[llvm-commits] CVS: llvm/lib/CodeGen/IfConversion.cpp
Evan Cheng
evan.cheng at apple.com
Wed May 23 00:23:38 PDT 2007
Changes in directory llvm/lib/CodeGen:
IfConversion.cpp updated: 1.11 -> 1.12
---
Log message:
Preliminary iterative if-conversion support.
---
Diffs of the changes: (+166 -96)
IfConversion.cpp | 262 ++++++++++++++++++++++++++++++++++---------------------
1 files changed, 166 insertions(+), 96 deletions(-)
Index: llvm/lib/CodeGen/IfConversion.cpp
diff -u llvm/lib/CodeGen/IfConversion.cpp:1.11 llvm/lib/CodeGen/IfConversion.cpp:1.12
--- llvm/lib/CodeGen/IfConversion.cpp:1.11 Mon May 21 17:22:58 2007
+++ llvm/lib/CodeGen/IfConversion.cpp Wed May 23 02:23:16 2007
@@ -28,7 +28,8 @@
namespace {
class IfConverter : public MachineFunctionPass {
enum BBICKind {
- ICInvalid, // BB data invalid.
+ ICNotAnalyzed, // BB has not been analyzed.
+ ICReAnalyze, // BB must be re-analyzed.
ICNotClassfied, // BB data valid, but not classified.
ICEarlyExit, // BB is entry of an early-exit sub-CFG.
ICTriangle, // BB is entry of a triangle sub-CFG.
@@ -43,19 +44,31 @@
/// classification, and common tail block of its successors (if it's a
/// diamond shape), its size, whether it's predicable, and whether any
/// instruction can clobber the 'would-be' predicate.
+ ///
+ /// Kind - Type of block. See BBICKind.
+ /// NonPredSize - Number of non-predicated instructions.
+ /// isPredicable - Is it predicable. (FIXME: Remove.)
+ /// hasEarlyExit - Ends with a return, indirect jump or br to jumptable.
+ /// ModifyPredicate - FIXME: Not used right now. True if BB would modify
+ /// the predicate (e.g. has cmp, call, etc.)
+ /// BB - Corresponding MachineBasicBlock.
+ /// TrueBB / FalseBB- See AnalyzeBranch().
+ /// BrCond - Conditions for end of block conditional branches.
+ /// Predicate - Predicate used in the BB.
struct BBInfo {
BBICKind Kind;
- unsigned Size;
+ unsigned NonPredSize;
bool isPredicable;
- bool ClobbersPred;
bool hasEarlyExit;
+ bool ModifyPredicate;
MachineBasicBlock *BB;
MachineBasicBlock *TrueBB;
MachineBasicBlock *FalseBB;
MachineBasicBlock *TailBB;
- std::vector<MachineOperand> Cond;
- BBInfo() : Kind(ICInvalid), Size(0), isPredicable(false),
- ClobbersPred(false), hasEarlyExit(false),
+ std::vector<MachineOperand> BrCond;
+ std::vector<MachineOperand> Predicate;
+ BBInfo() : Kind(ICNotAnalyzed), NonPredSize(0), isPredicable(false),
+ hasEarlyExit(false), ModifyPredicate(false),
BB(0), TrueBB(0), FalseBB(0), TailBB(0) {}
};
@@ -75,13 +88,15 @@
private:
void StructuralAnalysis(MachineBasicBlock *BB);
- void FeasibilityAnalysis(BBInfo &BBI);
- void InitialFunctionAnalysis(MachineFunction &MF,
- std::vector<BBInfo*> &Candidates);
+ void FeasibilityAnalysis(BBInfo &BBI,
+ std::vector<MachineOperand> &Cond);
+ void AnalyzeBlocks(MachineFunction &MF,
+ std::vector<BBInfo*> &Candidates);
+ void InvalidatePreds(MachineBasicBlock *BB);
bool IfConvertEarlyExit(BBInfo &BBI);
bool IfConvertTriangle(BBInfo &BBI);
bool IfConvertDiamond(BBInfo &BBI);
- void PredicateBlock(MachineBasicBlock *BB,
+ void PredicateBlock(BBInfo &BBI,
std::vector<MachineOperand> &Cond,
bool IgnoreTerm = false);
void MergeBlocks(BBInfo &TrueBBI, BBInfo &FalseBBI);
@@ -101,26 +116,34 @@
BBAnalysis.resize(NumBBs);
std::vector<BBInfo*> Candidates;
- // Do an intial analysis for each basic block and finding all the potential
- // candidates to perform if-convesion.
