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Make use of target specific block size limits; bug fixes.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37195 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2007-05-18 00:20:58 +00:00
parent 9f8cbd147c
commit 86cbfea33b
1 changed files with 148 additions and 63 deletions
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211
lib/CodeGen/IfConversion.cpp
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@ -16,6 +16,7 @@
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Support/Debug.h"
#include "llvm/ADT/Statistic.h"
@ -37,22 +38,24 @@ namespace {
/// BBInfo - One per MachineBasicBlock, this is used to cache the result
/// if-conversion feasibility analysis. This includes results from
/// TargetInstrInfo::AnalyzeBranch() (i.e. TBB, FBB, and Cond), and its
/// classification, and common merge block of its successors (if it's a
/// classification, and common tail block of its successors (if it's a
/// diamond shape).
struct BBInfo {
BBICKind Kind;
MachineBasicBlock *EBB;
MachineBasicBlock *TBB;
MachineBasicBlock *FBB;
MachineBasicBlock *CMBB;
MachineBasicBlock *BB;
MachineBasicBlock *TrueBB;
MachineBasicBlock *FalseBB;
MachineBasicBlock *TailBB;
std::vector<MachineOperand> Cond;
BBInfo() : Kind(ICInvalid), EBB(0), TBB(0), FBB(0), CMBB(0) {}
unsigned Size;
BBInfo() : Kind(ICInvalid), BB(0), TrueBB(0), FalseBB(0), TailBB(0), Size(0) {}
};
/// BBAnalysis - Results of if-conversion feasibility analysis indexed by
/// basic block number.
std::vector<BBInfo> BBAnalysis;
const TargetLowering *TLI;
const TargetInstrInfo *TII;
bool MadeChange;
public:
@ -72,7 +75,7 @@ namespace {
void PredicateBlock(MachineBasicBlock *BB,
std::vector<MachineOperand> &Cond,
bool IgnoreTerm = false);
void MergeBlocks(MachineBasicBlock *TBB, MachineBasicBlock *FBB);
void MergeBlocks(BBInfo &TrueBBI, BBInfo &FalseBBI);
};
char IfConverter::ID = 0;
}
@ -80,6 +83,7 @@ namespace {
FunctionPass *llvm::createIfConverterPass() { return new IfConverter(); }
bool IfConverter::runOnMachineFunction(MachineFunction &MF) {
TLI = MF.getTarget().getTargetLowering();
TII = MF.getTarget().getInstrInfo();
if (!TII) return false;
@ -95,7 +99,7 @@ bool IfConverter::runOnMachineFunction(MachineFunction &MF) {
InitialFunctionAnalysis(MF, Candidates);
for (unsigned i = 0, e = Candidates.size(); i != e; ++i) {
BBInfo &BBI = BBAnalysis[i];
BBInfo &BBI = BBAnalysis[Candidates[i]];
switch (BBI.Kind) {
default: assert(false && "Unexpected!");
break;
@ -111,11 +115,11 @@ bool IfConverter::runOnMachineFunction(MachineFunction &MF) {
}
static MachineBasicBlock *findFalseBlock(MachineBasicBlock *BB,
MachineBasicBlock *TBB) {
MachineBasicBlock *TrueBB) {
for (MachineBasicBlock::succ_iterator SI = BB->succ_begin(),
E = BB->succ_end(); SI != E; ++SI) {
MachineBasicBlock *SuccBB = *SI;
if (SuccBB != TBB)
if (SuccBB != TrueBB)
return SuccBB;
}
return NULL;
@ -126,36 +130,49 @@ void IfConverter::AnalyzeBlock(MachineBasicBlock *BB) {
if (BBI.Kind != ICInvalid)
return; // Always analyzed.
BBI.EBB = BB;
BBI.BB = BB;
BBI.Size = std::distance(BB->begin(), BB->end());
// Look for 'root' of a simple (non-nested) triangle or diamond.
BBI.Kind = ICNotClassfied;
if (TII->AnalyzeBranch(*BB, BBI.TBB, BBI.FBB, BBI.Cond)
|| !BBI.TBB || BBI.Cond.size() == 0)
if (TII->AnalyzeBranch(*BB, BBI.TrueBB, BBI.FalseBB, BBI.Cond)
|| !BBI.TrueBB || BBI.Cond.size() == 0)
return;
// Can't do it if 'true' block is already marked as to be if-converted.
AnalyzeBlock(BBI.TBB);
BBInfo &TBBI = BBAnalysis[BBI.TBB->getNumber()];
if (TBBI.Kind != ICNotClassfied)
// Not a candidate if 'true' block has another predecessor.
// FIXME: Use or'd predicate or predicated cmp.
if (BBI.TrueBB->pred_size() > 1)
return;
// Not a candidate if 'true' block is going to be if-converted.
