[clang] [llvm] [RegisterCoalescer] Improve register allocation for return values by limiting rematerialization (PR #163047)

[guan jian via llvm-commits]

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@@ -202,13 +202,13 @@ define { <4 x i8>, <4 x i1> } @always_usub_const_vector() nounwind {
 ; SSE-LABEL: always_usub_const_vector:
 ; SSE:       # %bb.0:
 ; SSE-NEXT:    pcmpeqd %xmm0, %xmm0
-; SSE-NEXT:    pcmpeqd %xmm1, %xmm1
+; SSE-NEXT:    movdqa %xmm0, %xmm1
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rez5427 wrote:

Well, I add this isZeroIdiom function check, and add a test case for this.

https://github.com/llvm/llvm-project/pull/163047