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llvm-mirror/lib/Target/SparcV9/ModuloScheduling/DependenceAnalyzer.cpp
Chris Lattner aafc339b4e Add explicit #includes of <iostream>
llvm-svn: 25515
2006-01-22 23:41:00 +00:00

306 lines
9.4 KiB
C++

//===-- DependenceAnalyzer.cpp - DependenceAnalyzer ------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
//
//
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "ModuloSched"
#include "DependenceAnalyzer.h"
#include "llvm/Type.h"
#include "llvm/Support/Debug.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Constants.h"
#include <iostream>
using namespace llvm;
namespace llvm {
/// Create ModuloSchedulingPass
FunctionPass *createDependenceAnalyzer() {
return new DependenceAnalyzer();
}
}
Statistic<> NoDeps("depanalyzer-nodeps", "Number of dependences eliminated");
Statistic<> NumDeps("depanalyzer-deps",
"Number of dependences could not eliminate");
Statistic<> AdvDeps("depanalyzer-advdeps",
"Number of dependences using advanced techniques");
bool DependenceAnalyzer::runOnFunction(Function &F) {
AA = &getAnalysis<AliasAnalysis>();
TD = &getAnalysis<TargetData>();
SE = &getAnalysis<ScalarEvolution>();
return false;
}
static RegisterAnalysis<DependenceAnalyzer>X("depanalyzer",
"Dependence Analyzer");
// - Get inter and intra dependences between loads and stores
//
// Overview of Method:
// Step 1: Use alias analysis to determine dependencies if values are loop
// invariant
// Step 2: If pointers are not GEP, then there is a dependence.
// Step 3: Compare GEP base pointers with AA. If no alias, no dependence.
// If may alias, then add a dependence. If must alias, then analyze
// further (Step 4)
// Step 4: do advanced analysis
void DependenceAnalyzer::AnalyzeDeps(Value *val, Value *val2, bool valLoad,
bool val2Load,
std::vector<Dependence> &deps,
BasicBlock *BB,
bool srcBeforeDest) {
bool loopInvariant = true;
//Check if both are instructions and prove not loop invariant if possible
if(Instruction *valInst = dyn_cast<Instruction>(val))
if(valInst->getParent() == BB)
loopInvariant = false;
if(Instruction *val2Inst = dyn_cast<Instruction>(val2))
if(val2Inst->getParent() == BB)
loopInvariant = false;
//If Loop invariant, let AA decide
if(loopInvariant) {
if(AA->alias(val, (unsigned)TD->getTypeSize(val->getType()),
val2,(unsigned)TD->getTypeSize(val2->getType()))
!= AliasAnalysis::NoAlias) {
createDep(deps, valLoad, val2Load, srcBeforeDest);
}
else
++NoDeps;
return;
}
//Otherwise, continue with step 2
GetElementPtrInst *GP = dyn_cast<GetElementPtrInst>(val);
GetElementPtrInst *GP2 = dyn_cast<GetElementPtrInst>(val2);
//If both are not GP instructions, we can not do further analysis
if(!GP || !GP2) {
createDep(deps, valLoad, val2Load, srcBeforeDest);
return;
}
//Otherwise, compare GEP bases (op #0) with Alias Analysis
Value *GPop = GP->getOperand(0);
Value *GP2op = GP2->getOperand(0);
int alias = AA->alias(GPop, (unsigned)TD->getTypeSize(GPop->getType()),
GP2op,(unsigned)TD->getTypeSize(GP2op->getType()));
if(alias == AliasAnalysis::MustAlias) {
//Further dep analysis to do
advancedDepAnalysis(GP, GP2, valLoad, val2Load, deps, srcBeforeDest);
++AdvDeps;
}
else if(alias == AliasAnalysis::MayAlias) {
createDep(deps, valLoad, val2Load, srcBeforeDest);
}
//Otherwise no dependence since there is no alias
else
++NoDeps;
}
// advancedDepAnalysis - Do advanced data dependence tests
void DependenceAnalyzer::advancedDepAnalysis(GetElementPtrInst *gp1,
GetElementPtrInst *gp2,
bool valLoad,
bool val2Load,
std::vector<Dependence> &deps,
bool srcBeforeDest) {
//Check if both GEPs are in a simple form: 3 ops, constant 0 as second arg
if(gp1->getNumOperands() != 3 || gp2->getNumOperands() != 3) {
createDep(deps, valLoad, val2Load, srcBeforeDest);
return;
}
//Check second arg is constant 0
bool GPok = false;
if(Constant *c1 = dyn_cast<Constant>(gp1->getOperand(1)))
if(Constant *c2 = dyn_cast<Constant>(gp2->getOperand(1)))
if(c1->isNullValue() && c2->isNullValue())
GPok = true;
if(!GPok) {
createDep(deps, valLoad, val2Load, srcBeforeDest);
return;
}
Value *Gep1Idx = gp1->getOperand(2);
Value *Gep2Idx = gp2->getOperand(2);
