2007-05-16 10:00:57 +08:00
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//===-- IfConversion.cpp - Machine code if conversion pass. ---------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by the Evan Cheng and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the machine instruction level if-conversion pass.
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//
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//===----------------------------------------------------------------------===//
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2007-06-01 08:12:12 +08:00
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#define DEBUG_TYPE "ifcvt"
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#include "llvm/Function.h"
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2007-05-16 10:00:57 +08:00
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/CodeGen/MachineModuleInfo.h"
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#include "llvm/CodeGen/MachineFunctionPass.h"
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#include "llvm/Target/TargetInstrInfo.h"
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#include "llvm/Target/TargetLowering.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Support/Debug.h"
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2007-05-19 03:26:33 +08:00
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#include "llvm/ADT/DepthFirstIterator.h"
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2007-05-16 10:00:57 +08:00
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#include "llvm/ADT/Statistic.h"
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using namespace llvm;
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STATISTIC(NumIfConvBBs, "Number of if-converted blocks");
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namespace {
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class IfConverter : public MachineFunctionPass {
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enum BBICKind {
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ICNotAnalyzed, // BB has not been analyzed.
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ICReAnalyze, // BB must be re-analyzed.
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ICNotClassfied, // BB data valid, but not classified.
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ICEarlyExit, // BB is entry of an early-exit sub-CFG.
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ICEarlyExitFalse,// Same as ICEarlyExit, but on the false path.
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ICTriangle, // BB is entry of a triangle sub-CFG.
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ICDiamond, // BB is entry of a diamond sub-CFG.
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ICChild, // BB is part of the sub-CFG that'll be predicated.
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ICDead // BB has been converted and merged, it's now dead.
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};
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/// BBInfo - One per MachineBasicBlock, this is used to cache the result
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/// if-conversion feasibility analysis. This includes results from
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/// TargetInstrInfo::AnalyzeBranch() (i.e. TBB, FBB, and Cond), and its
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2007-05-18 08:20:58 +08:00
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/// classification, and common tail block of its successors (if it's a
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2007-05-19 02:14:37 +08:00
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/// diamond shape), its size, whether it's predicable, and whether any
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/// instruction can clobber the 'would-be' predicate.
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///
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/// Kind - Type of block. See BBICKind.
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/// NonPredSize - Number of non-predicated instructions.
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/// isPredicable - Is it predicable. (FIXME: Remove.)
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/// hasEarlyExit - Ends with a return, indirect jump or br to jumptable.
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/// ModifyPredicate - FIXME: Not used right now. True if BB would modify
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/// the predicate (e.g. has cmp, call, etc.)
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/// BB - Corresponding MachineBasicBlock.
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/// TrueBB / FalseBB- See AnalyzeBranch().
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/// BrCond - Conditions for end of block conditional branches.
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/// Predicate - Predicate used in the BB.
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struct BBInfo {
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BBICKind Kind;
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unsigned NonPredSize;
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bool isPredicable;
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bool hasEarlyExit;
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bool ModifyPredicate;
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MachineBasicBlock *BB;
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MachineBasicBlock *TrueBB;
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MachineBasicBlock *FalseBB;
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MachineBasicBlock *TailBB;
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std::vector<MachineOperand> BrCond;
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std::vector<MachineOperand> Predicate;
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BBInfo() : Kind(ICNotAnalyzed), NonPredSize(0), isPredicable(false),
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hasEarlyExit(false), ModifyPredicate(false),
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BB(0), TrueBB(0), FalseBB(0), TailBB(0) {}
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};
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2007-05-31 03:49:19 +08:00
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/// Roots - Basic blocks that do not have successors. These are the starting
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/// points of Graph traversal.
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std::vector<MachineBasicBlock*> Roots;
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2007-05-16 10:00:57 +08:00
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/// BBAnalysis - Results of if-conversion feasibility analysis indexed by
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/// basic block number.
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std::vector<BBInfo> BBAnalysis;
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const TargetLowering *TLI;
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const TargetInstrInfo *TII;
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bool MadeChange;
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public:
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static char ID;
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IfConverter() : MachineFunctionPass((intptr_t)&ID) {}
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virtual bool runOnMachineFunction(MachineFunction &MF);
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virtual const char *getPassName() const { return "If converter"; }
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private:
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void StructuralAnalysis(MachineBasicBlock *BB);
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void FeasibilityAnalysis(BBInfo &BBI,
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std::vector<MachineOperand> &Cond);
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bool AttemptRestructuring(BBInfo &BBI);
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bool AnalyzeBlocks(MachineFunction &MF,
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std::vector<BBInfo*> &Candidates);
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2007-05-31 03:49:19 +08:00
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void ReTryPreds(MachineBasicBlock *BB);
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2007-05-22 06:22:58 +08:00
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bool IfConvertEarlyExit(BBInfo &BBI);
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bool IfConvertTriangle(BBInfo &BBI);
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bool IfConvertDiamond(BBInfo &BBI);
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void PredicateBlock(BBInfo &BBI,
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std::vector<MachineOperand> &Cond,
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bool IgnoreTerm = false);
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void MergeBlocks(BBInfo &TrueBBI, BBInfo &FalseBBI);
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2007-06-01 08:12:12 +08:00
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// IfcvtCandidateCmp - Used to sort if-conversion candidates.
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static bool IfcvtCandidateCmp(BBInfo* C1, BBInfo* C2){
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// Favor diamond over triangle, etc.
