[InstCombine] Take in account the size in sext->lshr->trunc patterns.
Otherwise we end up miscompiling, transforming:
define i8 @tinky() {
%sext = sext i1 1 to i16
%hibit = lshr i16 %sext, 15
%tr = trunc i16 %hibit to i8
ret i8 %tr
}
into:
%sext = sext i1 1 to i8
ret i8 %sext
and the first get folded to ret i8 1, while the second gets folded
to ret i8 -1.
Eventually we should get rid of this transform entirely, but for now,
this at least fixes a know correctness bug.
Differential Revision: https://reviews.llvm.org/D33338
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@303513
91177308-0d34-0410-b5e6-
96231b3b80d8