commit 81d8ef219671241c1486ca08b07ec6e8b1b7531e
author Carlos Alberto Enciso <carlos.alberto.enciso@gmail.com> Mon Oct 01 08:14:44 2018 +0000
committer Carlos Alberto Enciso <carlos.alberto.enciso@gmail.com> Mon Oct 01 08:14:44 2018 +0000
tree 19ff3f9bf91854c19d360d1e1977b481862fbd8d
parent ce4caff0de60e115974b05fcf240f294f9b7ff7f

[DebugInfo][Dexter] Incorrect DBG_VALUE after MCP dead copy instruction removal.

When MachineCopyPropagation eliminates a dead 'copy', its associated debug information becomes invalid. as the recorded register has been removed.  It causes the debugger to display wrong variable value.

Differential Revision: https://reviews.llvm.org/D52614

llvm-svn: 343445

llvm/lib/CodeGen/MachineCSE.cpp

diff --git a/llvm/lib/CodeGen/MachineCSE.cpp b/llvm/lib/CodeGen/MachineCSE.cpp
index fa785ac..dcb6f7c 100644
--- a/llvm/lib/CodeGen/MachineCSE.cpp
+++ b/llvm/lib/CodeGen/MachineCSE.cpp
@@ -181,12 +181,8 @@
     LLVM_DEBUG(dbgs() << "Coalescing: " << *DefMI);
     LLVM_DEBUG(dbgs() << "***     to: " << *MI);
 
-    // Collect matching debug values.
-    SmallVector<MachineInstr *, 2> DbgValues;
-    DefMI->collectDebugValues(DbgValues);
-    // Propagate SrcReg to debug value instructions.
-    for (auto *DBI : DbgValues)
-      DBI->getOperand(0).setReg(SrcReg);
+    // Update matching debug values.
+    DefMI->changeDebugValuesDefReg(SrcReg);
 
     // Propagate SrcReg of copies to MI.
     MO.setReg(SrcReg);

llvm/lib/CodeGen/MachineCopyPropagation.cpp

diff --git a/llvm/lib/CodeGen/MachineCopyPropagation.cpp b/llvm/lib/CodeGen/MachineCopyPropagation.cpp
index b530908..dfaa946 100644
--- a/llvm/lib/CodeGen/MachineCopyPropagation.cpp
+++ b/llvm/lib/CodeGen/MachineCopyPropagation.cpp
@@ -598,6 +598,11 @@
       LLVM_DEBUG(dbgs() << "MCP: Removing copy due to no live-out succ: ";
                  MaybeDead->dump());
       assert(!MRI->isReserved(MaybeDead->getOperand(0).getReg()));
+
+      // Update matching debug values.
+      assert(MaybeDead->isCopy());
+      MaybeDead->changeDebugValuesDefReg(MaybeDead->getOperand(1).getReg());
+
       MaybeDead->eraseFromParent();
       Changed = true;
       ++NumDeletes;

llvm/lib/CodeGen/MachineInstr.cpp

diff --git a/llvm/lib/CodeGen/MachineInstr.cpp b/llvm/lib/CodeGen/MachineInstr.cpp
index 092e585..f302901 100644
--- a/llvm/lib/CodeGen/MachineInstr.cpp
+++ b/llvm/lib/CodeGen/MachineInstr.cpp
@@ -2092,3 +2092,13 @@
       DbgValues.push_back(&*DI);
   }
 }
+
+void MachineInstr::changeDebugValuesDefReg(unsigned Reg) {
+  // Collect matching debug values.
+  SmallVector<MachineInstr *, 2> DbgValues;
+  collectDebugValues(DbgValues);
+
+  // Propagate Reg to debug value instructions.
+  for (auto *DBI : DbgValues)
+    DBI->getOperand(0).setReg(Reg);
+}