[ADT] Use memcpy for type punning in MathExtras.
[ADT] Use memcpy for type punning in MathExtras.

Summary: Previously we type-punned through a union, which is not safe.

Reviewers: rnk

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D28161

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@290715 91177308-0d34-0410-b5e6-96231b3b80d8

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