[PATCH] D152502: [MCP] Do not remove redundant copy for COPY from undef
Pierre van Houtryve via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Fri Jun 9 05:24:18 PDT 2023
This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rGdf1782c2a2af: [MCP] Do not remove redundant copy for COPY from undef (authored by Pierre-vh).
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D152502/new/
https://reviews.llvm.org/D152502
Files:
llvm/lib/CodeGen/MachineCopyPropagation.cpp
llvm/test/CodeGen/X86/machine-copy-prop.mir
Index: llvm/test/CodeGen/X86/machine-copy-prop.mir
===================================================================
--- llvm/test/CodeGen/X86/machine-copy-prop.mir
+++ llvm/test/CodeGen/X86/machine-copy-prop.mir
@@ -14,6 +14,7 @@
define void @nocopyprop3() { ret void }
define void @nocopyprop4() { ret void }
define void @nocopyprop5() { ret void }
+ define void @nocopyprop6() { ret void }
...
---
# The second copy is redundant and will be removed, check that we also remove
@@ -213,3 +214,24 @@
$rip = COPY $rax
$rip = COPY $rax
...
+---
+# The copies are obviously redundant, but the earlier COPY copies from "undef".
+# That copy may be lowered to a KILL instead and thus we cannot remove the
+# second COPY, otherwise we risk making $rax undef.
+# CHECK-LABEL: name: nocopyprop6
+# CHECK: bb.0:
+# CHECK: $rax = COPY undef $rdi
+# CHECK-NEXT: NOOP implicit killed $rax
+# CHECK-NEXT: $rax = COPY $rdi
+# CHECK-NEXT: NOOP implicit $rax, implicit $rdi
+name: nocopyprop6
+tracksRegLiveness: true
+body: |
+ bb.0:
+ liveins: $rdi
+
+ $rax = COPY undef $rdi
+ NOOP implicit killed $rax
+ $rax = COPY $rdi
+ NOOP implicit $rax, implicit $rdi
+...
Index: llvm/lib/CodeGen/MachineCopyPropagation.cpp
===================================================================
--- llvm/lib/CodeGen/MachineCopyPropagation.cpp
+++ llvm/lib/CodeGen/MachineCopyPropagation.cpp
@@ -462,7 +462,8 @@
auto PrevCopyOperands = isCopyInstr(*PrevCopy, *TII, UseCopyInstr);
// Check that the existing copy uses the correct sub registers.
- if (PrevCopyOperands->Destination->isDead())
+ if (PrevCopyOperands->Destination->isDead() ||
+ PrevCopyOperands->Source->isUndef())
return false;
if (!isNopCopy(*PrevCopy, Src, Def, TRI, TII, UseCopyInstr))
return false;
-------------- next part --------------
A non-text attachment was scrubbed...
Name: D152502.529924.patch
Type: text/x-patch
Size: 1816 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20230609/c4c37a02/attachment.bin>
More information about the llvm-commits
mailing list