[X86] Selectively mark the FMA variants inside a family as isCommutable. Given a FMA family (e.g., 213, 231), not all the variants (i.e., register or memory) are commutable. E.g., for the 213 family (with the syntax src1, src2, src3): fmaXXX213 A, B, reg3/mem3 == fmaXXX213 B, A, reg3/mem3
[X86] Selectively mark the FMA variants inside a family as isCommutable.
Given a FMA family (e.g., 213, 231), not all the variants (i.e., register or
memory) are commutable.
E.g., for the 213 family (with the syntax src1, src2, src3):
fmaXXX213 A, B, reg3/mem3 == fmaXXX213 B, A, reg3/mem3

Now consider the 231 family:
fmaXXX231 A, B, reg3 == fmaXXX231 A, reg3, B
But
fmaXXX231 A, B, mem3 != fmaXXX231 A, mem3, B
Indeed, mem3 cannot be the second argument of the memory variant of fmaXXX231.

Working on a reduced test case!

<rdar://problem/16800495>


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@208252 91177308-0d34-0410-b5e6-96231b3b80d8

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