[DebugInfo] Reduce SalvageDebugInfo() functions

- Now all SalvageDebugInfo() calls will mark undef if the salvage
  attempt fails.

 Reviewed by: vsk, Orlando

 Differential Revision: https://reviews.llvm.org/D78369

llvm/include/llvm/Transforms/Utils/Local.h

@@ -368,13 +368,10 @@ AllocaInst *findAllocaForValue(Value *V,
                                DenseMap<Value *, AllocaInst *> &AllocaForValue);
 
 /// Assuming the instruction \p I is going to be deleted, attempt to salvage
-/// debug users of \p I by writing the effect of \p I in a DIExpression.
-/// Returns true if any debug users were updated.
-bool salvageDebugInfo(Instruction &I);
+/// debug users of \p I by writing the effect of \p I in a DIExpression. If it
+/// cannot be salvaged changes its debug uses to undef.
+void salvageDebugInfo(Instruction &I);
 
-/// Salvage all debug users of the instruction \p I or mark it as undef if it
-/// cannot be salvaged.
-void salvageDebugInfoOrMarkUndef(Instruction &I);
 
 /// Implementation of salvageDebugInfo, applying only to instructions in
 /// \p Insns, rather than all debug users of \p I.

llvm/lib/Transforms/InstCombine/InstCombineInternal.h

@@ -721,7 +721,7 @@ public:
   Instruction *eraseInstFromFunction(Instruction &I) {
     LLVM_DEBUG(dbgs() << "IC: ERASE " << I << '\n');
     assert(I.use_empty() && "Cannot erase instruction that is used!");
-    salvageDebugInfoOrMarkUndef(I);
+    salvageDebugInfo(I);
 
     // Make sure that we reprocess all operands now that we reduced their
     // use counts.

llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp

@@ -88,7 +88,7 @@ bool InstCombiner::SimplifyDemandedBits(Instruction *I, unsigned OpNo,
                                           Depth, I);
   if (!NewVal) return false;
   if (Instruction* OpInst = dyn_cast<Instruction>(U))
-    salvageDebugInfoOrMarkUndef(*OpInst);
+    salvageDebugInfo(*OpInst);
     
   replaceUse(U, NewVal);
   return true;

llvm/lib/Transforms/InstCombine/InstructionCombining.cpp

@@ -3650,7 +3650,7 @@ static bool prepareICWorklistFromFunction(Function &F, const DataLayout &DL,
     if (isInstructionTriviallyDead(Inst, TLI)) {
       ++NumDeadInst;
       LLVM_DEBUG(dbgs() << "IC: DCE: " << *Inst << '\n');
-      salvageDebugInfoOrMarkUndef(*Inst);
+      salvageDebugInfo(*Inst);
       Inst->eraseFromParent();
       MadeIRChange = true;
       continue;

llvm/lib/Transforms/Scalar/BDCE.cpp

@@ -102,7 +102,7 @@ static bool bitTrackingDCE(Function &F, DemandedBits &DB) {
         (I.getType()->isIntOrIntVectorTy() &&
          DB.getDemandedBits(&I).isNullValue() &&
          wouldInstructionBeTriviallyDead(&I))) {
-      salvageDebugInfoOrMarkUndef(I);
+      salvageDebugInfo(I);
       Worklist.push_back(&I);
       I.dropAllReferences();
       Changed = true;

llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp

@@ -146,7 +146,7 @@ deleteDeadInstruction(Instruction *I, BasicBlock::iterator *BBI,
     ++NumFastOther;
 
     // Try to preserve debug information attached to the dead instruction.
-    salvageDebugInfoOrMarkUndef(*DeadInst);
+    salvageDebugInfo(*DeadInst);
     salvageKnowledge(DeadInst);
 
     // This instruction is dead, zap it, in stages.  Start by removing it from

llvm/lib/Transforms/Scalar/EarlyCSE.cpp

@@ -966,7 +966,7 @@ bool EarlyCSE::processNode(DomTreeNode *Node) {
       }
 
       salvageKnowledge(&Inst, &AC);
-      salvageDebugInfoOrMarkUndef(Inst);
+      salvageDebugInfo(Inst);
       removeMSSA(Inst);
       Inst.eraseFromParent();
       Changed = true;

llvm/lib/Transforms/Scalar/LICM.cpp

@@ -504,7 +504,7 @@ bool llvm::sinkRegion(DomTreeNode *N, AliasAnalysis *AA, LoopInfo *LI,
         if (sink(I, LI, DT, CurLoop, SafetyInfo, MSSAU, ORE)) {
           if (!FreeInLoop) {
             ++II;
-            salvageDebugInfoOrMarkUndef(I);
+            salvageDebugInfo(I);
             eraseInstruction(I, *SafetyInfo, CurAST, MSSAU);
           }
           Changed = true;

llvm/lib/Transforms/Scalar/Reassociate.cpp

@@ -1903,7 +1903,7 @@ void ReassociatePass::RecursivelyEraseDeadInsts(Instruction *I,
   ValueRankMap.erase(I);
   Insts.remove(I);
   RedoInsts.remove(I);
-  llvm::salvageDebugInfoOrMarkUndef(*I);
+  llvm::salvageDebugInfo(*I);
   I->eraseFromParent();
   for (auto Op : Ops)
     if (Instruction *OpInst = dyn_cast<Instruction>(Op))
@@ -1920,7 +1920,7 @@ void ReassociatePass::EraseInst(Instruction *I) {
   // Erase the dead instruction.
   ValueRankMap.erase(I);
   RedoInsts.remove(I);
-  llvm::salvageDebugInfoOrMarkUndef(*I);
+  llvm::salvageDebugInfo(*I);
   I->eraseFromParent();
   // Optimize its operands.
   SmallPtrSet<Instruction *, 8> Visited; // Detect self-referential nodes.

llvm/lib/Transforms/Utils/Local.cpp

@@ -1628,7 +1628,7 @@ static MetadataAsValue *wrapValueInMetadata(LLVMContext &C, Value *V) {
   return MetadataAsValue::get(C, ValueAsMetadata::get(V));
 }
 
-bool llvm::salvageDebugInfo(Instruction &I) {
+static bool attemptToSalvageDebugInfo(Instruction &I) {
   SmallVector<DbgVariableIntrinsic *, 1> DbgUsers;
   findDbgUsers(DbgUsers, &I);
   if (DbgUsers.empty())
@@ -1637,8 +1637,8 @@ bool llvm::salvageDebugInfo(Instruction &I) {
   return salvageDebugInfoForDbgValues(I, DbgUsers);
 }
 
-void llvm::salvageDebugInfoOrMarkUndef(Instruction &I) {
-  if (!salvageDebugInfo(I))
+void llvm::salvageDebugInfo(Instruction &I) {
+  if (!attemptToSalvageDebugInfo(I))
     replaceDbgUsesWithUndef(&I);
 }
 
@@ -1822,7 +1822,7 @@ static bool rewriteDebugUsers(
 
   if (!UndefOrSalvage.empty()) {
     // Try to salvage the remaining debug users.
-    salvageDebugInfoOrMarkUndef(From);
+    salvageDebugInfo(From);
     Changed = true;
   }