- InitialFunctionAnalysis(MF, Candidates);
-
MadeChange = false;
- for (unsigned i = 0, e = Candidates.size(); i != e; ++i) {
- BBInfo &BBI = *Candidates[i];
- switch (BBI.Kind) {
- default: assert(false && "Unexpected!");
- break;
- case ICEarlyExit:
- MadeChange |= IfConvertEarlyExit(BBI);
- break;
- case ICTriangle:
- MadeChange |= IfConvertTriangle(BBI);
- break;
- case ICDiamond:
- MadeChange |= IfConvertDiamond(BBI);
- break;
+ while (true) {
+ bool Change = false;
+
+ // Do an intial analysis for each basic block and finding all the potential
+ // candidates to perform if-convesion.
+ AnalyzeBlocks(MF, Candidates);
+ while (!Candidates.empty()) {
+ BBInfo &BBI = *Candidates.back();
+ Candidates.pop_back();
+ switch (BBI.Kind) {
+ default: assert(false && "Unexpected!");
+ break;
+ case ICEarlyExit:
+ Change |= IfConvertEarlyExit(BBI);
+ break;
+ case ICTriangle:
+ Change |= IfConvertTriangle(BBI);
+ break;
+ case ICDiamond:
+ Change |= IfConvertDiamond(BBI);
+ break;
+ }
}
+
+ MadeChange |= Change;
+ if (!Change)
+ break;
}
BBAnalysis.clear();
@@ -145,18 +168,21 @@
void IfConverter::StructuralAnalysis(MachineBasicBlock *BB) {
BBInfo &BBI = BBAnalysis[BB->getNumber()];
- if (BBI.Kind != ICInvalid)
- return; // Already analyzed.
- BBI.BB = BB;
- BBI.Size = std::distance(BB->begin(), BB->end());
+ if (BBI.Kind != ICReAnalyze) {
+ if (BBI.Kind != ICNotAnalyzed)
+ return; // Already analyzed.
+ BBI.BB = BB;
+ BBI.NonPredSize = std::distance(BB->begin(), BB->end());
- // Look for 'root' of a simple (non-nested) triangle or diamond.
- BBI.Kind = ICNotClassfied;
- bool CanAnalyze = !TII->AnalyzeBranch(*BB, BBI.TrueBB, BBI.FalseBB, BBI.Cond);
- // Does it end with a return, indirect jump, or jumptable branch?
- BBI.hasEarlyExit = TII->BlockHasNoFallThrough(*BB) && !BBI.TrueBB;
- if (!CanAnalyze || !BBI.TrueBB || BBI.Cond.size() == 0)
- return;
+ // Look for 'root' of a simple (non-nested) triangle or diamond.
+ BBI.Kind = ICNotClassfied;
+ bool CanAnalyze = !TII->AnalyzeBranch(*BB, BBI.TrueBB, BBI.FalseBB,
+ BBI.BrCond);
+ // Does it end with a return, indirect jump, or jumptable branch?
+ BBI.hasEarlyExit = TII->BlockHasNoFallThrough(*BB) && !BBI.TrueBB;
+ if (!CanAnalyze || !BBI.TrueBB || BBI.BrCond.size() == 0)
+ return;
+ }
// Not a candidate if 'true' block is going to be if-converted.
StructuralAnalysis(BBI.TrueBB);
@@ -165,7 +191,7 @@
return;
// TODO: Only handle very simple cases for now.
- if (TrueBBI.FalseBB || TrueBBI.Cond.size())
+ if (TrueBBI.FalseBB || TrueBBI.BrCond.size())
return;
// No false branch. This BB must end with a conditional branch and a
@@ -181,7 +207,7 @@
return;
// TODO: Only handle very simple cases for now.
