Summary:
When optimizing for size, sqrt calls can be incorrectly selected as
AVX512 VSQRT instructions. This is because X86InstrAVX512.td has a
`Requires<[OptForSize]>` in its `avx512_sqrt_scalar` multiclass
definition. Even if the target does not support AVX512, the class can
apparently still be chosen, leading to an incorrect selection of
`vsqrtss`.
In PR26625, this lead to an assertion: Reg >= X86::FP0 && Reg <=
X86::FP6 && "Expected FP register!", because the `vsqrtss` instruction
requires an XMM register, which is not available on i686 CPUs.
Reviewers: grosbach, resistor, joker.eph
Subscribers: spatel, emaste, llvm-commits
Differential Revision: http://reviews.llvm.org/D17414
llvm-svn: 261360
Dimitry Andric