mirror of
https://github.com/c64scene-ar/llvm-6502.git
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135375 91177308-0d34-0410-b5e6-96231b3b80d8
1162 lines
40 KiB
C++
1162 lines
40 KiB
C++
//===- CodeGenPrepare.cpp - Prepare a function for code generation --------===//
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//
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// The LLVM Compiler Infrastructure
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//
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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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//===----------------------------------------------------------------------===//
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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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//===----------------------------------------------------------------------===//
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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/Dominators.h"
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#include "llvm/Analysis/InstructionSimplify.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/Transforms/Utils/BuildLibCalls.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/ADT/Statistic.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/CommandLine.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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#include "llvm/Support/IRBuilder.h"
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#include "llvm/Support/ValueHandle.h"
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using namespace llvm;
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using namespace llvm::PatternMatch;
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STATISTIC(NumBlocksElim, "Number of blocks eliminated");
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STATISTIC(NumPHIsElim, "Number of trivial PHIs eliminated");
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STATISTIC(NumGEPsElim, "Number of GEPs converted to casts");
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STATISTIC(NumCmpUses, "Number of uses of Cmp expressions replaced with uses of "
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"sunken Cmps");
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STATISTIC(NumCastUses, "Number of uses of Cast expressions replaced with uses "
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"of sunken Casts");
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STATISTIC(NumMemoryInsts, "Number of memory instructions whose address "
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"computations were sunk");
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STATISTIC(NumExtsMoved, "Number of [s|z]ext instructions combined with loads");
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STATISTIC(NumExtUses, "Number of uses of [s|z]ext instructions optimized");
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STATISTIC(NumRetsDup, "Number of return instructions duplicated");
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static cl::opt<bool> DisableBranchOpts(
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"disable-cgp-branch-opts", cl::Hidden, cl::init(false),
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cl::desc("Disable branch optimizations in CodeGenPrepare"));
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namespace {
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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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DominatorTree *DT;
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ProfileInfo *PFI;
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/// CurInstIterator - As we scan instructions optimizing them, this is the
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/// next instruction to optimize. Xforms that can invalidate this should
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/// update it.
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BasicBlock::iterator CurInstIterator;
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/// Keeps track of non-local addresses that have been sunk into a block.
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/// This allows us to avoid inserting duplicate code for blocks with
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/// multiple load/stores of the same address.
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DenseMap<Value*, Value*> SunkAddrs;
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/// ModifiedDT - If CFG is modified in anyway, dominator tree may need to
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/// be updated.
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bool ModifiedDT;
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public:
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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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initializeCodeGenPreparePass(*PassRegistry::getPassRegistry());
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}
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bool runOnFunction(Function &F);
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.addPreserved<DominatorTree>();
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AU.addPreserved<ProfileInfo>();
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}
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private:
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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 OptimizeInst(Instruction *I);
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bool OptimizeMemoryInst(Instruction *I, Value *Addr, Type *AccessTy);
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bool OptimizeInlineAsmInst(CallInst *CS);
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bool OptimizeCallInst(CallInst *CI);
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bool MoveExtToFormExtLoad(Instruction *I);
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bool OptimizeExtUses(Instruction *I);
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bool DupRetToEnableTailCallOpts(ReturnInst *RI);
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};
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}
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char CodeGenPrepare::ID = 0;
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INITIALIZE_PASS(CodeGenPrepare, "codegenprepare",
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"Optimize for code generation", false, false)
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FunctionPass *llvm::createCodeGenPreparePass(const TargetLowering *TLI) {
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return new CodeGenPrepare(TLI);
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}
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bool CodeGenPrepare::runOnFunction(Function &F) {
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bool EverMadeChange = false;
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ModifiedDT = false;
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DT = getAnalysisIfAvailable<DominatorTree>();
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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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bool MadeChange = true;
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while (MadeChange) {
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MadeChange = false;
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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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MadeChange |= OptimizeBlock(*BB);
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}
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EverMadeChange |= MadeChange;
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}
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SunkAddrs.clear();
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if (!DisableBranchOpts) {
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MadeChange = false;
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for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
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MadeChange |= ConstantFoldTerminator(BB, true);
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if (MadeChange)
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ModifiedDT = true;
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EverMadeChange |= MadeChange;
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}
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if (ModifiedDT && DT)
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DT->DT->recalculate(F);
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return EverMadeChange;
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}
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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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/// want them.
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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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continue;
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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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--BBI;
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while (isa<DbgInfoIntrinsic>(BBI)) {
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if (BBI == BB->begin())
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break;
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--BBI;
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}
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if (!isa<DbgInfoIntrinsic>(BBI) && !isa<PHINode>(BBI))
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continue;
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}
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// Do not break infinite loops.
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BasicBlock *DestBB = BI->getSuccessor(0);
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if (DestBB == BB)
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continue;
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if (!CanMergeBlocks(BB, DestBB))
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continue;
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EliminateMostlyEmptyBlock(BB);
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MadeChange = true;
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}
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return MadeChange;
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}
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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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/// instructions.
