[PATCH] D32892: Handle a COPY with undef source operand in LowerCopy().
Jonas Paulsson via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Thu May 11 00:06:51 PDT 2017
jonpa updated this revision to Diff 98587.
jonpa added a comment.
Ah, I see.
Your test seemed to work fine (without the machine verifier) :-)
https://reviews.llvm.org/D32892
Files:
lib/CodeGen/ExpandPostRAPseudos.cpp
test/CodeGen/SystemZ/lower-copy-undef-src.mir
Index: test/CodeGen/SystemZ/lower-copy-undef-src.mir
===================================================================
--- /dev/null
+++ 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
Index: lib/CodeGen/ExpandPostRAPseudos.cpp
===================================================================
--- lib/CodeGen/ExpandPostRAPseudos.cpp
+++ lib/CodeGen/ExpandPostRAPseudos.cpp
@@ -142,8 +142,9 @@
MachineOperand &DstMO = MI->getOperand(0);
MachineOperand &SrcMO = MI->getOperand(1);
- if (SrcMO.getReg() == DstMO.getReg()) {
- DEBUG(dbgs() << "identity copy: " << *MI);
+ bool IdentityCopy = (SrcMO.getReg() == DstMO.getReg());
+ if (IdentityCopy || SrcMO.isUndef()) {
+ DEBUG(dbgs() << (IdentityCopy ? "identity copy: " : "undef copy: ") << *MI);
// No need to insert an identity copy instruction, but replace with a KILL
// if liveness is changed.
if (SrcMO.isUndef() || MI->getNumOperands() > 2) {
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