Handle a COPY with undef source operand in LowerCopy()
Llvm-stress discovered that a COPY may end up in ExpandPostRA::LowerCopy()
with an undef source operand. It is not possible for the target to handle
this, as this flag is not passed to TII->copyPhysReg().
This patch solves this by treating such a COPY as an identity COPY.
Review: Matthias Braun
https://reviews.llvm.org/D32892
llvm-svn: 302877
diff --git a/llvm/test/CodeGen/SystemZ/lower-copy-undef-src.mir b/llvm/test/CodeGen/SystemZ/lower-copy-undef-src.mir
new file mode 100644
index 0000000..322460d
--- /dev/null
+++ b/llvm/test/CodeGen/SystemZ/lower-copy-undef-src.mir
@@ -0,0 +1,14 @@
+# RUN: llc -mtriple=s390x-linux-gnu -mcpu=z13 -run-pass=postrapseudos -o - %s | FileCheck %s
+#
+# Test that a COPY with an undef source operand gets handled like an identity
+# copy rather than lowered into a target instruction with the undef flag
+# dropped.
+---
+# CHECK-LABEL: name: undef_copy
+# CHECK: %r13d = KILL undef %r0d, implicit killed %r12q, implicit-def %r12q
+name: undef_copy
+tracksRegLiveness: true
+body: |
+ bb.0:
+ liveins: %r12q
+ %r13d = COPY undef %r0d, implicit killed %r12q, implicit-def %r12q