[PATCH #2] Introduce smul_highpart and umul_highpart RTX for high-part multiplications

["Roger Sayle" <roger@nextmovesoftware.com>]

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Hi Richard,

All excellent suggestions.  The revised patch below implements all of
your (and Andreas') recommendations.  I'm happy to restrict GCC's support
for saturating arithmetic to integer types, even though I do know of one
target (nvptx) that supports saturating floating point math, where results
are clamped to [0.0, 1.0], but I've not investigated how NaNs or signed
zeros are handled.

Good catch on my min/max typo.  It convinced me to work harder to come
up with some test cases for these simplifications, which I've managed to
trigger on x86_64-pc-linux-gnu in the four new attached test cases.

This patch has been tested on x86_64-pc-linux-gnu with "make bootstrap"
and "make -k check" with no new failures.  Ok for mainline?

2021-09-29  Roger Sayle  <roger@nextmovesoftware.com>
	    Richard Sandiford  <richard.sandiford@arm.com>

gcc/ChangeLog
	* gcc/rtl.def (SMUL_HIGHPART, UMUL_HIGHPART): New RTX codes for
	representing signed and unsigned high-part multiplication resp.
	* gcc/simplify-rtx.c (simplify_binary_operation_1) [SMUL_HIGHPART,
	UMUL_HIGHPART]: Simplify high-part multiplications by zero.
	[SS_PLUS, US_PLUS, SS_MINUS, US_MINUS, SS_MULT, US_MULT,
	SS_DIV, US_DIV]: Similar simplifications for saturating
	arithmetic.
	(simplify_const_binary_operation) [SS_PLUS, US_PLUS, SS_MINUS,
	US_MINUS, SS_MULT, US_MULT, SMUL_HIGHPART, UMUL_HIGHPART]:
	Implement compile-time evaluation for constant operands.

	* gcc/dwarf2out.c (mem_loc_descriptor): Skip SMUL_HIGHPART and
	UMUL_HIGHPART.
	* doc/rtl.texi (smul_highpart, umul_highpart): Document RTX codes.
	* doc/md.texi (smul@var{m}3_highpart, umul@var{m3}_highpart):
	Mention the new smul_highpart and umul_highpart RTX codes.
	* doc/invoke.texi: Silence @xref "compilation" warnings.

gcc/testsuite/ChangeLog
	* gcc.target/i386/sse2-mmx-paddsb-2.c: New test case.
	* gcc.target/i386/sse2-mmx-paddusb-2.c: New test case.
	* gcc.target/i386/sse2-mmx-subsb-2.c: New test case.
	* gcc.target/i386/sse2-mmx-subusb-2.c: New test case.

Roger
--

-----Original Message-----
From: Richard Sandiford <richard.sandiford@arm.com> 
Sent: 27 September 2021 16:44
To: Roger Sayle <roger@nextmovesoftware.com>
Cc: 'GCC Patches' <gcc-patches@gcc.gnu.org>
Subject: Re: [PATCH] Introduce sh_mul and uh_mul RTX codes for high-part multiplications

"Roger Sayle" <roger@nextmovesoftware.com> writes:
> This patch introduces new RTX codes to allow the RTL passes and 
> backends to consistently represent high-part multiplications.
> Currently, the RTL used by different backends for expanding 
> smul<mode>3_highpart and umul<mode>3_highpart varies greatly, with 
> many but not all choosing to express this something like:
>
> (define_insn "smuldi3_highpart"
>   [(set (match_operand:DI 0 "nvptx_register_operand" "=R")
>        (truncate:DI
>         (lshiftrt:TI
>          (mult:TI (sign_extend:TI
>                    (match_operand:DI 1 "nvptx_register_operand" "R"))
>                   (sign_extend:TI
>                    (match_operand:DI 2 "nvptx_register_operand" "R")))
>          (const_int 64))))]
>   ""
>   "%.\\tmul.hi.s64\\t%0, %1, %2;")
>
> One complication with using this "widening multiplication" 
> representation is that it requires an intermediate in a wider mode, 
> making it difficult or impossible to encode a high-part multiplication 
> of the widest supported integer mode.

Yeah.  It's also a problem when representing vector ops.

