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-rw-r--r--lib/Transforms/IPO/PartialSpecialization.cpp216
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diff --git a/lib/Transforms/IPO/PartialSpecialization.cpp b/lib/Transforms/IPO/PartialSpecialization.cpp
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--- a/lib/Transforms/IPO/PartialSpecialization.cpp
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-//===-- PartialSpecialization.cpp - Specialize for common constants--------===//
-//
-// The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This pass finds function arguments that are often a common constant and
-// specializes a version of the called function for that constant.
-//
-// This pass simply does the cloning for functions it specializes. It depends
-// on IPSCCP and DAE to clean up the results.
-//
-// The initial heuristic favors constant arguments that are used in control
-// flow.
-//
-//===----------------------------------------------------------------------===//
-
-#define DEBUG_TYPE "partialspecialization"
-#include "llvm/Transforms/IPO.h"
-#include "llvm/Constant.h"
-#include "llvm/Instructions.h"
-#include "llvm/Module.h"
-#include "llvm/Pass.h"
-#include "llvm/ADT/Statistic.h"
-#include "llvm/Transforms/Utils/Cloning.h"
-#include "llvm/Support/CallSite.h"
-#include "llvm/ADT/DenseSet.h"
-#include <map>
-using namespace llvm;
-
-STATISTIC(numSpecialized, "Number of specialized functions created");
-STATISTIC(numReplaced, "Number of callers replaced by specialization");
-
-// Maximum number of arguments markable interested
-static const int MaxInterests = 6;
-
-// Call must be used at least occasionally
-static const int CallsMin = 5;
-
-// Must have 10% of calls having the same constant to specialize on
-static const double ConstValPercent = .1;
-
-namespace {
- typedef SmallVector<int, MaxInterests> InterestingArgVector;
- class PartSpec : public ModulePass {
- void scanForInterest(Function&, InterestingArgVector&);
- int scanDistribution(Function&, int, std::map<Constant*, int>&);
- public :
- static char ID; // Pass identification, replacement for typeid
- PartSpec() : ModulePass(ID) {}
- bool runOnModule(Module &M);
- };
-}
-
-char PartSpec::ID = 0;
-INITIALIZE_PASS(PartSpec, "partialspecialization",
- "Partial Specialization", false, false);
-
-// Specialize F by replacing the arguments (keys) in replacements with the
-// constants (values). Replace all calls to F with those constants with
-// a call to the specialized function. Returns the specialized function
-static Function*
-SpecializeFunction(Function* F,
- ValueMap<const Value*, Value*>& replacements) {
- // arg numbers of deleted arguments
- DenseMap<unsigned, const Argument*> deleted;
- for (ValueMap<const Value*, Value*>::iterator
- repb = replacements.begin(), repe = replacements.end();
- repb != repe; ++repb) {
- Argument const *arg = cast<const Argument>(repb->first);
- deleted[arg->getArgNo()] = arg;
- }
-
- Function* NF = CloneFunction(F, replacements,
- /*ModuleLevelChanges=*/false);
- NF->setLinkage(GlobalValue::InternalLinkage);
- F->getParent()->getFunctionList().push_back(NF);
-
- for (Value::use_iterator ii = F->use_begin(), ee = F->use_end();
- ii != ee; ) {
- Value::use_iterator i = ii;
- ++ii;
- User *U = *i;
- CallSite CS(U);
- if (CS) {
- if (CS.getCalledFunction() == F) {
- SmallVector<Value*, 6> args;
- // Assemble the non-specialized arguments for the updated callsite.
- // In the process, make sure that the specialized arguments are
- // constant and match the specialization. If that's not the case,
- // this callsite needs to call the original or some other
- // specialization; don't change it here.
