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

[vsk]

Summary

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

[vsk]

This was committed in a2cc80bc95703b99afefddb1d9d545c639ac4ff5.

llvm/include/llvm/IR/DebugInfo.h

 // the information in the global variables that's needed when constructing the
 // DWARF information.
 //
 //===----------------------------------------------------------------------===//
 
 #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"
 #include "llvm/IR/DebugInfoMetadata.h"
 
 namespace llvm {
 
 class DbgDeclareInst;
 class DbgValueInst;
+class Instruction;
 class Module;
 
 /// Find subprogram that is enclosing this scope.
 DISubprogram *getDISubprogram(const MDNode *Scope);
 
 /// Strip debug info in the module if it exists.
 ///
 /// To do this, we remove all calls to the debugger intrinsics and any named

 ///   1) Delete all debug intrinsics.
 ///   2) Delete all non-CU named metadata debug info nodes.
 ///   3) Create new DebugLocs for each instruction.
 ///   4) Create a new CU debug info, and similarly for every metadata node
 ///      that's reachable from the CU debug info.
 ///   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);
 
 /// Utility to find all debug info in a module.
 ///
 /// DebugInfoFinder tries to list all debug info MDNodes used in a module. To
 /// list debug info MDNodes used by an instruction, DebugInfoFinder uses
 /// processDeclare, processValue and processLocation to handle DbgDeclareInst,

llvm/lib/IR/DebugInfo.cpp

bool DebugInfoFinder::addScope(DIScope *Scope) {
   if (Scope->getNumOperands() == 0)
     return false;
   if (!NodesSeen.insert(Scope).second)
     return false;
   Scopes.push_back(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?");
 
   // if there is no debug location, we do not have to rewrite this MDNode.
   if (std::none_of(N->op_begin() + 1, N->op_end(), [](const MDOperand &Op) {
         return isa<DILocation>(Op.get());
       }))
     return N;
 
   // If there is only the debug location without any actual loop metadata, we
   // can remove the metadata.
   if (std::none_of(N->op_begin() + 1, N->op_end(), [](const MDOperand &Op) {
         return !isa<DILocation>(Op.get());
       }))
     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) {
   bool Changed = false;
   if (F.hasMetadata(LLVMContext::MD_dbg)) {
     Changed = true;
     F.setSubprogram(nullptr);
   }

llvm/lib/Transforms/Utils/InlineFunction.cpp

 static DebugLoc inlineDebugLoc(DebugLoc OrigDL, DILocation *InlinedAt,
                                LLVMContext &Ctx,
                                DenseMap<const MDNode *, MDNode *> &IANodes) {
   auto IA = DebugLoc::appendInlinedAt(OrigDL, InlinedAt, Ctx, IANodes);
   return DebugLoc::get(OrigDL.getLine(), OrigDL.getCol(), OrigDL.getScope(),
                        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,
                              Instruction *TheCall, bool CalleeHasDebugInfo) {
   const DebugLoc &TheCallDL = TheCall->getDebugLoc();
   if (!TheCallDL)
     return;
 
static void fixupLineNumbers(Function *Fn, Function::iterator FI,
   // the call site location instead.
   bool NoInlineLineTables = Fn->hasFnAttribute("no-inline-line-tables");
 
   for (; FI != Fn->end(); ++FI) {
     for (BasicBlock::iterator BI = FI->begin(), BE = FI->end();
          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()) {
           DebugLoc IDL =
               inlineDebugLoc(DL, InlinedAtNode, BI->getContext(), IANodes);
           BI->setDebugLoc(IDL);
           continue;
         }