[PATCH] D55987: [CodeGen] Skip over dbg-instr in twoaddr pass

[Markus Lavin via Phabricator via llvm-commits]

markus created this revision.
markus added a reviewer: MatzeB.

A DBG_VALUE between a two-address instruction and a following COPY would prevent rescheduleMIBelowKill optimization inside TwoAddressInstructionPass.


Repository:
  rL LLVM

https://reviews.llvm.org/D55987

Files:
  lib/CodeGen/TwoAddressInstructionPass.cpp
  test/CodeGen/X86/twoaddr-dbg-value.mir


Index: test/CodeGen/X86/twoaddr-dbg-value.mir
===================================================================
--- /dev/null
+++ test/CodeGen/X86/twoaddr-dbg-value.mir
@@ -0,0 +1,27 @@
+# RUN: llc -run-pass=livevars,twoaddressinstruction -mtriple=x86_64-- -o - %s | FileCheck %s
+---
+name:            foo
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $edi
+
+    %0:gr32 = COPY killed $edi
+    %1:gr32 = COPY killed %0
+    %4:gr32 = XOR32ri8 %1, 1, implicit-def dead $eflags
+    DBG_VALUE %4
+    %5:gr32 = COPY %4
+    PUSH32r killed %1, implicit-def $esp, implicit $esp
+    $eax = COPY killed %5
+    RETQ implicit killed $eax
+
+...
+
+# Verify that the DBG_VALUE instruction does not inhibit
+# TwoAddressInstructionPass::rescheduleMIBelowKill optimization
+
+# CHECK: PUSH32r %1, implicit-def $esp, implicit $esp
+# CHECK-NEXT: %2:gr32 = COPY killed %1
+# CHECK-NEXT: %2:gr32 = XOR32ri8 %2, 1, implicit-def dead $eflags
+# CHECK-NEXT: DBG_VALUE %2
+# CHECK-NEXT: %3:gr32 = COPY killed %2
Index: lib/CodeGen/TwoAddressInstructionPass.cpp
===================================================================
--- lib/CodeGen/TwoAddressInstructionPass.cpp
+++ lib/CodeGen/TwoAddressInstructionPass.cpp
@@ -929,9 +929,11 @@
   MachineBasicBlock::iterator Begin = MI;
   MachineBasicBlock::iterator AfterMI = std::next(Begin);
   MachineBasicBlock::iterator End = AfterMI;
-  while (End->isCopy() &&
-         regOverlapsSet(Defs, End->getOperand(1).getReg(), TRI)) {
-    Defs.push_back(End->getOperand(0).getReg());
+  while (End->isDebugInstr() ||
+         (End->isCopy() &&
+          regOverlapsSet(Defs, End->getOperand(1).getReg(), TRI))) {
+    if (!End->isDebugInstr())
+      Defs.push_back(End->getOperand(0).getReg());
     ++End;
   }
 


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