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Let IfConverter loose. Allow more aggressive subsumptions; reorder basic blocks to expose more ifcvt opportunities; code clean up and fixes.
llvm-svn: 37409
This commit is contained in:
Evan Cheng
parent
0dbe4d04db
commit
c86e3086da
@ -24,6 +24,10 @@
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#include "llvm/ADT/Statistic.h"
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using namespace llvm;
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STATISTIC(NumSimple, "Number of simple if-conversions performed");
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STATISTIC(NumSimpleRev, "Number of simple (reversed) if-conversions performed");
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STATISTIC(NumTriangle, "Number of triangle if-conversions performed");
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STATISTIC(NumDiamonds, "Number of diamond if-conversions performed");
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STATISTIC(NumIfConvBBs, "Number of if-converted blocks");
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namespace {
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@ -32,8 +36,8 @@ namespace {
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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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ICSimple, // BB is entry of an one split, no rejoin sub-CFG.
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ICSimpleFalse, // Same as ICSimple, 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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@ -49,8 +53,7 @@ namespace {
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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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/// IsAnalyzable - True if AnalyzeBranch() returns false.
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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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@ -60,8 +63,7 @@ namespace {
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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 IsAnalyzable;
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bool ModifyPredicate;
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MachineBasicBlock *BB;
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MachineBasicBlock *TrueBB;
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@ -69,8 +71,8 @@ namespace {
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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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BBInfo() : Kind(ICNotAnalyzed), NonPredSize(0),
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IsAnalyzable(false), ModifyPredicate(false),
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BB(0), TrueBB(0), FalseBB(0), TailBB(0) {}
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};
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@ -93,14 +95,16 @@ namespace {
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virtual const char *getPassName() const { return "If converter"; }
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private:
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bool ReverseBranchCondition(BBInfo &BBI);
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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 FeasibilityAnalysis(BBInfo &BBI,
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std::vector<MachineOperand> &Cond,
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bool IgnoreTerm = false);
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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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void ReTryPreds(MachineBasicBlock *BB);
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bool IfConvertEarlyExit(BBInfo &BBI);
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bool IfConvertSimple(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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@ -137,39 +141,49 @@ bool IfConverter::runOnMachineFunction(MachineFunction &MF) {
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std::vector<BBInfo*> Candidates;
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MadeChange = false;
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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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bool 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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bool RetVal = false;
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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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case ICSimple:
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case ICSimpleFalse:
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DOUT << "Ifcvt (Simple" << (BBI.Kind == ICSimpleFalse ? " false" : "")
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<< "): BB#" << BBI.BB->getNumber() << " ";
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RetVal = IfConvertSimple(BBI);
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DOUT << (RetVal ? "succeeded!" : "failed!") << "\n";
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if (RetVal)
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if (BBI.Kind == ICSimple) NumSimple++;
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else NumSimpleRev++;
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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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DOUT << "Ifcvt (Triangle): BB#" << BBI.BB->getNumber() << " ";
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RetVal = IfConvertTriangle(BBI);
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DOUT << (RetVal ? "succeeded!" : "failed!") << "\n";
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if (RetVal) NumTriangle++;
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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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DOUT << "Ifcvt (Diamond): BB#" << BBI.BB->getNumber() << " ";
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RetVal = IfConvertDiamond(BBI);
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DOUT << (RetVal ? "succeeded!" : "failed!") << "\n";
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if (RetVal) NumDiamonds++;
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break;
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}
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Change |= RetVal;
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}
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MadeChange |= Change;
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if (!Change)
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break;
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MadeChange |= Change;
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}
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Roots.clear();
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@ -189,13 +203,25 @@ static MachineBasicBlock *findFalseBlock(MachineBasicBlock *BB,
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return NULL;
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}
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bool IfConverter::ReverseBranchCondition(BBInfo &BBI) {
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if (!TII->ReverseBranchCondition(BBI.BrCond)) {
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TII->RemoveBranch(*BBI.BB);
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TII->InsertBranch(*BBI.BB, BBI.FalseBB, BBI.TrueBB, BBI.BrCond);
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std::swap(BBI.TrueBB, BBI.FalseBB);
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return true;
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}
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return false;
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}
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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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if (BBI.Kind != ICReAnalyze) {
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if (BBI.Kind == ICReAnalyze)
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BBI.BrCond.clear();
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else {
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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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@ -204,57 +230,64 @@ void IfConverter::StructuralAnalysis(MachineBasicBlock *BB) {
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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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BBI.IsAnalyzable =
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!TII->AnalyzeBranch(*BB, BBI.TrueBB, BBI.FalseBB, BBI.BrCond);
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if (!BBI.IsAnalyzable || BBI.BrCond.size() == 0)
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return;
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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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// 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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// No false branch. This BB must end with a conditional branch and a
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// fallthrough.