AnalyzeBlock(BBI.TrueBB);
BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()];
if (TrueBBI.Kind != ICNotClassfied)
return;
// No false branch. This BB must end with a conditional branch and a
// fallthrough.
if (!BBI.FBB)
BBI.FBB = findFalseBlock(BB, BBI.TBB);
assert(BBI.FBB && "Expected to find the fallthrough block!");
if (!BBI.FalseBB)
BBI.FalseBB = findFalseBlock(BB, BBI.TrueBB);
assert(BBI.FalseBB && "Expected to find the fallthrough block!");
// Can't do it if 'false' block is already marked as to be if-converted.
AnalyzeBlock(BBI.FBB);
BBInfo &FBBI = BBAnalysis[BBI.FBB->getNumber()];
if (FBBI.Kind != ICNotClassfied)
// Not a candidate if 'false' block has another predecessor.
// FIXME: Invert condition and swap 'true' / 'false' blocks?
if (BBI.FalseBB->pred_size() > 1)
return;
// Not a candidate if 'false' block is going to be if-converted.
AnalyzeBlock(BBI.FalseBB);
BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
if (FalseBBI.Kind != ICNotClassfied)
return;
// TODO: Only handle very simple cases for now.
if (TBBI.FBB || FBBI.FBB || TBBI.Cond.size() > 1 || FBBI.Cond.size() > 1)
if (TrueBBI.FalseBB || FalseBBI.FalseBB ||
TrueBBI.Cond.size() || FalseBBI.Cond.size())
return;
if (TBBI.TBB && TBBI.TBB == BBI.FBB) {
if (TrueBBI.TrueBB && TrueBBI.TrueBB == BBI.FalseBB) {
// Triangle:
// EBB
// | \_
@ -164,19 +181,19 @@ void IfConverter::AnalyzeBlock(MachineBasicBlock *BB) {
// | /
// FBB
BBI.Kind = ICTriangleEntry;
TBBI.Kind = FBBI.Kind = ICTriangle;
} else if (TBBI.TBB == FBBI.TBB) {
TrueBBI.Kind = FalseBBI.Kind = ICTriangle;
} else if (TrueBBI.TrueBB == FalseBBI.TrueBB) {
// Diamond:
// EBB
// / \_
// | |
// TBB FBB
// \ /
// MBB
// TailBB
// Note MBB can be empty in case both TBB and FBB are return blocks.
BBI.Kind = ICDiamondEntry;
TBBI.Kind = FBBI.Kind = ICDiamond;
BBI.CMBB = TBBI.TBB;
TrueBBI.Kind = FalseBBI.Kind = ICDiamond;
BBI.TailBB = TrueBBI.TrueBB;
}
return;
}
@ -194,24 +211,55 @@ void IfConverter::InitialFunctionAnalysis(MachineFunction &MF,
}
}
/// 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);
}
}
/// IfConvertTriangle - If convert a triangle sub-CFG.
///
bool IfConverter::IfConvertTriangle(BBInfo &BBI) {
if (isBlockPredicable(BBI.TBB)) {
if (isBlockPredicable(BBI.TrueBB)) {
BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()];
BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
// Predicate the 'true' block after removing its branch.
TII->RemoveBranch(*BBI.TBB);
PredicateBlock(BBI.TBB, BBI.Cond);
TrueBBI.Size -= TII->RemoveBranch(*BBI.TrueBB);
PredicateBlock(BBI.TrueBB, BBI.Cond);
// Join the 'true' and 'false' blocks by copying the instructions
// from the 'false' block to the 'true' block.
MergeBlocks(BBI.TBB, BBI.FBB);
BBI.TrueBB->removeSuccessor(BBI.FalseBB);
MergeBlocks(TrueBBI, FalseBBI);
// Adjust entry block, it should have but a single unconditional
// branch.
BBI.EBB->removeSuccessor(BBI.FBB);
TII->RemoveBranch(*BBI.EBB);
std::vector<MachineOperand> NoCond;
TII->InsertBranch(*BBI.EBB, BBI.TBB, NULL, NoCond);
// Now merge the entry of the triangle with the true block.
BBI.Size -= TII->RemoveBranch(*BBI.BB);
MergeBlocks(BBI, TrueBBI);
// Update block info.
TrueBBI.Kind = ICInvalid;
FalseBBI.Kind = ICInvalid;
// FIXME: Must maintain LiveIns.
NumIfConvBBs++;
@ -223,14 +271,14 @@ bool IfConverter::IfConvertTriangle(BBInfo &BBI) {
/// IfConvertDiamond - If convert a diamond sub-CFG.
///
bool IfConverter::IfConvertDiamond(BBInfo &BBI) {
if (isBlockPredicable(BBI.TBB) && isBlockPredicable(BBI.FBB)) {
if (isBlockPredicable(BBI.TrueBB) && isBlockPredicable(BBI.FalseBB)) {
std::vector<MachineInstr*> Dups;
if (!BBI.CMBB) {
if (!BBI.TailBB) {
// No common merge block. Check if the terminators (e.g. return) are
// the same or predicable.
