[DebugInfo] Update loop metadata for inlined loops

Summary:
Currently, when a loop is cloned while inlining function (A) into function (B) the loop metadata is copied and then not modified at all. The loop metadata can encode the loop's start and end DILocations. Therefore, the new inlined loop in function (B) may have loop metadata which shows start and end locations residing in function (A).

This patch ensures loop metadata is updated while inlining so that the start and end DILocations are given the "inlinedAt" operand. I've also added a regression test for this.

This fix is required for D60831 because that patch uses loop metadata to determine the DILocation for the branches of new loop preheaders.

Reviewers: aprantl, dblaikie, anemet

Reviewed By: aprantl

Subscribers: eraman, hiraditya, llvm-commits

Tags: #debug-info, #llvm

Differential Revision: https://reviews.llvm.org/D61933

llvm-svn: 361132

1 files changed, 48 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/Utils/InlineFunction.cpp b/llvm/lib/Transforms/Utils/InlineFunction.cpp
index 6438d2d..9bcc0434 100644
--- a/llvm/lib/Transforms/Utils/InlineFunction.cpp
+++ b/llvm/lib/Transforms/Utils/InlineFunction.cpp
@@ -1351,6 +1351,44 @@ static bool allocaWouldBeStaticInEntry(const AllocaInst *AI ) {
   return isa<Constant>(AI->getArraySize()) && !AI->isUsedWithInAlloca();
 }
 
+/// Returns a DebugLoc for a new DILocation which is a clone of \p OrigDL
+/// inlined at \p InlinedAt. \p IANodes is an inlined-at cache.
+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,
@@ -1376,10 +1414,17 @@ static void fixupLineNumbers(Function *Fn, Function::iterator FI,
   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);
+      }
+
       if (DebugLoc DL = BI->getDebugLoc()) {
-        auto IA = DebugLoc::appendInlinedAt(DL, InlinedAtNode, BI->getContext(),
-                                            IANodes);
-        auto IDL = DebugLoc::get(DL.getLine(), DL.getCol(), DL.getScope(), IA);
+        DebugLoc IDL =
+            inlineDebugLoc(DL, InlinedAtNode, BI->getContext(), IANodes);
         BI->setDebugLoc(IDL);
         continue;
       }