[clang] [llvm] Reapply "[llvm][IR] Extend BranchWeightMetadata to track provenance o… (PR #95281)

[David Li via cfe-commits]

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@@ -241,9 +264,11 @@ void scaleProfData(Instruction &I, uint64_t S, uint64_t T) {
   if (ProfDataName->getString() == "branch_weights" &&
       ProfileData->getNumOperands() > 0) {
     // Using APInt::div may be expensive, but most cases should fit 64 bits.
-    APInt Val(128, mdconst::dyn_extract<ConstantInt>(ProfileData->getOperand(1))
-                       ->getValue()
-                       .getZExtValue());
+    APInt Val(128,
+              mdconst::dyn_extract<ConstantInt>(
+                  ProfileData->getOperand(getBranchWeightOffset(ProfileData)))
+                  ->getValue()
+                  .getZExtValue());
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david-xl wrote:

How can we prevent this in the future? Is it possible to put branch origin data at the end? If not, probably better introduce some helper to get branch weight instead of doing getOperand(getBranchWeightOffset(..)).

https://github.com/llvm/llvm-project/pull/95281