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From: "slyfox at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/115115] New: [12/13/14/15 Regression] highway-1.0.7
 wrong _mm_cvttps_epi32() constant fold
Date: Wed, 15 May 2024 21:38:37 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D115115

            Bug ID: 115115
           Summary: [12/13/14/15 Regression] highway-1.0.7 wrong
                    _mm_cvttps_epi32() constant fold
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: slyfox at gcc dot gnu.org
  Target Milestone: ---

Initially I observed the testsuite failure on highway-1.0.7 library as on
r15-523-g1a05332bbac98a.

I reduced it down to the following:

```c
// $ cat bug.c
#include <emmintrin.h>
#include <stdio.h>
#include <stdint.h>
#include <string.h>

__attribute__((noipa))
static void dump_m128i(const char * prefix, const __m128i * v) {
  uint32_t p[4];
  memcpy(p, v, 16);
  fprintf(stderr, "%s:", prefix);
  for (size_t i =3D 0; i < 4; ++i) {
    fprintf(stderr, " %#08x", p[i]);
  }
  fprintf(stderr, "\n");
}

__attribute__((noipa))
static void assert_m128i(const __m128i * v) {
  uint32_t p[4];
  memcpy(p, v, 16);
  uint32_t q[4] =3D {
      0x80000000,
      0x80000000,
      0x80000000,
      0x80000000,
  };
  if (memcmp(p, q, 16) !=3D 0) __builtin_abort();
}

__attribute__((noipa))
static void TestAllF2IPromoteTo() {
  const __m128i iv =3D _mm_set_epi32(0x4f000000, 0x4f000000, 0x4f000000,
0x4f000000);
  const __m128  fv =3D _mm_castsi128_ps(iv);
  const __m128i riv =3D _mm_cvttps_epi32(fv);

  dump_m128i("riv", &riv);
  assert_m128i(&riv);
}

int main() {
    TestAllF2IPromoteTo();
}
```

Triggering:

$ gcc-15 bug.c -o a -O0 && ./a
riv: 0x80000000 0x80000000 0x80000000 0x80000000
# ok?

$ gcc-15 bug.c -o a -O1 && ./a
riv: 0x7fffffff 0x7fffffff 0x7fffffff 0x7fffffff
Aborted (core dumped)
# bad?

I think highway expect the former. At least gcc-8/9/10/11 pass the test.
gcc-12/13/14/15 all fail it.

$ gcc -v
Using built-in specs.
COLLECT_GCC=3D/<<NIX>>/gcc-15.0.0/bin/gcc
COLLECT_LTO_WRAPPER=3D/<<NIX>>/gcc-15.0.0/libexec/gcc/x86_64-unknown-linux-=
gnu/15.0.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../source/configure --prefix=3D/<<NIX>>/gcc-15.0.0
--with-gmp-include=3D/<<NIX>>/gmp-6.3.0-dev/include
--with-gmp-lib=3D/<<NIX>>/gmp-6.3.0/lib
--with-mpfr-include=3D/<<NIX>>/mpfr-4.2.1-dev/include
--with-mpfr-lib=3D/<<NIX>>/mpfr-4.2.1/lib --with-mpc=3D/<<NIX>>/libmpc-1.3.1
--with-native-system-header-dir=3D/<<NIX>>/glibc-2.39-52-dev/include
--with-build-sysroot=3D/
--with-gxx-include-dir=3D/<<NIX>>/gcc-15.0.0/include/c++/15.0.0/
--program-prefix=3D --enable-lto --disable-libstdcxx-pch
--without-included-gettext --with-system-zlib --enable-checking=3Drelease
--enable-static --enable-languages=3Dc,c++ --disable-multilib --enable-plug=
in
--disable-libcc1 --with-isl=3D/<<NIX>>/isl-0.20 --disable-bootstrap
--build=3Dx86_64-unknown-linux-gnu --host=3Dx86_64-unknown-linux-gnu
--target=3Dx86_64-unknown-linux-gnu
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 15.0.0 99999999 (experimental) (GCC)=