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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::const_use_iterator UI = PN->use_begin(), E = PN->use_end();
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UI != E; ++UI) {
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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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return false;
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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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return false;
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}
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}
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}
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}
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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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} else {
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BBPreds.insert(pred_begin(BB), pred_end(BB));
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}
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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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}
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}
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}
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return true;
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}
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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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// just collapse it.
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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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return;
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}
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}
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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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PHINode *PN;
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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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} else {
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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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} else {
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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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}
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}
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}
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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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if (DT && !ModifiedDT) {
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BasicBlock *BBIDom = DT->getNode(BB)->getIDom()->getBlock();
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BasicBlock *DestBBIDom = DT->getNode(DestBB)->getIDom()->getBlock();
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BasicBlock *NewIDom = DT->findNearestCommonDominator(BBIDom, DestBBIDom);
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DT->changeImmediateDominator(DestBB, NewIDom);
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DT->eraseNode(BB);
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}
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if (PFI) {
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PFI->replaceAllUses(BB, DestBB);
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PFI->removeEdge(ProfileInfo::getEdge(BB, DestBB));
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}
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BB->eraseFromParent();
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++NumBlocksElim;
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DEBUG(dbgs() << "AFTER:\n" << *DestBB << "\n\n\n");
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}
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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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///
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/// Return true if any changes are made.
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///
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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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return false;
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// If this is an extension, it will be a zero or sign extension, which
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// isn't a noop.
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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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// are.
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if (TLI.getTypeAction(CI->getContext(), SrcVT) ==
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TargetLowering::TypePromoteInteger)
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SrcVT = TLI.getTypeToTransformTo(CI->getContext(), SrcVT);
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if (TLI.getTypeAction(CI->getContext(), DstVT) ==
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TargetLowering::TypePromoteInteger)
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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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if (SrcVT != DstVT)
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return false;
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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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UI != E; ) {
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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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}
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// Preincrement use iterator so we don't invalidate it.
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++UI;
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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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if (!InsertedCast) {
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BasicBlock::iterator InsertPt = UserBB->getFirstNonPHI();
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InsertedCast =
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CastInst::Create(CI->getOpcode(), CI->getOperand(0), CI->getType(), "",
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InsertPt);
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MadeChange = true;
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}
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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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++NumCastUses;
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}
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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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MadeChange = true;
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}
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return MadeChange;
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}
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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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///
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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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UI != E; ) {
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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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++UI;
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// Don't bother for PHI nodes.
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if (isa<PHINode>(User))
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continue;
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|
|
// Figure out which BB this cmp is used in.
|
|
BasicBlock *UserBB = User->getParent();
|
|
|
|
// If this user is in the same block as the cmp, don't change the cmp.
|
|
if (UserBB == DefBB) continue;
|
|
|
|
// If we have already inserted a cmp into this block, use it.
|
|
CmpInst *&InsertedCmp = InsertedCmps[UserBB];
|
|
|
|
if (!InsertedCmp) {
|
|
BasicBlock::iterator InsertPt = UserBB->getFirstNonPHI();
|
|
|
|
InsertedCmp =
|
|
CmpInst::Create(CI->getOpcode(),
|
|
CI->getPredicate(), CI->getOperand(0),
|
|
CI->getOperand(1), "", InsertPt);
|
|
MadeChange = true;
|
|
}
|
|
|
|
// Replace a use of the cmp with a use of the new cmp.
|
|
TheUse = InsertedCmp;
|
|
++NumCmpUses;
|
|
}
|
|
|
|
// If we removed all uses, nuke the cmp.
|
|
if (CI->use_empty())
|
|
CI->eraseFromParent();
|
|
|
|
return MadeChange;
|
|
}
|
|
|
|
namespace {
|
|
class CodeGenPrepareFortifiedLibCalls : public SimplifyFortifiedLibCalls {
|
|
protected:
|
|
void replaceCall(Value *With) {
|
|
CI->replaceAllUsesWith(With);
|
|
CI->eraseFromParent();
|
|
}
|
|
bool isFoldable(unsigned SizeCIOp, unsigned, bool) const {
|
|
if (ConstantInt *SizeCI =
|
|
dyn_cast<ConstantInt>(CI->getArgOperand(SizeCIOp)))
|
|
return SizeCI->isAllOnesValue();
|
|
return false;
|
|
}
|
|
};
|
|
} // end anonymous namespace
|
|
|
|
bool CodeGenPrepare::OptimizeCallInst(CallInst *CI) {
|
|
BasicBlock *BB = CI->getParent();
|
|
|
|
// Lower inline assembly if we can.
|
|
// If we found an inline asm expession, and if the target knows how to
|
|
// lower it to normal LLVM code, do so now.
|
|
if (TLI && isa<InlineAsm>(CI->getCalledValue())) {
|
|
if (TLI->ExpandInlineAsm(CI)) {
|
|
// Avoid invalidating the iterator.