> A second is that it can interfere with optimization; for example 
> simplify-rtx.c contains the comment:
>
>    case TRUNCATE:
>       /* Don't optimize (lshiftrt (mult ...)) as it would interfere
>          with the umulXi3_highpart patterns.  */
>
> Hopefully these problems are solved (or reduced) by introducing a new 
> canonical form for high-part multiplications in RTL passes.
> This also simplifies insn patterns when one operand is constant.
>
> Whilst implementing some constant folding simplifications and 
> compile-time evaluation of these new RTX codes, I noticed that this 
> functionality could also be added for the existing saturating 
> arithmetic RTX codes.  Then likewise when documenting these new RTX 
> codes, I also took the opportunity to silence the @xref warnings in 
> invoke.texi.
>
> This patch has been tested on x86_64-pc-linux-gnu with "make bootstrap"
> and "make -k check" with no new failures.  Ok for mainline?
>
>
> 2021-09-25  Roger Sayle  <roger@nextmovesoftware.com>
>
> gcc/ChangeLog
> 	* gcc/rtl.def (SH_MULT, UH_MULT): New RTX codes for representing
> 	signed and unsigned high-part multiplication respectively.
> 	* gcc/simplify-rtx.c (simplify_binary_operation_1) [SH_MULT,
> 	UH_MULT]: Simplify high-part multiplications by zero.
> 	[SS_PLUS, US_PLUS, SS_MINUS, US_MINUS, SS_MULT, US_MULT,
> 	SS_DIV, US_DIV]: Similar simplifications for saturating
> 	arithmetic.
> 	(simplify_const_binary_operation) [SS_PLUS, US_PLUS, SS_MINUS,
> 	US_MINUS, SS_MULT, US_MULT, SH_MULT, UH_MULT]: Implement
> 	compile-time evaluation for constant operands.
> 	* gcc/dwarf2out.c (mem_loc_descriptor): Skip SH_MULT and UH_MULT.
> 	* doc/rtl.texi (sh_mult, uhmult): Document new RTX codes.
> 	* doc/md.texi (smul@var{m}3_highpart, umul@var{m3}_highpart):
> 	Mention the new sh_mul and uh_mul RTX codes.
> 	* doc/invoke.texi: Silence @xref "compilation" warnings.

Look like a good idea to me.  Only real comment is on the naming:
if possible, I think we should try to avoid introducing yet more differences between optab names and rtl codes.  How about umul_highpart for the unsigned code, to match both the optab and the existing convention of adding “u” directly to the front of non-saturating operations?

Things are more inconsistent for signed rtx codes: sometimes the “s” is present and sometimes it isn't.  But since “smin” and “smax”
have it, I think we can justify having it here too.

So I think we should use smul_highpart and umul_highpart.
It's a bit more wordy than sh_mul, but still a lot shorter than the status quo ;-)

> diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c index 
> ebad5cb..b4b04b9 100644
> --- a/gcc/simplify-rtx.c
> +++ b/gcc/simplify-rtx.c
> @@ -4142,11 +4142,40 @@ simplify_context::simplify_binary_operation_1 (rtx_code code,
>      case US_PLUS:
>      case SS_MINUS:
>      case US_MINUS:
> +      /* Simplify x + 0 to x, if possible.  */

Nit: +/-

> +      if (trueop1 == CONST0_RTX (mode) && !HONOR_SIGNED_ZEROS (mode))

The HONOR_SIGNED_ZEROS check is redundant, since these ops don't support modes with signed zero.

Same for the other HONOR_* macros in the patch.  E.g. I don't think we should try to guess how infinities and saturation work together.

> +	return op0;
> +      return 0;
> +
>      case SS_MULT:
>      case US_MULT:
> +      /* Simplify x * 0 to 0, if possible.  */
> +      if (trueop1 == CONST0_RTX (mode)
> +	  && !HONOR_NANS (mode)
> +	  && !HONOR_SIGNED_ZEROS (mode)
> +	  && !side_effects_p (op0))
> +	return op1;
> +
> +      /* Simplify x * 1 to x, if possible.  */
> +      if (trueop1 == CONST1_RTX (mode) && !HONOR_SNANS (mode))
> +	return op0;
> +      return 0;
> +
> +    case SH_MULT:
> +    case UH_MULT:
> +      /* Simplify x * 0 to 0, if possible.  */
> +      if (trueop1 == CONST0_RTX (mode)
> +	  && !HONOR_NANS (mode)
> +	  && !HONOR_SIGNED_ZEROS (mode)
> +	  && !side_effects_p (op0))
> +	return op1;
> +      return 0;
> +
>      case SS_DIV:
>      case US_DIV:
> -      /* ??? There are simplifications that can be done.  */
> +      /* Simplify x / 1 to x, if possible.  */
> +      if (trueop1 == CONST1_RTX (mode) && !HONOR_SNANS (mode))
> +	return op0;
>        return 0;
>  
>      case VEC_SERIES:
> @@ -5011,6 +5040,63 @@ simplify_const_binary_operation (enum rtx_code code, machine_mode mode,
>  	      }
>  	    break;
>  	  }
> +
> +	case SS_PLUS:
> +	  result = wi::add (pop0, pop1, SIGNED, &overflow);

I think a goto label would be good here, so that later signed ops can reuse this code instead of having to repeat it.
Same idea for the unsigned case.