- CallSite::arg_iterator as = CS.arg_begin(), ae = CS.arg_end();
- for (CallSite::arg_iterator ai = as; ai != ae; ++ai) {
- DenseMap<unsigned, const Argument*>::iterator delit = deleted.find(
- std::distance(as, ai));
- if (delit == deleted.end())
- args.push_back(cast<Value>(ai));
- else {
- Constant *ci = dyn_cast<Constant>(ai);
- if (!(ci && ci == replacements[delit->second]))
- goto next_use;
- }
- }
- Value* NCall;
- if (CallInst *CI = dyn_cast<CallInst>(U)) {
- NCall = CallInst::Create(NF, args.begin(), args.end(),
- CI->getName(), CI);
- cast<CallInst>(NCall)->setTailCall(CI->isTailCall());
- cast<CallInst>(NCall)->setCallingConv(CI->getCallingConv());
- } else {
- InvokeInst *II = cast<InvokeInst>(U);
- NCall = InvokeInst::Create(NF, II->getNormalDest(),
- II->getUnwindDest(),
- args.begin(), args.end(),
- II->getName(), II);
- cast<InvokeInst>(NCall)->setCallingConv(II->getCallingConv());
- }
- CS.getInstruction()->replaceAllUsesWith(NCall);
- CS.getInstruction()->eraseFromParent();
- ++numReplaced;
- }
- }
- next_use:;
- }
- return NF;
-}
-
-
-bool PartSpec::runOnModule(Module &M) {
- bool Changed = false;
- for (Module::iterator I = M.begin(); I != M.end(); ++I) {
- Function &F = *I;
- if (F.isDeclaration() || F.mayBeOverridden()) continue;
- InterestingArgVector interestingArgs;
- scanForInterest(F, interestingArgs);
-
- // Find the first interesting Argument that we can specialize on
- // If there are multiple interesting Arguments, then those will be found
- // when processing the cloned function.
- bool breakOuter = false;
- for (unsigned int x = 0; !breakOuter && x < interestingArgs.size(); ++x) {
- std::map<Constant*, int> distribution;
- int total = scanDistribution(F, interestingArgs[x], distribution);
- if (total > CallsMin)
- for (std::map<Constant*, int>::iterator ii = distribution.begin(),
- ee = distribution.end(); ii != ee; ++ii)
- if (total > ii->second && ii->first &&
- ii->second > total * ConstValPercent) {
- ValueMap<const Value*, Value*> m;
- Function::arg_iterator arg = F.arg_begin();
- for (int y = 0; y < interestingArgs[x]; ++y)
- ++arg;
- m[&*arg] = ii->first;
- SpecializeFunction(&F, m);
- ++numSpecialized;
- breakOuter = true;
- Changed = true;
- }
- }
- }
- return Changed;
-}
-
-/// scanForInterest - This function decides which arguments would be worth
-/// specializing on.
-void PartSpec::scanForInterest(Function& F, InterestingArgVector& args) {
- for(Function::arg_iterator ii = F.arg_begin(), ee = F.arg_end();
- ii != ee; ++ii) {
- for(Value::use_iterator ui = ii->use_begin(), ue = ii->use_end();
- ui != ue; ++ui) {
-
- bool interesting = false;
- User *U = *ui;
- if (isa<CmpInst>(U)) interesting = true;
- else if (isa<CallInst>(U))
- interesting = ui->getOperand(0) == ii;
- else if (isa<InvokeInst>(U))
- interesting = ui->getOperand(0) == ii;
- else if (isa<SwitchInst>(U)) interesting = true;
- else if (isa<BranchInst>(U)) interesting = true;
-
- if (interesting) {
- args.push_back(std::distance(F.arg_begin(), ii));
- break;
- }
- }
- }
-}
-
-/// scanDistribution - Construct a histogram of constants for arg of F at arg.
-int PartSpec::scanDistribution(Function& F, int arg,
- std::map<Constant*, int>& dist) {
- bool hasIndirect = false;
- int total = 0;
- for (Value::use_iterator ii = F.use_begin(), ee = F.use_end();
- ii != ee; ++ii) {
- User *U = *ii;
- CallSite CS(U);
- if (CS && CS.getCalledFunction() == &F) {
- ++dist[dyn_cast<Constant>(CS.getArgument(arg))];
- ++total;
- } else
- hasIndirect = true;
- }
-
- // Preserve the original address taken function even if all other uses
- // will be specialized.
- if (hasIndirect) ++total;
- return total;
-}
-
-ModulePass* llvm::createPartialSpecializationPass() { return new PartSpec(); }
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