|
|
CurInstIterator = BB->begin();
|
|
// Avoid processing instructions out of order, which could cause
|
|
// reuse before a value is defined.
|
|
SunkAddrs.clear();
|
|
return true;
|
|
}
|
|
// Sink address computing for memory operands into the block.
|
|
if (OptimizeInlineAsmInst(CI))
|
|
return true;
|
|
}
|
|
|
|
// Lower all uses of llvm.objectsize.*
|
|
IntrinsicInst *II = dyn_cast<IntrinsicInst>(CI);
|
|
if (II && II->getIntrinsicID() == Intrinsic::objectsize) {
|
|
bool Min = (cast<ConstantInt>(II->getArgOperand(1))->getZExtValue() == 1);
|
|
Type *ReturnTy = CI->getType();
|
|
Constant *RetVal = ConstantInt::get(ReturnTy, Min ? 0 : -1ULL);
|
|
|
|
// Substituting this can cause recursive simplifications, which can
|
|
// invalidate our iterator. Use a WeakVH to hold onto it in case this
|
|
// happens.
|
|
WeakVH IterHandle(CurInstIterator);
|
|
|
|
ReplaceAndSimplifyAllUses(CI, RetVal, TLI ? TLI->getTargetData() : 0,
|
|
ModifiedDT ? 0 : DT);
|
|
|
|
// If the iterator instruction was recursively deleted, start over at the
|
|
// start of the block.
|
|
if (IterHandle != CurInstIterator) {
|
|
CurInstIterator = BB->begin();
|
|
SunkAddrs.clear();
|
|
}
|
|
return true;
|
|
}
|
|
|
|
// From here on out we're working with named functions.
|
|
if (CI->getCalledFunction() == 0) return false;
|
|
|
|
// llvm.dbg.value is far away from the value then iSel may not be able
|
|
// handle it properly. iSel will drop llvm.dbg.value if it can not
|
|
// find a node corresponding to the value.
|
|
if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(CI))
|
|
if (Instruction *VI = dyn_cast_or_null<Instruction>(DVI->getValue()))
|
|
if (!VI->isTerminator() &&
|
|
(DVI->getParent() != VI->getParent() || DT->dominates(DVI, VI))) {
|
|
DEBUG(dbgs() << "Moving Debug Value before :\n" << *DVI << ' ' << *VI);
|
|
DVI->removeFromParent();
|
|
if (isa<PHINode>(VI))
|
|
DVI->insertBefore(VI->getParent()->getFirstNonPHI());
|
|
else
|
|
DVI->insertAfter(VI);
|
|
return true;
|
|
}
|
|
|
|
// We'll need TargetData from here on out.
|
|
const TargetData *TD = TLI ? TLI->getTargetData() : 0;
|
|
if (!TD) return false;
|
|
|
|
// Lower all default uses of _chk calls. This is very similar
|
|
// to what InstCombineCalls does, but here we are only lowering calls
|
|
// that have the default "don't know" as the objectsize. Anything else
|
|
// should be left alone.
|
|
CodeGenPrepareFortifiedLibCalls Simplifier;
|
|
return Simplifier.fold(CI, TD);
|
|
}
|
|
|
|
/// DupRetToEnableTailCallOpts - Look for opportunities to duplicate return
|
|
/// instructions to the predecessor to enable tail call optimizations. The
|
|
/// case it is currently looking for is:
|
|
/// bb0:
|
|
/// %tmp0 = tail call i32 @f0()
|
|
/// br label %return
|
|
/// bb1:
|
|
/// %tmp1 = tail call i32 @f1()
|
|
/// br label %return
|
|
/// bb2:
|
|
/// %tmp2 = tail call i32 @f2()
|
|
/// br label %return
|
|
/// return:
|
|
/// %retval = phi i32 [ %tmp0, %bb0 ], [ %tmp1, %bb1 ], [ %tmp2, %bb2 ]
|
|
/// ret i32 %retval
|
|
///
|
|
/// =>
|
|
///
|
|
/// bb0:
|
|
/// %tmp0 = tail call i32 @f0()
|
|
/// ret i32 %tmp0
|
|
/// bb1:
|
|
/// %tmp1 = tail call i32 @f1()
|
|
/// ret i32 %tmp1
|
|
/// bb2:
|
|
/// %tmp2 = tail call i32 @f2()
|
|
/// ret i32 %tmp2
|
|
///
|
|
bool CodeGenPrepare::DupRetToEnableTailCallOpts(ReturnInst *RI) {
|
|
if (!TLI)
|
|
return false;
|
|
|
|
Value *V = RI->getReturnValue();
|
|
PHINode *PN = V ? dyn_cast<PHINode>(V) : NULL;
|
|
if (V && !PN)
|
|
return false;
|
|
|
|
BasicBlock *BB = RI->getParent();
|
|
if (PN && PN->getParent() != BB)
|
|
return false;
|
|
|
|
// It's not safe to eliminate the sign / zero extension of the return value.