- if (FalseBBI.FalseBB || FalseBBI.Cond.size())
+ if (FalseBBI.FalseBB || FalseBBI.BrCond.size())
return;
unsigned TrueNumPreds = BBI.TrueBB->pred_size();
@@ -228,8 +254,9 @@
/// predicable unless it's the last instruction. Note, this function assumes
/// all the terminator instructions can be converted or deleted so it ignore
/// them.
-void IfConverter::FeasibilityAnalysis(BBInfo &BBI) {
- if (BBI.Size == 0 || BBI.Size > TLI->getIfCvtBlockSizeLimit())
+void IfConverter::FeasibilityAnalysis(BBInfo &BBI,
+ std::vector<MachineOperand> &Cond) {
+ if (BBI.NonPredSize == 0 || BBI.NonPredSize > TLI->getIfCvtBlockSizeLimit())
return;
for (MachineBasicBlock::iterator I = BBI.BB->begin(), E = BBI.BB->end();
@@ -241,13 +268,16 @@
return;
}
+ if (BBI.Predicate.size() && !TII->SubsumesPredicate(BBI.Predicate, Cond))
+ return;
+
BBI.isPredicable = true;
}
-/// InitialFunctionAnalysis - Analyze all blocks and find entries for all
+/// AnalyzeBlocks - Analyze all blocks and find entries for all
/// if-conversion candidates.
-void IfConverter::InitialFunctionAnalysis(MachineFunction &MF,
- std::vector<BBInfo*> &Candidates) {
+void IfConverter::AnalyzeBlocks(MachineFunction &MF,
+ std::vector<BBInfo*> &Candidates) {
std::set<MachineBasicBlock*> Visited;
MachineBasicBlock *Entry = MF.begin();
for (df_ext_iterator<MachineBasicBlock*> DFI = df_ext_begin(Entry, Visited),
@@ -299,42 +329,58 @@
return MachineFunction::iterator(ToBB) == ++Fallthrough;
}
+/// InvalidatePreds - Invalidate predecessor BB info so it would be re-analyzed
+/// to determine if it can be if-converted.
+void IfConverter::InvalidatePreds(MachineBasicBlock *BB) {
+ for (MachineBasicBlock::pred_iterator PI = BB->pred_begin(),
+ E = BB->pred_end(); PI != E; ++PI) {
+ BBInfo &PBBI = BBAnalysis[(*PI)->getNumber()];
+ PBBI.Kind = ICReAnalyze;
+ }
+}
+
/// IfConvertEarlyExit - If convert a early exit sub-CFG.
///
bool IfConverter::IfConvertEarlyExit(BBInfo &BBI) {
+ BBI.Kind = ICNotClassfied;
+
BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()];
BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
BBInfo *CvtBBI = &TrueBBI;
BBInfo *NextBBI = &FalseBBI;
+
bool ReserveCond = false;
if (TrueBBI.Kind != ICChild) {
std::swap(CvtBBI, NextBBI);
ReserveCond = true;
}
- FeasibilityAnalysis(*CvtBBI);
- if (!CvtBBI->isPredicable) {
- BBI.Kind = ICNotClassfied;
- return false;
- }
-
- std::vector<MachineOperand> NewCond(BBI.Cond);
+ std::vector<MachineOperand> NewCond(BBI.BrCond);
if (ReserveCond)
TII->ReverseBranchCondition(NewCond);
- PredicateBlock(CvtBBI->BB, NewCond);
+ FeasibilityAnalysis(*CvtBBI, NewCond);
+ if (!CvtBBI->isPredicable)
+ return false;
+
+ PredicateBlock(*CvtBBI, NewCond);
// Merge converted block into entry block. Also convert the end of the
// block conditional branch (to the non-converted block) into an
// unconditional one.
- BBI.Size -= TII->RemoveBranch(*BBI.BB);
- BBI.BB->removeSuccessor(CvtBBI->BB);
+ BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
MergeBlocks(BBI, *CvtBBI);
if (!isNextBlock(BBI.BB, NextBBI->BB)) {
std::vector<MachineOperand> NoCond;
TII->InsertBranch(*BBI.BB, NextBBI->BB, NULL, NoCond);
}
+ std::copy(NewCond.begin(), NewCond.end(), std::back_inserter(BBI.Predicate));
- // Update block info.
+ // 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);
+ InvalidatePreds(BBI.BB);
CvtBBI->Kind = ICDead;
// FIXME: Must maintain LiveIns.