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return (unsigned)C1->Kind < (unsigned)C2->Kind;
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}
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};
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char IfConverter::ID = 0;
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}
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FunctionPass *llvm::createIfConverterPass() { return new IfConverter(); }
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bool IfConverter::runOnMachineFunction(MachineFunction &MF) {
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TLI = MF.getTarget().getTargetLowering();
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TII = MF.getTarget().getInstrInfo();
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if (!TII) return false;
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2007-06-01 08:12:12 +08:00
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DOUT << "\nIfcvt: function \'" << MF.getFunction()->getName() << "\'\n";
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MF.RenumberBlocks();
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BBAnalysis.resize(MF.getNumBlockIDs());
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2007-05-31 03:49:19 +08:00
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// Look for root nodes, i.e. blocks without successors.
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for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
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if (I->succ_size() == 0)
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Roots.push_back(I);
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2007-05-19 03:32:08 +08:00
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std::vector<BBInfo*> Candidates;
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2007-05-18 09:55:58 +08:00
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MadeChange = false;
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2007-05-23 15:23:16 +08:00
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while (true) {
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bool Change = false;
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// Do an intial analysis for each basic block and finding all the potential
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// candidates to perform if-convesion.
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Change |= AnalyzeBlocks(MF, Candidates);
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while (!Candidates.empty()) {
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BBInfo &BBI = *Candidates.back();
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Candidates.pop_back();
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switch (BBI.Kind) {
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default: assert(false && "Unexpected!");
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break;
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case ICReAnalyze:
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// One or more of 'childrean' have been modified, abort!
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break;
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case ICEarlyExit:
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case ICEarlyExitFalse:
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DOUT << "Ifcvt (Early exit): BB#" << BBI.BB->getNumber() << "\n";
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Change |= IfConvertEarlyExit(BBI);
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break;
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case ICTriangle:
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DOUT << "Ifcvt (Triangle): BB#" << BBI.BB->getNumber() << "\n";
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Change |= IfConvertTriangle(BBI);
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break;
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case ICDiamond:
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DOUT << "Ifcvt (Diamond): BB#" << BBI.BB->getNumber() << "\n";
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Change |= IfConvertDiamond(BBI);
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break;
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}
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}
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2007-05-23 15:23:16 +08:00
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MadeChange |= Change;
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if (!Change)
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break;
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}
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2007-05-18 09:55:58 +08:00
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2007-05-31 03:49:19 +08:00
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Roots.clear();
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2007-05-18 09:55:58 +08:00
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BBAnalysis.clear();
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2007-05-16 10:00:57 +08:00
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return MadeChange;
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}
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static MachineBasicBlock *findFalseBlock(MachineBasicBlock *BB,
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MachineBasicBlock *TrueBB) {
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for (MachineBasicBlock::succ_iterator SI = BB->succ_begin(),
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E = BB->succ_end(); SI != E; ++SI) {
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MachineBasicBlock *SuccBB = *SI;
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if (SuccBB != TrueBB)
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return SuccBB;
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}
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return NULL;
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}
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2007-05-19 02:14:37 +08:00
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/// StructuralAnalysis - Analyze the structure of the sub-CFG starting from
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/// the specified block. Record its successors and whether it looks like an
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/// if-conversion candidate.
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void IfConverter::StructuralAnalysis(MachineBasicBlock *BB) {
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BBInfo &BBI = BBAnalysis[BB->getNumber()];
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2007-05-23 15:23:16 +08:00
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if (BBI.Kind != ICReAnalyze) {
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if (BBI.Kind != ICNotAnalyzed)
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return; // Already analyzed.
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BBI.BB = BB;
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BBI.NonPredSize = std::distance(BB->begin(), BB->end());
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}
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2007-05-18 08:20:58 +08:00
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2007-05-25 08:59:01 +08:00
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// Look for 'root' of a simple (non-nested) triangle or diamond.
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BBI.Kind = ICNotClassfied;
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bool CanAnalyze = !TII->AnalyzeBranch(*BB, BBI.TrueBB, BBI.FalseBB,
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BBI.BrCond);
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// Does it end with a return, indirect jump, or jumptable branch?
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BBI.hasEarlyExit = TII->BlockHasNoFallThrough(*BB) && !BBI.TrueBB;
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if (!CanAnalyze || !BBI.TrueBB || BBI.BrCond.size() == 0)
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return;
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2007-05-18 08:20:58 +08:00
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// Not a candidate if 'true' block is going to be if-converted.
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StructuralAnalysis(BBI.TrueBB);
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BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()];
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2007-05-17 05:54:37 +08:00
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2007-05-18 09:55:58 +08:00
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// TODO: Only handle very simple cases for now.
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if (TrueBBI.FalseBB || TrueBBI.BrCond.size())
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return;
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2007-05-17 05:54:37 +08:00
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// No false branch. This BB must end with a conditional branch and a
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// fallthrough.
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2007-05-18 08:20:58 +08:00
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if (!BBI.FalseBB)
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BBI.FalseBB = findFalseBlock(BB, BBI.TrueBB);
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assert(BBI.FalseBB && "Expected to find the fallthrough block!");
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// Not a candidate if 'false' block is going to be if-converted.
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2007-05-19 02:14:37 +08:00
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StructuralAnalysis(BBI.FalseBB);
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2007-05-18 08:20:58 +08:00
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BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
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2007-05-16 10:00:57 +08:00
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// TODO: Only handle very simple cases for now.