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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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StructuralAnalysis(BBI.FalseBB);
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BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
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// TODO: Only handle very simple cases for now.
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if (FalseBBI.FalseBB || FalseBBI.BrCond.size())
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// Look for more opportunities to if-convert a triangle. Try to restructure
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// the CFG to form a triangle with the 'false' path.
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std::vector<MachineOperand> RevCond(BBI.BrCond);
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bool CanRevCond = !TII->ReverseBranchCondition(RevCond);
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if (FalseBBI.FalseBB) {
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if (TrueBBI.TrueBB && TrueBBI.TrueBB == BBI.FalseBB)
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return;
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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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BBI.Kind = ICEarlyExitFalse;
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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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std::vector<MachineOperand> Cond(BBI.BrCond);
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if (CanRevCond &&
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FalseBBI.TrueBB && FalseBBI.BB->pred_size() == 1 &&
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FeasibilityAnalysis(FalseBBI, RevCond, true)) {
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std::vector<MachineOperand> FalseCond(FalseBBI.BrCond);
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if (FalseBBI.TrueBB == BBI.TrueBB &&
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TII->SubsumesPredicate(FalseCond, BBI.BrCond)) {
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// Reverse 'true' and 'false' paths.
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ReverseBranchCondition(BBI);
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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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FalseBBI.Kind = ICChild;
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} else if (FalseBBI.FalseBB == BBI.TrueBB &&
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!TII->ReverseBranchCondition(FalseCond) &&
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TII->SubsumesPredicate(FalseCond, BBI.BrCond)) {
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// Reverse 'false' block's 'true' and 'false' paths and then
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// reverse 'true' and 'false' paths.
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ReverseBranchCondition(FalseBBI);
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ReverseBranchCondition(BBI);
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BBI.Kind = ICTriangle;
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FalseBBI.Kind = ICChild;
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}
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}
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} else if (TrueBBI.TrueBB == FalseBBI.TrueBB && CanRevCond &&
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TrueBBI.BB->pred_size() == 1 &&
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TrueBBI.BB->pred_size() == 1 &&
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// Check the 'true' and 'false' blocks if either isn't ended with
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// a branch. If the block does not fallthrough to another block
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// then we need to add a branch to its successor.
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!(TrueBBI.ModifyPredicate &&
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!TrueBBI.TrueBB && TrueBBI.BB->succ_size()) &&
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!(FalseBBI.ModifyPredicate &&
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!FalseBBI.TrueBB && FalseBBI.BB->succ_size()) &&
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FeasibilityAnalysis(TrueBBI, BBI.BrCond) &&
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FeasibilityAnalysis(FalseBBI, RevCond)) {
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// Diamond:
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// EBB
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// / \_
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@ -266,6 +299,44 @@ void IfConverter::StructuralAnalysis(MachineBasicBlock *BB) {
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BBI.Kind = ICDiamond;
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TrueBBI.Kind = FalseBBI.Kind = ICChild;
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BBI.TailBB = TrueBBI.TrueBB;
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} else {
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// FIXME: Consider duplicating if BB is small.
