[Bug target/115161] New: [15 Regression] highway-1.0.7 miscompilation of some SSE2 intrinsics

["slyfox at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115161

            Bug ID: 115161
           Summary: [15 Regression] highway-1.0.7 miscompilation of some
                    SSE2 intrinsics
           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: ---

Created attachment 58250
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=58250&action=edit
bug.cc

Initially observed at r15-656-ge1a7e2c54d52d0 on highway-1.0.7 where
HwyConvertTestGroup/HwyConvertTest.TestAllF2IPromoteTo/SSE2 was failing as:

[ RUN      ] HwyConvertTestGroup/HwyConvertTest.TestAllF2IPromoteTo/SSE2


i64x2 expect [0+ ->]:
  0x7fffffffffffffff,0x7fffffffffffffff,
i64x2 actual [0+ ->]:
  0x7fffffff00000000,0x7fffffff00000000,
Abort at convert_test.cc:41: SSE2, i64x2 lane 0 mismatch: expected
'0x7fffffffffffffff', got '0x7fffffff00000000'.

I extracted it down to attached bug.cc. It's 5kb of straightforward
self-contained code.

Crashing:

$ g++-15 bug.cc -o bug -O0 && ./bug
exponent_adj(i): 0x00002000000020 0x00002000000020
     adj_v(f): 0x4f8000004f800000 0x4f8000004f800000
lo64_or_mask(i): 0xffffffffffffffff 0xffffffffffffffff
         i(f): 0x5f8000005f800000 0x5f8000005f800000
  expected(i): 0xffffffffffffffff 0xffffffffffffffff
    actual(i): 0xffffffffffffffff 0xffffffffffffffff

Expected example:

$ g++-15 bug.cc -o bug -O2 && ./bug
exponent_adj(i): 0x00002000000020 0x00002000000020
     adj_v(f): 0x4f8000004f800000 0x4f8000004f800000
lo64_or_mask(i): 0000000000000000 0000000000000000
         i(f): 0x5f8000005f800000 0x5f8000005f800000
  expected(i): 0xffffffffffffffff 0xffffffffffffffff
    actual(i): 0000000000000000 0000000000000000
Illegal instruction (core dumped)

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