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Change traversal order to bottom up in preparation for more aggressive if-conversion.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37365 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2007-05-30 19:49:19 +00:00
parent 4e7e6cd13a
commit 8258210ed4
1 changed files with 69 additions and 23 deletions
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92
lib/CodeGen/IfConversion.cpp
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@ -72,6 +72,10 @@ namespace {
BB(0), TrueBB(0), FalseBB(0), TailBB(0) {}
};
/// Roots - Basic blocks that do not have successors. These are the starting
/// points of Graph traversal.
std::vector<MachineBasicBlock*> Roots;
/// BBAnalysis - Results of if-conversion feasibility analysis indexed by
/// basic block number.
std::vector<BBInfo> BBAnalysis;
@ -90,9 +94,10 @@ namespace {
void StructuralAnalysis(MachineBasicBlock *BB);
void FeasibilityAnalysis(BBInfo &BBI,
std::vector<MachineOperand> &Cond);
void AnalyzeBlocks(MachineFunction &MF,
bool AttemptRestructuring(BBInfo &BBI);
bool AnalyzeBlocks(MachineFunction &MF,
std::vector<BBInfo*> &Candidates);
void InvalidatePreds(MachineBasicBlock *BB);
void ReTryPreds(MachineBasicBlock *BB);
bool IfConvertEarlyExit(BBInfo &BBI);
bool IfConvertTriangle(BBInfo &BBI);
bool IfConvertDiamond(BBInfo &BBI);
@ -115,6 +120,11 @@ bool IfConverter::runOnMachineFunction(MachineFunction &MF) {
unsigned NumBBs = MF.getNumBlockIDs();
BBAnalysis.resize(NumBBs);
// Look for root nodes, i.e. blocks without successors.
for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
if (I->succ_size() == 0)
Roots.push_back(I);
std::vector<BBInfo*> Candidates;
MadeChange = false;
while (true) {
@ -122,7 +132,7 @@ bool IfConverter::runOnMachineFunction(MachineFunction &MF) {
// Do an intial analysis for each basic block and finding all the potential
// candidates to perform if-convesion.
AnalyzeBlocks(MF, Candidates);
Change |= AnalyzeBlocks(MF, Candidates);
while (!Candidates.empty()) {
BBInfo &BBI = *Candidates.back();
Candidates.pop_back();
@ -146,6 +156,7 @@ bool IfConverter::runOnMachineFunction(MachineFunction &MF) {
break;
}
Roots.clear();
BBAnalysis.clear();
return MadeChange;
@ -274,26 +285,60 @@ void IfConverter::FeasibilityAnalysis(BBInfo &BBI,
BBI.isPredicable = true;
}
/// AnalyzeBlocks - Analyze all blocks and find entries for all
/// if-conversion candidates.
void IfConverter::AnalyzeBlocks(MachineFunction &MF,
/// 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,
std::vector<BBInfo*> &Candidates) {
bool Change = false;
std::set<MachineBasicBlock*> Visited;
MachineBasicBlock *Entry = MF.begin();
for (df_ext_iterator<MachineBasicBlock*> DFI = df_ext_begin(Entry, Visited),
E = df_ext_end(Entry, Visited); DFI != E; ++DFI) {
MachineBasicBlock *BB = *DFI;
StructuralAnalysis(BB);
BBInfo &BBI = BBAnalysis[BB->getNumber()];
switch (BBI.Kind) {
default: break;
case ICEarlyExit:
case ICTriangle:
case ICDiamond:
Candidates.push_back(&BBI);
break;
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:
case ICTriangle:
case ICDiamond:
Candidates.push_back(&BBI);
break;
default:
Change |= AttemptRestructuring(BBI);
break;
}
}
}
return Change;
}
/// TransferPreds - Transfer all the predecessors of FromBB to ToBB.
@ -329,9 +374,9 @@ static bool isNextBlock(MachineBasicBlock *BB, MachineBasicBlock *ToBB) {
return MachineFunction::iterator(ToBB) == ++Fallthrough;
}
/// InvalidatePreds - Invalidate predecessor BB info so it would be re-analyzed
/// ReTryPreds - Invalidate predecessor BB info so it would be re-analyzed
/// to determine if it can be if-converted.
void IfConverter::InvalidatePreds(MachineBasicBlock *BB) {
void IfConverter::ReTryPreds(MachineBasicBlock *BB) {
for (MachineBasicBlock::pred_iterator PI = BB->pred_begin(),
E = BB->pred_end(); PI != E; ++PI) {
BBInfo &PBBI = BBAnalysis[(*PI)->getNumber()];
@ -386,7 +431,7 @@ bool IfConverter::IfConvertEarlyExit(BBInfo &BBI) {
BBI.TrueBB = BBI.FalseBB = NULL;
BBI.BrCond.clear();
TII->AnalyzeBranch(*BBI.BB, BBI.TrueBB, BBI.FalseBB, BBI.BrCond);
InvalidatePreds(BBI.BB);
ReTryPreds(BBI.BB);
CvtBBI->Kind = ICDead;
// FIXME: Must maintain LiveIns.
@ -424,6 +469,7 @@ bool IfConverter::IfConvertTriangle(BBInfo &BBI) {
BBI.TrueBB = BBI.FalseBB = NULL;
BBI.BrCond.clear();
TII->AnalyzeBranch(*BBI.BB, BBI.TrueBB, BBI.FalseBB, BBI.BrCond);
ReTryPreds(BBI.BB);
TrueBBI.Kind = ICDead;
// FIXME: Must maintain LiveIns.
@ -572,7 +618,7 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI) {
BBI.TrueBB = BBI.FalseBB = NULL;
BBI.BrCond.clear();
TII->AnalyzeBranch(*BBI.BB, BBI.TrueBB, BBI.FalseBB, BBI.BrCond);
InvalidatePreds(BBI.BB);
ReTryPreds(BBI.BB);
}
TrueBBI.Kind = ICDead;
FalseBBI.Kind = ICDead;