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bool TryTriangle = TrueBBI.TrueBB && TrueBBI.TrueBB == BBI.FalseBB &&
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BBI.TrueBB->pred_size() == 1;
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bool TrySimple = TrueBBI.BrCond.size() == 0 && BBI.TrueBB->pred_size() == 1;
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if ((TryTriangle || TrySimple) &&
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FeasibilityAnalysis(TrueBBI, BBI.BrCond)) {
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if (TryTriangle) {
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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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BBI.Kind = ICTriangle;
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TrueBBI.Kind = ICChild;
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} else {
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// Simple (split, no rejoin):
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// EBB
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// | \_
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// | |
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// | TBB---> exit
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// |
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// FBB
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BBI.Kind = ICSimple;
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TrueBBI.Kind = ICChild;
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}
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} else if (FalseBBI.BrCond.size() == 0 && BBI.FalseBB->pred_size() == 1) {
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// Try 'simple' on the other path...
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std::vector<MachineOperand> RevCond(BBI.BrCond);
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if (TII->ReverseBranchCondition(RevCond))
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assert(false && "Unable to reverse branch condition!");
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if (FeasibilityAnalysis(FalseBBI, RevCond)) {
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BBI.Kind = ICSimpleFalse;
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FalseBBI.Kind = ICChild;
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}
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}
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}
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return;
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}
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@ -274,25 +345,37 @@ void IfConverter::StructuralAnalysis(MachineBasicBlock *BB) {
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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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void IfConverter::FeasibilityAnalysis(BBInfo &BBI,
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std::vector<MachineOperand> &Cond) {
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/// predicable unless it's the last instruction. If IgnoreTerm is true then
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/// all the terminator instructions are skipped.
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bool IfConverter::FeasibilityAnalysis(BBInfo &BBI,
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std::vector<MachineOperand> &Cond,
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bool IgnoreTerm) {
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// If the block is dead, or it is going to be the entry block of a sub-CFG
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// that will be if-converted, then it cannot be predicated.
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if (BBI.Kind != ICNotAnalyzed &&
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BBI.Kind != ICNotClassfied &&
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BBI.Kind != ICChild)
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return false;
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// Check predication threshold.
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if (BBI.NonPredSize == 0 || BBI.NonPredSize > TLI->getIfCvtBlockSizeLimit())
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return;
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return false;
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// If it is already predicated, check if its predicate subsumes the new
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// predicate.
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if (BBI.Predicate.size() && !TII->SubsumesPredicate(BBI.Predicate, Cond))
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return false;
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for (MachineBasicBlock::iterator I = BBI.BB->begin(), E = BBI.BB->end();
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I != E; ++I) {
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if (IgnoreTerm && TII->isTerminatorInstr(I->getOpcode()))
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continue;
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// TODO: check if instruction clobbers predicate.
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if (!I->isPredicable())
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return;
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return false;
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}
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if (BBI.Predicate.size() && !TII->SubsumesPredicate(BBI.Predicate, Cond))
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return;
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BBI.isPredicable = true;
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return true;
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}
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/// AttemptRestructuring - Restructure the sub-CFG rooted in the given block to
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@ -336,8 +419,8 @@ bool IfConverter::AnalyzeBlocks(MachineFunction &MF,
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StructuralAnalysis(BB);
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BBInfo &BBI = BBAnalysis[BB->getNumber()];
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switch (BBI.Kind) {
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case ICEarlyExit:
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case ICEarlyExitFalse:
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case ICSimple:
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case ICSimpleFalse:
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case ICTriangle:
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case ICDiamond:
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Candidates.push_back(&BBI);
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@ -355,37 +438,14 @@ bool IfConverter::AnalyzeBlocks(MachineFunction &MF,
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return Change;
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}
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/// TransferPreds - Transfer all the predecessors of FromBB to ToBB.
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///
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static void TransferPreds(MachineBasicBlock *ToBB, MachineBasicBlock *FromBB) {
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std::vector<MachineBasicBlock*> Preds(FromBB->pred_begin(),
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FromBB->pred_end());
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for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
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MachineBasicBlock *Pred = Preds[i];
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Pred->removeSuccessor(FromBB);
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if (!Pred->isSuccessor(ToBB))
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Pred->addSuccessor(ToBB);
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}
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}
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/// TransferSuccs - Transfer all the successors of FromBB to ToBB.