|
|
// See llvm::isInTailCallPosition().
|
|
const Function *F = BB->getParent();
|
|
unsigned CallerRetAttr = F->getAttributes().getRetAttributes();
|
|
if ((CallerRetAttr & Attribute::ZExt) || (CallerRetAttr & Attribute::SExt))
|
|
return false;
|
|
|
|
// Make sure there are no instructions between the PHI and return, or that the
|
|
// return is the first instruction in the block.
|
|
if (PN) {
|
|
BasicBlock::iterator BI = BB->begin();
|
|
do { ++BI; } while (isa<DbgInfoIntrinsic>(BI));
|
|
if (&*BI != RI)
|
|
return false;
|
|
} else {
|
|
BasicBlock::iterator BI = BB->begin();
|
|
while (isa<DbgInfoIntrinsic>(BI)) ++BI;
|
|
if (&*BI != RI)
|
|
return false;
|
|
}
|
|
|
|
/// Only dup the ReturnInst if the CallInst is likely to be emitted as a tail
|
|
/// call.
|
|
SmallVector<CallInst*, 4> TailCalls;
|
|
if (PN) {
|
|
for (unsigned I = 0, E = PN->getNumIncomingValues(); I != E; ++I) {
|
|
CallInst *CI = dyn_cast<CallInst>(PN->getIncomingValue(I));
|
|
// Make sure the phi value is indeed produced by the tail call.
|
|
if (CI && CI->hasOneUse() && CI->getParent() == PN->getIncomingBlock(I) &&
|
|
TLI->mayBeEmittedAsTailCall(CI))
|
|
TailCalls.push_back(CI);
|
|
}
|
|
} else {
|
|
SmallPtrSet<BasicBlock*, 4> VisitedBBs;
|
|
for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE; ++PI) {
|
|
if (!VisitedBBs.insert(*PI))
|
|
continue;
|
|
|
|
BasicBlock::InstListType &InstList = (*PI)->getInstList();
|
|
BasicBlock::InstListType::reverse_iterator RI = InstList.rbegin();
|
|
BasicBlock::InstListType::reverse_iterator RE = InstList.rend();
|
|
do { ++RI; } while (RI != RE && isa<DbgInfoIntrinsic>(&*RI));
|
|
if (RI == RE)
|
|
continue;
|
|
|
|
CallInst *CI = dyn_cast<CallInst>(&*RI);
|
|
if (CI && CI->use_empty() && TLI->mayBeEmittedAsTailCall(CI))
|
|
TailCalls.push_back(CI);
|
|
}
|
|
}
|
|
|
|
bool Changed = false;
|
|
for (unsigned i = 0, e = TailCalls.size(); i != e; ++i) {
|
|
CallInst *CI = TailCalls[i];
|
|
CallSite CS(CI);
|
|
|
|
// Conservatively require the attributes of the call to match those of the
|
|
// return. Ignore noalias because it doesn't affect the call sequence.
|
|
unsigned CalleeRetAttr = CS.getAttributes().getRetAttributes();
|
|
if ((CalleeRetAttr ^ CallerRetAttr) & ~Attribute::NoAlias)
|
|
continue;
|
|
|
|
// Make sure the call instruction is followed by an unconditional branch to
|
|
// the return block.
|
|
BasicBlock *CallBB = CI->getParent();
|
|
BranchInst *BI = dyn_cast<BranchInst>(CallBB->getTerminator());
|
|
if (!BI || !BI->isUnconditional() || BI->getSuccessor(0) != BB)
|
|
continue;
|
|
|
|
// Duplicate the return into CallBB.
|
|
(void)FoldReturnIntoUncondBranch(RI, BB, CallBB);
|
|
ModifiedDT = Changed = true;
|
|
++NumRetsDup;
|
|
}
|
|
|
|
// If we eliminated all predecessors of the block, delete the block now.
|
|
if (Changed && pred_begin(BB) == pred_end(BB))
|
|
BB->eraseFromParent();
|
|
|
|
return Changed;
|
|
}
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// Memory Optimization
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
/// IsNonLocalValue - Return true if the specified values are defined in a
|
|
/// different basic block than BB.
|
|
static bool IsNonLocalValue(Value *V, BasicBlock *BB) {
|
|
if (Instruction *I = dyn_cast<Instruction>(V))
|
|
return I->getParent() != BB;
|
|
return false;
|
|
}
|
|
|
|
/// OptimizeMemoryInst - Load and Store Instructions often have
|
|
/// addressing modes that can do significant amounts of computation. As such,
|
|
/// instruction selection will try to get the load or store to do as much
|
|
/// computation as possible for the program. The problem is that isel can only
|
|
/// see within a single block. As such, we sink as much legal addressing mode
|
|
/// stuff into the block as possible.
