Add function entry count metadata.

Summary:
This adds three Function methods to handle function entry counts:
setEntryCount() and getEntryCount().

Entry counts are stored under the MD_prof metadata node with the name
"function_entry_count". They are unsigned 64 bit values set by profilers
(instrumentation and sample profiler changes coming up).

Added documentation for new profile metadata and tests.

Reviewers: dexonsmith, bogner

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D9628

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237260 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/docs/BranchWeightMetadata.rst b/docs/BranchWeightMetadata.rst
index aff7923d18656d4531208c9e0afefabf8fbc0a11..2ebc6c32416eaf2281d58b4f6cb3e2348a1cc008 100644 (file)
--- a/docs/BranchWeightMetadata.rst
+++ b/docs/BranchWeightMetadata.rst
@@ -115,3 +115,26 @@ CFG Modifications
 Branch Weight Metatada is not proof against CFG changes. If terminator operands'
 are changed some action should be taken. In other case some misoptimizations may
 occur due to incorrent branch prediction information.
+
+Function Entry Counts
+=====================
+
+To allow comparing different functions durint inter-procedural analysis and
+optimization, ``MD_prof`` nodes can also be assigned to a function definition.
+The first operand is a string indicating the name of the associated counter.
+
+Currently, one counter is supported: "function_entry_count". This is a 64-bit
+counter that indicates the number of times that this function was invoked (in
+the case of instrumentation-based profiles). In the case of sampling-based
+profiles, this counter is an approximation of how many times the function was
+invoked.
+
+For example, in the code below, the instrumentation for function foo()
+indicates that it was called 2,590 times at runtime.
+
+.. code-block:: llvm
+
+  define i32 @foo() !prof !1 {
+    ret i32 0
+  }
+  !1 = !{!"function_entry_count", i64 2590}

diff --git a/include/llvm/IR/Function.h b/include/llvm/IR/Function.h
index 3ec080aeb0608d60bc6816915703cc81d3ada4b4..33602a3a8c194d2e3867f446e9dd68c2fed30072 100644 (file)
--- a/include/llvm/IR/Function.h
+++ b/include/llvm/IR/Function.h
@@ -19,6 +19,7 @@
 #define LLVM_IR_FUNCTION_H
 
 #include "llvm/ADT/iterator_range.h"
+#include "llvm/ADT/Optional.h"
 #include "llvm/IR/Argument.h"
 #include "llvm/IR/Attributes.h"
 #include "llvm/IR/BasicBlock.h"
@@ -194,6 +195,12 @@ public:
                                  AttributeSet::FunctionIndex, Kind, Value));
   }
 
+  /// Set the entry count for this function.
+  void setEntryCount(uint64_t Count);
+
+  /// Get the entry count for this function.
+  Optional<uint64_t> getEntryCount() const;
+
   /// @brief Return true if the function has the attribute.
   bool hasFnAttribute(Attribute::AttrKind Kind) const {
     return AttributeSets.hasAttribute(AttributeSet::FunctionIndex, Kind);

diff --git a/include/llvm/IR/MDBuilder.h b/include/llvm/IR/MDBuilder.h
index 51b8b02d8e6d03c0e3f4b14562fbc9032ecf4b56..ba14457f71855ee5a55a01271971161696bde7f6 100644 (file)
--- a/include/llvm/IR/MDBuilder.h
+++ b/include/llvm/IR/MDBuilder.h
@@ -60,6 +60,9 @@ public:
   /// \brief Return metadata containing a number of branch weights.
   MDNode *createBranchWeights(ArrayRef<uint32_t> Weights);
 