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///
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static void TransferSuccs(MachineBasicBlock *ToBB, MachineBasicBlock *FromBB) {
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std::vector<MachineBasicBlock*> Succs(FromBB->succ_begin(),
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FromBB->succ_end());
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for (unsigned i = 0, e = Succs.size(); i != e; ++i) {
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MachineBasicBlock *Succ = Succs[i];
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FromBB->removeSuccessor(Succ);
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if (!ToBB->isSuccessor(Succ))
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ToBB->addSuccessor(Succ);
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}
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}
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/// isNextBlock - Returns true if ToBB the next basic block after BB.
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///
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/// isNextBlock - Returns true either if ToBB the next block after BB or
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/// that all the intervening blocks are empty.
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static bool isNextBlock(MachineBasicBlock *BB, MachineBasicBlock *ToBB) {
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MachineFunction::iterator Fallthrough = BB;
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return MachineFunction::iterator(ToBB) == ++Fallthrough;
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MachineFunction::iterator I = BB;
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while (++I != MachineFunction::iterator(ToBB))
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if (!I->empty())
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return false;
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return true;
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}
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/// ReTryPreds - Invalidate predecessor BB info so it would be re-analyzed
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@ -406,10 +466,10 @@ static void InsertUncondBranch(MachineBasicBlock *BB, MachineBasicBlock *ToBB,
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TII->InsertBranch(*BB, ToBB, NULL, NoCond);
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}
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/// IfConvertEarlyExit - If convert a early exit sub-CFG.
|
||||
/// IfConvertSimple - If convert a simple (split, no rejoin) sub-CFG.
|
||||
///
|
||||
bool IfConverter::IfConvertEarlyExit(BBInfo &BBI) {
|
||||
bool ReverseCond = BBI.Kind == ICEarlyExitFalse;
|
||||
bool IfConverter::IfConvertSimple(BBInfo &BBI) {
|
||||
bool ReverseCond = BBI.Kind == ICSimpleFalse;
|
||||
|
||||
BBI.Kind = ICNotClassfied;
|
||||
|
||||
@ -418,25 +478,29 @@ bool IfConverter::IfConvertEarlyExit(BBInfo &BBI) {
|
||||
BBInfo *CvtBBI = &TrueBBI;
|
||||
BBInfo *NextBBI = &FalseBBI;
|
||||
|
||||
std::vector<MachineOperand> NewCond(BBI.BrCond);
|
||||
std::vector<MachineOperand> Cond(BBI.BrCond);
|
||||
if (ReverseCond) {
|
||||
std::swap(CvtBBI, NextBBI);
|
||||
TII->ReverseBranchCondition(NewCond);
|
||||
TII->ReverseBranchCondition(Cond);
|
||||
}
|
||||
FeasibilityAnalysis(*CvtBBI, NewCond);
|
||||
if (!CvtBBI->isPredicable)
|
||||
return false;
|
||||
|
||||
PredicateBlock(*CvtBBI, NewCond);
|
||||
PredicateBlock(*CvtBBI, Cond);
|
||||
// If the 'true' block ends without a branch, add a conditional branch
|
||||
// to its successor unless that happens to be the 'false' block.
|
||||
if (CvtBBI->IsAnalyzable && CvtBBI->TrueBB == NULL) {
|
||||
assert(CvtBBI->BB->succ_size() == 1 && "Unexpected!");
|
||||
MachineBasicBlock *SuccBB = *CvtBBI->BB->succ_begin();
|
||||
if (SuccBB != NextBBI->BB)
|
||||
TII->InsertBranch(*CvtBBI->BB, SuccBB, NULL, Cond);
|
||||
}
|
||||
|
||||
// Merge converted block into entry block. Also convert the end of the
|
||||
// block conditional branch (to the non-converted block) into an
|
||||
// unconditional one.
