[PATCH] x86: Skip EXT_REX_SSE_REG_P for vzeroupper optimization

[H.J. Lu]

Skip EXT_REX_SSE_REG_P for vzeroupper optimization since upper 16 vector
registers don't trigger SSE <-> AVX transition penalty.

gcc/

	PR target/95791
	* config/i386/i386.c (ix86_dirflag_mode_needed): Skip
	EXT_REX_SSE_REG_P.

gcc/testsuite/

	PR target/95791
	* gcc.target/i386/pr95791.c: New test.
---
 gcc/config/i386/i386.c                  |  4 +++-
 gcc/testsuite/gcc.target/i386/pr95791.c | 10 ++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.target/i386/pr95791.c

diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 3b776c08a22..37aaa49996d 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -13846,7 +13846,9 @@ ix86_dirflag_mode_needed (rtx_insn *insn)
 static bool
 ix86_check_avx_upper_register (const_rtx exp)
 {
-  return SSE_REG_P (exp) && GET_MODE_BITSIZE (GET_MODE (exp)) > 128;
+  return (SSE_REG_P (exp)
+	  && !EXT_REX_SSE_REG_P (exp)
+	  && GET_MODE_BITSIZE (GET_MODE (exp)) > 128);
 }
 
 /* Return needed mode for entity in optimize_mode_switching pass.  */
diff --git a/gcc/testsuite/gcc.target/i386/pr95791.c b/gcc/testsuite/gcc.target/i386/pr95791.c
new file mode 100644
index 00000000000..26a96d47354
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr95791.c
@@ -0,0 +1,10 @@
+/* { dg-do compile { target { ! ia32 } } } */
+/* { dg-options "-O2 -mavx512f -mvzeroupper" } */
+
+void
+f(void)
+{
+  __asm__ __volatile__("" ::: "zmm16");
+}
+
+/* { dg-final { scan-assembler-not "vzeroupper" } } */
-- 
2.26.2