[llvm] [CodeGen][NFC] Guard copy propagation in machine CSE against undefs (PR #97413)

[Matt Arsenault via llvm-commits]

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@@ -0,0 +1,21 @@
+# RUN: llc -mtriple=amdgcn -run-pass=machine-cse -verify-machineinstrs -o - %s | FileCheck %s
+
+# Test to ensure that this does not crash on undefs
+# CHECK-LABEL: name: machine-cse-copyprop
+# CHECK: IMPLICIT_DEF
+# CHECK-NOT: COPY
+# CHECK: S_ADD_I32
+---
+name: machine-cse-copyprop
+tracksRegLiveness: true
+body:               |
+  bb.0:
+    %0:sreg_32 = IMPLICIT_DEF
+    %1:sreg_32 = IMPLICIT_DEF
+    %2:sreg_32 = COPY %0
+    %3:sreg_32 = COPY %1
+    %4:sreg_64 = REG_SEQUENCE undef %10:sreg_32, %subreg.sub0, %2:sreg_32, %subreg.sub1
+    %5:sreg_64 = REG_SEQUENCE undef %11:sreg_32, %subreg.sub0, %3:sreg_32, %subreg.sub1
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arsenm wrote:

How did these get produced in the first place? 

https://github.com/llvm/llvm-project/pull/97413