[PATCH] SROA: Handle a case of store size being smaller than allocation size

[Chandler Carruth]

Looks good with a slightly compactified test.

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Comment at: test/Transforms/SROA/slice-width.ll:65
@@ +64,3 @@
+  %x_i8 = bitcast %union.Foo* %x to i8*
+  call void @llvm.memset.p0i8.i32(i8* %x_i8, i8 -1, i32 32, i32 16, i1 false)
+
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Just test memset in the function above? We don't run other optimizations here, it's not going to forward or do dead store elim...

http://reviews.llvm.org/D5012