PGO: instrumentation based profiling sets function attributes.

We collect a maximal function count among all functions in the pgo data file.
For functions that are hot, we set its InlineHint attribute. For functions that
are cold, we set its Cold attribute.

We currently treat functions with >= 30% of the maximal function count as hot
and functions with <= 1% of the maximal function count are treated as cold.
These two numbers are from preliminary tuning on SPEC.

This commit should not affect non-PGO builds and should boost performance on
instrumentation based PGO.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@200874 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 10 insertions, 0 deletions

diff --git a/lib/CodeGen/CodeGenPGO.h b/lib/CodeGen/CodeGenPGO.h
index 2d1193bab0..6409a10525 100644
--- a/lib/CodeGen/CodeGenPGO.h
+++ b/lib/CodeGen/CodeGenPGO.h
@@ -33,12 +33,22 @@ private:
   llvm::OwningPtr<llvm::MemoryBuffer> DataBuffer;
   /// Offsets into DataBuffer for each function's counters
   llvm::StringMap<unsigned> DataOffsets;
+  /// Execution counts for each function.
+  llvm::StringMap<uint64_t> FunctionCounts;
+  /// The maximal execution count among all functions.
+  uint64_t MaxFunctionCount;
   CodeGenModule &CGM;
 public:
   PGOProfileData(CodeGenModule &CGM, std::string Path);
   /// Fill Counts with the profile data for the given function name. Returns
   /// false on success.
   bool getFunctionCounts(StringRef MangledName, std::vector<uint64_t> &Counts);
+  /// Return true if a function is hot. If we know nothing about the function,
+  /// return false.
+  bool isHotFunction(StringRef MangledName);
+  /// Return true if a function is cold. If we know nothing about the function,
+  /// return false.
+  bool isColdFunction(StringRef MangledName);
 };
 
 /// Per-function PGO state. This class should generally not be used directly,