[llvm] [SelectionDAG] Handle more opcodes in canCreateUndefOrPoison (PR #84921)

[Simon Pilgrim via llvm-commits]

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@@ -581,19 +581,41 @@ define i32 @freeze_lshr_exact(i32 %a0) nounwind {
 ; X86-LABEL: freeze_lshr_exact:
 ; X86:       # %bb.0:
 ; X86-NEXT:    movl {{[0-9]+}}(%esp), %eax
+; X86-NEXT:    shrl $8, %eax
+; X86-NEXT:    retl
+;
+; X64-LABEL: freeze_lshr_exact:
+; X64:       # %bb.0:
+; X64-NEXT:    movl %edi, %eax
+; X64-NEXT:    shrl $8, %eax
+; X64-NEXT:    retq
+  %x = lshr exact i32 %a0, 3
+  %y = freeze i32 %x
+  %z = lshr i32 %y, 5
+  ret i32 %z
+}
+
+define i32 @freeze_lshr_exact_extra_use(i32 %a0, ptr %escape) nounwind {
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RKSimon wrote:

pre-commit this test so we see the diff

https://github.com/llvm/llvm-project/pull/84921