[PATCH] i386: Use existing temporary register in rounding functions

[Uros Bizjak via Gcc-patches]

It is possible to avoid the call to force_reg and use existing
temporary register in ix86_expand_trunc, ix86_expand_round and
ix86_expand_rounddf_32 expanders.

2020-12-28  Uroš Bizjak  <ubiz...@gmail.com>

gcc/
    * config/i386/i386-expand.c (ix86_expand_trunc): Use
    existing temporary register to avoid a call to force_reg.

Bootstrapped and regression tested on x86_64-linux-gnu {,-m32}.

Pushed to mainline.

Uros.

diff --git a/gcc/config/i386/i386-expand.c b/gcc/config/i386/i386-expand.c
index c856489c046..5fe38052056 100644
--- a/gcc/config/i386/i386-expand.c
+++ b/gcc/config/i386/i386-expand.c
@@ -16513,13 +16513,15 @@ ix86_expand_trunc (rtx operand0, rtx operand1)
   /* if (!isless (xa, TWO52)) goto label; */
   label = ix86_expand_sse_compare_and_jump (UNLE, TWO52, xa, false);
 
-  /* x = (double)(long)x */
+  /* xa = (double)(long)x */
   xi = gen_reg_rtx (mode == DFmode ? DImode : SImode);
   expand_fix (xi, res, 0);
-  expand_float (res, xi, 0);
+  expand_float (xa, xi, 0);
 
   if (HONOR_SIGNED_ZEROS (mode))
-    ix86_sse_copysign_to_positive (res, res, force_reg (mode, operand1), mask);
+    ix86_sse_copysign_to_positive (xa, xa, res, mask);
+
+  emit_move_insn (res, xa);
 
   emit_label (label);
   LABEL_NUSES (label) = 1;
@@ -16629,7 +16631,7 @@ ix86_expand_round (rtx operand0, rtx operand1)
   expand_float (xa, xi, 0);
 
   /* res = copysign (xa, operand1) */
-  ix86_sse_copysign_to_positive (res, xa, force_reg (mode, operand1), mask);
+  ix86_sse_copysign_to_positive (res, xa, res, mask);
 
   emit_label (label);
   LABEL_NUSES (label) = 1;
@@ -16700,7 +16702,7 @@ ix86_expand_rounddf_32 (rtx operand0, rtx operand1)
   xa2 = expand_simple_binop (mode, PLUS, xa2, tmp, NULL_RTX, 0, OPTAB_DIRECT);
 
   /* res = copysign (xa2, operand1) */
-  ix86_sse_copysign_to_positive (res, xa2, force_reg (mode, operand1), mask);
+  ix86_sse_copysign_to_positive (res, xa2, res, mask);
 
   emit_label (label);
   LABEL_NUSES (label) = 1;