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Subject: [Bug target/106322] i386: Wrong code at O2 level (O0 / O1 are working)
Date: Mon, 18 Jul 2022 14:40:09 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106322

--- Comment #9 from Mathieu Malaterre <malat at debian dot org> ---
(In reply to Andrew Pinski from comment #8)
> Does -fwrapv fix the issue?

No. This seems like the exact same symptoms:

% ./tests/mul_test
"--gtest_filter=3DHwyMulTestGroup/HwyMulTest.TestAllMulHigh/Emu128"=20=20=
=20=20=20=20=20=20=20=20
Running main() from ./googletest/src/gtest_main.cc
Note: Google Test filter =3D HwyMulTestGroup/HwyMulTest.TestAllMulHigh/Emu1=
28
[=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D] Running 1 test from 1 test suite.
[----------] Global test environment set-up.
[----------] 1 test from HwyMulTestGroup/HwyMulTest
[ RUN      ] HwyMulTestGroup/HwyMulTest.TestAllMulHigh/Emu128


i16x8 expect [0+ ->]:
  0x3FFF,0x0FFF,0x03FF,0x00FF,0x003F,0x000F,0x0003,
i16x8 actual [0+ ->]:
  0xBFFF,0x0FFF,0xE400,0x00FF,0xF840,0x000F,0xFE04,
Abort at
/home/malat/highway-0.17.1~git20220711.f0a396a/hwy/tests/mul_test.cc:131:
Emu128, i16x8 lane 0 mismatch: expected '0x3FFF', got '0xBFFF'.


Technically I can also execute the `uint16` portion of the unit test and
produce a failure (so this seems to be consistent behavior with signed
counterpart):

```
HWY_NOINLINE void TestAllMulHigh() {
  ForPartialVectors<TestMulHigh> test;
//  test(int16_t());
  test(uint16_t());
}
```

And then:


```
% ./tests/mul_test
"--gtest_filter=3DHwyMulTestGroup/HwyMulTest.TestAllMulHigh/Emu128"=20=20=
=20=20=20=20=20=20=20=20
Running main() from ./googletest/src/gtest_main.cc
Note: Google Test filter =3D HwyMulTestGroup/HwyMulTest.TestAllMulHigh/Emu1=
28
[=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D] Running 1 test from 1 test suite.
[----------] Global test environment set-up.
[----------] 1 test from HwyMulTestGroup/HwyMulTest
[ RUN      ] HwyMulTestGroup/HwyMulTest.TestAllMulHigh/Emu128


u16x8 expect [0+ ->]:
  0xFFFE,0x3FFF,0x0FFF,0x03FF,0x00FF,0x003F,0x000F,
u16x8 actual [0+ ->]:
  0xFFFF,0x3FFF,0xD000,0x03FF,0xF100,0x003F,0xFC10,
Abort at
/home/malat/highway-0.17.1~git20220711.f0a396a/hwy/tests/mul_test.cc:131:
Emu128, u16x8 lane 0 mismatch: expected '0xFFFE', got '0xFFFF'.
```=