|
||||
// Merge converted block into entry block. Also add an unconditional branch
|
||||
// to the 'false' branch.
|
||||
BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
|
||||
MergeBlocks(BBI, *CvtBBI);
|
||||
if (!isNextBlock(BBI.BB, NextBBI->BB))
|
||||
InsertUncondBranch(BBI.BB, NextBBI->BB, TII);
|
||||
std::copy(NewCond.begin(), NewCond.end(), std::back_inserter(BBI.Predicate));
|
||||
std::copy(Cond.begin(), Cond.end(), std::back_inserter(BBI.Predicate));
|
||||
|
||||
// Update block info. BB can be iteratively if-converted.
|
||||
BBI.Kind = ICNotAnalyzed;
|
||||
@ -447,7 +511,6 @@ bool IfConverter::IfConvertEarlyExit(BBInfo &BBI) {
|
||||
CvtBBI->Kind = ICDead;
|
||||
|
||||
// FIXME: Must maintain LiveIns.
|
||||
NumIfConvBBs++;
|
||||
return true;
|
||||
}
|
||||
|
||||
@ -457,19 +520,12 @@ bool IfConverter::IfConvertTriangle(BBInfo &BBI) {
|
||||
BBI.Kind = ICNotClassfied;
|
||||
|
||||
BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()];
|
||||
FeasibilityAnalysis(TrueBBI, BBI.BrCond);
|
||||
if (!TrueBBI.isPredicable)
|
||||
return false;
|
||||
|
||||
// FIXME: Consider duplicating if BB is small.
|
||||
if (BBI.TrueBB->pred_size() > 1)
|
||||
return false;
|
||||
|
||||
// Predicate the 'true' block after removing its branch.
|
||||
TrueBBI.NonPredSize -= TII->RemoveBranch(*BBI.TrueBB);
|
||||
PredicateBlock(TrueBBI, BBI.BrCond);
|
||||
|
||||
// If 'true' block has a 'false' successor, add a early exit branch to it.
|
||||
// If 'true' block has a 'false' successor, add an exit branch to it.
|
||||
if (TrueBBI.FalseBB) {
|
||||
std::vector<MachineOperand> RevCond(TrueBBI.BrCond);
|
||||
if (TII->ReverseBranchCondition(RevCond))
|
||||
@ -482,7 +538,7 @@ bool IfConverter::IfConvertTriangle(BBInfo &BBI) {
|
||||
BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
|
||||
if (FalseBBI.BB->pred_size() == 2)
|
||||
MergeBlocks(TrueBBI, FalseBBI);
|
||||
else
|
||||
else if (!isNextBlock(TrueBBI.BB, FalseBBI.BB))
|
||||
InsertUncondBranch(TrueBBI.BB, FalseBBI.BB, TII);
|
||||
|
||||
// Now merge the entry of the triangle with the true block.
|
||||
@ -500,7 +556,6 @@ bool IfConverter::IfConvertTriangle(BBInfo &BBI) {
|
||||
TrueBBI.Kind = ICDead;
|
||||
|
||||
// FIXME: Must maintain LiveIns.
|
||||
NumIfConvBBs++;
|
||||
return true;
|
||||
}
|
||||
|
||||
@ -509,33 +564,10 @@ bool IfConverter::IfConvertTriangle(BBInfo &BBI) {
|
||||
bool IfConverter::IfConvertDiamond(BBInfo &BBI) {
|
||||
BBI.Kind = ICNotClassfied;
|
||||
|
||||
bool TrueNeedBr;
|
||||
bool FalseNeedBr;
|
||||
BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()];
|
||||
BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
|
||||
FeasibilityAnalysis(TrueBBI, BBI.BrCond);
|
||||
std::vector<MachineOperand> RevCond(BBI.BrCond);
|
||||
TII->ReverseBranchCondition(RevCond);
|
||||
FeasibilityAnalysis(FalseBBI, RevCond);
|
||||
|
||||
SmallVector<MachineInstr*, 2> Dups;
|
||||
bool Proceed = TrueBBI.isPredicable && FalseBBI.isPredicable;
|
||||
if (Proceed) {
|
||||
// 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
|
||||
// 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) {
|
||||
TrueBBI.isPredicable = false;
|
||||
Proceed = false;
|
||||
}
|
||||
if (FalseNeedBr && FalseBBI.ModifyPredicate) {
|
||||
FalseBBI.isPredicable = false;
|
||||
Proceed = false;
|
||||
}
|
||||
|
||||
if (Proceed) {
|
||||
if (!BBI.TailBB) {
|
||||
// No common merge block. Check if the terminators (e.g. return) are
|
||||
// the same or predicable.
