From fed890ea3a948170438a963b60acc158858a7d98 Mon Sep 17 00:00:00 2001
From: Dehao Chen <dehao@google.com>
Date: Fri, 31 Mar 2017 15:59:52 +0000
Subject: [PATCH] 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
---
 llvm/lib/IR/Metadata.cpp                           | 25 +++++++++-----
 .../Transforms/InstCombine/InstCombineCalls.cpp    |  6 ++++
 .../InstCombine/cast-call-combine-prof.ll          | 38 ++++++++++++++++++++++
 3 files changed, 61 insertions(+), 8 deletions(-)
 create mode 100644 llvm/test/Transforms/InstCombine/cast-call-combine-prof.ll

diff --git a/llvm/lib/IR/Metadata.cpp b/llvm/lib/IR/Metadata.cpp
index ec96b0f..7228de3 100644
--- a/llvm/lib/IR/Metadata.cpp
+++ b/llvm/lib/IR/Metadata.cpp
@@ -1337,17 +1337,26 @@ bool Instruction::extractProfTotalWeight(uint64_t &TotalVal) const {
     return false;
 
   auto *ProfDataName = dyn_cast<MDString>(ProfileData->getOperand(0));
-  if (!ProfDataName || !ProfDataName->getString().equals("branch_weights"))
+  if (!ProfDataName)
     return false;
 
-  TotalVal = 0;
-  for (unsigned i = 1; i < ProfileData->getNumOperands(); i++) {
-    auto *V = mdconst::dyn_extract<ConstantInt>(ProfileData->getOperand(i));
-    if (!V)
-      return false;
-    TotalVal += V->getValue().getZExtValue();
+  if (ProfDataName->getString().equals("branch_weights")) {
+    TotalVal = 0;
+    for (unsigned i = 1; i < ProfileData->getNumOperands(); i++) {
+      auto *V = mdconst::dyn_extract<ConstantInt>(ProfileData->getOperand(i));
+      if (!V)
+        return false;
+      TotalVal += V->getValue().getZExtValue();
+    }
+    return true;
+  } else if (ProfDataName->getString().equals("VP") &&
+             ProfileData->getNumOperands() > 3) {
+    TotalVal = mdconst::dyn_extract<ConstantInt>(ProfileData->getOperand(2))
+                   ->getValue()
+                   .getZExtValue();
+    return true;
   }
-  return true;
+  return false;
 }
 
 void Instruction::clearMetadataHashEntries() {
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index f3fc1e2..71ca14d 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);
diff --git a/llvm/test/Transforms/InstCombine/cast-call-combine-prof.ll b/llvm/test/Transforms/InstCombine/cast-call-combine-prof.ll
new file mode 100644
index 0000000..e48c14c
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/cast-call-combine-prof.ll
@@ -0,0 +1,38 @@
+; RUN: opt -instcombine -inline -S -inline-threshold=0 -hot-callsite-threshold=100 < %s | FileCheck %s
+; Checks if VP profile is used for hotness checks in inlining after instcombine
+; converted the call to a direct call.
+
+declare void @bar(i16 *)
+
+define void @foo(i16* %a) {
+  call void @bar(i16* %a)
+  call void @bar(i16* %a)
+  ret void
+}
+
+; CHECK-LABEL: @test()
+; CHECK-NEXT: call void @bar
+; CHECK-NEXT: call void @bar
+define void @test() {
+  call void bitcast (void (i16*)* @foo to void (i8*)*) (i8* null), !prof !0
+  ret void
+}
+
+!0 = !{!"VP", i32 0, i64 2000, i64 -3913987384944532146, i64 2000}
+
+!llvm.module.flags = !{!1}
+
+!1 = !{i32 1, !"ProfileSummary", !2}
+!2 = !{!3, !4, !5, !6, !7, !8, !9, !10}
+!3 = !{!"ProfileFormat", !"InstrProf"}
+!4 = !{!"TotalCount", i64 10000}
+!5 = !{!"MaxCount", i64 1000}
+!6 = !{!"MaxInternalCount", i64 1}
+!7 = !{!"MaxFunctionCount", i64 1000}
+!8 = !{!"NumCounts", i64 3}
+!9 = !{!"NumFunctions", i64 3}
+!10 = !{!"DetailedSummary", !11}
+!11 = !{!12, !13, !14}
+!12 = !{i32 10000, i64 1000, i32 1}
+!13 = !{i32 999000, i64 1000, i32 1}
+!14 = !{i32 999999, i64 1, i32 2}
-- 
2.7.4