> +          if (overflow == wi::OVF_OVERFLOW)
> +	    result = wi::max_value (GET_MODE_PRECISION (int_mode), SIGNED);
> +	  else if (overflow == wi::OVF_UNDERFLOW)
> +	    result = wi::max_value (GET_MODE_PRECISION (int_mode), SIGNED);

Should be min_value.  Same for the other underflow handlers.

Like Andreas said, @pxref would be better where applicable.

Thanks,
Richard

> +          else if (overflow != wi::OVF_NONE)
> +	    return NULL_RTX;
> +	  break;
> +
> +	case US_PLUS:
> +	  result = wi::add (pop0, pop1, UNSIGNED, &overflow);
> +          if (overflow != wi::OVF_NONE)
> +	    result = wi::max_value (GET_MODE_PRECISION (int_mode), UNSIGNED);
> +	  break;
> +
> +	case SS_MINUS:
> +	  result = wi::sub (pop0, pop1, SIGNED, &overflow);
> +          if (overflow == wi::OVF_OVERFLOW)
> +	    result = wi::max_value (GET_MODE_PRECISION (int_mode), SIGNED);
> +	  else if (overflow == wi::OVF_UNDERFLOW)
> +	    result = wi::max_value (GET_MODE_PRECISION (int_mode), SIGNED);
> +          else if (overflow != wi::OVF_NONE)
> +	    return NULL_RTX;
> +	  break;
> +
> +	case US_MINUS:
> +	  result = wi::sub (pop0, pop1, UNSIGNED, &overflow);
> +          if (overflow != wi::OVF_NONE)
> +	    result = wi::min_value (GET_MODE_PRECISION (int_mode), UNSIGNED);
> +	  break;
> +
> +	case SS_MULT:
> +	  result = wi::mul (pop0, pop1, SIGNED, &overflow);
> +          if (overflow == wi::OVF_OVERFLOW)
> +	    result = wi::max_value (GET_MODE_PRECISION (int_mode), SIGNED);
> +	  else if (overflow == wi::OVF_UNDERFLOW)
> +	    result = wi::max_value (GET_MODE_PRECISION (int_mode), SIGNED);
> +          else if (overflow != wi::OVF_NONE)
> +	    return NULL_RTX;
> +	  break;
> +
> +	case US_MULT:
> +	  result = wi::mul (pop0, pop1, UNSIGNED, &overflow);
> +          if (overflow != wi::OVF_NONE)
> +	    result = wi::max_value (GET_MODE_PRECISION (int_mode), UNSIGNED);
> +	  break;
> +
> +	case SH_MULT:
> +	  result = wi::mul_high (pop0, pop1, SIGNED);
> +	  break;
> +
> +	case UH_MULT:
> +	  result = wi::mul_high (pop0, pop1, UNSIGNED);
> +	  break;
> +
>  	default:
>  	  return NULL_RTX;
>  	}

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diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 4acb941..7ed0c69 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -3125,7 +3125,7 @@ errors if these functions are not inlined everywhere they are called.
 @itemx -fno-modules-ts
 @opindex fmodules-ts
 @opindex fno-modules-ts
-Enable support for C++20 modules (@xref{C++ Modules}).  The
+Enable support for C++20 modules (@pxref{C++ Modules}).  The
 @option{-fno-modules-ts} is usually not needed, as that is the
 default.  Even though this is a C++20 feature, it is not currently
 implicitly enabled by selecting that standard version.
@@ -33553,7 +33553,7 @@ version selected, although in pre-C++20 versions, it is of course an
 extension.
 
 No new source file suffixes are required or supported.  If you wish to
-use a non-standard suffix (@xref{Overall Options}), you also need
+use a non-standard suffix (@pxref{Overall Options}), you also need
 to provide a @option{-x c++} option too.@footnote{Some users like to
 distinguish module interface files with a new suffix, such as naming
 the source @code{module.cppm}, which involves
@@ -33615,8 +33615,8 @@ to be resolved at the end of compilation.  Without this, imported
 macros are only resolved when expanded or (re)defined.  This option
 detects conflicting import definitions for all macros.
 