@@ -345,29 +391,33 @@
/// IfConvertTriangle - If convert a triangle sub-CFG.
///
bool IfConverter::IfConvertTriangle(BBInfo &BBI) {
- BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()];
- FeasibilityAnalysis(TrueBBI);
+ BBI.Kind = ICNotClassfied;
- if (!TrueBBI.isPredicable) {
- BBI.Kind = ICNotClassfied;
+ BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()];
+ FeasibilityAnalysis(TrueBBI, BBI.BrCond);
+ if (!TrueBBI.isPredicable)
return false;
- }
// Predicate the 'true' block after removing its branch.
- TrueBBI.Size -= TII->RemoveBranch(*BBI.TrueBB);
- PredicateBlock(BBI.TrueBB, BBI.Cond);
+ TrueBBI.NonPredSize -= TII->RemoveBranch(*BBI.TrueBB);
+ PredicateBlock(TrueBBI, BBI.BrCond);
// Join the 'true' and 'false' blocks by copying the instructions
// from the 'false' block to the 'true' block.
- BBI.TrueBB->removeSuccessor(BBI.FalseBB);
BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
MergeBlocks(TrueBBI, FalseBBI);
// Now merge the entry of the triangle with the true block.
- BBI.Size -= TII->RemoveBranch(*BBI.BB);
+ BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
MergeBlocks(BBI, TrueBBI);
+ std::copy(BBI.BrCond.begin(), BBI.BrCond.end(),
+ std::back_inserter(BBI.Predicate));
- // Update block info.
+ // 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);
TrueBBI.Kind = ICDead;
// FIXME: Must maintain LiveIns.
@@ -378,12 +428,16 @@
/// IfConvertDiamond - If convert a diamond sub-CFG.
///
bool IfConverter::IfConvertDiamond(BBInfo &BBI) {
+ BBI.Kind = ICNotClassfied;
+
bool TrueNeedCBr;
bool FalseNeedCBr;
BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()];
BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
- FeasibilityAnalysis(TrueBBI);
- FeasibilityAnalysis(FalseBBI);
+ 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;
@@ -393,11 +447,11 @@
// return. If it's the former, add a conditional branch to its successor.
TrueNeedCBr = !TrueBBI.TrueBB && BBI.TrueBB->succ_size();
FalseNeedCBr = !FalseBBI.TrueBB && BBI.FalseBB->succ_size();
- if (TrueNeedCBr && TrueBBI.ClobbersPred) {
+ if (TrueNeedCBr && TrueBBI.ModifyPredicate) {
TrueBBI.isPredicable = false;
Proceed = false;
}
- if (FalseNeedCBr && FalseBBI.ClobbersPred) {
+ if (FalseNeedCBr && FalseBBI.ModifyPredicate) {
FalseBBI.isPredicable = false;
Proceed = false;
}
@@ -435,45 +489,42 @@
}
}
- if (!Proceed) {
- BBI.Kind = ICNotClassfied;
+ if (!Proceed)
return false;
- }
// Remove the duplicated instructions from the 'true' block.
for (unsigned i = 0, e = Dups.size(); i != e; ++i) {
Dups[i]->eraseFromParent();
- --TrueBBI.Size;
+ --TrueBBI.NonPredSize;
}
// Predicate the 'true' block after removing its branch.
- TrueBBI.Size -= TII->RemoveBranch(*BBI.TrueBB);
- PredicateBlock(BBI.TrueBB, BBI.Cond);
+ TrueBBI.NonPredSize -= TII->RemoveBranch(*BBI.TrueBB);
+ PredicateBlock(TrueBBI, BBI.BrCond);
// Add a conditional branch to 'true' successor if needed.
- if (TrueNeedCBr && TrueBBI.ClobbersPred &&
+ if (TrueNeedCBr && TrueBBI.ModifyPredicate &&
isNextBlock(BBI.TrueBB, *BBI.TrueBB->succ_begin()))
TrueNeedCBr = false;
if (TrueNeedCBr)
- TII->InsertBranch(*BBI.TrueBB, *BBI.TrueBB->succ_begin(), NULL, BBI.Cond);
+ TII->InsertBranch(*BBI.TrueBB, *BBI.TrueBB->succ_begin(), NULL, BBI.BrCond);
// Predicate the 'false' block.
