DebugInfo: Factor out logic to update locations in MD_loop metadata, NFC

Factor out the logic needed to update debug locations contained within
MD_loop metadata.

This refactor is preparation for a future change that also needs to
rewrite MD_loop metadata.

rdar://45507940

Author: vedantk

llvm/include/llvm/IR/DebugInfo.h

@@ -16,6 +16,7 @@
 #ifndef LLVM_IR_DEBUGINFO_H
 #define LLVM_IR_DEBUGINFO_H
 
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/iterator_range.h"
@@ -25,6 +26,7 @@ namespace llvm {
 
 class DbgDeclareInst;
 class DbgValueInst;
+class Instruction;
 class Module;
 
 /// Find subprogram that is enclosing this scope.
@@ -50,6 +52,13 @@ bool stripDebugInfo(Function &F);
 ///   All debug type metadata nodes are unreachable and garbage collected.
 bool stripNonLineTableDebugInfo(Module &M);
 
+/// Update the debug locations contained within the MD_loop metadata attached
+/// to the instruction \p I, if one exists. \p Updater is applied to each debug
+/// location in the MD_loop metadata: the returned value is included in the
+/// updated loop metadata node if it is non-null.
+void updateLoopMetadataDebugLocations(
+    Instruction &I, function_ref<DILocation *(const DILocation &)> Updater);
+
 /// Return Debug Info Metadata Version by checking module flags.
 unsigned getDebugMetadataVersionFromModule(const Module &M);
 

llvm/lib/IR/DebugInfo.cpp

@@ -278,6 +278,41 @@ bool DebugInfoFinder::addScope(DIScope *Scope) {
   return true;
 }
 
+static MDNode *updateLoopMetadataDebugLocationsImpl(
+    MDNode *OrigLoopID,
+    function_ref<DILocation *(const DILocation &)> Updater) {
+  assert(OrigLoopID && OrigLoopID->getNumOperands() > 0 &&
+         "Loop ID needs at least one operand");
+  assert(OrigLoopID && OrigLoopID->getOperand(0).get() == OrigLoopID &&
+         "Loop ID should refer to itself");
+
+  // Save space for the self-referential LoopID.
+  SmallVector<Metadata *, 4> MDs = {nullptr};
+
+  for (unsigned i = 1; i < OrigLoopID->getNumOperands(); ++i) {
+    Metadata *MD = OrigLoopID->getOperand(i);
+    if (DILocation *DL = dyn_cast<DILocation>(MD)) {
+      if (DILocation *NewDL = Updater(*DL))
+        MDs.push_back(NewDL);
+    } else
+      MDs.push_back(MD);
+  }
+
+  MDNode *NewLoopID = MDNode::getDistinct(OrigLoopID->getContext(), MDs);
+  // Insert the self-referential LoopID.
+  NewLoopID->replaceOperandWith(0, NewLoopID);
+  return NewLoopID;
+}
+
+void llvm::updateLoopMetadataDebugLocations(
+    Instruction &I, function_ref<DILocation *(const DILocation &)> Updater) {
+  MDNode *OrigLoopID = I.getMetadata(LLVMContext::MD_loop);
+  if (!OrigLoopID)
+    return;
+  MDNode *NewLoopID = updateLoopMetadataDebugLocationsImpl(OrigLoopID, Updater);
+  I.setMetadata(LLVMContext::MD_loop, NewLoopID);
+}
+
 static MDNode *stripDebugLocFromLoopID(MDNode *N) {
   assert(!N->operands().empty() && "Missing self reference?");
 
@@ -294,20 +329,10 @@ static MDNode *stripDebugLocFromLoopID(MDNode *N) {
       }))
     return nullptr;
 
-  SmallVector<Metadata *, 4> Args;
-  // Reserve operand 0 for loop id self reference.
-  auto TempNode = MDNode::getTemporary(N->getContext(), None);
-  Args.push_back(TempNode.get());
-  // Add all non-debug location operands back.
-  for (auto Op = N->op_begin() + 1; Op != N->op_end(); Op++) {
-    if (!isa<DILocation>(*Op))
-      Args.push_back(*Op);
-  }
-
-  // Set the first operand to itself.
-  MDNode *LoopID = MDNode::get(N->getContext(), Args);
-  LoopID->replaceOperandWith(0, LoopID);
-  return LoopID;
+  auto dropDebugLoc = [](const DILocation &) -> DILocation * {
+    return nullptr;
+  };
+  return updateLoopMetadataDebugLocationsImpl(N, dropDebugLoc);
 }
 
 bool llvm::stripDebugInfo(Function &F) {

llvm/lib/Transforms/Utils/InlineFunction.cpp

@@ -1356,34 +1356,6 @@ static DebugLoc inlineDebugLoc(DebugLoc OrigDL, DILocation *InlinedAt,
                        IA);
 }
 
-/// Returns the LoopID for a loop which has has been cloned from another
-/// function for inlining with the new inlined-at start and end locs.
-static MDNode *inlineLoopID(const MDNode *OrigLoopId, DILocation *InlinedAt,
-                            LLVMContext &Ctx,
-                            DenseMap<const MDNode *, MDNode *> &IANodes) {
-  assert(OrigLoopId && OrigLoopId->getNumOperands() > 0 &&
-         "Loop ID needs at least one operand");
-  assert(OrigLoopId && OrigLoopId->getOperand(0).get() == OrigLoopId &&
-         "Loop ID should refer to itself");
-
-  // Save space for the self-referential LoopID.
-  SmallVector<Metadata *, 4> MDs = {nullptr};
-
-  for (unsigned i = 1; i < OrigLoopId->getNumOperands(); ++i) {
-    Metadata *MD = OrigLoopId->getOperand(i);
-    // Update the DILocations to encode the inlined-at metadata.
-    if (DILocation *DL = dyn_cast<DILocation>(MD))
-      MDs.push_back(inlineDebugLoc(DL, InlinedAt, Ctx, IANodes));
-    else
-      MDs.push_back(MD);
-  }
-
-  MDNode *NewLoopID = MDNode::getDistinct(Ctx, MDs);
-  // Insert the self-referential LoopID.
-  NewLoopID->replaceOperandWith(0, NewLoopID);
-  return NewLoopID;
-}
-
 /// Update inlined instructions' line numbers to
 /// to encode location where these instructions are inlined.
 static void fixupLineNumbers(Function *Fn, Function::iterator FI,
@@ -1415,11 +1387,11 @@ static void fixupLineNumbers(Function *Fn, Function::iterator FI,
          BI != BE; ++BI) {
       // Loop metadata needs to be updated so that the start and end locs
       // reference inlined-at locations.
-      if (MDNode *LoopID = BI->getMetadata(LLVMContext::MD_loop)) {
-        MDNode *NewLoopID =
-            inlineLoopID(LoopID, InlinedAtNode, BI->getContext(), IANodes);
-        BI->setMetadata(LLVMContext::MD_loop, NewLoopID);
-      }
+      auto updateLoopInfoLoc = [&Ctx, &InlinedAtNode, &IANodes](
+                                   const DILocation &Loc) -> DILocation * {
+        return inlineDebugLoc(&Loc, InlinedAtNode, Ctx, IANodes).get();
+      };
+      updateLoopMetadataDebugLocations(*BI, updateLoopInfoLoc);
 
       if (!NoInlineLineTables)
         if (DebugLoc DL = BI->getDebugLoc()) {