|
|
///
|
|
/// This method is used to optimize both load/store and inline asms with memory
|
|
/// operands.
|
|
bool CodeGenPrepare::OptimizeMemoryInst(Instruction *MemoryInst, Value *Addr,
|
|
Type *AccessTy) {
|
|
Value *Repl = Addr;
|
|
|
|
// Try to collapse single-value PHI nodes. This is necessary to undo
|
|
// unprofitable PRE transformations.
|
|
SmallVector<Value*, 8> worklist;
|
|
SmallPtrSet<Value*, 16> Visited;
|
|
worklist.push_back(Addr);
|
|
|
|
// Use a worklist to iteratively look through PHI nodes, and ensure that
|
|
// the addressing mode obtained from the non-PHI roots of the graph
|
|
// are equivalent.
|
|
Value *Consensus = 0;
|
|
unsigned NumUsesConsensus = 0;
|
|
bool IsNumUsesConsensusValid = false;
|
|
SmallVector<Instruction*, 16> AddrModeInsts;
|
|
ExtAddrMode AddrMode;
|
|
while (!worklist.empty()) {
|
|
Value *V = worklist.back();
|
|
worklist.pop_back();
|
|
|
|
// Break use-def graph loops.
|
|
if (Visited.count(V)) {
|
|
Consensus = 0;
|
|
break;
|
|
}
|
|
|
|
Visited.insert(V);
|
|
|
|
// For a PHI node, push all of its incoming values.
|
|
if (PHINode *P = dyn_cast<PHINode>(V)) {
|
|
for (unsigned i = 0, e = P->getNumIncomingValues(); i != e; ++i)
|
|
worklist.push_back(P->getIncomingValue(i));
|
|
continue;
|
|
}
|
|
|
|
// For non-PHIs, determine the addressing mode being computed.
|
|
SmallVector<Instruction*, 16> NewAddrModeInsts;
|
|
ExtAddrMode NewAddrMode =
|
|
AddressingModeMatcher::Match(V, AccessTy,MemoryInst,
|
|
NewAddrModeInsts, *TLI);
|
|
|
|
// This check is broken into two cases with very similar code to avoid using
|
|
// getNumUses() as much as possible. Some values have a lot of uses, so
|
|
// calling getNumUses() unconditionally caused a significant compile-time
|
|
// regression.
|
|
if (!Consensus) {
|
|
Consensus = V;
|
|
AddrMode = NewAddrMode;
|
|
AddrModeInsts = NewAddrModeInsts;
|
|
continue;
|
|
} else if (NewAddrMode == AddrMode) {
|
|
if (!IsNumUsesConsensusValid) {
|
|
NumUsesConsensus = Consensus->getNumUses();
|
|
IsNumUsesConsensusValid = true;
|
|
}
|
|
|
|
// Ensure that the obtained addressing mode is equivalent to that obtained
|
|
// for all other roots of the PHI traversal. Also, when choosing one
|
|
// such root as representative, select the one with the most uses in order
|
|
// to keep the cost modeling heuristics in AddressingModeMatcher
|
|
// applicable.
|
|
unsigned NumUses = V->getNumUses();
|
|
if (NumUses > NumUsesConsensus) {
|
|
Consensus = V;
|
|
NumUsesConsensus = NumUses;
|
|
AddrModeInsts = NewAddrModeInsts;
|
|
}
|
|
continue;
|
|
}
|
|
|
|
Consensus = 0;
|
|
break;
|
|
}
|
|
|
|
// If the addressing mode couldn't be determined, or if multiple different
|
|
// ones were determined, bail out now.
|
|
if (!Consensus) return false;
|
|
|
|
// Check to see if any of the instructions supersumed by this addr mode are
|
|
// non-local to I's BB.
|
|
bool AnyNonLocal = false;
|
|
for (unsigned i = 0, e = AddrModeInsts.size(); i != e; ++i) {
|
|
if (IsNonLocalValue(AddrModeInsts[i], MemoryInst->getParent())) {
|
|
AnyNonLocal = true;
|
|
break;
|
|
}
|
|
}
|
|
|
|
// If all the instructions matched are already in this BB, don't do anything.
|
|
if (!AnyNonLocal) {
|
|
DEBUG(dbgs() << "CGP: Found local addrmode: " << AddrMode << "\n");
|
|
return false;
|
|
}
|
|
|
|
// Insert this computation right after this user. Since our caller is
|
|
// scanning from the top of the BB to the bottom, reuse of the expr are
|
|
// guaranteed to happen later.
|
|
BasicBlock::iterator InsertPt = MemoryInst;
|
|
|
|
// Now that we determined the addressing expression we want to use and know
|
|
// that we have to sink it into this block. Check to see if we have already
|
|
// done this for some other load/store instr in this block. If so, reuse the
|
|
// computation.
