[Bug target/121227] dot_prodv16siv64qi uses unsupported insn

[rguenth at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121227

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|                            |x86_64-*-*
           Keywords|                            |ice-on-valid-code

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
In particular the target prefers V32QImode without AVX512BW but
ix86_vector_mode_supported_p happily accepts V64QImode.  The following
reproduces the issue, but the order of queries can trigger this without
a patch.

diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc
index 4682db85ce4..940ab0b32d8 100644
--- a/gcc/config/i386/i386.cc
+++ b/gcc/config/i386/i386.cc
@@ -25495,7 +25495,7 @@ ix86_preferred_simd_mode (scalar_mode mode)
   switch (mode)
     {
     case E_QImode:
-      if (TARGET_AVX512BW && !TARGET_PREFER_AVX256)
+      if (/*TARGET_AVX512BW &&*/ !TARGET_PREFER_AVX256)
        return V64QImode;
       else if (TARGET_AVX && !TARGET_PREFER_AVX128)
        return V32QImode;