-@xref{C++ Module Mapper} for details of the @option{-fmodule-mapper}
-family of options.
+For details of the @option{-fmodule-mapper} family of options,
+@pxref{C++ Module Mapper}.
 
 @menu
 * C++ Module Mapper::       Module Mapper
@@ -33833,8 +33833,8 @@ dialect used and imports of the module.@footnote{The precise contents
 of this output may change.} The timestamp is the same value as that
 provided by the @code{__DATE__} & @code{__TIME__} macros, and may be
 explicitly specified with the environment variable
-@code{SOURCE_DATE_EPOCH}.  @xref{Environment Variables} for further
-details.
+@code{SOURCE_DATE_EPOCH}.  For further details
+@pxref{Environment Variables}.
 
 A set of related CMIs may be copied, provided the relative pathnames
 are preserved.
diff --git a/gcc/doc/md.texi b/gcc/doc/md.texi
index 2b41cb7..ed35b8f 100644
--- a/gcc/doc/md.texi
+++ b/gcc/doc/md.texi
@@ -5776,11 +5776,13 @@ multiplication.
 @item @samp{smul@var{m}3_highpart}
 Perform a signed multiplication of operands 1 and 2, which have mode
 @var{m}, and store the most significant half of the product in operand 0.
-The least significant half of the product is discarded.
+The least significant half of the product is discarded.  This may be
+represented in RTL using a @code{smul_highpart} RTX expression.
 
 @cindex @code{umul@var{m}3_highpart} instruction pattern
 @item @samp{umul@var{m}3_highpart}
-Similar, but the multiplication is unsigned.
+Similar, but the multiplication is unsigned.  This may be represented
+in RTL using an @code{umul_highpart} RTX expression.
 
 @cindex @code{madd@var{m}@var{n}4} instruction pattern
 @item @samp{madd@var{m}@var{n}4}
diff --git a/gcc/doc/rtl.texi b/gcc/doc/rtl.texi
index e1e76a9..2058997 100644
--- a/gcc/doc/rtl.texi
+++ b/gcc/doc/rtl.texi
@@ -2524,7 +2524,19 @@ not be the same.
 For unsigned widening multiplication, use the same idiom, but with
 @code{zero_extend} instead of @code{sign_extend}.
 
+@findex smul_highpart
+@findex umul_highpart
+@cindex high-part multiplication
+@cindex multiplication high part
+@item (smul_highpart:@var{m} @var{x} @var{y})
+@itemx (umul_highpart:@var{m} @var{x} @var{y})
+Represents the high-part multiplication of @var{x} and @var{y} carried
+out in machine mode @var{m}.  @code{smul_highpart} returns the high part
+of a signed multiplication, @code{umul_highpart} returns the high part
+of an unsigned multiplication.
+
 @findex fma
+@cindex fused multiply-add
 @item (fma:@var{m} @var{x} @var{y} @var{z})
 Represents the @code{fma}, @code{fmaf}, and @code{fmal} builtin
 functions, which compute @samp{@var{x} * @var{y} + @var{z}}
diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c
index 9876750..20f2c5d 100644
--- a/gcc/dwarf2out.c
+++ b/gcc/dwarf2out.c
@@ -16809,6 +16809,8 @@ mem_loc_descriptor (rtx rtl, machine_mode mode,
     case CONST_FIXED:
     case CLRSB:
     case CLOBBER:
+    case SMUL_HIGHPART:
+    case UMUL_HIGHPART:
       break;
 
     case CONST_STRING:
diff --git a/gcc/rtl.def b/gcc/rtl.def
index c80144b..5710a2e 100644
--- a/gcc/rtl.def
+++ b/gcc/rtl.def
@@ -467,6 +467,11 @@ DEF_RTL_EXPR(SS_MULT, "ss_mult", "ee", RTX_COMM_ARITH)
 /* Multiplication with unsigned saturation */
 DEF_RTL_EXPR(US_MULT, "us_mult", "ee", RTX_COMM_ARITH)
 