|
|
Value *&SunkAddr = SunkAddrs[Addr];
|
|
if (SunkAddr) {
|
|
DEBUG(dbgs() << "CGP: Reusing nonlocal addrmode: " << AddrMode << " for "
|
|
<< *MemoryInst);
|
|
if (SunkAddr->getType() != Addr->getType())
|
|
SunkAddr = new BitCastInst(SunkAddr, Addr->getType(), "tmp", InsertPt);
|
|
} else {
|
|
DEBUG(dbgs() << "CGP: SINKING nonlocal addrmode: " << AddrMode << " for "
|
|
<< *MemoryInst);
|
|
Type *IntPtrTy =
|
|
TLI->getTargetData()->getIntPtrType(AccessTy->getContext());
|
|
|
|
Value *Result = 0;
|
|
|
|
// Start with the base register. Do this first so that subsequent address
|
|
// matching finds it last, which will prevent it from trying to match it
|
|
// as the scaled value in case it happens to be a mul. That would be
|
|
// problematic if we've sunk a different mul for the scale, because then
|
|
// we'd end up sinking both muls.
|
|
if (AddrMode.BaseReg) {
|
|
Value *V = AddrMode.BaseReg;
|
|
if (V->getType()->isPointerTy())
|
|
V = new PtrToIntInst(V, IntPtrTy, "sunkaddr", InsertPt);
|
|
if (V->getType() != IntPtrTy)
|
|
V = CastInst::CreateIntegerCast(V, IntPtrTy, /*isSigned=*/true,
|
|
"sunkaddr", InsertPt);
|
|
Result = V;
|
|
}
|
|
|
|
// Add the scale value.
|
|
if (AddrMode.Scale) {
|
|
Value *V = AddrMode.ScaledReg;
|
|
if (V->getType() == IntPtrTy) {
|
|
// done.
|
|
} else if (V->getType()->isPointerTy()) {
|
|
V = new PtrToIntInst(V, IntPtrTy, "sunkaddr", InsertPt);
|
|
} else if (cast<IntegerType>(IntPtrTy)->getBitWidth() <
|
|
cast<IntegerType>(V->getType())->getBitWidth()) {
|
|
V = new TruncInst(V, IntPtrTy, "sunkaddr", InsertPt);
|
|
} else {
|
|
V = new SExtInst(V, IntPtrTy, "sunkaddr", InsertPt);
|
|
}
|
|
if (AddrMode.Scale != 1)
|
|
V = BinaryOperator::CreateMul(V, ConstantInt::get(IntPtrTy,
|
|
AddrMode.Scale),
|
|
"sunkaddr", InsertPt);
|
|
if (Result)
|
|
Result = BinaryOperator::CreateAdd(Result, V, "sunkaddr", InsertPt);
|
|
else
|
|
Result = V;
|
|
}
|
|
|
|
// Add in the BaseGV if present.
|
|
if (AddrMode.BaseGV) {
|
|
Value *V = new PtrToIntInst(AddrMode.BaseGV, IntPtrTy, "sunkaddr",
|
|
InsertPt);
|
|
if (Result)
|
|
Result = BinaryOperator::CreateAdd(Result, V, "sunkaddr", InsertPt);
|
|
else
|
|
Result = V;
|
|
}
|
|
|
|
// Add in the Base Offset if present.
|
|
if (AddrMode.BaseOffs) {
|
|
Value *V = ConstantInt::get(IntPtrTy, AddrMode.BaseOffs);
|
|
if (Result)
|
|
Result = BinaryOperator::CreateAdd(Result, V, "sunkaddr", InsertPt);
|
|
else
|
|
Result = V;
|
|
}
|
|
|
|
if (Result == 0)
|
|
SunkAddr = Constant::getNullValue(Addr->getType());
|
|
else
|
|
SunkAddr = new IntToPtrInst(Result, Addr->getType(), "sunkaddr",InsertPt);
|
|
}
|
|
|
|
MemoryInst->replaceUsesOfWith(Repl, SunkAddr);
|
|
|
|
// If we have no uses, recursively delete the value and all dead instructions
|
|
// using it.
|
|
if (Repl->use_empty()) {
|
|
// This can cause recursive deletion, which can invalidate our iterator.
|
|
// Use a WeakVH to hold onto it in case this happens.
|
|
WeakVH IterHandle(CurInstIterator);
|
|
BasicBlock *BB = CurInstIterator->getParent();
|
|
|
|
RecursivelyDeleteTriviallyDeadInstructions(Repl);
|
|
|
|
if (IterHandle != CurInstIterator) {
|
|
// If the iterator instruction was recursively deleted, start over at the
|
|
// start of the block.
|
|
CurInstIterator = BB->begin();
|
|
SunkAddrs.clear();
|
|
} else {
|
|
// This address is now available for reassignment, so erase the table
|
|
// entry; we don't want to match some completely different instruction.
|
|
SunkAddrs[Addr] = 0;
|
|
}
|
|
}
|
|
++NumMemoryInsts;
|
|
return true;
|
|
}
|
|
|
|
/// OptimizeInlineAsmInst - If there are any memory operands, use
|
|
/// OptimizeMemoryInst to sink their address computing into the block when
|
|
/// possible / profitable.
