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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/98211] [11 Regression] Wrong code at -O3
 since r11-4482-gb626b00823af9ca9
Date: Thu, 10 Dec 2020 10:01:16 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D98211

--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
Hmm, OK, so besides the incomplete bool pattern matching the issue seems to=
 be
that while we reject the problematic conversion in vectorizable_conversion =
it
slips through via vectorizable_assignment because it does

      /* Conversion between boolean types of different sizes is
         a simple assignment in case their vectypes are same
         boolean vectors.  */
      && (!VECTOR_BOOLEAN_TYPE_P (vectype)
          || !VECTOR_BOOLEAN_TYPE_P (vectype_in)))

as opposed to vectorizable_conversions

  if (VECTOR_BOOLEAN_TYPE_P (vectype_out)
      && !VECTOR_BOOLEAN_TYPE_P (vectype_in))

that was added by g:2dab46d5fc9f95de16bd9bf0f219be5e64324d1f without a test=
case
or PR reference so it's difficult to tell what it was supposed to allow.  N=
ow,
for the case in question the conversion would have slipped though anyway si=
nce
the only difference in the types is the sign and that one is BOOLEAN_TYPE
and the other INTEGER_TYPE.  So the exception above seems to intent to allow
conversions with different precisions (note we now have precision 1 for all
vector bools).

So I'm going to just copy the vectorizable_conversion condition into
vectorizable_assignment as well.=