|
||||
@ -544,32 +576,27 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI) {
|
||||
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!
|
||||
}
|
||||
else if (!TT->isPredicable() && !FT->isPredicable())
|
||||
return false; // 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())
|
||||
while (TT != BBI.TrueBB->end()) {
|
||||
if (!TT->isPredicable()) {
|
||||
Proceed = false;
|
||||
break; // Can't if-convert. Abort!
|
||||
return false; // Can't if-convert. Abort!
|
||||
}
|
||||
while (Proceed && FT != BBI.FalseBB->end())
|
||||
++TT;
|
||||
}
|
||||
while (FT != BBI.FalseBB->end()) {
|
||||
if (!FT->isPredicable()) {
|
||||
Proceed = false;
|
||||
break; // Can't if-convert. Abort!
|
||||
return false; // Can't if-convert. Abort!
|
||||
}
|
||||
++FT;
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
if (!Proceed)
|
||||
return false;
|
||||
|
||||
// Remove the duplicated instructions from the 'true' block.
|
||||
for (unsigned i = 0, e = Dups.size(); i != e; ++i) {
|
||||
@ -577,6 +604,19 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI) {
|
||||
--TrueBBI.NonPredSize;
|
||||
}
|
||||
|
||||
// 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
|
||||
// return. If it's the former, add a branch to its successor.
|
||||
bool TrueNeedBr = !TrueBBI.TrueBB && BBI.TrueBB->succ_size();
|
||||
bool FalseNeedBr = !FalseBBI.TrueBB && BBI.FalseBB->succ_size();
|
||||
|
||||
// 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.
|
||||
std::vector<MachineOperand> RevCond(BBI.BrCond);
|
||||
TII->ReverseBranchCondition(RevCond);
|
||||
BBInfo *CvtBBI;
|
||||
if (!TrueBBI.ModifyPredicate) {
|
||||
// Predicate the 'true' block after removing its branch.
|
||||
TrueBBI.NonPredSize -= TII->RemoveBranch(*BBI.TrueBB);
|
||||
PredicateBlock(TrueBBI, BBI.BrCond);
|
||||
@ -584,12 +624,6 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI) {
|
||||
// Predicate the 'false' block.
|
||||
PredicateBlock(FalseBBI, RevCond, true);
|
||||
|
||||
// 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;
|
||||
if (!TrueBBI.ModifyPredicate) {
|
||||
// Add a conditional branch from 'true' to 'true' successor if needed.
|
||||
if (TrueNeedBr)
|
||||
TII->InsertBranch(*BBI.TrueBB, *BBI.TrueBB->succ_begin(), NULL,
|
||||
BBI.BrCond);
|
||||
@ -601,6 +635,13 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI) {
|
||||
MergeBlocks(TrueBBI, FalseBBI);
|
||||
CvtBBI = &TrueBBI;
|
||||
} else {
|
||||
// Predicate the 'false' block after removing its branch.
|
||||
FalseBBI.NonPredSize -= TII->RemoveBranch(*BBI.FalseBB);
|
||||
PredicateBlock(FalseBBI, RevCond);
|
||||
|
||||
// Predicate the 'false' block.
|
||||
PredicateBlock(TrueBBI, BBI.BrCond, true);
|
||||
|
||||
// Add a conditional branch from 'false' to 'false' successor if needed.
