[PATCH] i386: Disable ix86_expand_vecop_qihi2 when !TARGET_AVX512BW

[Haochen Jiang]

Hi all,

Since vpermq is really slow, we should avoid using it when it is
the only instruction could be used for ix86_expand_vecop_qihi2.

Bootstrapped and regtested on x86_64-pc-linux-gnu. Ok for trunk?

Thx,
Haochen

gcc/ChangeLog:

        PR target/115069
        * config/i386/i386-expand.cc (ix86_expand_vecop_qihi2):
        Do not enable the optimization when AVX512BW is not enabled.
---
 gcc/config/i386/i386-expand.cc | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/gcc/config/i386/i386-expand.cc b/gcc/config/i386/i386-expand.cc
index a6132911e6a..f24c800bb4f 100644
--- a/gcc/config/i386/i386-expand.cc
+++ b/gcc/config/i386/i386-expand.cc
@@ -24323,6 +24323,11 @@ ix86_expand_vecop_qihi2 (enum rtx_code code, rtx dest, 
rtx op1, rtx op2)
   bool op2vec = GET_MODE_CLASS (GET_MODE (op2)) == MODE_VECTOR_INT;
   bool uns_p = code != ASHIFTRT;
 
+  /* vpermq is slow and we should not fall into the optimization when
+     it is the only instruction to be selected.  */
+  if (!TARGET_AVX512BW)
+    return false;
+
   if ((qimode == V16QImode && !TARGET_AVX2)
       || (qimode == V32QImode && (!TARGET_AVX512BW || !TARGET_EVEX512))
       /* There are no V64HImode instructions.  */
-- 
2.31.1