+/* Signed high-part multiplication.  */
+DEF_RTL_EXPR(SMUL_HIGHPART, "smul_highpart", "ee", RTX_COMM_ARITH)
+/* Unsigned high-part multiplication.  */
+DEF_RTL_EXPR(UMUL_HIGHPART, "umul_highpart", "ee", RTX_COMM_ARITH)
+
 /* Operand 0 divided by operand 1.  */
 DEF_RTL_EXPR(DIV, "div", "ee", RTX_BIN_ARITH)
 /* Division with signed saturation */
diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c
index ebad5cb..7e8e2c3 100644
--- a/gcc/simplify-rtx.c
+++ b/gcc/simplify-rtx.c
@@ -4142,11 +4142,36 @@ simplify_context::simplify_binary_operation_1 (rtx_code code,
     case US_PLUS:
     case SS_MINUS:
     case US_MINUS:
+      /* Simplify x +/- 0 to x, if possible.  */
+      if (trueop1 == CONST0_RTX (mode))
+	return op0;
+      return 0;
+
     case SS_MULT:
     case US_MULT:
+      /* Simplify x * 0 to 0, if possible.  */
+      if (trueop1 == CONST0_RTX (mode)
+	  && !side_effects_p (op0))
+	return op1;
+
+      /* Simplify x * 1 to x, if possible.  */
+      if (trueop1 == CONST1_RTX (mode))
+	return op0;
+      return 0;
+
+    case SMUL_HIGHPART:
+    case UMUL_HIGHPART:
+      /* Simplify x * 0 to 0, if possible.  */
+      if (trueop1 == CONST0_RTX (mode)
+	  && !side_effects_p (op0))
+	return op1;
+      return 0;
+
     case SS_DIV:
     case US_DIV:
-      /* ??? There are simplifications that can be done.  */
+      /* Simplify x / 1 to x, if possible.  */
+      if (trueop1 == CONST1_RTX (mode))
+	return op0;
       return 0;
 
     case VEC_SERIES:
@@ -5011,6 +5036,51 @@ simplify_const_binary_operation (enum rtx_code code, machine_mode mode,
 	      }
 	    break;
 	  }
+
+	case SS_PLUS:
+	  result = wi::add (pop0, pop1, SIGNED, &overflow);
+ clamp_signed_saturation:
+	  if (overflow == wi::OVF_OVERFLOW)
+	    result = wi::max_value (GET_MODE_PRECISION (int_mode), SIGNED);
+	  else if (overflow == wi::OVF_UNDERFLOW)
+	    result = wi::min_value (GET_MODE_PRECISION (int_mode), SIGNED);
+	  else if (overflow != wi::OVF_NONE)
+	    return NULL_RTX;
+	  break;
+
+	case US_PLUS:
+	  result = wi::add (pop0, pop1, UNSIGNED, &overflow);
+ clamp_unsigned_saturation: 
+	  if (overflow != wi::OVF_NONE)
+	    result = wi::max_value (GET_MODE_PRECISION (int_mode), UNSIGNED);
+	  break;
+
+	case SS_MINUS:
+	  result = wi::sub (pop0, pop1, SIGNED, &overflow);
+	  goto clamp_signed_saturation;
+
+	case US_MINUS:
+	  result = wi::sub (pop0, pop1, UNSIGNED, &overflow);
+	  if (overflow != wi::OVF_NONE)
+	    result = wi::min_value (GET_MODE_PRECISION (int_mode), UNSIGNED);
+	  break;
+
+	case SS_MULT:
+	  result = wi::mul (pop0, pop1, SIGNED, &overflow);
+	  goto clamp_signed_saturation;
+
+	case US_MULT:
+	  result = wi::mul (pop0, pop1, UNSIGNED, &overflow);
+	  goto clamp_unsigned_saturation;
+
+	case SMUL_HIGHPART:
+	  result = wi::mul_high (pop0, pop1, SIGNED);
+	  break;
+
+	case UMUL_HIGHPART:
+	  result = wi::mul_high (pop0, pop1, UNSIGNED);
+	  break;
+
 	default:
 	  return NULL_RTX;
 	}

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/* { dg-do compile } */
/* { dg-options "-O2" } */

typedef char v8qi __attribute__ ((vector_size (8)));

char foo()
{
  v8qi tx = { 1, 0, 0, 0, 0, 0, 0, 0 };
  v8qi ty = { 2, 0, 0, 0, 0, 0, 0, 0 };
  v8qi t = __builtin_ia32_paddsb(tx, ty);
  return t[0];
}

char bar()
{
  v8qi tx = { 100, 0, 0, 0, 0, 0, 0, 0 };
  v8qi ty = { 100, 0, 0, 0, 0, 0, 0, 0 };
  v8qi t = __builtin_ia32_paddsb(tx, ty);
  return t[0];
}

char baz()
{
  v8qi tx = { -100, 0, 0, 0, 0, 0, 0, 0 };
  v8qi ty = { -100, 0, 0, 0, 0, 0, 0, 0 };
  v8qi t = __builtin_ia32_paddsb(tx, ty);
  return t[0];
}