MachineBasicBlock::iterator TT = BBI.TBB->getFirstTerminator();
MachineBasicBlock::iterator FT = BBI.FBB->getFirstTerminator();
while (TT != BBI.TBB->end() && FT != BBI.FBB->end()) {
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())
@ -240,37 +288,65 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI) {
}
// One of the two pathes have more terminators, make sure they are all
// predicable.
while (TT != BBI.TBB->end())
while (TT != BBI.TrueBB->end())
if (!TT->isPredicable())
return false; // Can't if-convert. Abort!
while (FT != BBI.FBB->end())
while (FT != BBI.FalseBB->end())
if (!FT->isPredicable())
return false; // Can't if-convert. Abort!
}
BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()];
BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
// Remove the duplicated instructions from the 'true' block.
for (unsigned i = 0, e = Dups.size(); i != e; ++i)
for (unsigned i = 0, e = Dups.size(); i != e; ++i) {
Dups[i]->eraseFromParent();
--TrueBBI.Size;
}
// Predicate the 'true' block after removing its branch.
TII->RemoveBranch(*BBI.TBB);
PredicateBlock(BBI.TBB, BBI.Cond);
TrueBBI.Size -= TII->RemoveBranch(*BBI.TrueBB);
PredicateBlock(BBI.TrueBB, BBI.Cond);
// Predicate the 'false' block.
std::vector<MachineOperand> NewCond(BBI.Cond);
TII->ReverseBranchCondition(NewCond);
PredicateBlock(BBI.FBB, NewCond, true);
PredicateBlock(BBI.FalseBB, NewCond, true);
// Join the 'true' and 'false' blocks by copying the instructions
// Merge the 'true' and 'false' blocks by copying the instructions
// from the 'false' block to the 'true' block.
MergeBlocks(BBI.TBB, BBI.FBB);
MergeBlocks(TrueBBI, FalseBBI);
// Adjust entry block, it should have but a single unconditional
// branch .
BBI.EBB->removeSuccessor(BBI.FBB);
TII->RemoveBranch(*BBI.EBB);
std::vector<MachineOperand> NoCond;
TII->InsertBranch(*BBI.EBB, BBI.TBB, NULL, NoCond);
// Remove the conditional branch from entry to the blocks.
BBI.Size -= TII->RemoveBranch(*BBI.BB);
// Merge the combined block into the entry of the diamond if the entry
// block is the only predecessor. Otherwise, insert an unconditional
// branch.
BBInfo *CvtBBI = &TrueBBI;
if (BBI.TrueBB->pred_size() == 1) {
BBI.BB->removeSuccessor(BBI.TrueBB);
MergeBlocks(BBI, TrueBBI);
CvtBBI = &BBI;
} else {
std::vector<MachineOperand> NoCond;
TII->InsertBranch(*BBI.BB, BBI.TrueBB, NULL, NoCond);
}
// If the if-converted block fallthrough into the tail block, then
// fold the tail block in as well.
if (BBI.TailBB && CvtBBI->BB->succ_size() == 1) {
CvtBBI->Size -= TII->RemoveBranch(*CvtBBI->BB);
CvtBBI->BB->removeSuccessor(BBI.TailBB);
BBInfo TailBBI = BBAnalysis[BBI.TailBB->getNumber()];
MergeBlocks(*CvtBBI, TailBBI);
TailBBI.Kind = ICInvalid;
}
// Update block info.
TrueBBI.Kind = ICInvalid;
FalseBBI.Kind = ICInvalid;
// FIXME: Must maintain LiveIns.
NumIfConvBBs += 2;
@ -283,6 +359,10 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI) {
/// cases, that means all the instructions in the block has M_PREDICABLE flag.
/// It assume all the terminator instructions can be converted or deleted.
bool IfConverter::isBlockPredicable(MachineBasicBlock *BB) const {
const BBInfo &BBI = BBAnalysis[BB->getNumber()];
if (BBI.Size == 0 || BBI.Size > TLI->getIfCvtBlockSizeLimit())
return false;
for (MachineBasicBlock::iterator I = BB->begin(), E = BB->end();
I != E; ++I) {
if (TII->isTerminatorInstr(I->getOpcode()))
@ -309,8 +389,13 @@ void IfConverter::PredicateBlock(MachineBasicBlock *BB,
}
}
/// MergeBlocks - Move all instructions from FBB to the end of TBB.
/// MergeBlocks - Move all instructions from FromBB to the end of ToBB.
///
void IfConverter::MergeBlocks(MachineBasicBlock *TBB, MachineBasicBlock *FBB) {
TBB->splice(TBB->end(), FBB, FBB->begin(), FBB->end());
void IfConverter::MergeBlocks(BBInfo &ToBBI, BBInfo &FromBBI) {
ToBBI.BB->splice(ToBBI.BB->end(),
FromBBI.BB, FromBBI.BB->begin(), FromBBI.BB->end());
TransferPreds(ToBBI.BB, FromBBI.BB);
TransferSuccs(ToBBI.BB, FromBBI.BB);
ToBBI.Size += FromBBI.Size;
FromBBI.Size = 0;
}