Index: llvm/lib/Analysis/InlineCost.cpp
===================================================================
--- llvm/lib/Analysis/InlineCost.cpp
+++ llvm/lib/Analysis/InlineCost.cpp
@@ -27,6 +27,7 @@
 #include "llvm/Analysis/TargetTransformInfo.h"
 #include "llvm/Analysis/ValueTracking.h"
 #include "llvm/Config/llvm-config.h"
+#include "llvm/IR/AssemblyAnnotationWriter.h"
 #include "llvm/IR/CallingConv.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/Dominators.h"
@@ -38,6 +39,7 @@
 #include "llvm/IR/PatternMatch.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
+#include "llvm/Support/FormattedStream.h"
 #include "llvm/Support/raw_ostream.h"
 
 using namespace llvm;
@@ -46,6 +48,9 @@
 
 STATISTIC(NumCallsAnalyzed, "Number of call sites analyzed");
 
+static cl::opt<bool> EnableCostAnnotationWriter("print-cost-annotation-writer",
+                                             cl::Hidden, cl::init(false));
+
 static cl::opt<int> InlineThreshold(
     "inline-threshold", cl::Hidden, cl::init(225), cl::ZeroOrMore,
     cl::desc("Control the amount of inlining to perform (default = 225)"));
@@ -94,10 +99,23 @@
 
 namespace {
 
+class CostAnnotationWriter : public AssemblyAnnotationWriter {
+public:
+  // The first value of DenseMap is the instruction with which the following
+  // pair of Cost and Threshold is associated.
+  llvm::DenseMap <const Instruction *, std::pair<int, int>> CostThresholdMap;
+
+  virtual void emitInstructionAnnot(const llvm::Instruction *I,
+                                    llvm::formatted_raw_ostream &OS);
+};
+
 class CallAnalyzer : public InstVisitor<CallAnalyzer, bool> {
   typedef InstVisitor<CallAnalyzer, bool> Base;
   friend class InstVisitor<CallAnalyzer, bool>;
 
+  /// Annotation Writer for cost annotation
+  CostAnnotationWriter Writer;
+
   /// The TargetTransformInfo available for this compilation.
   const TargetTransformInfo &TTI;
 
@@ -363,6 +381,17 @@
   disableLoadElimination();
 }
 
+void CostAnnotationWriter::emitInstructionAnnot(
+    const Instruction *I, formatted_raw_ostream &OS) {
+    // The cost of inlining of the given instruction is printed always.
+    // The threshold delta is printed only when it is non-zero. It happens
+    // when we decided to give a bonus at a particular instruction.
+    OS << "; cost = " << CostThresholdMap[I].first;
+    if (CostThresholdMap[I].second)
+        OS << ", threshold delta = " << CostThresholdMap[I].second;
+    OS << "\n";
+}
+
 /// If 'V' maps to a SROA candidate, disable SROA for it.
 void CallAnalyzer::disableSROA(Value *V) {
   Value *SROAArg;
@@ -1585,12 +1614,21 @@
     // instruction. Visit the instructions using our InstVisitor to account for
     // all of the per-instruction logic. The visit tree returns true if we
     // consumed the instruction in any way, and false if the instruction's base
-    // cost should count against inlining.
+    // cost should count against inlining. The deltas are saved for the
+    // CostAnnotationWriter.
+    int InitialCost = getCost();
+    int InitialThreshold = getThreshold();
+
     if (Base::visit(&*I))
       ++NumInstructionsSimplified;
     else
       addCost(InlineConstants::InstrCost);
 
+    if (EnableCostAnnotationWriter)
+    {
+        Writer.CostThresholdMap[&*I].first = getCost() - InitialCost;
+        Writer.CostThresholdMap[&*I].second = getThreshold() - InitialThreshold;
+    }
     using namespace ore;
     // If the visit this instruction detected an uninlinable pattern, abort.
     InlineResult IR;
@@ -1943,6 +1981,8 @@
 /// Dump stats about this call's analysis.
 LLVM_DUMP_METHOD void CallAnalyzer::dump() {
 #define DEBUG_PRINT_STAT(x) dbgs() << "      " #x ": " << x << "\n"
+  if (EnableCostAnnotationWriter)
+    F.print(dbgs(), &Writer);
   DEBUG_PRINT_STAT(NumConstantArgs);
   DEBUG_PRINT_STAT(NumConstantOffsetPtrArgs);
   DEBUG_PRINT_STAT(NumAllocaArgs);