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in scary and unknown ways before we promote it. This fixes the miscompilation of 188.ammp that has been plauging us since a globalopt patch went in. Thanks a ton to Tanya for helping me diagnose the problem! git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@18418 91177308-0d34-0410-b5e6-96231b3b80d8
946 lines
37 KiB
C++
946 lines
37 KiB
C++
//===- GlobalOpt.cpp - Optimize Global Variables --------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by the LLVM research group and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This pass transforms simple global variables that never have their address
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// taken. If obviously true, it marks read/write globals as constant, deletes
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// variables only stored to, etc.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "globalopt"
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#include "llvm/Transforms/IPO.h"
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#include "llvm/Constants.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Instructions.h"
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#include "llvm/Module.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Target/TargetData.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/ADT/StringExtras.h"
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#include <set>
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#include <algorithm>
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using namespace llvm;
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namespace {
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Statistic<> NumMarked ("globalopt", "Number of globals marked constant");
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Statistic<> NumSRA ("globalopt", "Number of aggregate globals broken "
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"into scalars");
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Statistic<> NumSubstitute("globalopt",
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"Number of globals with initializers stored into them");
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Statistic<> NumDeleted ("globalopt", "Number of globals deleted");
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Statistic<> NumFnDeleted("globalopt", "Number of functions deleted");
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Statistic<> NumGlobUses ("globalopt", "Number of global uses devirtualized");
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struct GlobalOpt : public ModulePass {
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.addRequired<TargetData>();
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}
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bool runOnModule(Module &M);
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private:
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bool ProcessInternalGlobal(GlobalVariable *GV, Module::giterator &GVI);
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};
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RegisterOpt<GlobalOpt> X("globalopt", "Global Variable Optimizer");
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}
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ModulePass *llvm::createGlobalOptimizerPass() { return new GlobalOpt(); }
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/// GlobalStatus - As we analyze each global, keep track of some information
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/// about it. If we find out that the address of the global is taken, none of
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/// this info will be accurate.
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struct GlobalStatus {
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/// isLoaded - True if the global is ever loaded. If the global isn't ever
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/// loaded it can be deleted.
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bool isLoaded;
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/// StoredType - Keep track of what stores to the global look like.
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///
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enum StoredType {
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/// NotStored - There is no store to this global. It can thus be marked
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/// constant.
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NotStored,
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/// isInitializerStored - This global is stored to, but the only thing
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/// stored is the constant it was initialized with. This is only tracked
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/// for scalar globals.
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isInitializerStored,
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/// isStoredOnce - This global is stored to, but only its initializer and
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/// one other value is ever stored to it. If this global isStoredOnce, we
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/// track the value stored to it in StoredOnceValue below. This is only
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/// tracked for scalar globals.
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isStoredOnce,
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/// isStored - This global is stored to by multiple values or something else
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/// that we cannot track.
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isStored
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} StoredType;
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/// StoredOnceValue - If only one value (besides the initializer constant) is
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/// ever stored to this global, keep track of what value it is.
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Value *StoredOnceValue;
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/// isNotSuitableForSRA - Keep track of whether any SRA preventing users of
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/// the global exist. Such users include GEP instruction with variable
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/// indexes, and non-gep/load/store users like constant expr casts.
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bool isNotSuitableForSRA;
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GlobalStatus() : isLoaded(false), StoredType(NotStored), StoredOnceValue(0),
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isNotSuitableForSRA(false) {}
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};
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/// ConstantIsDead - Return true if the specified constant is (transitively)
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/// dead. The constant may be used by other constants (e.g. constant arrays and
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/// constant exprs) as long as they are dead, but it cannot be used by anything
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/// else.
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static bool ConstantIsDead(Constant *C) {
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if (isa<GlobalValue>(C)) return false;
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for (Value::use_iterator UI = C->use_begin(), E = C->use_end(); UI != E; ++UI)
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if (Constant *CU = dyn_cast<Constant>(*UI)) {
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if (!ConstantIsDead(CU)) return false;
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} else
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return false;
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return true;
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}
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/// AnalyzeGlobal - Look at all uses of the global and fill in the GlobalStatus
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/// structure. If the global has its address taken, return true to indicate we
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/// can't do anything with it.
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///
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static bool AnalyzeGlobal(Value *V, GlobalStatus &GS,
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std::set<PHINode*> &PHIUsers) {
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for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
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if (ConstantExpr *CE = dyn_cast<ConstantExpr>(*UI)) {
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if (AnalyzeGlobal(CE, GS, PHIUsers)) return true;
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if (CE->getOpcode() != Instruction::GetElementPtr)
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GS.isNotSuitableForSRA = true;
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else if (!GS.isNotSuitableForSRA) {
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// Check to see if this ConstantExpr GEP is SRA'able. In particular, we
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// don't like < 3 operand CE's, and we don't like non-constant integer
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// indices.