if(CastInst *c1 = dyn_cast<CastInst>(Gep1Idx))
Gep1Idx = c1->getOperand(0);
if(CastInst *c2 = dyn_cast<CastInst>(Gep2Idx))
Gep2Idx = c2->getOperand(0);
//Get SCEV for each index into the area
SCEVHandle SV1 = SE->getSCEV(Gep1Idx);
SCEVHandle SV2 = SE->getSCEV(Gep2Idx);
//Now handle special cases of dependence analysis
//SV1->print(std::cerr);
//std::cerr << "\n";
//SV2->print(std::cerr);
//std::cerr << "\n";
//Check if we have an SCEVAddExpr, cause we can only handle those
SCEVAddRecExpr *SVAdd1 = dyn_cast<SCEVAddRecExpr>(SV1);
SCEVAddRecExpr *SVAdd2 = dyn_cast<SCEVAddRecExpr>(SV2);
//Default to having a dependence since we can't analyze further
if(!SVAdd1 || !SVAdd2) {
createDep(deps, valLoad, val2Load, srcBeforeDest);
return;
}
//Check if not Affine, we can't handle those
if(!SVAdd1->isAffine( ) || !SVAdd2->isAffine()) {
createDep(deps, valLoad, val2Load, srcBeforeDest);
return;
}
//We know the SCEV is in the form A + B*x, check that B is the same for both
SCEVConstant *B1 = dyn_cast<SCEVConstant>(SVAdd1->getOperand(1));
SCEVConstant *B2 = dyn_cast<SCEVConstant>(SVAdd2->getOperand(1));
if(B1->getValue() != B2->getValue()) {
createDep(deps, valLoad, val2Load, srcBeforeDest);
return;
}
if(B1->getValue()->getRawValue() != 1 || B2->getValue()->getRawValue() != 1) {
createDep(deps, valLoad, val2Load, srcBeforeDest);
return;
}
SCEVConstant *A1 = dyn_cast<SCEVConstant>(SVAdd1->getOperand(0));
SCEVConstant *A2 = dyn_cast<SCEVConstant>(SVAdd2->getOperand(0));
//Come back and deal with nested SCEV!
if(!A1 || !A2) {
createDep(deps, valLoad, val2Load, srcBeforeDest);
return;
}
//If equal, create dep as normal
if(A1->getValue() == A2->getValue()) {
createDep(deps, valLoad, val2Load, srcBeforeDest);
return;
}
//Eliminate a dep if this is a intra dep
else if(srcBeforeDest) {
++NoDeps;
return;
}
//Find constant index difference
int diff = A1->getValue()->getRawValue() - A2->getValue()->getRawValue();
//std::cerr << diff << "\n";
if(diff > 5)
diff = 2;
if(diff > 0)
createDep(deps, valLoad, val2Load, srcBeforeDest, diff);
//assert(diff > 0 && "Expected diff to be greater then 0");
}
// Create dependences once its determined these two instructions
// references the same memory
void DependenceAnalyzer::createDep(std::vector<Dependence> &deps,
bool valLoad, bool val2Load,
bool srcBeforeDest, int diff) {
//If the source instruction occurs after the destination instruction
//(execution order), then this dependence is across iterations
if(!srcBeforeDest && (diff==0))
diff = 1;
//If load/store pair
if(valLoad && !val2Load) {
if(srcBeforeDest)
//Anti Dep
deps.push_back(Dependence(diff, Dependence::AntiDep));
else
deps.push_back(Dependence(diff, Dependence::TrueDep));
++NumDeps;
}
//If store/load pair
else if(!valLoad && val2Load) {
if(srcBeforeDest)
//True Dep
deps.push_back(Dependence(diff, Dependence::TrueDep));
else
deps.push_back(Dependence(diff, Dependence::AntiDep));
++NumDeps;
}
//If store/store pair
else if(!valLoad && !val2Load) {
//True Dep
deps.push_back(Dependence(diff, Dependence::OutputDep));
++NumDeps;
}
}
//Get Dependence Info for a pair of Instructions
DependenceResult DependenceAnalyzer::getDependenceInfo(Instruction *inst1,
Instruction *inst2,
bool srcBeforeDest) {
std::vector<Dependence> deps;
DEBUG(std::cerr << "Inst1: " << *inst1 << "\n");
DEBUG(std::cerr << "Inst2: " << *inst2 << "\n");
//No self deps
if(inst1 == inst2)
return DependenceResult(deps);
if(LoadInst *ldInst = dyn_cast<LoadInst>(inst1)) {
if(StoreInst *stInst = dyn_cast<StoreInst>(inst2))
AnalyzeDeps(ldInst->getOperand(0), stInst->getOperand(1),
true, false, deps, ldInst->getParent(), srcBeforeDest);
}
else if(StoreInst *stInst = dyn_cast<StoreInst>(inst1)) {
if(LoadInst *ldInst = dyn_cast<LoadInst>(inst2))
AnalyzeDeps(stInst->getOperand(1), ldInst->getOperand(0), false, true,
deps, ldInst->getParent(), srcBeforeDest);
else if(StoreInst *stInst2 = dyn_cast<StoreInst>(inst2))
AnalyzeDeps(stInst->getOperand(1), stInst2->getOperand(1), false, false,
deps, stInst->getParent(), srcBeforeDest);
}
else
assert(0 && "Expected a load or a store\n");
DependenceResult dr = DependenceResult(deps);
return dr;
}