[CodeGen] Skip over dbg-instr in twoaddr pass

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

Differential Revision: https://reviews.llvm.org/D55987

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@350289 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/TwoAddressInstructionPass.cpp

@@ -929,9 +929,12 @@ rescheduleMIBelowKill(MachineBasicBlock::iterator &mi,
   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 != MBB->end()) {
+    End = skipDebugInstructionsForward(End, MBB->end());
+    if (End->isCopy() && regOverlapsSet(Defs, End->getOperand(1).getReg(), TRI))
+      Defs.push_back(End->getOperand(0).getReg());
+    else
+      break;
     ++End;
   }
 

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