[AMDGPU] Add perf hints to functions

This is adoption of HSAIL perfhint pass. Two types of hints are produced:

1. Function is memory bound.
2. Kernel can use wave limiter.

Currently these hints are used in the scheduler. If a function is suspected
to be memory bound we allow occupancy to decrease to 4 waves in the course
of scheduling.

Differential Revision: https://reviews.llvm.org/D46992

llvm-svn: 333289

1 files changed, 55 insertions, 0 deletions

diff --git a/llvm/lib/Target/AMDGPU/AMDGPUPerfHintAnalysis.h b/llvm/lib/Target/AMDGPU/AMDGPUPerfHintAnalysis.h
new file mode 100644
index 00000000000..0dfaf08a134
--- /dev/null
+++ b/llvm/lib/Target/AMDGPU/AMDGPUPerfHintAnalysis.h
@@ -0,0 +1,55 @@
+//===- AMDGPUPerfHintAnalysis.h - analysis of functions memory traffic ----===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+/// \file
+/// \brief Analyzes if a function potentially memory bound and if a kernel
+/// kernel may benefit from limiting number of waves to reduce cache thrashing.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIB_TARGET_AMDGPU_MDGPUPERFHINTANALYSIS_H
+#define LLVM_LIB_TARGET_AMDGPU_MDGPUPERFHINTANALYSIS_H
+#include "llvm/IR/ValueMap.h"
+#include "llvm/Pass.h"
+
+namespace llvm {
+
+struct AMDGPUPerfHintAnalysis : public FunctionPass {
+  static char ID;
+
+public:
+  AMDGPUPerfHintAnalysis() : FunctionPass(ID) {}
+
+  bool runOnFunction(Function &F) override;
+
+  void getAnalysisUsage(AnalysisUsage &AU) const {
+    AU.setPreservesAll();
+  }
+
+  bool isMemoryBound(const Function *F) const;
+
+  bool needsWaveLimiter(const Function *F) const;
+
+  struct FuncInfo {
+    unsigned MemInstCount;
+    unsigned InstCount;
+    unsigned IAMInstCount; // Indirect access memory instruction count
+    unsigned LSMInstCount; // Large stride memory instruction count
+    FuncInfo() : MemInstCount(0), InstCount(0), IAMInstCount(0),
+                 LSMInstCount(0) {}
+  };
+
+  typedef ValueMap<const Function*, FuncInfo> FuncInfoMap;
+
+private:
+
+  FuncInfoMap FIM;
+};
+} // namespace llvm
+#endif // LLVM_LIB_TARGET_AMDGPU_MDGPUPERFHINTANALYSIS_H