Fix the InstCombine to reserve the VP metadata and sets correct call count.

Summary: Currently the VP metadata was dropped when InstCombine converts a call to direct call. This patch converts the VP metadata to branch_weights so that its hotness is recorded.

Reviewers: eraman, davidxl

Reviewed By: davidxl

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D31344

llvm-svn: 299228

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index f3fc1e2d631..71ca14dee58 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -4143,6 +4143,12 @@ bool InstCombiner::transformConstExprCastCall(CallSite CS) {
     CallInst *CI = cast<CallInst>(Caller);
     NC = Builder->CreateCall(Callee, Args, OpBundles);
     NC->takeName(CI);
+    // Preserve the weight metadata for the new call instruction. The metadata
+    // is used by SamplePGO to check callsite's hotness.
+    uint64_t W;
+    if (CI->extractProfTotalWeight(W))
+      NC->setProfWeight(W);
+
     cast<CallInst>(NC)->setTailCallKind(CI->getTailCallKind());
     cast<CallInst>(NC)->setCallingConv(CI->getCallingConv());
     cast<CallInst>(NC)->setAttributes(NewCallerPAL);