Updates branch_weights annotation for call instructions during inlining.

Summary: Inliner should update the branch_weights annotation to scale it to proper value.

Reviewers: davidxl, eraman

Reviewed By: eraman

Subscribers: zzheng, llvm-commits

Differential Revision: https://reviews.llvm.org/D30767

llvm-svn: 298270

1 files changed, 23 insertions, 0 deletions

diff --git a/llvm/lib/IR/Instruction.cpp b/llvm/lib/IR/Instruction.cpp
index 2ca496e2dc7..fc453d4f8d7 100644
--- a/llvm/lib/IR/Instruction.cpp
+++ b/llvm/lib/IR/Instruction.cpp
@@ -17,6 +17,7 @@
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/Module.h"
+#include "llvm/IR/MDBuilder.h"
 #include "llvm/IR/Operator.h"
 #include "llvm/IR/Type.h"
 using namespace llvm;
@@ -629,3 +630,25 @@ Instruction *Instruction::clone() const {
   New->copyMetadata(*this);
   return New;
 }
+
+void Instruction::updateProfWeight(uint64_t S, uint64_t T) {
+  auto *ProfileData = getMetadata(LLVMContext::MD_prof);
+  if (ProfileData == nullptr)
+    return;
+
+  auto *ProfDataName = dyn_cast<MDString>(ProfileData->getOperand(0));
+  if (!ProfDataName || !ProfDataName->getString().equals("branch_weights"))
+    return;
+
+  SmallVector<uint32_t, 4> Weights;
+  for (unsigned i = 1; i < ProfileData->getNumOperands(); i++) {
+    // Using APInt::div may be expensive, but most cases should fit in 64 bits.
+    APInt Val(128, mdconst::dyn_extract<ConstantInt>(ProfileData->getOperand(i))
+                       ->getValue()
+                       .getZExtValue());
+    Val *= APInt(128, S);
+    Weights.push_back(Val.udiv(APInt(128, T)).getLimitedValue());
+  }
+  MDBuilder MDB(getContext());
+  setMetadata(LLVMContext::MD_prof, MDB.createBranchWeights(Weights));
+}