2 files changed, 32 insertions, 18 deletions

diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index 879145cea6b..da9167f06a4 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -2529,6 +2529,34 @@ void llvm::dropDebugUsers(Instruction &I) {
     DII->eraseFromParent();
 }
 
+void llvm::hoistAllInstructionsInto(BasicBlock *DomBlock,Instruction *InsertPt,
+                                    BasicBlock *IfBlock) {
+  // Since we are moving the instructions out of its basic block, we do not
+  // retain their original debug locations (DILocations) and debug intrinsic
+  // instructions (dbg.values).
+  //
+  // Doing so would degrade the debugging experience and adversely affect the
+  // accuracy of profiling information.
+  //
+  // Currently, when hoisting the instructions, we take the following actions:
+  // - Remove their dbg.values.
+  // - Set their debug locations to the values from the insertion point.
+  //
+  // See PR38762 for more details.
+  //
+  // TODO: Extend llvm.dbg.value to take more than one SSA Value (PR39141) to
+  // encode predicated DIExpressions that yield different results on different
+  // code paths.
+  for (auto &I : *IfBlock) {
+    I.dropUnknownNonDebugMetadata();
+    dropDebugUsers(I);
+    I.setDebugLoc(InsertPt->getDebugLoc());
+  }
+  DomBlock->getInstList().splice(InsertPt->getIterator(),
+                                 IfBlock->getInstList(), IfBlock->begin(),
+                                 IfBlock->getTerminator()->getIterator());
+}
+
 namespace {
 
 /// A potential constituent of a bitreverse or bswap expression. See
diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index ebbcf800254..3e73c537292 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -2375,24 +2375,10 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetTransformInfo &TTI,
 
   // Move all 'aggressive' instructions, which are defined in the
   // conditional parts of the if's up to the dominating block.
-  if (IfBlock1) {
-    for (auto &I : *IfBlock1) {
-      I.dropUnknownNonDebugMetadata();
-      dropDebugUsers(I);
-    }
-    DomBlock->getInstList().splice(InsertPt->getIterator(),
-                                   IfBlock1->getInstList(), IfBlock1->begin(),
-                                   IfBlock1->getTerminator()->getIterator());
-  }
-  if (IfBlock2) {
-    for (auto &I : *IfBlock2) {
-      I.dropUnknownNonDebugMetadata();
-      dropDebugUsers(I);
-    }
-    DomBlock->getInstList().splice(InsertPt->getIterator(),
-                                   IfBlock2->getInstList(), IfBlock2->begin(),
-                                   IfBlock2->getTerminator()->getIterator());
-  }
+  if (IfBlock1)
+    hoistAllInstructionsInto(DomBlock, InsertPt, IfBlock1);
+  if (IfBlock2)
+    hoistAllInstructionsInto(DomBlock, InsertPt, IfBlock2);
 
   while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
     // Change the PHI node into a select instruction.