[PATCH 3/3] LoongArch: Redundant sign extension elimination optimization 2.

[Lulu Cheng]

From: liwei <li...@loongson.cn>

Eliminate the redundant sign extension that exists after the conditional
move when the target register is SImode.

gcc/ChangeLog:

        * config/loongarch/loongarch.cc (loongarch_expand_conditional_move):
        Adjust.

gcc/testsuite/ChangeLog:

        * gcc.target/loongarch/sign-extend-2.c: Adjust.
---
 gcc/config/loongarch/loongarch.cc                  | 2 ++
 gcc/testsuite/gcc.target/loongarch/sign-extend-2.c | 2 +-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/gcc/config/loongarch/loongarch.cc 
b/gcc/config/loongarch/loongarch.cc
index ec376a7228a..4b757b30b64 100644
--- a/gcc/config/loongarch/loongarch.cc
+++ b/gcc/config/loongarch/loongarch.cc
@@ -5371,6 +5371,8 @@ loongarch_expand_conditional_move (rtx *operands)
          rtx temp3 = gen_reg_rtx (mode);
          emit_insn (gen_rtx_SET (temp3, gen_rtx_IOR (mode, temp, temp2)));
          temp3 = gen_lowpart (GET_MODE (operands[0]), temp3);
+         SUBREG_PROMOTED_VAR_P (temp3) = 1;
+         SUBREG_PROMOTED_SET (temp3, SRP_SIGNED);
          loongarch_emit_move (operands[0], temp3);
        }
       else
diff --git a/gcc/testsuite/gcc.target/loongarch/sign-extend-2.c 
b/gcc/testsuite/gcc.target/loongarch/sign-extend-2.c
index a45dde4f73f..428535cb8e3 100644
--- a/gcc/testsuite/gcc.target/loongarch/sign-extend-2.c
+++ b/gcc/testsuite/gcc.target/loongarch/sign-extend-2.c
@@ -1,6 +1,6 @@
 /* { dg-do compile } */
 /* { dg-options "-mabi=lp64d -O2" } */
-/* { dg-final { scan-assembler-times "slli.w\t\\\$r\[0-9\]+,\\\$r\[0-9\]+,0" 1 
} } */
+/* { dg-final { scan-assembler-times "slli.w\t\\\$r\[0-9\]+,\\\$r\[0-9\]+,0" 0 
} } */
 
 #include <stdint.h>
 #define my_min(x, y) ((x) < (y) ? (x) : (y))
-- 
2.39.3