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if (CE->getNumOperands() < 3 || !CE->getOperand(1)->isNullValue())
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GS.isNotSuitableForSRA = true;
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else {
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for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
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if (!isa<ConstantInt>(CE->getOperand(i))) {
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GS.isNotSuitableForSRA = true;
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break;
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}
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}
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}
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} else if (Instruction *I = dyn_cast<Instruction>(*UI)) {
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if (isa<LoadInst>(I)) {
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GS.isLoaded = true;
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} else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
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// Don't allow a store OF the address, only stores TO the address.
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if (SI->getOperand(0) == V) return true;
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// If this is a direct store to the global (i.e., the global is a scalar
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// value, not an aggregate), keep more specific information about
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// stores.
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if (GS.StoredType != GlobalStatus::isStored)
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if (GlobalVariable *GV = dyn_cast<GlobalVariable>(SI->getOperand(1))){
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Value *StoredVal = SI->getOperand(0);
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if (StoredVal == GV->getInitializer()) {
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if (GS.StoredType < GlobalStatus::isInitializerStored)
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GS.StoredType = GlobalStatus::isInitializerStored;
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} else if (isa<LoadInst>(StoredVal) &&
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cast<LoadInst>(StoredVal)->getOperand(0) == GV) {
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// G = G
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if (GS.StoredType < GlobalStatus::isInitializerStored)
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GS.StoredType = GlobalStatus::isInitializerStored;
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} else if (GS.StoredType < GlobalStatus::isStoredOnce) {
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GS.StoredType = GlobalStatus::isStoredOnce;
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GS.StoredOnceValue = StoredVal;
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} else if (GS.StoredType == GlobalStatus::isStoredOnce &&
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GS.StoredOnceValue == StoredVal) {
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// noop.
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} else {
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GS.StoredType = GlobalStatus::isStored;
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}
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} else {
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GS.StoredType = GlobalStatus::isStored;
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}
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} else if (I->getOpcode() == Instruction::GetElementPtr) {
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if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
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// If the first two indices are constants, this can be SRA'd.
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if (isa<GlobalVariable>(I->getOperand(0))) {
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if (I->getNumOperands() < 3 || !isa<Constant>(I->getOperand(1)) ||
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!cast<Constant>(I->getOperand(1))->isNullValue() ||
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!isa<ConstantInt>(I->getOperand(2)))
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GS.isNotSuitableForSRA = true;
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} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(I->getOperand(0))){
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if (CE->getOpcode() != Instruction::GetElementPtr ||
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CE->getNumOperands() < 3 || I->getNumOperands() < 2 ||
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!isa<Constant>(I->getOperand(0)) ||
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!cast<Constant>(I->getOperand(0))->isNullValue())
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GS.isNotSuitableForSRA = true;
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} else {
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GS.isNotSuitableForSRA = true;
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}
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} else if (I->getOpcode() == Instruction::Select) {
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if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
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GS.isNotSuitableForSRA = true;
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} else if (PHINode *PN = dyn_cast<PHINode>(I)) {
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// PHI nodes we can check just like select or GEP instructions, but we
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// have to be careful about infinite recursion.
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if (PHIUsers.insert(PN).second) // Not already visited.
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if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
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GS.isNotSuitableForSRA = true;
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} else if (isa<SetCondInst>(I)) {
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GS.isNotSuitableForSRA = true;
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} else {
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return true; // Any other non-load instruction might take address!
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}
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} else if (Constant *C = dyn_cast<Constant>(*UI)) {
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// We might have a dead and dangling constant hanging off of here.
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if (!ConstantIsDead(C))
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return true;
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} else {
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// Otherwise must be a global or some other user.
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return true;
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}
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return false;
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}
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static Constant *getAggregateConstantElement(Constant *Agg, Constant *Idx) {
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ConstantInt *CI = dyn_cast<ConstantInt>(Idx);
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if (!CI) return 0;
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uint64_t IdxV = CI->getRawValue();
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if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Agg)) {
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if (IdxV < CS->getNumOperands()) return CS->getOperand(IdxV);
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} else if (ConstantArray *CA = dyn_cast<ConstantArray>(Agg)) {
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if (IdxV < CA->getNumOperands()) return CA->getOperand(IdxV);
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} else if (ConstantPacked *CP = dyn_cast<ConstantPacked>(Agg)) {
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if (IdxV < CP->getNumOperands()) return CP->getOperand(IdxV);
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} else if (isa<ConstantAggregateZero>(Agg)) {
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if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) {
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if (IdxV < STy->getNumElements())
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return Constant::getNullValue(STy->getElementType(IdxV));
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} else if (const SequentialType *STy =
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dyn_cast<SequentialType>(Agg->getType())) {
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return Constant::getNullValue(STy->getElementType());
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}
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} else if (isa<UndefValue>(Agg)) {
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if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) {
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if (IdxV < STy->getNumElements())
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return UndefValue::get(STy->getElementType(IdxV));
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} else if (const SequentialType *STy =
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dyn_cast<SequentialType>(Agg->getType())) {
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return UndefValue::get(STy->getElementType());
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}
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}
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return 0;
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}
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static Constant *TraverseGEPInitializer(User *GEP, Constant *Init) {
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if (GEP->getNumOperands() == 1 ||
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!isa<Constant>(GEP->getOperand(1)) ||
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!cast<Constant>(GEP->getOperand(1))->isNullValue())
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return 0;
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for (unsigned i = 2, e = GEP->getNumOperands(); i != e; ++i) {
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ConstantInt *Idx = dyn_cast<ConstantInt>(GEP->getOperand(i));
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if (!Idx) return 0;
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Init = getAggregateConstantElement(Init, Idx);
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if (Init == 0) return 0;
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}
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return Init;
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}
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/// CleanupConstantGlobalUsers - We just marked GV constant. Loop over all
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/// users of the global, cleaning up the obvious ones. This is largely just a
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/// quick scan over the use list to clean up the easy and obvious cruft. This
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/// returns true if it made a change.
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static bool CleanupConstantGlobalUsers(Value *V, Constant *Init) {
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bool Changed = false;
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for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;) {
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User *U = *UI++;
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if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
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// Replace the load with the initializer.
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LI->replaceAllUsesWith(Init);
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LI->eraseFromParent();
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Changed = true;
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} else if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
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// Store must be unreachable or storing Init into the global.
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SI->eraseFromParent();
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Changed = true;
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} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
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if (CE->getOpcode() == Instruction::GetElementPtr) {
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if (Constant *SubInit = TraverseGEPInitializer(CE, Init))
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Changed |= CleanupConstantGlobalUsers(CE, SubInit);
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if (CE->use_empty()) {
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CE->destroyConstant();
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Changed = true;
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}
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}
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} else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
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if (Constant *SubInit = TraverseGEPInitializer(GEP, Init))
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Changed |= CleanupConstantGlobalUsers(GEP, SubInit);
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else {
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// If this GEP has variable indexes, we should still be able to delete
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// any stores through it.
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for (Value::use_iterator GUI = GEP->use_begin(), E = GEP->use_end();
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GUI != E;)
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if (StoreInst *SI = dyn_cast<StoreInst>(*GUI++)) {
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SI->eraseFromParent();
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Changed = true;
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}
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}
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if (GEP->use_empty()) {
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GEP->eraseFromParent();
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Changed = true;
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}
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} else if (Constant *C = dyn_cast<Constant>(U)) {
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// If we have a chain of dead constantexprs or other things dangling from
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// us, and if they are all dead, nuke them without remorse.
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if (ConstantIsDead(C)) {
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C->destroyConstant();
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// This could have incalidated UI, start over from scratch.x
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CleanupConstantGlobalUsers(V, Init);
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return true;
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}
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}
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}
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return Changed;
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}
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/// SRAGlobal - Perform scalar replacement of aggregates on the specified global
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/// variable. This opens the door for other optimizations by exposing the
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/// behavior of the program in a more fine-grained way. We have determined that
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/// this transformation is safe already. We return the first global variable we
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/// insert so that the caller can reprocess it.
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static GlobalVariable *SRAGlobal(GlobalVariable *GV) {
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assert(GV->hasInternalLinkage() && !GV->isConstant());
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Constant *Init = GV->getInitializer();
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const Type *Ty = Init->getType();
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std::vector<GlobalVariable*> NewGlobals;
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Module::GlobalListType &Globals = GV->getParent()->getGlobalList();
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if (const StructType *STy = dyn_cast<StructType>(Ty)) {
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NewGlobals.reserve(STy->getNumElements());
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for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
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Constant *In = getAggregateConstantElement(Init,
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ConstantUInt::get(Type::UIntTy, i));
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assert(In && "Couldn't get element of initializer?");
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GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false,
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GlobalVariable::InternalLinkage,
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In, GV->getName()+"."+utostr(i));
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Globals.insert(GV, NGV);
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NewGlobals.push_back(NGV);
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}
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} else if (const SequentialType *STy = dyn_cast<SequentialType>(Ty)) {
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unsigned NumElements = 0;
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if (const ArrayType *ATy = dyn_cast<ArrayType>(STy))
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NumElements = ATy->getNumElements();
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else if (const PackedType *PTy = dyn_cast<PackedType>(STy))
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NumElements = PTy->getNumElements();
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else
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assert(0 && "Unknown aggregate sequential type!");
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if (NumElements > 16 && GV->use_size() > 16) return 0; // It's not worth it.
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NewGlobals.reserve(NumElements);
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for (unsigned i = 0, e = NumElements; i != e; ++i) {
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Constant *In = getAggregateConstantElement(Init,
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ConstantUInt::get(Type::UIntTy, i));
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assert(In && "Couldn't get element of initializer?");
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GlobalVariable *NGV = new GlobalVariable(STy->getElementType(), false,
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GlobalVariable::InternalLinkage,
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In, GV->getName()+"."+utostr(i));
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Globals.insert(GV, NGV);
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NewGlobals.push_back(NGV);
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}
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}
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if (NewGlobals.empty())
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return 0;
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DEBUG(std::cerr << "PERFORMING GLOBAL SRA ON: " << *GV);
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Constant *NullInt = Constant::getNullValue(Type::IntTy);
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// Loop over all of the uses of the global, replacing the constantexpr geps,
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// with smaller constantexpr geps or direct references.
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while (!GV->use_empty()) {
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User *GEP = GV->use_back();
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assert(((isa<ConstantExpr>(GEP) &&
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cast<ConstantExpr>(GEP)->getOpcode()==Instruction::GetElementPtr)||
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isa<GetElementPtrInst>(GEP)) && "NonGEP CE's are not SRAable!");
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// Ignore the 1th operand, which has to be zero or else the program is quite
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// broken (undefined). Get the 2nd operand, which is the structure or array
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// index.
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unsigned Val = cast<ConstantInt>(GEP->getOperand(2))->getRawValue();
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if (Val >= NewGlobals.size()) Val = 0; // Out of bound array access.
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Value *NewPtr = NewGlobals[Val];
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// Form a shorter GEP if needed.
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if (GEP->getNumOperands() > 3)
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if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP)) {
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std::vector<Constant*> Idxs;
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Idxs.push_back(NullInt);
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for (unsigned i = 3, e = CE->getNumOperands(); i != e; ++i)
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Idxs.push_back(CE->getOperand(i));
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NewPtr = ConstantExpr::getGetElementPtr(cast<Constant>(NewPtr), Idxs);
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} else {
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GetElementPtrInst *GEPI = cast<GetElementPtrInst>(GEP);
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std::vector<Value*> Idxs;
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Idxs.push_back(NullInt);
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for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i)
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Idxs.push_back(GEPI->getOperand(i));
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NewPtr = new GetElementPtrInst(NewPtr, Idxs,
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GEPI->getName()+"."+utostr(Val), GEPI);
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}
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GEP->replaceAllUsesWith(NewPtr);
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if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(GEP))
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GEPI->eraseFromParent();
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else
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cast<ConstantExpr>(GEP)->destroyConstant();
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}
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// Delete the old global, now that it is dead.
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Globals.erase(GV);
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++NumSRA;
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// Loop over the new globals array deleting any globals that are obviously
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// dead. This can arise due to scalarization of a structure or an array that
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// has elements that are dead.
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unsigned FirstGlobal = 0;
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for (unsigned i = 0, e = NewGlobals.size(); i != e; ++i)
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if (NewGlobals[i]->use_empty()) {
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Globals.erase(NewGlobals[i]);
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if (FirstGlobal == i) ++FirstGlobal;
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}
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|
|
return FirstGlobal != NewGlobals.size() ? NewGlobals[FirstGlobal] : 0;
|
|
}
|
|
|
|
/// AllUsesOfValueWillTrapIfNull - Return true if all users of the specified
|
|
/// value will trap if the value is dynamically null.
|
|
static bool AllUsesOfValueWillTrapIfNull(Value *V) {
|
|
for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
|
|
if (isa<LoadInst>(*UI)) {
|
|
// Will trap.
|
|
} else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
|
|
if (SI->getOperand(0) == V) {
|
|
//std::cerr << "NONTRAPPING USE: " << **UI;
|
|
return false; // Storing the value.
|
|
}
|
|
} else if (CallInst *CI = dyn_cast<CallInst>(*UI)) {
|
|
if (CI->getOperand(0) != V) {
|
|
//std::cerr << "NONTRAPPING USE: " << **UI;
|
|
return false; // Not calling the ptr
|
|
}
|
|
} else if (InvokeInst *II = dyn_cast<InvokeInst>(*UI)) {
|
|
if (II->getOperand(0) != V) {
|
|
//std::cerr << "NONTRAPPING USE: " << **UI;
|
|
return false; // Not calling the ptr
|
|
}
|
|
} else if (CastInst *CI = dyn_cast<CastInst>(*UI)) {
|
|
if (!AllUsesOfValueWillTrapIfNull(CI)) return false;
|
|
} else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI)) {
|
|
if (!AllUsesOfValueWillTrapIfNull(GEPI)) return false;
|
|
} else if (isa<SetCondInst>(*UI) &&
|
|
isa<ConstantPointerNull>(UI->getOperand(1))) {
|
|
// Ignore setcc X, null
|
|
} else {
|
|
//std::cerr << "NONTRAPPING USE: " << **UI;
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
/// AllUsesOfLoadedValueWillTrapIfNull - Return true if all uses of any loads
|
|
/// from GV will trap if the loaded value is null. Note that this also permits
|
|
/// comparisons of the loaded value against null, as a special case.
|
|
static bool AllUsesOfLoadedValueWillTrapIfNull(GlobalVariable *GV) {
|
|
for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI!=E; ++UI)
|
|
if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
|
|
if (!AllUsesOfValueWillTrapIfNull(LI))
|
|
return false;
|
|
} else if (isa<StoreInst>(*UI)) {
|
|
// Ignore stores to the global.
|
|
} else {
|
|
// We don't know or understand this user, bail out.
|
|
//std::cerr << "UNKNOWN USER OF GLOBAL!: " << **UI;
|
|
return false;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV) {
|
|
bool Changed = false;
|
|
for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) {
|
|
Instruction *I = cast<Instruction>(*UI++);
|
|
if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
|
|
LI->setOperand(0, NewV);
|
|
Changed = true;
|
|
} else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
|
|
if (SI->getOperand(1) == V) {
|
|
SI->setOperand(1, NewV);
|
|
Changed = true;
|
|
}
|
|
} else if (isa<CallInst>(I) || isa<InvokeInst>(I)) {
|
|
if (I->getOperand(0) == V) {
|
|
// Calling through the pointer! Turn into a direct call, but be careful
|
|
// that the pointer is not also being passed as an argument.
|
|
I->setOperand(0, NewV);
|
|
Changed = true;
|
|
bool PassedAsArg = false;
|
|
for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i)
|
|
if (I->getOperand(i) == V) {
|
|
PassedAsArg = true;
|
|
I->setOperand(i, NewV);
|
|
}
|
|
|
|
if (PassedAsArg) {
|
|
// Being passed as an argument also. Be careful to not invalidate UI!
|
|
UI = V->use_begin();
|
|
}
|
|
}
|
|
} else if (CastInst *CI = dyn_cast<CastInst>(I)) {
|
|
Changed |= OptimizeAwayTrappingUsesOfValue(CI,
|
|
ConstantExpr::getCast(NewV, CI->getType()));
|
|
if (CI->use_empty()) {
|
|
Changed = true;
|
|
CI->eraseFromParent();
|
|
}
|
|
} else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
|
|
// Should handle GEP here.
|
|
std::vector<Constant*> Indices;
|
|
Indices.reserve(GEPI->getNumOperands()-1);
|
|
for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i)
|
|
if (Constant *C = dyn_cast<Constant>(GEPI->getOperand(i)))
|
|
Indices.push_back(C);
|
|
else
|
|
break;
|
|
if (Indices.size() == GEPI->getNumOperands()-1)
|
|
Changed |= OptimizeAwayTrappingUsesOfValue(GEPI,
|
|
ConstantExpr::getGetElementPtr(NewV, Indices));
|
|
if (GEPI->use_empty()) {
|
|
Changed = true;
|
|
GEPI->eraseFromParent();
|
|
}
|
|
}
|
|
}
|
|
|
|
return Changed;
|
|
}
|
|
|
|
|
|
/// OptimizeAwayTrappingUsesOfLoads - The specified global has only one non-null
|
|
/// value stored into it. If there are uses of the loaded value that would trap
|
|
/// if the loaded value is dynamically null, then we know that they cannot be
|
|
/// reachable with a null optimize away the load.
|
|
static bool OptimizeAwayTrappingUsesOfLoads(GlobalVariable *GV, Constant *LV) {
|
|
std::vector<LoadInst*> Loads;
|
|
bool Changed = false;
|
|
|
|
// Replace all uses of loads with uses of uses of the stored value.
|
|
for (Value::use_iterator GUI = GV->use_begin(), E = GV->use_end();
|
|
GUI != E; ++GUI)
|
|
if (LoadInst *LI = dyn_cast<LoadInst>(*GUI)) {
|
|
Loads.push_back(LI);
|
|
Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV);
|
|
} else {
|
|
assert(isa<StoreInst>(*GUI) && "Only expect load and stores!");
|
|
}
|
|
|
|
if (Changed) {
|
|
DEBUG(std::cerr << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV);
|
|
++NumGlobUses;
|
|
}
|
|
|
|
// Delete all of the loads we can, keeping track of whether we nuked them all!
|
|
bool AllLoadsGone = true;
|
|
while (!Loads.empty()) {
|
|
LoadInst *L = Loads.back();
|
|
if (L->use_empty()) {
|
|
L->eraseFromParent();
|
|
Changed = true;
|
|
} else {
|
|
AllLoadsGone = false;
|
|
}
|
|
Loads.pop_back();
|
|
}
|
|
|
|
// If we nuked all of the loads, then none of the stores are needed either,
|
|
// nor is the global.
|
|
if (AllLoadsGone) {
|
|
DEBUG(std::cerr << " *** GLOBAL NOW DEAD!\n");
|
|
CleanupConstantGlobalUsers(GV, 0);
|
|
if (GV->use_empty()) {
|
|
GV->eraseFromParent();
|
|
++NumDeleted;
|
|
}
|
|
Changed = true;
|
|
}
|
|
return Changed;
|
|
}
|
|
|
|
/// ConstantPropUsersOf - Walk the use list of V, constant folding all of the
|
|
/// instructions that are foldable.
|
|
static void ConstantPropUsersOf(Value *V) {
|
|
for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; )
|
|
if (Instruction *I = dyn_cast<Instruction>(*UI++))
|
|
if (Constant *NewC = ConstantFoldInstruction(I)) {
|
|
I->replaceAllUsesWith(NewC);
|
|
|
|
// Back up UI to avoid invalidating it!
|
|
bool AtBegin = false;
|
|
if (UI == V->use_begin())
|
|
AtBegin = true;
|
|
else
|
|
--UI;
|
|
I->eraseFromParent();
|
|
if (AtBegin)
|
|
UI = V->use_begin();
|
|
else
|
|
++UI;
|
|
}
|
|
}
|
|
|
|
/// OptimizeGlobalAddressOfMalloc - This function takes the specified global
|
|
/// variable, and transforms the program as if it always contained the result of
|
|
/// the specified malloc. Because it is always the result of the specified
|
|
/// malloc, there is no reason to actually DO the malloc. Instead, turn the
|
|
/// malloc into a global, and any laods of GV as uses of the new global.
|
|
static GlobalVariable *OptimizeGlobalAddressOfMalloc(GlobalVariable *GV,
|
|
MallocInst *MI) {
|
|
DEBUG(std::cerr << "PROMOTING MALLOC GLOBAL: " << *GV << " MALLOC = " <<*MI);
|
|
ConstantInt *NElements = cast<ConstantInt>(MI->getArraySize());
|
|
|
|
if (NElements->getRawValue() != 1) {
|
|
// If we have an array allocation, transform it to a single element
|
|
// allocation to make the code below simpler.
|
|
Type *NewTy = ArrayType::get(MI->getAllocatedType(),
|
|
NElements->getRawValue());
|
|
MallocInst *NewMI =
|
|
new MallocInst(NewTy, Constant::getNullValue(Type::UIntTy),
|
|
MI->getName(), MI);
|
|
std::vector<Value*> Indices;
|
|
Indices.push_back(Constant::getNullValue(Type::IntTy));
|
|
Indices.push_back(Indices[0]);
|
|
Value *NewGEP = new GetElementPtrInst(NewMI, Indices,
|
|
NewMI->getName()+".el0", MI);
|
|
MI->replaceAllUsesWith(NewGEP);
|
|
MI->eraseFromParent();
|
|
MI = NewMI;
|
|
}
|
|
|
|
// Create the new global variable. The contents of the malloc'd memory is
|
|
// undefined, so initialize with an undef value.
|
|
Constant *Init = UndefValue::get(MI->getAllocatedType());
|
|
GlobalVariable *NewGV = new GlobalVariable(MI->getAllocatedType(), false,
|
|
GlobalValue::InternalLinkage, Init,
|
|
GV->getName()+".body");
|
|
GV->getParent()->getGlobalList().insert(GV, NewGV);
|
|
|
|
// Anything that used the malloc now uses the global directly.
|
|
MI->replaceAllUsesWith(NewGV);
|
|
|
|
Constant *RepValue = NewGV;
|
|
if (NewGV->getType() != GV->getType()->getElementType())
|
|
RepValue = ConstantExpr::getCast(RepValue, GV->getType()->getElementType());
|
|
|
|
// If there is a comparison against null, we will insert a global bool to
|
|
// keep track of whether the global was initialized yet or not.
|
|
GlobalVariable *InitBool =
|
|
new GlobalVariable(Type::BoolTy, false, GlobalValue::InternalLinkage,
|
|
ConstantBool::False, GV->getName()+".init");
|
|
bool InitBoolUsed = false;
|
|
|
|
// Loop over all uses of GV, processing them in turn.
|
|
std::vector<StoreInst*> Stores;
|
|
while (!GV->use_empty())
|
|
if (LoadInst *LI = dyn_cast<LoadInst>(GV->use_back())) {
|
|
while (!LI->use_empty()) {
|
|
// FIXME: the iterator should expose a getUse() method.
|
|
Use &LoadUse = *(const iplist<Use>::iterator&)LI->use_begin();
|
|
if (!isa<SetCondInst>(LoadUse.getUser()))
|
|
LoadUse = RepValue;
|
|
else {
|
|
// Replace the setcc X, 0 with a use of the bool value.
|
|
SetCondInst *SCI = cast<SetCondInst>(LoadUse.getUser());
|
|
Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", SCI);
|
|
InitBoolUsed = true;
|
|
switch (SCI->getOpcode()) {
|
|
default: assert(0 && "Unknown opcode!");
|
|
case Instruction::SetLT:
|
|
LV = ConstantBool::False; // X < null -> always false
|
|
break;
|
|
case Instruction::SetEQ:
|
|
case Instruction::SetLE:
|
|
LV = BinaryOperator::createNot(LV, "notinit", SCI);
|
|
break;
|
|
case Instruction::SetNE:
|
|
case Instruction::SetGE:
|
|
case Instruction::SetGT:
|
|
break; // no change.
|
|
}
|
|
SCI->replaceAllUsesWith(LV);
|
|
SCI->eraseFromParent();
|
|
}
|
|
}
|
|
LI->eraseFromParent();
|
|
} else {
|
|
StoreInst *SI = cast<StoreInst>(GV->use_back());
|
|
// The global is initialized when the store to it occurs.
|
|
new StoreInst(ConstantBool::True, InitBool, SI);
|
|
SI->eraseFromParent();
|
|
}
|
|
|
|
// If the initialization boolean was used, insert it, otherwise delete it.
|
|
if (!InitBoolUsed) {
|
|
while (!InitBool->use_empty()) // Delete initializations
|
|
cast<Instruction>(InitBool->use_back())->eraseFromParent();
|
|
delete InitBool;
|
|
} else
|
|
GV->getParent()->getGlobalList().insert(GV, InitBool);
|
|
|
|
|
|
// Now the GV is dead, nuke it and the malloc.
|
|
GV->eraseFromParent();
|
|
MI->eraseFromParent();
|
|
|
|
// To further other optimizations, loop over all users of NewGV and try to
|
|
// constant prop them. This will promote GEP instructions with constant
|
|
// indices into GEP constant-exprs, which will allow global-opt to hack on it.
|
|
ConstantPropUsersOf(NewGV);
|
|
if (RepValue != NewGV)
|
|
ConstantPropUsersOf(RepValue);
|
|
|
|
return NewGV;
|
|
}
|
|
|
|
/// ValueIsOnlyUsedLocallyOrStoredToOneGlobal - Scan the use-list of V checking
|
|
/// to make sure that there are no complex uses of V. We permit simple things
|
|
/// like dereferencing the pointer, but not storing through the address, unless
|
|
/// it is to the specified global.
|
|
static bool ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Instruction *V,
|
|
GlobalVariable *GV) {
|
|
for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI)
|
|
if (isa<LoadInst>(*UI) || isa<SetCondInst>(*UI)) {
|
|
// Fine, ignore.
|
|
} else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
|
|
if (SI->getOperand(0) == V && SI->getOperand(1) != GV)
|
|
return false; // Storing the pointer itself... bad.
|
|
// Otherwise, storing through it, or storing into GV... fine.
|
|
} else if (isa<GetElementPtrInst>(*UI) || isa<SelectInst>(*UI)) {
|
|
if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(cast<Instruction>(*UI),GV))
|
|
return false;
|
|
} else {
|
|
return false;
|
|
}
|
|
return true;
|
|
|
|
}
|
|
|
|
// OptimizeOnceStoredGlobal - Try to optimize globals based on the knowledge
|
|
// that only one value (besides its initializer) is ever stored to the global.
|
|
static bool OptimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal,
|
|
Module::giterator &GVI, TargetData &TD) {
|
|
if (CastInst *CI = dyn_cast<CastInst>(StoredOnceVal))
|
|
StoredOnceVal = CI->getOperand(0);
|
|
else if (GetElementPtrInst *GEPI =dyn_cast<GetElementPtrInst>(StoredOnceVal)){
|
|
// "getelementptr Ptr, 0, 0, 0" is really just a cast.
|
|
bool IsJustACast = true;
|
|
for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i)
|
|
if (!isa<Constant>(GEPI->getOperand(i)) ||
|
|
!cast<Constant>(GEPI->getOperand(i))->isNullValue()) {
|
|
IsJustACast = false;
|
|
break;
|
|
}
|
|
if (IsJustACast)
|
|
StoredOnceVal = GEPI->getOperand(0);
|
|
}
|
|
|
|
// If we are dealing with a pointer global that is initialized to null and
|
|
// only has one (non-null) value stored into it, then we can optimize any
|
|
// users of the loaded value (often calls and loads) that would trap if the
|
|
// value was null.
|
|
if (isa<PointerType>(GV->getInitializer()->getType()) &&
|
|
GV->getInitializer()->isNullValue()) {
|
|
if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) {
|
|
if (GV->getInitializer()->getType() != SOVC->getType())
|
|
SOVC = ConstantExpr::getCast(SOVC, GV->getInitializer()->getType());
|
|
|
|
// Optimize away any trapping uses of the loaded value.
|
|
if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC))
|
|
return true;
|
|
} else if (MallocInst *MI = dyn_cast<MallocInst>(StoredOnceVal)) {
|
|
// If we have a global that is only initialized with a fixed size malloc,
|
|
// and if all users of the malloc trap, and if the malloc'd address is not
|
|
// put anywhere else, transform the program to use global memory instead
|
|
// of malloc'd memory. This eliminates dynamic allocation (good) and
|
|
// exposes the resultant global to further GlobalOpt (even better). Note
|
|
// that we restrict this transformation to only working on small
|
|
// allocations (2048 bytes currently), as we don't want to introduce a 16M
|
|
// global or something.
|
|
if (ConstantInt *NElements = dyn_cast<ConstantInt>(MI->getArraySize()))
|
|
if (MI->getAllocatedType()->isSized() &&
|
|
NElements->getRawValue()*
|
|
TD.getTypeSize(MI->getAllocatedType()) < 2048 &&
|
|
AllUsesOfLoadedValueWillTrapIfNull(GV) &&
|
|
ValueIsOnlyUsedLocallyOrStoredToOneGlobal(MI, GV)) {
|
|
GVI = OptimizeGlobalAddressOfMalloc(GV, MI);
|
|
return true;
|
|
}
|
|
}
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
/// ProcessInternalGlobal - Analyze the specified global variable and optimize
|
|
/// it if possible. If we make a change, return true.
