[llvm-branch-commits] [llvm][IR] Extend BranchWeightMetadata to track provenance of weights (PR #86609)

[Matthias Braun via llvm-branch-commits]

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@@ -1210,12 +1210,22 @@ Instruction *Instruction::cloneImpl() const {
 
 void Instruction::swapProfMetadata() {
   MDNode *ProfileData = getBranchWeightMDNode(*this);
-  if (!ProfileData || ProfileData->getNumOperands() != 3)
+  if (!isBranchWeightMD(ProfileData))
     return;
 
-  // The first operand is the name. Fetch them backwards and build a new one.
-  Metadata *Ops[] = {ProfileData->getOperand(0), ProfileData->getOperand(2),
-                     ProfileData->getOperand(1)};
+  SmallVector<Metadata *, 4> Ops;
+  unsigned int FirstIdx = getBranchWeightOffset(ProfileData);
+  unsigned int SecondIdx = FirstIdx + 1;
+  // If there are more weights past the second, we can't swap them
+  if (ProfileData->getNumOperands() > SecondIdx + 1)
+    return;
+  Ops.push_back(ProfileData->getOperand(0));
+  if (hasExpectedProvenance(ProfileData)) {
+    Ops.push_back(ProfileData->getOperand(1));
+  }
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MatzeB wrote:

Maybe this (I just have a feeling that leaving it more generic may help in case new sources are added one day):

```suggestion
  for (unsigned I = 0; I < FirstIdx; I++) {
     Ops.push_back(ProfileData->getOperand(I));
 }
```

https://github.com/llvm/llvm-project/pull/86609