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2007-05-23 15:23:16 +08:00
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if (FalseBBI.FalseBB || FalseBBI.BrCond.size())
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return;
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2007-05-22 06:22:58 +08:00
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unsigned TrueNumPreds = BBI.TrueBB->pred_size();
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unsigned FalseNumPreds = BBI.FalseBB->pred_size();
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if ((TrueBBI.hasEarlyExit && TrueNumPreds <= 1) &&
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!(FalseBBI.hasEarlyExit && FalseNumPreds <=1)) {
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BBI.Kind = ICEarlyExit;
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TrueBBI.Kind = ICChild;
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} else if (!(TrueBBI.hasEarlyExit && TrueNumPreds <= 1) &&
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(FalseBBI.hasEarlyExit && FalseNumPreds <=1)) {
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2007-06-02 04:29:21 +08:00
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BBI.Kind = ICEarlyExitFalse;
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2007-05-22 06:22:58 +08:00
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FalseBBI.Kind = ICChild;
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} else if (TrueBBI.TrueBB && TrueBBI.TrueBB == BBI.FalseBB) {
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// Triangle:
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// EBB
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// | \_
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// | |
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// | TBB
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// | /
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// FBB
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2007-05-22 06:22:58 +08:00
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BBI.Kind = ICTriangle;
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TrueBBI.Kind = FalseBBI.Kind = ICChild;
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} else if (TrueBBI.TrueBB == FalseBBI.TrueBB &&
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TrueNumPreds <= 1 && FalseNumPreds <= 1) {
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2007-05-16 10:00:57 +08:00
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// Diamond:
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// EBB
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// / \_
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// | |
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// TBB FBB
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// \ /
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// TailBB
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// Note MBB can be empty in case both TBB and FBB are return blocks.
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2007-05-22 06:22:58 +08:00
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BBI.Kind = ICDiamond;
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TrueBBI.Kind = FalseBBI.Kind = ICChild;
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2007-05-18 08:20:58 +08:00
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BBI.TailBB = TrueBBI.TrueBB;
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2007-05-16 10:00:57 +08:00
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}
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return;
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}
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2007-05-19 02:14:37 +08:00
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/// FeasibilityAnalysis - Determine if the block is predicable. In most
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/// cases, that means all the instructions in the block has M_PREDICABLE flag.
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/// Also checks if the block contains any instruction which can clobber a
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/// predicate (e.g. condition code register). If so, the block is not
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/// predicable unless it's the last instruction. Note, this function assumes
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/// all the terminator instructions can be converted or deleted so it ignore
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/// them.
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2007-05-23 15:23:16 +08:00
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void IfConverter::FeasibilityAnalysis(BBInfo &BBI,
|
|
|
|
std::vector<MachineOperand> &Cond) {
|
|
|
|
if (BBI.NonPredSize == 0 || BBI.NonPredSize > TLI->getIfCvtBlockSizeLimit())
|
2007-05-19 02:14:37 +08:00
|
|
|
return;
|
|
|
|
|
|
|
|
for (MachineBasicBlock::iterator I = BBI.BB->begin(), E = BBI.BB->end();
|
|
|
|
I != E; ++I) {
|
|
|
|
// TODO: check if instruction clobbers predicate.
|
|
|
|
if (!I->isPredicable())
|
|
|
|
return;
|
|
|
|
}
|
|
|
|
|
2007-05-23 15:23:16 +08:00
|
|
|
if (BBI.Predicate.size() && !TII->SubsumesPredicate(BBI.Predicate, Cond))
|
|
|
|
return;
|
|
|
|
|
2007-05-19 02:14:37 +08:00
|
|
|
BBI.isPredicable = true;
|
|
|
|
}
|
|
|
|
|
2007-05-31 03:49:19 +08:00
|
|
|
/// AttemptRestructuring - Restructure the sub-CFG rooted in the given block to
|
|
|
|
/// expose more if-conversion opportunities. e.g.
|
|
|
|
///
|
|
|
|
/// cmp
|
|
|
|
/// b le BB1
|
|
|
|
/// / \____
|
|
|
|
/// / |
|
|
|
|
/// cmp |
|
|
|
|
/// b eq BB1 |
|
|
|
|
/// / \____ |
|
|
|
|
/// / \ |
|
|
|
|
/// BB1
|
|
|
|
/// ==>
|
|
|
|
///
|
|
|
|
/// cmp
|
|
|
|
/// b eq BB1
|
|
|
|
/// / \____
|
|
|
|
/// / |
|
|
|
|
/// cmp |
|
|
|
|
/// b le BB1 |
|
|
|
|
/// / \____ |
|
|
|
|
/// / \ |
|
|
|
|
/// BB1
|
|
|
|
bool IfConverter::AttemptRestructuring(BBInfo &BBI) {
|
|
|
|
return false;
|
|
|
|
}
|
|
|
|
|
|
|
|
/// AnalyzeBlocks - Analyze all blocks and find entries for all if-conversion
|
|
|
|
/// candidates. It returns true if any CFG restructuring is done to expose more
|
|
|
|
/// if-conversion opportunities.
|
|
|
|
bool IfConverter::AnalyzeBlocks(MachineFunction &MF,
|
2007-05-23 15:23:16 +08:00
|
|
|
std::vector<BBInfo*> &Candidates) {
|
2007-05-31 03:49:19 +08:00
|
|
|
bool Change = false;
|
2007-05-19 03:26:33 +08:00
|
|
|
std::set<MachineBasicBlock*> Visited;
|
2007-05-31 03:49:19 +08:00
|
|
|
for (unsigned i = 0, e = Roots.size(); i != e; ++i) {
|
|
|
|
for (idf_ext_iterator<MachineBasicBlock*> I=idf_ext_begin(Roots[i],Visited),
|
|
|
|
E = idf_ext_end(Roots[i], Visited); I != E; ++I) {
|
|
|
|
MachineBasicBlock *BB = *I;
|
|
|
|
StructuralAnalysis(BB);
|
|
|
|
BBInfo &BBI = BBAnalysis[BB->getNumber()];
|
|
|
|
switch (BBI.Kind) {
|
|
|
|
case ICEarlyExit:
|
2007-06-02 04:29:21 +08:00
|
|
|
case ICEarlyExitFalse:
|
2007-05-31 03:49:19 +08:00
|
|
|
case ICTriangle:
|
|
|
|
case ICDiamond:
|
|
|
|
Candidates.push_back(&BBI);
|
|
|
|
break;
|
|
|
|
default:
|
|
|
|
Change |= AttemptRestructuring(BBI);
|
|
|
|
break;
|
|
|
|
}
|
2007-05-22 06:22:58 +08:00
|
|
|
}
|
2007-05-16 10:00:57 +08:00
|
|
|
}
|
2007-05-31 03:49:19 +08:00
|
|
|
|
2007-06-01 08:12:12 +08:00
|
|
|
// Sort to favor more complex ifcvt scheme.
|
|
|
|
std::stable_sort(Candidates.begin(), Candidates.end(), IfcvtCandidateCmp);
|
|
|
|
|
2007-05-31 03:49:19 +08:00
|
|
|
return Change;
|
2007-05-16 10:00:57 +08:00
|
|
|
}
|
|
|
|
|
2007-05-18 08:20:58 +08:00
|
|
|
/// TransferPreds - Transfer all the predecessors of FromBB to ToBB.
|
|
|
|
///
|
|
|
|
static void TransferPreds(MachineBasicBlock *ToBB, MachineBasicBlock *FromBB) {
|
|
|
|
std::vector<MachineBasicBlock*> Preds(FromBB->pred_begin(),
|
|
|
|
FromBB->pred_end());
|
|
|
|
for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
|
|
|
|
MachineBasicBlock *Pred = Preds[i];
|
|
|
|
Pred->removeSuccessor(FromBB);
|
|
|
|
if (!Pred->isSuccessor(ToBB))
|
|
|
|
Pred->addSuccessor(ToBB);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/// TransferSuccs - Transfer all the successors of FromBB to ToBB.
|
|
|
|
///
|
|
|
|
static void TransferSuccs(MachineBasicBlock *ToBB, MachineBasicBlock *FromBB) {
|
|
|
|
std::vector<MachineBasicBlock*> Succs(FromBB->succ_begin(),
|
|
|
|
FromBB->succ_end());
|
|
|
|
for (unsigned i = 0, e = Succs.size(); i != e; ++i) {
|
|
|
|
MachineBasicBlock *Succ = Succs[i];
|
|
|
|
FromBB->removeSuccessor(Succ);
|
|
|
|
if (!ToBB->isSuccessor(Succ))
|
|
|
|
ToBB->addSuccessor(Succ);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2007-05-22 06:22:58 +08:00
|
|
|
/// isNextBlock - Returns true if ToBB the next basic block after BB.
|
|
|
|
///
|
|
|
|
static bool isNextBlock(MachineBasicBlock *BB, MachineBasicBlock *ToBB) {
|
|
|
|
MachineFunction::iterator Fallthrough = BB;
|
|
|
|
return MachineFunction::iterator(ToBB) == ++Fallthrough;
|
|
|
|
}
|
|
|
|
|
2007-05-31 03:49:19 +08:00
|
|
|
/// ReTryPreds - Invalidate predecessor BB info so it would be re-analyzed
|
2007-05-23 15:23:16 +08:00
|
|
|
/// to determine if it can be if-converted.
|
2007-05-31 03:49:19 +08:00
|
|
|
void IfConverter::ReTryPreds(MachineBasicBlock *BB) {
|
2007-05-23 15:23:16 +08:00
|
|
|
for (MachineBasicBlock::pred_iterator PI = BB->pred_begin(),
|
|
|
|
E = BB->pred_end(); PI != E; ++PI) {
|
|
|
|
BBInfo &PBBI = BBAnalysis[(*PI)->getNumber()];
|
|
|
|
PBBI.Kind = ICReAnalyze;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2007-05-30 06:31:16 +08:00
|
|
|
/// InsertUncondBranch - Inserts an unconditional branch from BB to ToBB.
|
|
|
|
///
|
|
|
|
static void InsertUncondBranch(MachineBasicBlock *BB, MachineBasicBlock *ToBB,
|
|
|
|
const TargetInstrInfo *TII) {
|
|
|
|
std::vector<MachineOperand> NoCond;
|
|
|
|
TII->InsertBranch(*BB, ToBB, NULL, NoCond);
|
|
|
|
}
|
|
|
|
|
2007-05-22 06:22:58 +08:00
|
|
|
/// IfConvertEarlyExit - If convert a early exit sub-CFG.
|
|
|
|
///
|
|
|
|
bool IfConverter::IfConvertEarlyExit(BBInfo &BBI) {
|
2007-06-02 04:29:21 +08:00
|
|
|
bool ReverseCond = BBI.Kind == ICEarlyExitFalse;
|
|
|
|
|
2007-05-23 15:23:16 +08:00
|
|
|
BBI.Kind = ICNotClassfied;
|
|
|
|
|
2007-05-22 06:22:58 +08:00
|
|
|
BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()];
|
|
|
|
BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
|
|
|
|
BBInfo *CvtBBI = &TrueBBI;
|
|
|
|
BBInfo *NextBBI = &FalseBBI;
|
2007-05-23 15:23:16 +08:00
|
|
|
|
|
|
|
std::vector<MachineOperand> NewCond(BBI.BrCond);
|
2007-06-02 04:29:21 +08:00
|
|
|
if (ReverseCond) {
|
|
|
|
std::swap(CvtBBI, NextBBI);
|
2007-05-22 06:22:58 +08:00
|
|
|
TII->ReverseBranchCondition(NewCond);
|
2007-06-02 04:29:21 +08:00
|
|
|
}
|
2007-05-23 15:23:16 +08:00
|
|
|
FeasibilityAnalysis(*CvtBBI, NewCond);
|
|
|
|
if (!CvtBBI->isPredicable)
|
|
|
|
return false;
|
|
|
|
|
|
|
|
PredicateBlock(*CvtBBI, NewCond);
|
2007-05-22 06:22:58 +08:00
|
|
|
|
|
|
|
// Merge converted block into entry block. Also convert the end of the
|
|
|
|
// block conditional branch (to the non-converted block) into an
|
|
|
|
// unconditional one.
|
2007-05-23 15:23:16 +08:00
|
|
|
BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
|
2007-05-22 06:22:58 +08:00
|
|
|
MergeBlocks(BBI, *CvtBBI);
|
2007-05-30 06:31:16 +08:00
|
|
|
if (!isNextBlock(BBI.BB, NextBBI->BB))
|
|
|
|
InsertUncondBranch(BBI.BB, NextBBI->BB, TII);
|
2007-05-23 15:23:16 +08:00
|
|
|
std::copy(NewCond.begin(), NewCond.end(), std::back_inserter(BBI.Predicate));
|
|
|
|
|
|
|
|
// Update block info. BB can be iteratively if-converted.
|
|
|
|
BBI.Kind = ICNotAnalyzed;
|
|
|
|
BBI.TrueBB = BBI.FalseBB = NULL;
|
|
|
|
BBI.BrCond.clear();
|
|
|
|
TII->AnalyzeBranch(*BBI.BB, BBI.TrueBB, BBI.FalseBB, BBI.BrCond);
|
2007-05-31 03:49:19 +08:00
|
|
|
ReTryPreds(BBI.BB);
|
2007-05-22 06:22:58 +08:00
|
|
|
CvtBBI->Kind = ICDead;
|
|
|
|
|
|
|
|
// FIXME: Must maintain LiveIns.
|
|
|
|
NumIfConvBBs++;
|
|
|
|
return true;
|
|
|
|
}
|
|
|
|
|
2007-05-17 05:54:37 +08:00
|
|
|
/// IfConvertTriangle - If convert a triangle sub-CFG.
|
|
|
|
///
|
2007-05-16 10:00:57 +08:00
|
|
|
bool IfConverter::IfConvertTriangle(BBInfo &BBI) {
|
2007-05-23 15:23:16 +08:00
|
|
|
BBI.Kind = ICNotClassfied;
|
2007-05-19 02:14:37 +08:00
|
|
|
|
2007-05-23 15:23:16 +08:00
|
|
|
BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()];
|
|
|
|
FeasibilityAnalysis(TrueBBI, BBI.BrCond);
|
|
|
|
if (!TrueBBI.isPredicable)
|
2007-05-22 06:22:58 +08:00
|
|
|
return false;
|
2007-05-18 08:20:58 +08:00
|
|
|
|
2007-06-01 15:41:07 +08:00
|
|
|
// FIXME: Consider duplicating if BB is small.
|
|
|
|
if (BBI.TrueBB->pred_size() > 1)
|
|
|
|
return false;
|
|
|
|
|
2007-05-22 06:22:58 +08:00
|
|
|
// Predicate the 'true' block after removing its branch.
|
2007-05-23 15:23:16 +08:00
|
|
|
TrueBBI.NonPredSize -= TII->RemoveBranch(*BBI.TrueBB);
|
|
|
|
PredicateBlock(TrueBBI, BBI.BrCond);
|
2007-05-16 10:00:57 +08:00
|
|
|
|
2007-06-01 15:41:07 +08:00
|
|
|
// If 'true' block has a 'false' successor, add a early exit branch to it.
|
|
|
|
if (TrueBBI.FalseBB) {
|
|
|
|
std::vector<MachineOperand> RevCond(TrueBBI.BrCond);
|
|
|
|
if (TII->ReverseBranchCondition(RevCond))
|
|
|
|
assert(false && "Unable to reverse branch condition!");
|
|
|
|
TII->InsertBranch(*BBI.TrueBB, TrueBBI.FalseBB, NULL, RevCond);
|
|
|
|
}
|
|
|
|
|
|
|
|
// Join the 'true' and 'false' blocks if the 'false' block has no other
|
|
|
|
// predecessors. Otherwise, add a unconditional branch from 'true' to 'false'.
|
2007-05-22 06:22:58 +08:00
|
|
|
BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
|
2007-06-01 15:41:07 +08:00
|
|
|
if (FalseBBI.BB->pred_size() == 2)
|
|
|
|
MergeBlocks(TrueBBI, FalseBBI);
|
|
|
|
else
|
|
|
|
InsertUncondBranch(TrueBBI.BB, FalseBBI.BB, TII);
|
2007-05-16 10:00:57 +08:00
|
|
|
|
2007-05-22 06:22:58 +08:00
|
|
|
// Now merge the entry of the triangle with the true block.
|
2007-05-23 15:23:16 +08:00
|
|
|
BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
|
2007-05-22 06:22:58 +08:00
|
|
|
MergeBlocks(BBI, TrueBBI);
|
2007-05-23 15:23:16 +08:00
|
|
|
std::copy(BBI.BrCond.begin(), BBI.BrCond.end(),
|
|
|
|
std::back_inserter(BBI.Predicate));
|
2007-05-18 08:20:58 +08:00
|
|
|
|
2007-05-23 15:23:16 +08:00
|
|
|
// Update block info. BB can be iteratively if-converted.
|
|
|
|
BBI.Kind = ICNotClassfied;
|
|
|
|
BBI.TrueBB = BBI.FalseBB = NULL;
|
|
|
|
BBI.BrCond.clear();
|
|
|
|
TII->AnalyzeBranch(*BBI.BB, BBI.TrueBB, BBI.FalseBB, BBI.BrCond);
|
2007-05-31 03:49:19 +08:00
|
|
|
ReTryPreds(BBI.BB);
|
2007-05-22 06:22:58 +08:00
|
|
|
TrueBBI.Kind = ICDead;
|
2007-05-16 10:00:57 +08:00
|
|
|
|
2007-05-22 06:22:58 +08:00
|
|
|
// FIXME: Must maintain LiveIns.
|
|
|
|
NumIfConvBBs++;
|
|
|
|
return true;
|
2007-05-16 10:00:57 +08:00
|
|
|
}
|
|
|
|
|
2007-05-17 05:54:37 +08:00
|
|
|
/// IfConvertDiamond - If convert a diamond sub-CFG.
|
|
|
|
///
|
2007-05-16 10:00:57 +08:00
|
|
|
bool IfConverter::IfConvertDiamond(BBInfo &BBI) {
|
2007-05-23 15:23:16 +08:00
|
|
|
BBI.Kind = ICNotClassfied;
|
|
|
|
|
2007-05-30 06:31:16 +08:00
|
|
|
bool TrueNeedBr;
|
|
|
|
bool FalseNeedBr;
|
2007-05-19 02:14:37 +08:00
|
|
|
BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()];
|
|
|
|
BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
|
2007-05-23 15:23:16 +08:00
|
|
|
FeasibilityAnalysis(TrueBBI, BBI.BrCond);
|
|
|
|
std::vector<MachineOperand> RevCond(BBI.BrCond);
|
|
|
|
TII->ReverseBranchCondition(RevCond);
|
|
|
|
FeasibilityAnalysis(FalseBBI, RevCond);
|
2007-05-19 02:14:37 +08:00
|
|
|
|
2007-05-22 06:22:58 +08:00
|
|
|
SmallVector<MachineInstr*, 2> Dups;
|
|
|
|
bool Proceed = TrueBBI.isPredicable && FalseBBI.isPredicable;
|
|
|
|
if (Proceed) {
|
2007-05-19 02:14:37 +08:00
|
|
|
// Check the 'true' and 'false' blocks if either isn't ended with a branch.
|
|
|
|
// Either the block fallthrough to another block or it ends with a
|
2007-05-30 06:31:16 +08:00
|
|
|
// return. If it's the former, add a branch to its successor.
|
|
|
|
TrueNeedBr = !TrueBBI.TrueBB && BBI.TrueBB->succ_size();
|
|
|
|
FalseNeedBr = !FalseBBI.TrueBB && BBI.FalseBB->succ_size();
|
|
|
|
if (TrueNeedBr && TrueBBI.ModifyPredicate) {
|
2007-05-19 02:14:37 +08:00
|
|
|
TrueBBI.isPredicable = false;
|
|
|
|
Proceed = false;
|
|
|
|
}
|
2007-05-30 06:31:16 +08:00
|
|
|
if (FalseNeedBr && FalseBBI.ModifyPredicate) {
|
2007-05-19 02:14:37 +08:00
|
|
|
FalseBBI.isPredicable = false;
|
|
|
|
Proceed = false;
|
|
|
|
}
|
2007-05-16 10:00:57 +08:00
|
|
|
|
2007-05-22 06:22:58 +08:00
|
|
|
if (Proceed) {
|
|
|
|
if (!BBI.TailBB) {
|
|
|
|
// No common merge block. Check if the terminators (e.g. return) are
|
|
|
|
// the same or predicable.
|
|
|
|
MachineBasicBlock::iterator TT = BBI.TrueBB->getFirstTerminator();
|
|
|
|
MachineBasicBlock::iterator FT = BBI.FalseBB->getFirstTerminator();
|
|
|
|
while (TT != BBI.TrueBB->end() && FT != BBI.FalseBB->end()) {
|
|
|
|
if (TT->isIdenticalTo(FT))
|
|
|
|
Dups.push_back(TT); // Will erase these later.
|
|
|
|
else if (!TT->isPredicable() && !FT->isPredicable()) {
|
|
|
|
Proceed = false;
|
|
|
|
break; // Can't if-convert. Abort!
|
|
|
|
}
|
|
|
|
++TT;
|
|
|
|
++FT;
|
|
|
|
}
|
|
|
|
|
|
|
|
// One of the two pathes have more terminators, make sure they are
|
|
|
|
// all predicable.
|
|
|
|
while (Proceed && TT != BBI.TrueBB->end())
|
|
|
|
if (!TT->isPredicable()) {
|
|
|
|
Proceed = false;
|
|
|
|
break; // Can't if-convert. Abort!
|
|
|
|
}
|
|
|
|
while (Proceed && FT != BBI.FalseBB->end())
|
|
|
|
if (!FT->isPredicable()) {
|
|
|
|
Proceed = false;
|
|
|
|
break; // Can't if-convert. Abort!
|
|
|
|
}
|
|
|
|
}
|
2007-05-18 08:20:58 +08:00
|
|
|
}
|
2007-05-22 06:22:58 +08:00
|
|
|
}
|
2007-05-16 10:00:57 +08:00
|
|
|
|
2007-05-23 15:23:16 +08:00
|
|
|
if (!Proceed)
|
2007-05-22 06:22:58 +08:00
|
|
|
return false;
|
2007-05-18 09:55:58 +08:00
|
|
|
|
2007-05-22 06:22:58 +08:00
|
|
|
// Remove the duplicated instructions from the 'true' block.
|
|
|
|
for (unsigned i = 0, e = Dups.size(); i != e; ++i) {
|
|
|
|
Dups[i]->eraseFromParent();
|
2007-05-23 15:23:16 +08:00
|
|
|
--TrueBBI.NonPredSize;
|
2007-05-22 06:22:58 +08:00
|
|
|
}
|
|
|
|
|
|
|
|
// Predicate the 'true' block after removing its branch.
|
2007-05-23 15:23:16 +08:00
|
|
|
TrueBBI.NonPredSize -= TII->RemoveBranch(*BBI.TrueBB);
|
|
|
|
PredicateBlock(TrueBBI, BBI.BrCond);
|
2007-05-22 06:22:58 +08:00
|
|
|
|
|
|
|
// Predicate the 'false' block.
|
2007-05-23 15:23:16 +08:00
|
|
|
PredicateBlock(FalseBBI, RevCond, true);
|
2007-05-22 06:22:58 +08:00
|
|
|
|
|
|
|
// Merge the 'true' and 'false' blocks by copying the instructions
|
|
|
|
// from the 'false' block to the 'true' block. That is, unless the true
|
|
|
|
// block would clobber the predicate, in that case, do the opposite.
|
|
|
|
BBInfo *CvtBBI;
|
2007-05-23 15:23:16 +08:00
|
|
|
if (!TrueBBI.ModifyPredicate) {
|
2007-05-30 06:31:16 +08:00
|
|
|
// Add a conditional branch from 'true' to 'true' successor if needed.
|
|
|
|
if (TrueNeedBr)
|
|
|
|
TII->InsertBranch(*BBI.TrueBB, *BBI.TrueBB->succ_begin(), NULL,
|
|
|
|
BBI.BrCond);
|
|
|
|
// Add an unconditional branch from 'false' to to 'false' successor if it
|
|
|
|
// will not be the fallthrough block.
|
|
|
|
if (FalseNeedBr &&
|
|
|
|
!isNextBlock(BBI.BB, *BBI.FalseBB->succ_begin()))
|
|
|
|
InsertUncondBranch(BBI.FalseBB, *BBI.FalseBB->succ_begin(), TII);
|
2007-05-22 06:22:58 +08:00
|
|
|
MergeBlocks(TrueBBI, FalseBBI);
|
|
|
|
CvtBBI = &TrueBBI;
|
|
|
|
} else {
|
2007-05-30 06:31:16 +08:00
|
|
|
// Add a conditional branch from 'false' to 'false' successor if needed.
|
|
|
|
if (FalseNeedBr)
|
|
|
|
TII->InsertBranch(*BBI.FalseBB, *BBI.FalseBB->succ_begin(), NULL,
|
|
|
|
RevCond);
|
|
|
|
// Add an unconditional branch from 'true' to to 'true' successor if it
|
|
|
|
// will not be the fallthrough block.
|
|
|
|
if (TrueNeedBr &&
|
|
|
|
!isNextBlock(BBI.BB, *BBI.TrueBB->succ_begin()))
|
|
|
|
InsertUncondBranch(BBI.TrueBB, *BBI.TrueBB->succ_begin(), TII);
|
2007-05-22 06:22:58 +08:00
|
|
|
MergeBlocks(FalseBBI, TrueBBI);
|
|
|
|
CvtBBI = &FalseBBI;
|
|
|
|
}
|
2007-05-16 10:00:57 +08:00
|
|
|
|
2007-05-22 06:22:58 +08:00
|
|
|
// Remove the conditional branch from entry to the blocks.
|
2007-05-23 15:23:16 +08:00
|
|
|
BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
|
2007-05-22 06:22:58 +08:00
|
|
|
|
2007-05-23 15:23:16 +08:00
|
|
|
bool OkToIfcvt = true;
|
2007-05-22 06:22:58 +08:00
|
|
|
// Merge the combined block into the entry of the diamond if the entry
|
|
|
|
// block is its only predecessor. Otherwise, insert an unconditional
|
|
|
|
// branch from entry to the if-converted block.
|
|
|
|
if (CvtBBI->BB->pred_size() == 1) {
|
|
|
|
MergeBlocks(BBI, *CvtBBI);
|
|
|
|
CvtBBI = &BBI;
|
2007-05-23 15:23:16 +08:00
|
|
|
OkToIfcvt = false;
|
2007-05-30 06:31:16 +08:00
|
|
|
} else
|
|
|
|
InsertUncondBranch(BBI.BB, CvtBBI->BB, TII);
|
2007-05-18 08:20:58 +08:00
|
|
|
|
2007-05-30 07:37:20 +08:00
|
|
|
// If the if-converted block fallthrough or unconditionally branch into the
|
|
|
|
// tail block, and the tail block does not have other predecessors, then
|
2007-05-22 06:22:58 +08:00
|
|
|
// fold the tail block in as well.
|
2007-05-30 07:37:20 +08:00
|
|
|
if (BBI.TailBB &&
|
2007-06-01 04:53:33 +08:00
|
|
|
BBI.TailBB->pred_size() == 1 && CvtBBI->BB->succ_size() == 1) {
|
2007-05-23 15:23:16 +08:00
|
|
|
CvtBBI->NonPredSize -= TII->RemoveBranch(*CvtBBI->BB);
|
2007-05-22 06:22:58 +08:00
|
|
|
BBInfo TailBBI = BBAnalysis[BBI.TailBB->getNumber()];
|
|
|
|
MergeBlocks(*CvtBBI, TailBBI);
|
|
|
|
TailBBI.Kind = ICDead;
|
|
|
|
}
|
2007-05-18 08:20:58 +08:00
|
|
|
|
2007-05-23 15:23:16 +08:00
|
|
|
// Update block info. BB may be iteratively if-converted.
|
|
|
|
if (OkToIfcvt) {
|
|
|
|
BBI.Kind = ICNotClassfied;
|
|
|
|
BBI.TrueBB = BBI.FalseBB = NULL;
|
|
|
|
BBI.BrCond.clear();
|
|
|
|
TII->AnalyzeBranch(*BBI.BB, BBI.TrueBB, BBI.FalseBB, BBI.BrCond);
|
2007-05-31 03:49:19 +08:00
|
|
|
ReTryPreds(BBI.BB);
|
2007-05-23 15:23:16 +08:00
|
|
|
}
|
2007-05-22 06:22:58 +08:00
|
|
|
TrueBBI.Kind = ICDead;
|
|
|
|
FalseBBI.Kind = ICDead;
|
2007-05-16 10:00:57 +08:00
|
|
|
|
2007-05-22 06:22:58 +08:00
|
|
|
// FIXME: Must maintain LiveIns.
|
|
|
|
NumIfConvBBs += 2;
|
|
|
|
return true;
|
2007-05-16 10:00:57 +08:00
|
|
|
}
|
|
|
|
|
|
|
|
/// PredicateBlock - Predicate every instruction in the block with the specified
|
|
|
|
/// condition. If IgnoreTerm is true, skip over all terminator instructions.
|
2007-05-23 15:23:16 +08:00
|
|
|
void IfConverter::PredicateBlock(BBInfo &BBI,
|
2007-05-16 10:00:57 +08:00
|
|
|
std::vector<MachineOperand> &Cond,
|
|
|
|
bool IgnoreTerm) {
|
2007-05-23 15:23:16 +08:00
|
|
|
for (MachineBasicBlock::iterator I = BBI.BB->begin(), E = BBI.BB->end();
|
2007-05-16 10:00:57 +08:00
|
|
|
I != E; ++I) {
|
2007-05-23 15:23:16 +08:00
|
|
|
MachineInstr *MI = I;
|
|
|
|
if (IgnoreTerm && TII->isTerminatorInstr(MI->getOpcode()))
|
|
|
|
continue;
|
|
|
|
if (TII->isPredicated(MI))
|
2007-05-16 10:00:57 +08:00
|
|
|
continue;
|
2007-05-23 15:23:16 +08:00
|
|
|
if (!TII->PredicateInstruction(MI, Cond)) {
|
2007-06-01 08:55:26 +08:00
|
|
|
cerr << "Unable to predicate " << *I << "!\n";
|
2007-05-17 05:54:37 +08:00
|
|
|
abort();
|
|
|
|
}
|
2007-05-16 10:00:57 +08:00
|
|
|
}
|
2007-05-23 15:23:16 +08:00
|
|
|
|
|
|
|
BBI.NonPredSize = 0;
|
2007-05-16 10:00:57 +08:00
|
|
|
}
|
|
|
|
|
2007-05-18 08:20:58 +08:00
|
|
|
/// MergeBlocks - Move all instructions from FromBB to the end of ToBB.
|
2007-05-16 10:00:57 +08:00
|
|
|
///
|
2007-05-18 08:20:58 +08:00
|
|
|
void IfConverter::MergeBlocks(BBInfo &ToBBI, BBInfo &FromBBI) {
|
|
|
|
ToBBI.BB->splice(ToBBI.BB->end(),
|
|
|
|
FromBBI.BB, FromBBI.BB->begin(), FromBBI.BB->end());
|
2007-05-23 15:23:16 +08:00
|
|
|
|
|
|
|
// If FromBBI is previously a successor, remove it from ToBBI's successor
|
|
|
|
// list and update its TrueBB / FalseBB field if needed.
|
|
|
|
if (ToBBI.BB->isSuccessor(FromBBI.BB))
|
|
|
|
ToBBI.BB->removeSuccessor(FromBBI.BB);
|
|
|
|
|
|
|
|
// Transfer preds / succs and update size.
|
2007-05-18 08:20:58 +08:00
|
|
|
TransferPreds(ToBBI.BB, FromBBI.BB);
|
|
|
|
TransferSuccs(ToBBI.BB, FromBBI.BB);
|
2007-05-23 15:23:16 +08:00
|
|
|
ToBBI.NonPredSize += FromBBI.NonPredSize;
|
|
|
|
FromBBI.NonPredSize = 0;
|
2007-05-16 10:00:57 +08:00
|
|
|
}
|