|
|
bool CodeGenPrepare::OptimizeInlineAsmInst(CallInst *CS) {
|
|
bool MadeChange = false;
|
|
|
|
TargetLowering::AsmOperandInfoVector
|
|
TargetConstraints = TLI->ParseConstraints(CS);
|
|
unsigned ArgNo = 0;
|
|
for (unsigned i = 0, e = TargetConstraints.size(); i != e; ++i) {
|
|
TargetLowering::AsmOperandInfo &OpInfo = TargetConstraints[i];
|
|
|
|
// Compute the constraint code and ConstraintType to use.
|
|
TLI->ComputeConstraintToUse(OpInfo, SDValue());
|
|
|
|
if (OpInfo.ConstraintType == TargetLowering::C_Memory &&
|
|
OpInfo.isIndirect) {
|
|
Value *OpVal = CS->getArgOperand(ArgNo++);
|
|
MadeChange |= OptimizeMemoryInst(CS, OpVal, OpVal->getType());
|
|
} else if (OpInfo.Type == InlineAsm::isInput)
|
|
ArgNo++;
|
|
}
|
|
|
|
return MadeChange;
|
|
}
|
|
|
|
/// MoveExtToFormExtLoad - Move a zext or sext fed by a load into the same
|
|
/// basic block as the load, unless conditions are unfavorable. This allows
|
|
/// SelectionDAG to fold the extend into the load.
|
|
///
|
|
bool CodeGenPrepare::MoveExtToFormExtLoad(Instruction *I) {
|
|
// Look for a load being extended.
|
|
LoadInst *LI = dyn_cast<LoadInst>(I->getOperand(0));
|
|
if (!LI) return false;
|
|
|
|
// If they're already in the same block, there's nothing to do.
|
|
if (LI->getParent() == I->getParent())
|
|
return false;
|
|
|
|
// If the load has other users and the truncate is not free, this probably
|
|
// isn't worthwhile.
|
|
if (!LI->hasOneUse() &&
|
|
TLI && (TLI->isTypeLegal(TLI->getValueType(LI->getType())) ||
|
|
!TLI->isTypeLegal(TLI->getValueType(I->getType()))) &&
|
|
!TLI->isTruncateFree(I->getType(), LI->getType()))
|
|
return false;
|
|
|
|
// Check whether the target supports casts folded into loads.
|
|
unsigned LType;
|
|
if (isa<ZExtInst>(I))
|
|
LType = ISD::ZEXTLOAD;
|
|
else {
|
|
assert(isa<SExtInst>(I) && "Unexpected ext type!");
|
|
LType = ISD::SEXTLOAD;
|
|
}
|
|
if (TLI && !TLI->isLoadExtLegal(LType, TLI->getValueType(LI->getType())))
|
|
return false;
|
|
|
|
// Move the extend into the same block as the load, so that SelectionDAG
|
|
// can fold it.
|
|
I->removeFromParent();
|
|
I->insertAfter(LI);
|
|
++NumExtsMoved;
|
|
return true;
|
|
}
|
|
|
|
bool CodeGenPrepare::OptimizeExtUses(Instruction *I) {
|
|
BasicBlock *DefBB = I->getParent();
|
|
|
|
// If the result of a {s|z}ext and its source are both live out, rewrite all
|
|
// other uses of the source with result of extension.
|
|
Value *Src = I->getOperand(0);
|
|
if (Src->hasOneUse())
|
|
return false;
|
|
|
|
// Only do this xform if truncating is free.
|
|
if (TLI && !TLI->isTruncateFree(I->getType(), Src->getType()))
|
|
return false;
|
|
|
|
// Only safe to perform the optimization if the source is also defined in
|
|
// this block.
|
|
if (!isa<Instruction>(Src) || DefBB != cast<Instruction>(Src)->getParent())
|
|
return false;
|
|
|
|
bool DefIsLiveOut = false;
|
|
for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
|
|
UI != E; ++UI) {
|
|
Instruction *User = cast<Instruction>(*UI);
|
|
|
|
// Figure out which BB this ext is used in.
|
|
BasicBlock *UserBB = User->getParent();
|
|
if (UserBB == DefBB) continue;
|
|
DefIsLiveOut = true;
|
|
break;
|
|
}
|
|
if (!DefIsLiveOut)
|
|
return false;
|
|
|
|
// Make sure non of the uses are PHI nodes.
|
|
for (Value::use_iterator UI = Src->use_begin(), E = Src->use_end();
|
|
UI != E; ++UI) {
|
|
Instruction *User = cast<Instruction>(*UI);
|
|
BasicBlock *UserBB = User->getParent();
|
|
if (UserBB == DefBB) continue;
|
|
// Be conservative. We don't want this xform to end up introducing
|
|
// reloads just before load / store instructions.