+  /// Return metadata containing the entry count for a function.
+  MDNode *createFunctionEntryCount(uint64_t Count);
+
   //===------------------------------------------------------------------===//
   // Range metadata.
   //===------------------------------------------------------------------===//

diff --git a/lib/IR/Function.cpp b/lib/IR/Function.cpp
index f312f711c60c2bef978e9a68d672c7ec61c3e0df..a5d4d1c4b1e15c5ba4e7636010fb965b4a483835 100644 (file)
--- a/lib/IR/Function.cpp
+++ b/lib/IR/Function.cpp
@@ -19,10 +19,13 @@
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/CodeGen/ValueTypes.h"
 #include "llvm/IR/CallSite.h"
+#include "llvm/IR/Constants.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/InstIterator.h"
 #include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/MDBuilder.h"
+#include "llvm/IR/Metadata.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Support/ManagedStatic.h"
 #include "llvm/Support/RWMutex.h"
@@ -986,3 +989,19 @@ void llvm::overrideFunctionAttribute(StringRef Kind, StringRef Value,
   Attrs = Attrs.addAttribute(Ctx, AttributeSet::FunctionIndex, Kind, Value);
   F.setAttributes(Attrs);
 }
+
+void Function::setEntryCount(uint64_t Count) {
+  MDBuilder MDB(getContext());
+  setMetadata(LLVMContext::MD_prof, MDB.createFunctionEntryCount(Count));
+}
+
+Optional<uint64_t> Function::getEntryCount() const {
+  MDNode *MD = getMetadata(LLVMContext::MD_prof);
+  if (MD && MD->getOperand(0))
+    if (MDString *MDS = dyn_cast<MDString>(MD->getOperand(0)))
+      if (MDS->getString().equals("function_entry_count")) {
+        ConstantInt *CI = mdconst::extract<ConstantInt>(MD->getOperand(1));
+        return CI->getValue().getZExtValue();
+      }
+  return None;
+}

diff --git a/lib/IR/MDBuilder.cpp b/lib/IR/MDBuilder.cpp
index a9010114044a44c645210af546ccc1e5b65acfd5..354592df4c96750a7022d77d81908659b82788f5 100644 (file)
--- a/lib/IR/MDBuilder.cpp
+++ b/lib/IR/MDBuilder.cpp
@@ -53,6 +53,16 @@ MDNode *MDBuilder::createBranchWeights(ArrayRef<uint32_t> Weights) {
   return MDNode::get(Context, Vals);
 }
 
+MDNode *MDBuilder::createFunctionEntryCount(uint64_t Count) {
+  SmallVector<Metadata *, 2> Vals(2);
+  Vals[0] = createString("function_entry_count");
+
+  Type *Int64Ty = Type::getInt64Ty(Context);
+  Vals[1] = createConstant(ConstantInt::get(Int64Ty, Count));
+
+  return MDNode::get(Context, Vals);
+}
+
 MDNode *MDBuilder::createRange(const APInt &Lo, const APInt &Hi) {
   assert(Lo.getBitWidth() == Hi.getBitWidth() && "Mismatched bitwidths!");
 

diff --git a/lib/IR/Verifier.cpp b/lib/IR/Verifier.cpp
index 003b6064cbe2f2ae4418133ec0d145d701369b8b..4e863cb99b5cd40f816ca10f5bf81f2748d51ee0 100644 (file)
--- a/lib/IR/Verifier.cpp
+++ b/lib/IR/Verifier.cpp
@@ -400,6 +400,8 @@ private:
                             bool isReturnValue, const Value *V);
   void VerifyFunctionAttrs(FunctionType *FT, AttributeSet Attrs,
                            const Value *V);
+  void VerifyFunctionMetadata(
+      const SmallVector<std::pair<unsigned, MDNode *>, 4> MDs);
 
   void VerifyConstantExprBitcastType(const ConstantExpr *CE);
   void VerifyStatepoint(ImmutableCallSite CS);
@@ -1463,6 +1465,36 @@ void Verifier::VerifyFunctionAttrs(FunctionType *FT, AttributeSet Attrs,
   }
 }
 
