[InstCombine] Expand the simplification of pow(x, 0.5) to sqrt(x)

Expand the number of cases when `pow(x, 0.5)` is simplified into `sqrt(x)`
by considering the math semantics with more granularity.

Differential revision: https://reviews.llvm.org/D50036

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@339887 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed