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//===- CodeGenPrepare.cpp - Prepare a function for code generation --------===//
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// The LLVM Compiler Infrastructure
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//===----------------------------------------------------------------------===//
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// This pass munges the code in the input function to better prepare it for
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// SelectionDAG-based code generation. This works around limitations in it's
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// basic-block-at-a-time approach. It should eventually be removed.
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "codegenprepare"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Constants.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Function.h"
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#include "llvm/InlineAsm.h"
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#include "llvm/Instructions.h"
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#include "llvm/IntrinsicInst.h"
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#include "llvm/Pass.h"
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#include "llvm/Analysis/ProfileInfo.h"
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#include "llvm/Target/TargetData.h"
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#include "llvm/Target/TargetLowering.h"
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#include "llvm/Transforms/Utils/AddrModeMatcher.h"
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#include "llvm/Transforms/Utils/BasicBlockUtils.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/SmallSet.h"
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#include "llvm/Assembly/Writer.h"
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#include "llvm/Support/CallSite.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/GetElementPtrTypeIterator.h"
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#include "llvm/Support/PatternMatch.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm::PatternMatch;
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class CodeGenPrepare : public FunctionPass {
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/// TLI - Keep a pointer of a TargetLowering to consult for determining
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/// transformation profitability.
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const TargetLowering *TLI;
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/// BackEdges - Keep a set of all the loop back edges.
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SmallSet<std::pair<const BasicBlock*, const BasicBlock*>, 8> BackEdges;
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static char ID; // Pass identification, replacement for typeid
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explicit CodeGenPrepare(const TargetLowering *tli = 0)
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: FunctionPass(&ID), TLI(tli) {}
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bool runOnFunction(Function &F);
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.addPreserved<ProfileInfo>();
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virtual void releaseMemory() {
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bool EliminateMostlyEmptyBlocks(Function &F);
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bool CanMergeBlocks(const BasicBlock *BB, const BasicBlock *DestBB) const;
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void EliminateMostlyEmptyBlock(BasicBlock *BB);
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bool OptimizeBlock(BasicBlock &BB);
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bool OptimizeMemoryInst(Instruction *I, Value *Addr, const Type *AccessTy,
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DenseMap<Value*,Value*> &SunkAddrs);
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bool OptimizeInlineAsmInst(Instruction *I, CallSite CS,
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DenseMap<Value*,Value*> &SunkAddrs);
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bool MoveExtToFormExtLoad(Instruction *I);
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bool OptimizeExtUses(Instruction *I);
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void findLoopBackEdges(const Function &F);
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char CodeGenPrepare::ID = 0;
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static RegisterPass<CodeGenPrepare> X("codegenprepare",
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"Optimize for code generation");
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FunctionPass *llvm::createCodeGenPreparePass(const TargetLowering *TLI) {
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return new CodeGenPrepare(TLI);
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/// findLoopBackEdges - Do a DFS walk to find loop back edges.
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void CodeGenPrepare::findLoopBackEdges(const Function &F) {
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SmallVector<std::pair<const BasicBlock*,const BasicBlock*>, 32> Edges;
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FindFunctionBackedges(F, Edges);
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BackEdges.insert(Edges.begin(), Edges.end());
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bool CodeGenPrepare::runOnFunction(Function &F) {
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bool EverMadeChange = false;
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PFI = getAnalysisIfAvailable<ProfileInfo>();
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// First pass, eliminate blocks that contain only PHI nodes and an
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// unconditional branch.
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EverMadeChange |= EliminateMostlyEmptyBlocks(F);
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// Now find loop back edges.
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findLoopBackEdges(F);
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bool MadeChange = true;
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for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
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MadeChange |= OptimizeBlock(*BB);
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EverMadeChange |= MadeChange;
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return EverMadeChange;
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/// EliminateMostlyEmptyBlocks - eliminate blocks that contain only PHI nodes,
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/// debug info directives, and an unconditional branch. Passes before isel
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/// (e.g. LSR/loopsimplify) often split edges in ways that are non-optimal for
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/// isel. Start by eliminating these blocks so we can split them the way we
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bool CodeGenPrepare::EliminateMostlyEmptyBlocks(Function &F) {
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bool MadeChange = false;
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// Note that this intentionally skips the entry block.
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for (Function::iterator I = ++F.begin(), E = F.end(); I != E; ) {
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BasicBlock *BB = I++;
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// If this block doesn't end with an uncond branch, ignore it.
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BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator());
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if (!BI || !BI->isUnconditional())
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// If the instruction before the branch (skipping debug info) isn't a phi
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// node, then other stuff is happening here.
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BasicBlock::iterator BBI = BI;
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if (BBI != BB->begin()) {
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while (isa<DbgInfoIntrinsic>(BBI)) {
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if (BBI == BB->begin())
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if (!isa<DbgInfoIntrinsic>(BBI) && !isa<PHINode>(BBI))
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// Do not break infinite loops.
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BasicBlock *DestBB = BI->getSuccessor(0);
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if (!CanMergeBlocks(BB, DestBB))
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EliminateMostlyEmptyBlock(BB);
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/// CanMergeBlocks - Return true if we can merge BB into DestBB if there is a
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/// single uncond branch between them, and BB contains no other non-phi
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bool CodeGenPrepare::CanMergeBlocks(const BasicBlock *BB,
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const BasicBlock *DestBB) const {
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// We only want to eliminate blocks whose phi nodes are used by phi nodes in
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// the successor. If there are more complex condition (e.g. preheaders),
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// don't mess around with them.
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BasicBlock::const_iterator BBI = BB->begin();
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while (const PHINode *PN = dyn_cast<PHINode>(BBI++)) {
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for (Value::use_const_iterator UI = PN->use_begin(), E = PN->use_end();
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const Instruction *User = cast<Instruction>(*UI);
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if (User->getParent() != DestBB || !isa<PHINode>(User))
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// If User is inside DestBB block and it is a PHINode then check
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// incoming value. If incoming value is not from BB then this is
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// a complex condition (e.g. preheaders) we want to avoid here.
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if (User->getParent() == DestBB) {
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if (const PHINode *UPN = dyn_cast<PHINode>(User))
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for (unsigned I = 0, E = UPN->getNumIncomingValues(); I != E; ++I) {
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Instruction *Insn = dyn_cast<Instruction>(UPN->getIncomingValue(I));
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if (Insn && Insn->getParent() == BB &&
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Insn->getParent() != UPN->getIncomingBlock(I))
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// If BB and DestBB contain any common predecessors, then the phi nodes in BB
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// and DestBB may have conflicting incoming values for the block. If so, we
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// can't merge the block.
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const PHINode *DestBBPN = dyn_cast<PHINode>(DestBB->begin());
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if (!DestBBPN) return true; // no conflict.
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// Collect the preds of BB.
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SmallPtrSet<const BasicBlock*, 16> BBPreds;
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if (const PHINode *BBPN = dyn_cast<PHINode>(BB->begin())) {
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// It is faster to get preds from a PHI than with pred_iterator.
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for (unsigned i = 0, e = BBPN->getNumIncomingValues(); i != e; ++i)
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BBPreds.insert(BBPN->getIncomingBlock(i));
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BBPreds.insert(pred_begin(BB), pred_end(BB));
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// Walk the preds of DestBB.
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for (unsigned i = 0, e = DestBBPN->getNumIncomingValues(); i != e; ++i) {
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BasicBlock *Pred = DestBBPN->getIncomingBlock(i);
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if (BBPreds.count(Pred)) { // Common predecessor?
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BBI = DestBB->begin();
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while (const PHINode *PN = dyn_cast<PHINode>(BBI++)) {
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const Value *V1 = PN->getIncomingValueForBlock(Pred);
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const Value *V2 = PN->getIncomingValueForBlock(BB);
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// If V2 is a phi node in BB, look up what the mapped value will be.
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if (const PHINode *V2PN = dyn_cast<PHINode>(V2))
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if (V2PN->getParent() == BB)
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V2 = V2PN->getIncomingValueForBlock(Pred);
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// If there is a conflict, bail out.
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if (V1 != V2) return false;
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/// EliminateMostlyEmptyBlock - Eliminate a basic block that have only phi's and
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/// an unconditional branch in it.
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void CodeGenPrepare::EliminateMostlyEmptyBlock(BasicBlock *BB) {
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BranchInst *BI = cast<BranchInst>(BB->getTerminator());
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BasicBlock *DestBB = BI->getSuccessor(0);
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DEBUG(dbgs() << "MERGING MOSTLY EMPTY BLOCKS - BEFORE:\n" << *BB << *DestBB);
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// If the destination block has a single pred, then this is a trivial edge,
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if (BasicBlock *SinglePred = DestBB->getSinglePredecessor()) {
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if (SinglePred != DestBB) {
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// Remember if SinglePred was the entry block of the function. If so, we
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// will need to move BB back to the entry position.
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bool isEntry = SinglePred == &SinglePred->getParent()->getEntryBlock();
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MergeBasicBlockIntoOnlyPred(DestBB, this);
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if (isEntry && BB != &BB->getParent()->getEntryBlock())
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BB->moveBefore(&BB->getParent()->getEntryBlock());
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DEBUG(dbgs() << "AFTER:\n" << *DestBB << "\n\n\n");
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// Otherwise, we have multiple predecessors of BB. Update the PHIs in DestBB
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// to handle the new incoming edges it is about to have.
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for (BasicBlock::iterator BBI = DestBB->begin();
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(PN = dyn_cast<PHINode>(BBI)); ++BBI) {
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// Remove the incoming value for BB, and remember it.
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Value *InVal = PN->removeIncomingValue(BB, false);
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// Two options: either the InVal is a phi node defined in BB or it is some
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// value that dominates BB.
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PHINode *InValPhi = dyn_cast<PHINode>(InVal);
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if (InValPhi && InValPhi->getParent() == BB) {
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// Add all of the input values of the input PHI as inputs of this phi.
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for (unsigned i = 0, e = InValPhi->getNumIncomingValues(); i != e; ++i)
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PN->addIncoming(InValPhi->getIncomingValue(i),
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InValPhi->getIncomingBlock(i));
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// Otherwise, add one instance of the dominating value for each edge that
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// we will be adding.
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if (PHINode *BBPN = dyn_cast<PHINode>(BB->begin())) {
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for (unsigned i = 0, e = BBPN->getNumIncomingValues(); i != e; ++i)
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PN->addIncoming(InVal, BBPN->getIncomingBlock(i));
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for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
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PN->addIncoming(InVal, *PI);
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// The PHIs are now updated, change everything that refers to BB to use
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// DestBB and remove BB.
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BB->replaceAllUsesWith(DestBB);
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PFI->replaceAllUses(BB, DestBB);
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PFI->removeEdge(ProfileInfo::getEdge(BB, DestBB));
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BB->eraseFromParent();
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DEBUG(dbgs() << "AFTER:\n" << *DestBB << "\n\n\n");
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/// FindReusablePredBB - Check all of the predecessors of the block DestPHI
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/// lives in to see if there is a block that we can reuse as a critical edge
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static BasicBlock *FindReusablePredBB(PHINode *DestPHI, BasicBlock *TIBB) {
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BasicBlock *Dest = DestPHI->getParent();
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/// TIPHIValues - This array is lazily computed to determine the values of
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/// PHIs in Dest that TI would provide.
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SmallVector<Value*, 32> TIPHIValues;
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/// TIBBEntryNo - This is a cache to speed up pred queries for TIBB.
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unsigned TIBBEntryNo = 0;
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// Check to see if Dest has any blocks that can be used as a split edge for
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for (unsigned pi = 0, e = DestPHI->getNumIncomingValues(); pi != e; ++pi) {
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BasicBlock *Pred = DestPHI->getIncomingBlock(pi);
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// To be usable, the pred has to end with an uncond branch to the dest.
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BranchInst *PredBr = dyn_cast<BranchInst>(Pred->getTerminator());
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if (!PredBr || !PredBr->isUnconditional())
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// Must be empty other than the branch and debug info.
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BasicBlock::iterator I = Pred->begin();
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while (isa<DbgInfoIntrinsic>(I))
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// Cannot be the entry block; its label does not get emitted.
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if (Pred == &Dest->getParent()->getEntryBlock())
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// Finally, since we know that Dest has phi nodes in it, we have to make
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// sure that jumping to Pred will have the same effect as going to Dest in
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// terms of PHI values.
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unsigned PredEntryNo = pi;
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bool FoundMatch = true;
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for (BasicBlock::iterator I = Dest->begin();
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(PN = dyn_cast<PHINode>(I)); ++I, ++PHINo) {
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if (PHINo == TIPHIValues.size()) {
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if (PN->getIncomingBlock(TIBBEntryNo) != TIBB)
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TIBBEntryNo = PN->getBasicBlockIndex(TIBB);
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TIPHIValues.push_back(PN->getIncomingValue(TIBBEntryNo));
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// If the PHI entry doesn't work, we can't use this pred.
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if (PN->getIncomingBlock(PredEntryNo) != Pred)
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PredEntryNo = PN->getBasicBlockIndex(Pred);
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if (TIPHIValues[PHINo] != PN->getIncomingValue(PredEntryNo)) {
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// If we found a workable predecessor, change TI to branch to Succ.
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/// SplitEdgeNicely - Split the critical edge from TI to its specified
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/// successor if it will improve codegen. We only do this if the successor has
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/// phi nodes (otherwise critical edges are ok). If there is already another
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/// predecessor of the succ that is empty (and thus has no phi nodes), use it
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/// instead of introducing a new block.
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static void SplitEdgeNicely(TerminatorInst *TI, unsigned SuccNum,
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SmallSet<std::pair<const BasicBlock*,
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const BasicBlock*>, 8> &BackEdges,
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BasicBlock *TIBB = TI->getParent();
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BasicBlock *Dest = TI->getSuccessor(SuccNum);
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assert(isa<PHINode>(Dest->begin()) &&
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"This should only be called if Dest has a PHI!");
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PHINode *DestPHI = cast<PHINode>(Dest->begin());
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// Do not split edges to EH landing pads.
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if (InvokeInst *Invoke = dyn_cast<InvokeInst>(TI))
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if (Invoke->getSuccessor(1) == Dest)
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// As a hack, never split backedges of loops. Even though the copy for any
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// PHIs inserted on the backedge would be dead for exits from the loop, we
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// assume that the cost of *splitting* the backedge would be too high.
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if (BackEdges.count(std::make_pair(TIBB, Dest)))
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if (BasicBlock *ReuseBB = FindReusablePredBB(DestPHI, TIBB)) {
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ProfileInfo *PFI = P->getAnalysisIfAvailable<ProfileInfo>();
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PFI->splitEdge(TIBB, Dest, ReuseBB);
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Dest->removePredecessor(TIBB);
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TI->setSuccessor(SuccNum, ReuseBB);
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SplitCriticalEdge(TI, SuccNum, P, true);
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/// OptimizeNoopCopyExpression - If the specified cast instruction is a noop
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/// copy (e.g. it's casting from one pointer type to another, i32->i8 on PPC),
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/// sink it into user blocks to reduce the number of virtual
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/// registers that must be created and coalesced.
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/// Return true if any changes are made.
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static bool OptimizeNoopCopyExpression(CastInst *CI, const TargetLowering &TLI){
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// If this is a noop copy,
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EVT SrcVT = TLI.getValueType(CI->getOperand(0)->getType());
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EVT DstVT = TLI.getValueType(CI->getType());
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// This is an fp<->int conversion?
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if (SrcVT.isInteger() != DstVT.isInteger())
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// If this is an extension, it will be a zero or sign extension, which
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if (SrcVT.bitsLT(DstVT)) return false;
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// If these values will be promoted, find out what they will be promoted
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// to. This helps us consider truncates on PPC as noop copies when they
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if (TLI.getTypeAction(CI->getContext(), SrcVT) == TargetLowering::Promote)
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SrcVT = TLI.getTypeToTransformTo(CI->getContext(), SrcVT);
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if (TLI.getTypeAction(CI->getContext(), DstVT) == TargetLowering::Promote)
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DstVT = TLI.getTypeToTransformTo(CI->getContext(), DstVT);
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// If, after promotion, these are the same types, this is a noop copy.
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BasicBlock *DefBB = CI->getParent();
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/// InsertedCasts - Only insert a cast in each block once.
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DenseMap<BasicBlock*, CastInst*> InsertedCasts;
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bool MadeChange = false;
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for (Value::use_iterator UI = CI->use_begin(), E = CI->use_end();
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Use &TheUse = UI.getUse();
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Instruction *User = cast<Instruction>(*UI);
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// Figure out which BB this cast is used in. For PHI's this is the
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// appropriate predecessor block.
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BasicBlock *UserBB = User->getParent();
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if (PHINode *PN = dyn_cast<PHINode>(User)) {
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UserBB = PN->getIncomingBlock(UI);
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// Preincrement use iterator so we don't invalidate it.
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// If this user is in the same block as the cast, don't change the cast.
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if (UserBB == DefBB) continue;
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// If we have already inserted a cast into this block, use it.
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CastInst *&InsertedCast = InsertedCasts[UserBB];
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BasicBlock::iterator InsertPt = UserBB->getFirstNonPHI();
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CastInst::Create(CI->getOpcode(), CI->getOperand(0), CI->getType(), "",
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// Replace a use of the cast with a use of the new cast.
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TheUse = InsertedCast;
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// If we removed all uses, nuke the cast.
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if (CI->use_empty()) {
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CI->eraseFromParent();
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/// OptimizeCmpExpression - sink the given CmpInst into user blocks to reduce
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/// the number of virtual registers that must be created and coalesced. This is
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/// a clear win except on targets with multiple condition code registers
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/// (PowerPC), where it might lose; some adjustment may be wanted there.
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/// Return true if any changes are made.
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static bool OptimizeCmpExpression(CmpInst *CI) {
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BasicBlock *DefBB = CI->getParent();
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/// InsertedCmp - Only insert a cmp in each block once.
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DenseMap<BasicBlock*, CmpInst*> InsertedCmps;
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bool MadeChange = false;
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for (Value::use_iterator UI = CI->use_begin(), E = CI->use_end();
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Use &TheUse = UI.getUse();
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Instruction *User = cast<Instruction>(*UI);
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// Preincrement use iterator so we don't invalidate it.
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// Don't bother for PHI nodes.
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if (isa<PHINode>(User))
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// Figure out which BB this cmp is used in.
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BasicBlock *UserBB = User->getParent();
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// If this user is in the same block as the cmp, don't change the cmp.
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if (UserBB == DefBB) continue;
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// If we have already inserted a cmp into this block, use it.
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CmpInst *&InsertedCmp = InsertedCmps[UserBB];
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BasicBlock::iterator InsertPt = UserBB->getFirstNonPHI();
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CmpInst::Create(CI->getOpcode(),
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CI->getPredicate(), CI->getOperand(0),
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CI->getOperand(1), "", InsertPt);
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// Replace a use of the cmp with a use of the new cmp.
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TheUse = InsertedCmp;
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// If we removed all uses, nuke the cmp.
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CI->eraseFromParent();
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//===----------------------------------------------------------------------===//
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// Memory Optimization
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//===----------------------------------------------------------------------===//
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/// IsNonLocalValue - Return true if the specified values are defined in a
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/// different basic block than BB.
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static bool IsNonLocalValue(Value *V, BasicBlock *BB) {
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if (Instruction *I = dyn_cast<Instruction>(V))
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return I->getParent() != BB;
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/// OptimizeMemoryInst - Load and Store Instructions often have
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/// addressing modes that can do significant amounts of computation. As such,
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/// instruction selection will try to get the load or store to do as much
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/// computation as possible for the program. The problem is that isel can only
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/// see within a single block. As such, we sink as much legal addressing mode
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/// stuff into the block as possible.
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/// This method is used to optimize both load/store and inline asms with memory
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bool CodeGenPrepare::OptimizeMemoryInst(Instruction *MemoryInst, Value *Addr,
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const Type *AccessTy,
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DenseMap<Value*,Value*> &SunkAddrs) {
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// Figure out what addressing mode will be built up for this operation.
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SmallVector<Instruction*, 16> AddrModeInsts;
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ExtAddrMode AddrMode = AddressingModeMatcher::Match(Addr, AccessTy,MemoryInst,
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AddrModeInsts, *TLI);
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// Check to see if any of the instructions supersumed by this addr mode are
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// non-local to I's BB.
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bool AnyNonLocal = false;
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for (unsigned i = 0, e = AddrModeInsts.size(); i != e; ++i) {
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if (IsNonLocalValue(AddrModeInsts[i], MemoryInst->getParent())) {
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// If all the instructions matched are already in this BB, don't do anything.
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DEBUG(dbgs() << "CGP: Found local addrmode: " << AddrMode << "\n");
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// Insert this computation right after this user. Since our caller is
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// scanning from the top of the BB to the bottom, reuse of the expr are
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// guaranteed to happen later.
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BasicBlock::iterator InsertPt = MemoryInst;
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// Now that we determined the addressing expression we want to use and know
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// that we have to sink it into this block. Check to see if we have already
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// done this for some other load/store instr in this block. If so, reuse the
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Value *&SunkAddr = SunkAddrs[Addr];
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DEBUG(dbgs() << "CGP: Reusing nonlocal addrmode: " << AddrMode << " for "
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if (SunkAddr->getType() != Addr->getType())
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SunkAddr = new BitCastInst(SunkAddr, Addr->getType(), "tmp", InsertPt);
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DEBUG(dbgs() << "CGP: SINKING nonlocal addrmode: " << AddrMode << " for "
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const Type *IntPtrTy =
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TLI->getTargetData()->getIntPtrType(AccessTy->getContext());
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// Start with the base register. Do this first so that subsequent address
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// matching finds it last, which will prevent it from trying to match it
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// as the scaled value in case it happens to be a mul. That would be
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// problematic if we've sunk a different mul for the scale, because then
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// we'd end up sinking both muls.
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if (AddrMode.BaseReg) {
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Value *V = AddrMode.BaseReg;
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if (V->getType()->isPointerTy())
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V = new PtrToIntInst(V, IntPtrTy, "sunkaddr", InsertPt);
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if (V->getType() != IntPtrTy)
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V = CastInst::CreateIntegerCast(V, IntPtrTy, /*isSigned=*/true,
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"sunkaddr", InsertPt);
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// Add the scale value.
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if (AddrMode.Scale) {
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Value *V = AddrMode.ScaledReg;
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if (V->getType() == IntPtrTy) {
628
} else if (V->getType()->isPointerTy()) {
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V = new PtrToIntInst(V, IntPtrTy, "sunkaddr", InsertPt);
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} else if (cast<IntegerType>(IntPtrTy)->getBitWidth() <
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cast<IntegerType>(V->getType())->getBitWidth()) {
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V = new TruncInst(V, IntPtrTy, "sunkaddr", InsertPt);
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V = new SExtInst(V, IntPtrTy, "sunkaddr", InsertPt);
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if (AddrMode.Scale != 1)
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V = BinaryOperator::CreateMul(V, ConstantInt::get(IntPtrTy,
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"sunkaddr", InsertPt);
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Result = BinaryOperator::CreateAdd(Result, V, "sunkaddr", InsertPt);
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// Add in the BaseGV if present.
647
if (AddrMode.BaseGV) {
648
Value *V = new PtrToIntInst(AddrMode.BaseGV, IntPtrTy, "sunkaddr",
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Result = BinaryOperator::CreateAdd(Result, V, "sunkaddr", InsertPt);
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// Add in the Base Offset if present.
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if (AddrMode.BaseOffs) {
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Value *V = ConstantInt::get(IntPtrTy, AddrMode.BaseOffs);
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Result = BinaryOperator::CreateAdd(Result, V, "sunkaddr", InsertPt);
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SunkAddr = Constant::getNullValue(Addr->getType());
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SunkAddr = new IntToPtrInst(Result, Addr->getType(), "sunkaddr",InsertPt);
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MemoryInst->replaceUsesOfWith(Addr, SunkAddr);
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if (Addr->use_empty())
674
RecursivelyDeleteTriviallyDeadInstructions(Addr);
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/// OptimizeInlineAsmInst - If there are any memory operands, use
679
/// OptimizeMemoryInst to sink their address computing into the block when
680
/// possible / profitable.
681
bool CodeGenPrepare::OptimizeInlineAsmInst(Instruction *I, CallSite CS,
682
DenseMap<Value*,Value*> &SunkAddrs) {
683
bool MadeChange = false;
684
InlineAsm *IA = cast<InlineAsm>(CS.getCalledValue());
686
// Do a prepass over the constraints, canonicalizing them, and building up the
687
// ConstraintOperands list.
