[Bug target/110622] x87: Miscompilation at O2 level (O1 is working)

[malat at debian dot org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110622

--- Comment #11 from Mathieu Malaterre <malat at debian dot org> ---
Typical setup:

g++ -fno-asynchronous-unwind-tables -fno-exceptions -fno-rtti -DHIDESYMPTOM
-std=c++11 -g -m32 -fexcess-precision=fast -O2 -o works math_test.cc
-Wfatal-errors -Wall -Wextra -Wpedantic -Wconversion -Werror

and:

g++ -fno-asynchronous-unwind-tables -fno-exceptions -fno-rtti -std=c++11 -g
-m32 -fexcess-precision=fast -O2 -o fails math_test.cc -Wfatal-errors -Wall
-Wextra -Wpedantic -Wconversion -Werror

You can observe that the only difference is that I am preventing an elision :

```
% grep -A2 HIDE math_test.cc
#ifdef HIDESYMPTOM
  asm volatile("" : "+r"(y.raw[0]) : : "memory");
#endif
```