[Local] Sink salvageDI's early exit into helper functions, NFC

salvageDebugInfo() performs a check that allows it to exit early without
doing a DenseMap lookup. It's a bit neater and marginally more useful to
sink this early exit into the findDbg{Addr,Users,Values} helpers.

llvm-svn: 335642

llvm/lib/Transforms/Utils/Local.cpp

@@ -1478,6 +1478,10 @@ void llvm::insertDebugValuesForPHIs(BasicBlock *BB,
 /// 'V' points to. This may include a mix of dbg.declare and
 /// dbg.addr intrinsics.
 TinyPtrVector<DbgInfoIntrinsic *> llvm::FindDbgAddrUses(Value *V) {
+  // This function is hot. Check whether the value has any metadata to avoid a
+  // DenseMap lookup.
+  if (!V->isUsedByMetadata())
+    return {};
   auto *L = LocalAsMetadata::getIfExists(V);
   if (!L)
     return {};
@@ -1496,6 +1500,10 @@ TinyPtrVector<DbgInfoIntrinsic *> llvm::FindDbgAddrUses(Value *V) {
 }
 
 void llvm::findDbgValues(SmallVectorImpl<DbgValueInst *> &DbgValues, Value *V) {
+  // This function is hot. Check whether the value has any metadata to avoid a
+  // DenseMap lookup.
+  if (!V->isUsedByMetadata())
+    return;
   if (auto *L = LocalAsMetadata::getIfExists(V))
     if (auto *MDV = MetadataAsValue::getIfExists(V->getContext(), L))
       for (User *U : MDV->users())
@@ -1505,6 +1513,10 @@ void llvm::findDbgValues(SmallVectorImpl<DbgValueInst *> &DbgValues, Value *V) {
 
 void llvm::findDbgUsers(SmallVectorImpl<DbgInfoIntrinsic *> &DbgUsers,
                         Value *V) {
+  // This function is hot. Check whether the value has any metadata to avoid a
+  // DenseMap lookup.
+  if (!V->isUsedByMetadata())
+    return;
   if (auto *L = LocalAsMetadata::getIfExists(V))
     if (auto *MDV = MetadataAsValue::getIfExists(V->getContext(), L))
       for (User *U : MDV->users())
@@ -1579,11 +1591,6 @@ void llvm::replaceDbgValueForAlloca(AllocaInst *AI, Value *NewAllocaAddress,
 }
 
 void llvm::salvageDebugInfo(Instruction &I) {
-  // This function is hot. An early check to determine whether the instruction
-  // has any metadata to save allows it to return earlier on average.
-  if (!I.isUsedByMetadata())
-    return;
-
   SmallVector<DbgInfoIntrinsic *, 1> DbgUsers;
   findDbgUsers(DbgUsers, &I);
   if (DbgUsers.empty())