[PATCH] [ARM] Replacing variable swaps that use a temporary variable with a call to std::swap in gcc/config/arm/arm.c

[Bilyan Borisov]

Replacing variable swaps that use a temporary variable with a call to 
std::swap. Tested against arm-none-eabi target including a variant with neon 
enabled.

2015-XX-XX  Bilyan Borisov  

* config/arm/arm.c (thumb_output_move_mem_multiple): Replaced
operands[4] operands[5] swap with std::swap, removed tmp variable.
(arm_evpc_neon_vzip): Replaced in0/in1 and
out0/out1 swaps with std::swap, removed x variable.
(arm_evpc_neon_vtrn): Replaced in0/int1 and
out0/out1 swaos with std::swap, removed x variable.
(arm_expand_vec_perm_const_1): Replaced
d->op0/d->op1 swap with std::swap, removed x variable.
(arm_evpc_neon_vuzp): Replaced in0/in1 and
out0/out1 swaps with std::swap, removed x variable.

diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index fa4e083adfe215b5820237f3cc6b449dbdefc778..dc549fe470e5a82d740cf8014057ee2cc1d54085 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -25362,17 +25362,12 @@ thumb_load_double_from_address (rtx *operands)
 const char *
 thumb_output_move_mem_multiple (int n, rtx *operands)
 {
-  rtx tmp;
-
   switch (n)
 {
 case 2:
   if (REGNO (operands[4]) > REGNO (operands[5]))
-	{
-	  tmp = operands[4];
-	  operands[4] = operands[5];
-	  operands[5] = tmp;
-	}
+	std::swap (operands[4], operands[5]);
+
   output_asm_insn ("ldmia\t%1!, {%4, %5}", operands);
   output_asm_insn ("stmia\t%0!, {%4, %5}", operands);
   break;
@@ -27885,7 +27880,7 @@ static bool
 arm_evpc_neon_vuzp (struct expand_vec_perm_d *d)
 {
   unsigned int i, odd, mask, nelt = d->nelt;
-  rtx out0, out1, in0, in1, x;
+  rtx out0, out1, in0, in1;
   rtx (*gen)(rtx, rtx, rtx, rtx);
 
   if (GET_MODE_UNIT_SIZE (d->vmode) >= 8)
@@ -27929,14 +27924,14 @@ arm_evpc_neon_vuzp (struct expand_vec_perm_d *d)
   in1 = d->op1;
   if (BYTES_BIG_ENDIAN)
 {
-  x = in0, in0 = in1, in1 = x;
+  std::swap (in0, in1);
   odd = !odd;
 }
 
   out0 = d->target;
   out1 = gen_reg_rtx (d->vmode);
   if (odd)
-x = out0, out0 = out1, out1 = x;
+std::swap (out0, out1);
 
   emit_insn (gen (out0, in0, in1, out1));
   return true;
@@ -27948,7 +27943,7 @@ static bool
 arm_evpc_neon_vzip (struct expand_vec_perm_d *d)
 {
   unsigned int i, high, mask, nelt = d->nelt;
-  rtx out0, out1, in0, in1, x;
+  rtx out0, out1, in0, in1;
   rtx (*gen)(rtx, rtx, rtx, rtx);
 
   if (GET_MODE_UNIT_SIZE (d->vmode) >= 8)
@@ -27996,14 +27991,14 @@ arm_evpc_neon_vzip (struct expand_vec_perm_d *d)
   in1 = d->op1;
   if (BYTES_BIG_ENDIAN)
 {
-  x = in0, in0 = in1, in1 = x;
+  std::swap (in0, in1);
   high = !high;
 }
 
   out0 = d->target;
   out1 = gen_reg_rtx (d->vmode);
   if (high)
-x = out0, out0 = out1, out1 = x;
+std::swap (out0, out1);
 
   emit_insn (gen (out0, in0, in1, out1));
   return true;
@@ -28089,7 +28084,7 @@ static bool
 arm_evpc_neon_vtrn (struct expand_vec_perm_d *d)
 {
   unsigned int i, odd, mask, nelt = d->nelt;
-  rtx out0, out1, in0, in1, x;
+  rtx out0, out1, in0, in1;
   rtx (*gen)(rtx, rtx, rtx, rtx);
 
   if (GET_MODE_UNIT_SIZE (d->vmode) >= 8)
@@ -28134,14 +28129,14 @@ arm_evpc_neon_vtrn (struct expand_vec_perm_d *d)
   in1 = d->op1;
   if (BYTES_BIG_ENDIAN)
 {
-  x = in0, in0 = in1, in1 = x;
+  std::swap (in0, in1);
   odd = !odd;
 }
 
   out0 = d->target;
   out1 = gen_reg_rtx (d->vmode);
   if (odd)
-x = out0, out0 = out1, out1 = x;
+std::swap (out0, out1);
 
   emit_insn (gen (out0, in0, in1, out1));
   return true;
@@ -28264,14 +28259,11 @@ arm_expand_vec_perm_const_1 (struct expand_vec_perm_d *d)
   if (d->perm[0] >= d->nelt)
 {
   unsigned i, nelt = d->nelt;
-  rtx x;
 
   for (i = 0; i < nelt; ++i)
 	d->perm[i] = (d->perm[i] + nelt) & (2 * nelt - 1);
 
-  x = d->op0;
-  d->op0 = d->op1;
-  d->op1 = x;
+  std::swap (d->op0, d->op1);
 }
 
   if (TARGET_NEON)

Re: [PATCH] [ARM] Replacing variable swaps that use a temporary variable with a call to std::swap in gcc/config/arm/arm.c

[Kyrill Tkachov]

Hi Bilyan,

On 21/09/15 08:41, Bilyan Borisov wrote:

Replacing variable swaps that use a temporary variable with a call to 
std::swap. Tested against arm-none-eabi target including a variant with neon 
enabled.

2015-XX-XX  Bilyan Borisov  

* config/arm/arm.c (thumb_output_move_mem_multiple): Replaced
operands[4] operands[5] swap with std::swap, removed tmp variable.
(arm_evpc_neon_vzip): Replaced in0/in1 and
out0/out1 swaps with std::swap, removed x variable.
(arm_evpc_neon_vtrn): Replaced in0/int1 and
out0/out1 swaos with std::swap, removed x variable.
(arm_expand_vec_perm_const_1): Replaced
d->op0/d->op1 swap with std::swap, removed x variable.
(arm_evpc_neon_vuzp): Replaced in0/in1 and
out0/out1 swaps with std::swap, removed x variable.



This is ok for trunk.
I've committed this for you with r227963.

Thanks,
Kyrill