|
||||
if (FalseNeedBr)
|
||||
TII->InsertBranch(*BBI.FalseBB, *BBI.FalseBB->succ_begin(), NULL,
|
||||
@ -625,7 +666,7 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI) {
|
||||
MergeBlocks(BBI, *CvtBBI);
|
||||
CvtBBI = &BBI;
|
||||
OkToIfcvt = false;
|
||||
} else
|
||||
} else if (!isNextBlock(BBI.BB, CvtBBI->BB))
|
||||
InsertUncondBranch(BBI.BB, CvtBBI->BB, TII);
|
||||
|
||||
// If the if-converted block fallthrough or unconditionally branch into the
|
||||
@ -651,7 +692,6 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI) {
|
||||
FalseBBI.Kind = ICDead;
|
||||
|
||||
// FIXME: Must maintain LiveIns.
|
||||
NumIfConvBBs += 2;
|
||||
return true;
|
||||
}
|
||||
|
||||
@ -662,18 +702,41 @@ void IfConverter::PredicateBlock(BBInfo &BBI,
|
||||
bool IgnoreTerm) {
|
||||
for (MachineBasicBlock::iterator I = BBI.BB->begin(), E = BBI.BB->end();
|
||||
I != E; ++I) {
|
||||
MachineInstr *MI = I;
|
||||
if (IgnoreTerm && TII->isTerminatorInstr(MI->getOpcode()))
|
||||
if (IgnoreTerm && TII->isTerminatorInstr(I->getOpcode()))
|
||||
continue;
|
||||
if (TII->isPredicated(MI))
|
||||
if (TII->isPredicated(I))
|
||||
continue;
|
||||
if (!TII->PredicateInstruction(MI, Cond)) {
|
||||
if (!TII->PredicateInstruction(I, Cond)) {
|
||||
cerr << "Unable to predicate " << *I << "!\n";
|
||||
abort();
|
||||
}
|
||||
}
|
||||
|
||||
BBI.NonPredSize = 0;
|
||||
NumIfConvBBs++;
|
||||
}
|
||||
|
||||
/// TransferPreds - Transfer all the predecessors of FromBB to ToBB.
|
||||
///
|
||||
static void TransferPreds(MachineBasicBlock *ToBB, MachineBasicBlock *FromBB) {
|
||||
for (MachineBasicBlock::pred_iterator I = FromBB->pred_begin(),
|
||||
E = FromBB->pred_end(); I != E; ++I) {
|
||||
MachineBasicBlock *Pred = *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) {
|
||||
for (MachineBasicBlock::succ_iterator I = FromBB->succ_begin(),
|
||||
E = FromBB->succ_end(); I != E; ++I) {
|
||||
FromBB->removeSuccessor(*I);
|
||||
if (!ToBB->isSuccessor(*I))
|
||||
ToBB->addSuccessor(*I);
|
||||
}
|
||||
}
|
||||
|
||||
/// MergeBlocks - Move all instructions from FromBB to the end of ToBB.
|
||||
@ -687,6 +750,11 @@ void IfConverter::MergeBlocks(BBInfo &ToBBI, BBInfo &FromBBI) {
|
||||
if (ToBBI.BB->isSuccessor(FromBBI.BB))
|
||||
ToBBI.BB->removeSuccessor(FromBBI.BB);
|
||||
|
||||
// Redirect all branches to FromBB to ToBB.
|
||||
for (MachineBasicBlock::pred_iterator I = FromBBI.BB->pred_begin(),
|
||||
E = FromBBI.BB->pred_end(); I != E; ++I)
|
||||
(*I)->ReplaceUsesOfBlockWith(FromBBI.BB, ToBBI.BB);
|
||||
|
||||
// Transfer preds / succs and update size.
|
||||
TransferPreds(ToBBI.BB, FromBBI.BB);
|
||||
TransferSuccs(ToBBI.BB, FromBBI.BB);
|
||||
|
||||
Loading…
Reference in New Issue
Block a user