|
|
bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV,
|
|
Module::giterator &GVI) {
|
|
std::set<PHINode*> PHIUsers;
|
|
GlobalStatus GS;
|
|
PHIUsers.clear();
|
|
GV->removeDeadConstantUsers();
|
|
|
|
if (GV->use_empty()) {
|
|
DEBUG(std::cerr << "GLOBAL DEAD: " << *GV);
|
|
GV->eraseFromParent();
|
|
++NumDeleted;
|
|
return true;
|
|
}
|
|
|
|
if (!AnalyzeGlobal(GV, GS, PHIUsers)) {
|
|
// If the global is never loaded (but may be stored to), it is dead.
|
|
// Delete it now.
|
|
if (!GS.isLoaded) {
|
|
DEBUG(std::cerr << "GLOBAL NEVER LOADED: " << *GV);
|
|
|
|
// Delete any stores we can find to the global. We may not be able to
|
|
// make it completely dead though.
|
|
bool Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer());
|
|
|
|
// If the global is dead now, delete it.
|
|
if (GV->use_empty()) {
|
|
GV->eraseFromParent();
|
|
++NumDeleted;
|
|
Changed = true;
|
|
}
|
|
return Changed;
|
|
|
|
} else if (GS.StoredType <= GlobalStatus::isInitializerStored) {
|
|
DEBUG(std::cerr << "MARKING CONSTANT: " << *GV);
|
|
GV->setConstant(true);
|
|
|
|
// Clean up any obviously simplifiable users now.
|
|
CleanupConstantGlobalUsers(GV, GV->getInitializer());
|
|
|
|
// If the global is dead now, just nuke it.
|
|
if (GV->use_empty()) {
|
|
DEBUG(std::cerr << " *** Marking constant allowed us to simplify "
|
|
"all users and delete global!\n");
|
|
GV->eraseFromParent();
|
|
++NumDeleted;
|
|
}
|
|
|
|
++NumMarked;
|
|
return true;
|
|
} else if (!GS.isNotSuitableForSRA &&
|
|
!GV->getInitializer()->getType()->isFirstClassType()) {
|
|
if (GlobalVariable *FirstNewGV = SRAGlobal(GV)) {
|
|
GVI = FirstNewGV; // Don't skip the newly produced globals!
|
|
return true;
|
|
}
|
|
} else if (GS.StoredType == GlobalStatus::isStoredOnce) {
|
|
// If the initial value for the global was an undef value, and if only one
|
|
// other value was stored into it, we can just change the initializer to
|
|
// be an undef value, then delete all stores to the global. This allows
|
|
// us to mark it constant.
|
|
if (isa<UndefValue>(GV->getInitializer()) &&
|
|
isa<Constant>(GS.StoredOnceValue)) {
|
|
// Change the initial value here.
|
|
GV->setInitializer(cast<Constant>(GS.StoredOnceValue));
|
|
|
|
// Clean up any obviously simplifiable users now.
|
|
CleanupConstantGlobalUsers(GV, GV->getInitializer());
|
|
|
|
if (GV->use_empty()) {
|
|
DEBUG(std::cerr << " *** Substituting initializer allowed us to "
|
|
"simplify all users and delete global!\n");
|
|
GV->eraseFromParent();
|
|
++NumDeleted;
|
|
} else {
|
|
GVI = GV;
|
|
}
|
|
++NumSubstitute;
|
|
return true;
|
|
}
|
|
|
|
// Try to optimize globals based on the knowledge that only one value
|
|
// (besides its initializer) is ever stored to the global.
|
|
if (OptimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GVI,
|
|
getAnalysis<TargetData>()))
|
|
return true;
|
|
}
|
|
}
|
|
return false;
|
|
}
|
|
|
|
|
|
bool GlobalOpt::runOnModule(Module &M) {
|
|
bool Changed = false;
|
|
|
|
// As a prepass, delete functions that are trivially dead.
|
|
bool LocalChange = true;
|
|
while (LocalChange) {
|
|
LocalChange = false;
|
|
for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) {
|
|
Function *F = FI++;
|
|
F->removeDeadConstantUsers();
|
|
if (F->use_empty() && (F->hasInternalLinkage() ||
|
|
F->hasLinkOnceLinkage())) {
|
|
M.getFunctionList().erase(F);
|
|
LocalChange = true;
|
|
++NumFnDeleted;
|
|
}
|
|
}
|
|
Changed |= LocalChange;
|
|
}
|
|
|
|
LocalChange = true;
|
|
while (LocalChange) {
|
|
LocalChange = false;
|
|
for (Module::giterator GVI = M.gbegin(), E = M.gend(); GVI != E;) {
|
|
GlobalVariable *GV = GVI++;
|
|
if (!GV->isConstant() && GV->hasInternalLinkage() &&
|
|
GV->hasInitializer())
|
|
LocalChange |= ProcessInternalGlobal(GV, GVI);
|
|
}
|
|
Changed |= LocalChange;
|
|
}
|
|
return Changed;
|
|
}
|