688
std::vector<InlineAsm::ConstraintInfo>
689
ConstraintInfos = IA->ParseConstraints();
691
/// ConstraintOperands - Information about all of the constraints.
692
std::vector<TargetLowering::AsmOperandInfo> ConstraintOperands;
693
unsigned ArgNo = 0; // ArgNo - The argument of the CallInst.
694
for (unsigned i = 0, e = ConstraintInfos.size(); i != e; ++i) {
696
push_back(TargetLowering::AsmOperandInfo(ConstraintInfos[i]));
697
TargetLowering::AsmOperandInfo &OpInfo = ConstraintOperands.back();
699
// Compute the value type for each operand.
700
switch (OpInfo.Type) {
701
case InlineAsm::isOutput:
702
if (OpInfo.isIndirect)
703
OpInfo.CallOperandVal = CS.getArgument(ArgNo++);
705
case InlineAsm::isInput:
706
OpInfo.CallOperandVal = CS.getArgument(ArgNo++);
708
case InlineAsm::isClobber:
713
// Compute the constraint code and ConstraintType to use.
714
TLI->ComputeConstraintToUse(OpInfo, SDValue(),
715
OpInfo.ConstraintType == TargetLowering::C_Memory);
717
if (OpInfo.ConstraintType == TargetLowering::C_Memory &&
719
Value *OpVal = OpInfo.CallOperandVal;
720
MadeChange |= OptimizeMemoryInst(I, OpVal, OpVal->getType(), SunkAddrs);
727
/// MoveExtToFormExtLoad - Move a zext or sext fed by a load into the same
728
/// basic block as the load, unless conditions are unfavorable. This allows
729
/// SelectionDAG to fold the extend into the load.
731
bool CodeGenPrepare::MoveExtToFormExtLoad(Instruction *I) {
732
// Look for a load being extended.
733
LoadInst *LI = dyn_cast<LoadInst>(I->getOperand(0));
734
if (!LI) return false;
736
// If they're already in the same block, there's nothing to do.
737
if (LI->getParent() == I->getParent())
740
// If the load has other users and the truncate is not free, this probably
742
if (!LI->hasOneUse() &&
743
TLI && !TLI->isTruncateFree(I->getType(), LI->getType()))
746
// Check whether the target supports casts folded into loads.
748
if (isa<ZExtInst>(I))
749
LType = ISD::ZEXTLOAD;
751
assert(isa<SExtInst>(I) && "Unexpected ext type!");
752
LType = ISD::SEXTLOAD;
754
if (TLI && !TLI->isLoadExtLegal(LType, TLI->getValueType(LI->getType())))
757
// Move the extend into the same block as the load, so that SelectionDAG
759
I->removeFromParent();
764
bool CodeGenPrepare::OptimizeExtUses(Instruction *I) {
765
BasicBlock *DefBB = I->getParent();
767
// If both result of the {s|z}xt and its source are live out, rewrite all
768
// other uses of the source with result of extension.
769
Value *Src = I->getOperand(0);
770
if (Src->hasOneUse())
773
// Only do this xform if truncating is free.
774
if (TLI && !TLI->isTruncateFree(I->getType(), Src->getType()))
777
// Only safe to perform the optimization if the source is also defined in
779
if (!isa<Instruction>(Src) || DefBB != cast<Instruction>(Src)->getParent())
782
bool DefIsLiveOut = false;
783
for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
785
Instruction *User = cast<Instruction>(*UI);
787
// Figure out which BB this ext is used in.
788
BasicBlock *UserBB = User->getParent();
789
if (UserBB == DefBB) continue;
796
// Make sure non of the uses are PHI nodes.
797
for (Value::use_iterator UI = Src->use_begin(), E = Src->use_end();
799
Instruction *User = cast<Instruction>(*UI);
800
BasicBlock *UserBB = User->getParent();
801
if (UserBB == DefBB) continue;
802
// Be conservative. We don't want this xform to end up introducing
803
// reloads just before load / store instructions.
804
if (isa<PHINode>(User) || isa<LoadInst>(User) || isa<StoreInst>(User))
808
// InsertedTruncs - Only insert one trunc in each block once.