/* { dg-final { scan-assembler-times "movl\[ \\t\]+\\\$3," 1 } } */
/* { dg-final { scan-assembler-times "movl\[ \\t\]+\\\$127," 1 } } */
/* { dg-final { scan-assembler-times "movl\[ \\t\]+\\\$-128," 1 } } */
/* { dg-final { scan-assembler-not "paddsb\[ \\t\]+%xmm\[0-9\]+" } } */

[-- Attachment #4: sse2-mmx-paddusb-2.c --]
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/* { dg-do compile } */
/* { dg-options "-O2" } */

typedef char v8qi __attribute__ ((vector_size (8)));

char foo()
{
  v8qi tx = { 1, 0, 0, 0, 0, 0, 0, 0 };
  v8qi ty = { 2, 0, 0, 0, 0, 0, 0, 0 };
  v8qi t = __builtin_ia32_paddusb(tx, ty);
  return t[0];
}

char bar()
{
  v8qi tx = { 200, 0, 0, 0, 0, 0, 0, 0 };
  v8qi ty = { 200, 0, 0, 0, 0, 0, 0, 0 };
  v8qi t = __builtin_ia32_paddusb(tx, ty);
  return t[0];
}

/* { dg-final { scan-assembler-times "movl\[ \\t\]+\\\$3," 1 } } */
/* { dg-final { scan-assembler-times "movl\[ \\t\]+\\\$-1," 1 } } */
/* { dg-final { scan-assembler-not "paddusb\[ \\t\]+%xmm\[0-9\]+" } } */


[-- Attachment #5: sse2-mmx-psubsb-2.c --]
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/* { dg-do compile } */
/* { dg-options "-O2" } */

typedef char v8qi __attribute__ ((vector_size (8)));

char foo()
{
  v8qi tx = { 5, 0, 0, 0, 0, 0, 0, 0 };
  v8qi ty = { 2, 0, 0, 0, 0, 0, 0, 0 };
  v8qi t = __builtin_ia32_psubsb(tx, ty);
  return t[0];
}

char bar()
{
  v8qi tx = { -100, 0, 0, 0, 0, 0, 0, 0 };
  v8qi ty = { 100, 0, 0, 0, 0, 0, 0, 0 };
  v8qi t = __builtin_ia32_psubsb(tx, ty);
  return t[0];
}

char baz()
{
  v8qi tx = { 100, 0, 0, 0, 0, 0, 0, 0 };
  v8qi ty = { -100, 0, 0, 0, 0, 0, 0, 0 };
  v8qi t = __builtin_ia32_psubsb(tx, ty);
  return t[0];
}

/* { dg-final { scan-assembler-times "movl\[ \\t\]+\\\$3," 1 } } */
/* { dg-final { scan-assembler-times "movl\[ \\t\]+\\\$-128," 1 } } */
/* { dg-final { scan-assembler-times "movl\[ \\t\]+\\\$127," 1 } } */
/* { dg-final { scan-assembler-not "paddsb\[ \\t\]+%xmm\[0-9\]+" } } */

[-- Attachment #6: sse2-mmx-psubusb-2.c --]
[-- Type: text/plain, Size: 647 bytes --]

/* { dg-do compile } */
/* { dg-options "-O2" } */

typedef char v8qi __attribute__ ((vector_size (8)));

char foo()
{
  v8qi tx = { 5, 0, 0, 0, 0, 0, 0, 0 };
  v8qi ty = { 2, 0, 0, 0, 0, 0, 0, 0 };
  v8qi t = __builtin_ia32_psubusb(tx, ty);
  return t[0];
}

char bar()
{
  v8qi tx = { 100, 0, 0, 0, 0, 0, 0, 0 };
  v8qi ty = { 200, 0, 0, 0, 0, 0, 0, 0 };
  v8qi t = __builtin_ia32_psubusb(tx, ty);
  return t[0];
}

/* { dg-final { scan-assembler-times "movl\[ \\t\]+\\\$3," 1 } } */
/* { dg-final { scan-assembler-times "xorl\[ \\t\]+" 1 } } */
/* { dg-final { scan-assembler-not "psubusb\[ \\t\]+%xmm\[0-9\]+" } } */