|
|
if (isa<PHINode>(User) || isa<LoadInst>(User) || isa<StoreInst>(User))
|
|
return false;
|
|
}
|
|
|
|
// InsertedTruncs - Only insert one trunc in each block once.
|
|
DenseMap<BasicBlock*, Instruction*> InsertedTruncs;
|
|
|
|
bool MadeChange = false;
|
|
for (Value::use_iterator UI = Src->use_begin(), E = Src->use_end();
|
|
UI != E; ++UI) {
|
|
Use &TheUse = UI.getUse();
|
|
Instruction *User = cast<Instruction>(*UI);
|
|
|
|
// Figure out which BB this ext is used in.
|
|
BasicBlock *UserBB = User->getParent();
|
|
if (UserBB == DefBB) continue;
|
|
|
|
// Both src and def are live in this block. Rewrite the use.
|
|
Instruction *&InsertedTrunc = InsertedTruncs[UserBB];
|
|
|
|
if (!InsertedTrunc) {
|
|
BasicBlock::iterator InsertPt = UserBB->getFirstNonPHI();
|
|
|
|
InsertedTrunc = new TruncInst(I, Src->getType(), "", InsertPt);
|
|
}
|
|
|
|
// Replace a use of the {s|z}ext source with a use of the result.
|
|
TheUse = InsertedTrunc;
|
|
++NumExtUses;
|
|
MadeChange = true;
|
|
}
|
|
|
|
return MadeChange;
|
|
}
|
|
|
|
bool CodeGenPrepare::OptimizeInst(Instruction *I) {
|
|
if (PHINode *P = dyn_cast<PHINode>(I)) {
|
|
// It is possible for very late stage optimizations (such as SimplifyCFG)
|
|
// to introduce PHI nodes too late to be cleaned up. If we detect such a
|
|
// trivial PHI, go ahead and zap it here.
|
|
if (Value *V = SimplifyInstruction(P)) {
|
|
P->replaceAllUsesWith(V);
|
|
P->eraseFromParent();
|
|
++NumPHIsElim;
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
if (CastInst *CI = dyn_cast<CastInst>(I)) {
|
|
// If the source of the cast is a constant, then this should have
|
|
// already been constant folded. The only reason NOT to constant fold
|
|
// it is if something (e.g. LSR) was careful to place the constant
|
|
// evaluation in a block other than then one that uses it (e.g. to hoist
|
|
// the address of globals out of a loop). If this is the case, we don't
|
|
// want to forward-subst the cast.
|
|
if (isa<Constant>(CI->getOperand(0)))
|
|
return false;
|
|
|
|
if (TLI && OptimizeNoopCopyExpression(CI, *TLI))
|
|
return true;
|
|
|
|
if (isa<ZExtInst>(I) || isa<SExtInst>(I)) {
|
|
bool MadeChange = MoveExtToFormExtLoad(I);
|
|
return MadeChange | OptimizeExtUses(I);
|
|
}
|
|
return false;
|
|
}
|
|
|
|
if (CmpInst *CI = dyn_cast<CmpInst>(I))
|
|
return OptimizeCmpExpression(CI);
|
|
|
|
if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
|
|
if (TLI)
|
|
return OptimizeMemoryInst(I, I->getOperand(0), LI->getType());
|
|
return false;
|
|
}
|
|
|
|
if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
|
|
if (TLI)
|
|
return OptimizeMemoryInst(I, SI->getOperand(1),
|
|
SI->getOperand(0)->getType());
|
|
return false;
|
|
}
|
|
|
|
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
|
|
if (GEPI->hasAllZeroIndices()) {
|
|
/// The GEP operand must be a pointer, so must its result -> BitCast
|
|
Instruction *NC = new BitCastInst(GEPI->getOperand(0), GEPI->getType(),
|
|
GEPI->getName(), GEPI);
|
|
GEPI->replaceAllUsesWith(NC);
|
|
GEPI->eraseFromParent();
|
|
++NumGEPsElim;
|
|
OptimizeInst(NC);
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
if (CallInst *CI = dyn_cast<CallInst>(I))
|
|
return OptimizeCallInst(CI);
|
|
|
|
if (ReturnInst *RI = dyn_cast<ReturnInst>(I))
|
|
return DupRetToEnableTailCallOpts(RI);
|
|
|
|
return false;
|
|
}
|
|
|
|
// In this pass we look for GEP and cast instructions that are used
|
|
// across basic blocks and rewrite them to improve basic-block-at-a-time
|
|
// selection.
|
|
bool CodeGenPrepare::OptimizeBlock(BasicBlock &BB) {
|
|
SunkAddrs.clear();
|
|
bool MadeChange = false;
|
|
|
|
CurInstIterator = BB.begin();
|
|
for (BasicBlock::iterator E = BB.end(); CurInstIterator != E; )
|
|
MadeChange |= OptimizeInst(CurInstIterator++);
|
|
|
|
return MadeChange;
|
|
}
|