[DebugInfo] Prefer setKillLocation rather than replacing operands with undef

NFC-ish. There is a functional change but the outputs are semantically
identical. Where we might've before replaced one operand with undef (which
means "this is a kill location marker") the use of `setKillLocation` will
replace all location operands with `undef` (which also means "this is a kill
location marker").

Related to https://discourse.llvm.org/t/auto-undef-debug-uses-of-a-deleted-value

Reviewed By: StephenTozer

Differential Revision: https://reviews.llvm.org/D140904

1 files changed, 5 insertions, 10 deletions

diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index 0b3799c..a1c4bc8 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -619,10 +619,8 @@ void llvm::RecursivelyDeleteTriviallyDeadInstructions(
 bool llvm::replaceDbgUsesWithUndef(Instruction *I) {
   SmallVector<DbgVariableIntrinsic *, 1> DbgUsers;
   findDbgUsers(DbgUsers, I);
-  for (auto *DII : DbgUsers) {
-    Value *Undef = UndefValue::get(I->getType());
-    DII->replaceVariableLocationOp(I, Undef);
-  }
+  for (auto *DII : DbgUsers)
+    DII->setKillLocation();
   return !DbgUsers.empty();
 }
 
@@ -1914,8 +1912,7 @@ void llvm::salvageDebugInfoForDbgValues(
       // using DIArgList for dbg.assign yet. FIXME: support this.
       // Also do not salvage if the resulting DIArgList would contain an
       // unreasonably large number of values.
-      Value *Undef = UndefValue::get(I.getOperand(0)->getType());
-      DII->replaceVariableLocationOp(I.getOperand(0), Undef);
+      DII->setKillLocation();
     }
     LLVM_DEBUG(dbgs() << "SALVAGE: " << *DII << '\n');
     Salvaged = true;
@@ -1924,10 +1921,8 @@ void llvm::salvageDebugInfoForDbgValues(
   if (Salvaged)
     return;
 
-  for (auto *DII : DbgUsers) {
-    Value *Undef = UndefValue::get(I.getType());
-    DII->replaceVariableLocationOp(&I, Undef);
-  }
+  for (auto *DII : DbgUsers)
+    DII->setKillLocation();
 }
 
 Value *getSalvageOpsForGEP(GetElementPtrInst *GEP, const DataLayout &DL,