Add a cost model analysis that allows us to estimate the cost of IR-level instructions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167324 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 175 insertions, 0 deletions

diff --git a/lib/Analysis/CostModel.cpp b/lib/Analysis/CostModel.cpp
new file mode 100644
index 0000000000..142d287384
--- /dev/null
+++ b/lib/Analysis/CostModel.cpp
@@ -0,0 +1,175 @@
+//===- CostModel.cpp ------ Cost Model Analysis ---------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the cost model analysis. It provides a very basic cost
+// estimation for LLVM-IR. The cost result can be thought of as cycles, but it
+// is really unit-less. The estimated cost is ment to be used for comparing
+// alternatives.
+//
+//===----------------------------------------------------------------------===//
+
+#define CM_NAME "cost-model"
+#define DEBUG_TYPE CM_NAME
+#include "llvm/Analysis/Passes.h"
+#include "llvm/Function.h"
+#include "llvm/Instructions.h"
+#include "llvm/Pass.h"
+#include "llvm/TargetTransformInfo.h"
+#include "llvm/Value.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+using namespace llvm;
+
+namespace {
+  class CostModelAnalysis : public FunctionPass {
+
+  public:
+    static char ID; // Class identification, replacement for typeinfo
+    CostModelAnalysis() : FunctionPass(ID), F(0), VTTI(0) {
+      initializeCostModelAnalysisPass(
+        *PassRegistry::getPassRegistry());
+    }
+
+    /// Returns the expected cost of the instruction.
+    /// Returns -1 if the cost is unknown.
+    /// Note, this method does not cache the cost calculation and it
+    /// can be expensive in some cases.
+    unsigned getInstructionCost(Instruction *I) const;
+
+  private:
+    virtual void getAnalysisUsage(AnalysisUsage &AU) const;
+    virtual bool runOnFunction(Function &F);
+    virtual void print(raw_ostream &OS, const Module*) const;
+
+    /// The function that we analyze.
+    Function *F;
+    /// Vector target information.
+    const VectorTargetTransformInfo *VTTI;
+  };
+}  // End of anonymous namespace
+
+// Register this pass.
+char CostModelAnalysis::ID = 0;
+static const char cm_name[] = "Cost Model Analysis";
+INITIALIZE_PASS_BEGIN(CostModelAnalysis, CM_NAME, cm_name, false, true)
+INITIALIZE_PASS_END  (CostModelAnalysis, CM_NAME, cm_name, false, true)
+
+FunctionPass *llvm::createCostModelAnalysisPass() {
+  return new CostModelAnalysis();
+}
+
+void
+CostModelAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
+  AU.setPreservesAll();
+}
+
+bool
+CostModelAnalysis::runOnFunction(Function &F) {
+ this->F = &F;
+
+ // Target information.
+ TargetTransformInfo *TTI;
+ TTI = getAnalysisIfAvailable<TargetTransformInfo>();
+ if (TTI)
+   VTTI = TTI->getVectorTargetTransformInfo();
+
+ return false;
+}
+
+unsigned CostModelAnalysis::getInstructionCost(Instruction *I) const {
+  if (!VTTI)
+    return -1;
+
+  switch (I->getOpcode()) {
+  case Instruction::Ret:
+  case Instruction::PHI:
+  case Instruction::Br: {
+    return VTTI->getCFInstrCost(I->getOpcode());
+  }
+  case Instruction::Add:
+  case Instruction::FAdd:
+  case Instruction::Sub:
+  case Instruction::FSub:
+  case Instruction::Mul:
+  case Instruction::FMul:
+  case Instruction::UDiv:
+  case Instruction::SDiv:
+  case Instruction::FDiv:
+  case Instruction::URem:
+  case Instruction::SRem:
+  case Instruction::FRem:
+  case Instruction::Shl:
+  case Instruction::LShr:
+  case Instruction::AShr:
+  case Instruction::And:
+  case Instruction::Or:
+  case Instruction::Xor: {
+    return VTTI->getArithmeticInstrCost(I->getOpcode(), I->getType());
+  }
+  case Instruction::Select: {
+    SelectInst *SI = cast<SelectInst>(I);
+    Type *CondTy = SI->getCondition()->getType();
+    return VTTI->getCmpSelInstrCost(I->getOpcode(), I->getType(), CondTy);
+  }
+  case Instruction::ICmp:
+  case Instruction::FCmp: {
+    Type *ValTy = I->getOperand(0)->getType();
+    return VTTI->getCmpSelInstrCost(I->getOpcode(), ValTy);
+  }
+  case Instruction::Store: {
+    StoreInst *SI = cast<StoreInst>(I);
+    Type *ValTy = SI->getValueOperand()->getType();
+    return VTTI->getMemoryOpCost(I->getOpcode(), ValTy,
+                                 SI->getAlignment(),
+                                 SI->getPointerAddressSpace());
+  }
+  case Instruction::Load: {
+    LoadInst *LI = cast<LoadInst>(I);
+    return VTTI->getMemoryOpCost(I->getOpcode(), I->getType(),
+                                 LI->getAlignment(),
+                                 LI->getPointerAddressSpace());
+  }
+  case Instruction::ZExt:
+  case Instruction::SExt:
+  case Instruction::FPToUI:
+  case Instruction::FPToSI:
+  case Instruction::FPExt:
+  case Instruction::PtrToInt:
+  case Instruction::IntToPtr:
+  case Instruction::SIToFP:
+  case Instruction::UIToFP:
+  case Instruction::Trunc:
+  case Instruction::FPTrunc:
+  case Instruction::BitCast: {
+    Type *SrcTy = I->getOperand(0)->getType();
+    return VTTI->getCastInstrCost(I->getOpcode(), I->getType(), SrcTy);
+  }
+  default:
+    // We don't have any information on this instruction.
+    return -1;
+  }
+}
+
+void CostModelAnalysis::print(raw_ostream &OS, const Module*) const {
+  if (!F)
+    return;
+
+  for (Function::iterator B = F->begin(), BE = F->end(); B != BE; ++B) {
+    for (BasicBlock::iterator it = B->begin(), e = B->end(); it != e; ++it) {
+      Instruction *Inst = it;
+      unsigned Cost = getInstructionCost(Inst);
+      if (Cost != (unsigned)-1)
+        OS << "Cost Model: Found an estimated cost of " << Cost;
+      else
+        OS << "Cost Model: Unknown cost";
+
+      OS << " for instruction: "<< *Inst << "\n";
+    }
+  }
+}