- std::vector<MachineOperand> NewCond(BBI.Cond);
- TII->ReverseBranchCondition(NewCond);
- PredicateBlock(BBI.FalseBB, NewCond, true);
+ PredicateBlock(FalseBBI, RevCond, true);
// Add a conditional branch to 'false' successor if needed.
- if (FalseNeedCBr && !TrueBBI.ClobbersPred &&
+ if (FalseNeedCBr && !TrueBBI.ModifyPredicate &&
isNextBlock(BBI.FalseBB, *BBI.FalseBB->succ_begin()))
FalseNeedCBr = false;
if (FalseNeedCBr)
- TII->InsertBranch(*BBI.FalseBB, *BBI.FalseBB->succ_begin(), NULL,NewCond);
+ TII->InsertBranch(*BBI.FalseBB, *BBI.FalseBB->succ_begin(), NULL,
+ RevCond);
// 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.ClobbersPred) {
+ if (!TrueBBI.ModifyPredicate) {
MergeBlocks(TrueBBI, FalseBBI);
CvtBBI = &TrueBBI;
} else {
@@ -482,15 +533,16 @@
}
// Remove the conditional branch from entry to the blocks.
- BBI.Size -= TII->RemoveBranch(*BBI.BB);
+ BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
+ bool OkToIfcvt = true;
// 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) {
- BBI.BB->removeSuccessor(CvtBBI->BB);
MergeBlocks(BBI, *CvtBBI);
CvtBBI = &BBI;
+ OkToIfcvt = false;
} else {
std::vector<MachineOperand> NoCond;
TII->InsertBranch(*BBI.BB, CvtBBI->BB, NULL, NoCond);
@@ -499,14 +551,20 @@
// 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);
+ CvtBBI->NonPredSize -= TII->RemoveBranch(*CvtBBI->BB);
BBInfo TailBBI = BBAnalysis[BBI.TailBB->getNumber()];
MergeBlocks(*CvtBBI, TailBBI);
TailBBI.Kind = ICDead;
}
- // Update block info.
+ // 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);
+ InvalidatePreds(BBI.BB);
+ }
TrueBBI.Kind = ICDead;
FalseBBI.Kind = ICDead;
@@ -517,18 +575,23 @@
/// PredicateBlock - Predicate every instruction in the block with the specified
/// condition. If IgnoreTerm is true, skip over all terminator instructions.
-void IfConverter::PredicateBlock(MachineBasicBlock *BB,
+void IfConverter::PredicateBlock(BBInfo &BBI,
std::vector<MachineOperand> &Cond,
bool IgnoreTerm) {
- for (MachineBasicBlock::iterator I = BB->begin(), E = BB->end();
+ for (MachineBasicBlock::iterator I = BBI.BB->begin(), E = BBI.BB->end();
I != E; ++I) {
- if (IgnoreTerm && TII->isTerminatorInstr(I->getOpcode()))
+ MachineInstr *MI = I;
+ if (IgnoreTerm && TII->isTerminatorInstr(MI->getOpcode()))
+ continue;
+ if (TII->isPredicated(MI))
continue;
- if (!TII->PredicateInstruction(&*I, Cond)) {
+ if (!TII->PredicateInstruction(MI, Cond)) {
cerr << "Unable to predication " << *I << "!\n";
abort();
}
}
+
+ BBI.NonPredSize = 0;
}
/// MergeBlocks - Move all instructions from FromBB to the end of ToBB.
@@ -536,8 +599,15 @@
void IfConverter::MergeBlocks(BBInfo &ToBBI, BBInfo &FromBBI) {
ToBBI.BB->splice(ToBBI.BB->end(),
FromBBI.BB, FromBBI.BB->begin(), FromBBI.BB->end());
+
+ // 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.
TransferPreds(ToBBI.BB, FromBBI.BB);
TransferSuccs(ToBBI.BB, FromBBI.BB);
- ToBBI.Size += FromBBI.Size;
- FromBBI.Size = 0;
+ ToBBI.NonPredSize += FromBBI.NonPredSize;
+ FromBBI.NonPredSize = 0;
}
More information about the llvm-commits
mailing list