[Intrinsic] Expand SMULFIX to MUL, MULH[US], or [US]MUL_LOHI on vector arguments

[Intrinsic] Expand SMULFIX to MUL, MULH[US], or [US]MUL_LOHI on vector arguments

r zero scale SMULFIX, expand into MUL which produces better code for X86.

For vector arguments, expand into MUL if SMULFIX is provided with a zero scale.
Otherwise, expand into MULH[US] or [US]MUL_LOHI.

Differential Revision: https://reviews.llvm.org/D56987

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@352783 91177308-0d34-0410-b5e6-96231b3b80d8