809
DenseMap<BasicBlock*, Instruction*> InsertedTruncs;
811
bool MadeChange = false;
812
for (Value::use_iterator UI = Src->use_begin(), E = Src->use_end();
814
Use &TheUse = UI.getUse();
815
Instruction *User = cast<Instruction>(*UI);
817
// Figure out which BB this ext is used in.
818
BasicBlock *UserBB = User->getParent();
819
if (UserBB == DefBB) continue;
821
// Both src and def are live in this block. Rewrite the use.
822
Instruction *&InsertedTrunc = InsertedTruncs[UserBB];
824
if (!InsertedTrunc) {
825
BasicBlock::iterator InsertPt = UserBB->getFirstNonPHI();
827
InsertedTrunc = new TruncInst(I, Src->getType(), "", InsertPt);
830
// Replace a use of the {s|z}ext source with a use of the result.
831
TheUse = InsertedTrunc;
839
// In this pass we look for GEP and cast instructions that are used
840
// across basic blocks and rewrite them to improve basic-block-at-a-time
842
bool CodeGenPrepare::OptimizeBlock(BasicBlock &BB) {
843
bool MadeChange = false;
845
// Split all critical edges where the dest block has a PHI.
846
TerminatorInst *BBTI = BB.getTerminator();
847
if (BBTI->getNumSuccessors() > 1 && !isa<IndirectBrInst>(BBTI)) {
848
for (unsigned i = 0, e = BBTI->getNumSuccessors(); i != e; ++i) {
849
BasicBlock *SuccBB = BBTI->getSuccessor(i);
850
if (isa<PHINode>(SuccBB->begin()) && isCriticalEdge(BBTI, i, true))
851
SplitEdgeNicely(BBTI, i, BackEdges, this);
855
// Keep track of non-local addresses that have been sunk into this block.
856
// This allows us to avoid inserting duplicate code for blocks with multiple
857
// load/stores of the same address.
858
DenseMap<Value*, Value*> SunkAddrs;
860
for (BasicBlock::iterator BBI = BB.begin(), E = BB.end(); BBI != E; ) {
861
Instruction *I = BBI++;
863
if (CastInst *CI = dyn_cast<CastInst>(I)) {
864
// If the source of the cast is a constant, then this should have
865
// already been constant folded. The only reason NOT to constant fold
866
// it is if something (e.g. LSR) was careful to place the constant
867
// evaluation in a block other than then one that uses it (e.g. to hoist
868
// the address of globals out of a loop). If this is the case, we don't
869
// want to forward-subst the cast.
870
if (isa<Constant>(CI->getOperand(0)))
875
Change = OptimizeNoopCopyExpression(CI, *TLI);
876
MadeChange |= Change;
879
if (!Change && (isa<ZExtInst>(I) || isa<SExtInst>(I))) {
880
MadeChange |= MoveExtToFormExtLoad(I);
881
MadeChange |= OptimizeExtUses(I);
883
} else if (CmpInst *CI = dyn_cast<CmpInst>(I)) {
884
MadeChange |= OptimizeCmpExpression(CI);
885
} else if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
887
MadeChange |= OptimizeMemoryInst(I, I->getOperand(0), LI->getType(),
889
} else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
891
MadeChange |= OptimizeMemoryInst(I, SI->getOperand(1),
892
SI->getOperand(0)->getType(),
894
} else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
895
if (GEPI->hasAllZeroIndices()) {
896
/// The GEP operand must be a pointer, so must its result -> BitCast
897
Instruction *NC = new BitCastInst(GEPI->getOperand(0), GEPI->getType(),
898
GEPI->getName(), GEPI);
899
GEPI->replaceAllUsesWith(NC);
900
GEPI->eraseFromParent();
904
} else if (CallInst *CI = dyn_cast<CallInst>(I)) {
905
// If we found an inline asm expession, and if the target knows how to
906
// lower it to normal LLVM code, do so now.
907
if (TLI && isa<InlineAsm>(CI->getCalledValue())) {
908
if (TLI->ExpandInlineAsm(CI)) {
910
// Avoid processing instructions out of order, which could cause
911
// reuse before a value is defined.
914
// Sink address computing for memory operands into the block.
915
MadeChange |= OptimizeInlineAsmInst(I, &(*CI), SunkAddrs);
added
removed
libclamav/c++/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp
