[Bug middle-end/112572] [14 regression] LLVM miscompiled since r14-5355-g3cd3a09b3f91a1

[slyfox at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112572

--- Comment #19 from Sergei Trofimovich <slyfox at gcc dot gnu.org> ---
I spent some time poking at the bug and was not able to reproduce it on my
toolchain.

I was able to get it to fail on gentoo's toolchain and arrived at problems in
lib/Target/X86/X86InterleavedAccess.cpp. My theory is that
X86InterleavedAccessGroup::decompose() gets compiled incorrectly.

`-fPIE` seems to be the flag that triggers gcc to generate slightly incorrect
prologue (wrong register is being used). I filed a separate issue in case it's
an invalid manual reduction: https://gcc.gnu.org/PR112613