+void Verifier::VerifyFunctionMetadata(
+    const SmallVector<std::pair<unsigned, MDNode *>, 4> MDs) {
+  if (MDs.empty())
+    return;
+
+  for (unsigned i = 0; i < MDs.size(); i++) {
+    if (MDs[i].first == LLVMContext::MD_prof) {
+      MDNode *MD = MDs[i].second;
+      Assert(MD->getNumOperands() == 2,
+             "!prof annotations should have exactly 2 operands", MD);
+
+      // Check first operand.
+      Assert(MD->getOperand(0) != nullptr, "first operand should not be null",
+             MD);
+      Assert(isa<MDString>(MD->getOperand(0)),
+             "expected string with name of the !prof annotation", MD);
+      MDString *MDS = cast<MDString>(MD->getOperand(0));
+      StringRef ProfName = MDS->getString();
+      Assert(ProfName.equals("function_entry_count"),
+             "first operand should be 'function_entry_count'", MD);
+
+      // Check second operand.
+      Assert(MD->getOperand(1) != nullptr, "second operand should not be null",
+             MD);
+      Assert(isa<ConstantAsMetadata>(MD->getOperand(1)),
+             "expected integer argument to function_entry_count", MD);
+    }
+  }
+}
+
 void Verifier::VerifyConstantExprBitcastType(const ConstantExpr *CE) {
   if (CE->getOpcode() != Instruction::BitCast)
     return;
@@ -1713,6 +1745,7 @@ void Verifier::visitFunction(const Function &F) {
   SmallVector<std::pair<unsigned, MDNode *>, 4> MDs;
   F.getAllMetadata(MDs);
   assert(F.hasMetadata() != MDs.empty() && "Bit out-of-sync");
+  VerifyFunctionMetadata(MDs);
 
   if (F.isMaterializable()) {
     // Function has a body somewhere we can't see.

diff --git a/test/Verifier/function-metadata-bad.ll b/test/Verifier/function-metadata-bad.ll
new file mode 100644 (file)
index 0000000..9e7ba22
--- /dev/null
+++ b/test/Verifier/function-metadata-bad.ll
@@ -0,0 +1,35 @@
+; RUN: not llvm-as < %s -o /dev/null 2>&1 | FileCheck %s
+
+define i32 @bad1() !prof !0 {
+  ret i32 0
+}
+
+!0 = !{i32 123, i32 3}
+; CHECK: assembly parsed, but does not verify as correct!
+; CHECK-NEXT: expected string with name of the !prof annotation
+; CHECK-NEXT: !0 = !{i32 123, i32 3}
+
+define i32 @bad2() !prof !1 {
+  ret i32 0
+}
+
+!1 = !{!"function_entry_count"}
+; CHECK-NEXT: !prof annotations should have exactly 2 operands
+; CHECK-NEXT: !1 = !{!"function_entry_count"}
+
+
+define i32 @bad3() !prof !2 {
+  ret i32 0
+}
+
+!2 = !{!"some_other_count", i64 200}
+; CHECK-NEXT: first operand should be 'function_entry_count'
+; CHECK-NEXT: !2 = !{!"some_other_count", i64 200}
+
+define i32 @bad4() !prof !3 {
+  ret i32 0
+}
+
+!3 = !{!"function_entry_count", !"string"}
+; CHECK-NEXT: expected integer argument to function_entry_count
+; CHECK-NEXT: !3 = !{!"function_entry_count", !"string"}

diff --git a/test/Verifier/function-metadata-good.ll b/test/Verifier/function-metadata-good.ll
new file mode 100644 (file)
index 0000000..3d73a1c
--- /dev/null
+++ b/test/Verifier/function-metadata-good.ll
@@ -0,0 +1,8 @@
+; RUN: llvm-as < %s -o /dev/null 2>&1
+
+; Function foo() is called 2,304 times at runtime.
+define i32 @foo() !prof !0 {
+  ret i32 0
+}
+
+!0 = !{!"function_entry_count", i32 2304}

diff --git a/unittests/IR/MetadataTest.cpp b/unittests/IR/MetadataTest.cpp
index 4b35f19ccc6a875d4828aed036366c81c8e2fca5..baba3e5bc5253fff1fcce881df42364354f01e47 100644 (file)
--- a/unittests/IR/MetadataTest.cpp
+++ b/unittests/IR/MetadataTest.cpp
@@ -2272,4 +2272,12 @@ TEST_F(FunctionAttachmentTest, Verifier) {
   EXPECT_FALSE(verifyFunction(*F));
 }
 
+TEST_F(FunctionAttachmentTest, EntryCount) {
+  Function *F = getFunction("foo");
+  EXPECT_FALSE(F->getEntryCount().hasValue());
+  F->setEntryCount(12304);
+  EXPECT_TRUE(F->getEntryCount().hasValue());
+  EXPECT_EQ(12304u, *F->getEntryCount());
+}
+
 }