Optimize square root squared (PR21126).

When unsafe-fp-math is enabled, we can turn sqrt(X) * sqrt(X) into X.

This can happen in the real world when calculating x ** 3/2. This occurs
in test-suite/SingleSource/Benchmarks/BenchmarkGame/n-body.c.

Differential Revision: http://reviews.llvm.org/D5584



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218906 91177308-0d34-0410-b5e6-96231b3b80d8
LTO: Document the Boolean argument from r218784

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218907 91177308-0d34-0410-b5e6-96231b3b80d8