[RFC PATCH, i386]: Implement ix86_set_reg_reg_cost, fix PR 53250 "Splitting reg" failure.

[RFC PATCH, i386]: Implement ix86_set_reg_reg_cost, fix PR 53250 "Splitting reg" failure.

[Uros Bizjak]

Hello!

Attached patch implements reg->reg move cost function for x86, as
required by new lower-subreg.c patch. The patch fixes:

FAIL: gcc.dg/lower-subreg-1.c scan-rtl-dump subreg1 "Splitting reg"

failure on 32bit x86 targets, and for following testcase:

long long test (long long a, long long b)
{
  return a * b;
}

reverts generated asm code from:

test:
        subl    $12, %esp
        movl    %edi, 8(%esp)
        movl    28(%esp), %edi
        movl    %ebx, (%esp)
        movl    16(%esp), %ecx
        movl    %esi, 4(%esp)
        movl    20(%esp), %ebx
        movl    24(%esp), %esi
        movl    %edi, %eax
        imull   %ecx, %eax
        imull   %esi, %ebx
        addl    %eax, %ebx
        movl    %ecx, %eax
        mull    %esi
        movl    4(%esp), %esi
        movl    %edx, %edi
        addl    %ebx, %edi
        movl    (%esp), %ebx
        movl    %edi, %edx
        movl    8(%esp), %edi
        addl    $12, %esp
        ret

back to:

test:
        pushl   %ebx
        movl    8(%esp), %edx
        movl    16(%esp), %eax
        movl    12(%esp), %ebx
        movl    20(%esp), %ecx
        imull   %eax, %ebx
        imull   %edx, %ecx
        mull    %edx
        addl    %ebx, %ecx
        addl    %ecx, %edx
        popl    %ebx
        ret

Patch was tested on x86_64-pc-linux-gnu {,-m32}.

I have also #define LOG_COST 1 temporarily and looked at generated
cost calculations for various -msse* settings.

I will wait for a day for possible comments on the implementation
before the patch will be committed to mainline SVN.

Uros.

Re: [RFC PATCH, i386]: Implement ix86_set_reg_reg_cost, fix PR 53250 "Splitting reg" failure.

[Uros Bizjak]

[-- Attachment #1: Type: text/plain, Size: 564 bytes --]

On Mon, May 7, 2012 at 10:35 PM, Uros Bizjak <ubizjak@gmail.com> wrote:

Now with a patch and ChangeLog:

2012-05-07  Uros Bizjak  <ubizjak@gmail.com>

	PR target/53250
	* config/i386/i386.c (ix86_set_reg_reg_cost): New function.
	(ix86_rtx_costs): Handle SET.

> Patch was tested on x86_64-pc-linux-gnu {,-m32}.
>
> I have also #define LOG_COST 1 temporarily and looked at generated
> cost calculations for various -msse* settings.
>
> I will wait for a day for possible comments on the implementation
> before the patch will be committed to mainline SVN.

Uros.

[-- Attachment #2: p.diff.txt --]
[-- Type: text/plain, Size: 2246 bytes --]

Index: config/i386/i386.c
===================================================================
--- config/i386/i386.c	(revision 187259)
+++ config/i386/i386.c	(working copy)
@@ -31861,6 +31861,52 @@ ix86_modes_tieable_p (enum machine_mode mode1, enu
   return false;
 }
 
+/* Return the cost of moving between two registers of mode MODE.  */
+
+static int
+ix86_set_reg_reg_cost (enum machine_mode mode)
+{
+  unsigned int units = UNITS_PER_WORD;
+
+  switch (GET_MODE_CLASS (mode))
+    {
+    default:
+      break;
+
+    case MODE_CC:
+      units = GET_MODE_SIZE (CCmode);
+      break;
+
+    case MODE_FLOAT:
+      if ((TARGET_SSE2 && mode == TFmode)
+	  || (TARGET_80387 && mode == XFmode)
+	  || ((TARGET_80387 || TARGET_SSE2) && mode == DFmode)
+	  || ((TARGET_80387 || TARGET_SSE) && mode == SFmode))
+	units = GET_MODE_SIZE (mode);
+      break;
+
+    case MODE_COMPLEX_FLOAT:
+      if ((TARGET_SSE2 && mode == TCmode)
+	  || (TARGET_80387 && mode == XCmode)
+	  || ((TARGET_80387 || TARGET_SSE2) && mode == DCmode)
+	  || ((TARGET_80387 || TARGET_SSE) && mode == SCmode))
+	units = GET_MODE_SIZE (mode);
+      break;
+
+    case MODE_VECTOR_INT:
+    case MODE_VECTOR_FLOAT:
+      if ((TARGET_AVX && VALID_AVX256_REG_MODE (mode))
+	  || (TARGET_SSE2 && VALID_SSE2_REG_MODE (mode))
+	  || (TARGET_SSE && VALID_SSE_REG_MODE (mode))
+	  || (TARGET_MMX && VALID_MMX_REG_MODE (mode)))
+	units = GET_MODE_SIZE (mode);
+    }
+
+  /* Return the cost of moving between two registers of mode MODE,
+     assuming that the move will be in pieces of at most UNITS bytes.  */
+  return COSTS_N_INSNS ((GET_MODE_SIZE (mode) + units - 1) / units);
+}
+
 /* Compute a (partial) cost for rtx X.  Return true if the complete
    cost has been computed, and false if subexpressions should be
    scanned.  In either case, *TOTAL contains the cost result.  */
@@ -31875,6 +31921,15 @@ ix86_rtx_costs (rtx x, int code, int outer_code_i,
 
   switch (code)
     {
+    case SET:
+      if (register_operand (SET_DEST (x), VOIDmode)
+	  && reg_or_0_operand (SET_SRC (x), VOIDmode))
+	{
+	  *total = ix86_set_reg_reg_cost (GET_MODE (SET_DEST (x)));
+	  return true;
+	}
+      return false;
+
     case CONST_INT:
     case CONST:
     case LABEL_REF:

Re: [RFC PATCH, i386]: Implement ix86_set_reg_reg_cost, fix PR 53250 "Splitting reg" failure.

[Uros Bizjak]

On Mon, May 7, 2012 at 10:40 PM, Uros Bizjak <ubizjak@gmail.com> wrote:

> 2012-05-07  Uros Bizjak  <ubizjak@gmail.com>
>
>        PR target/53250
>        * config/i386/i386.c (ix86_set_reg_reg_cost): New function.
>        (ix86_rtx_costs): Handle SET.
>
>> Patch was tested on x86_64-pc-linux-gnu {,-m32}.
>>
>> I have also #define LOG_COST 1 temporarily and looked at generated
>> cost calculations for various -msse* settings.
>>
>> I will wait for a day for possible comments on the implementation
>> before the patch will be committed to mainline SVN.

Committed to mainline SVN at r187289.

Uros.