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Bruno Cardoso Lopes
71a40e6fef
Reintroduce r245442. Remove an overly conservative assertion introduced in r245442. We could replace the assertion to use `shareSameRegisterFile` instead, but in that point in `insertPHI` we already lost the original Def subreg to check against. So drop the assertion completely. Original commit message: - Teaches the ValueTracker in the PeepholeOptimizer to look through PHI instructions. - Add findNextSourceAndRewritePHI method to lookup into multiple sources returnted by the ValueTracker and rewrite PHIs with new sources. With these changes we can find more register sources and rewrite more copies to allow coaslescing of bitcast instructions. Hence, we eliminate unnecessary VR64 <-> GR64 copies in x86, but it could be extended to other archs by marking "isBitcast" on target specific instructions. The x86 example follows: A: psllq %mm1, %mm0 movd %mm0, %r9 jmp C B: por %mm1, %mm0 movd %mm0, %r9 jmp C C: movd %r9, %mm0 pshufw $238, %mm0, %mm0 Becomes: A: psllq %mm1, %mm0 jmp C B: por %mm1, %mm0 jmp C C: pshufw $238, %mm0, %mm0 Differential Revision: http://reviews.llvm.org/D11197 rdar://problem/20404526 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@245479 91177308-0d34-0410-b5e6-96231b3b80d8
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