options "-mhard-float -mgp32 -O" } */
+register double g __asm__("$f20");
+
+NOMIPS16 void
+test (double a)
+{
+  g = -a;
+}



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