[llvm-commits] CVS: llvm/lib/CodeGen/IfConversion.cpp
Evan Cheng
evan.cheng at apple.com
Thu May 17 17:21:15 PDT 2007
Changes in directory llvm/lib/CodeGen:
IfConversion.cpp updated: 1.4 -> 1.5
---
Log message:
Make use of target specific block size limits; bug fixes.
---
Diffs of the changes: (+149 -64)
IfConversion.cpp | 213 ++++++++++++++++++++++++++++++++++++++-----------------
1 files changed, 149 insertions(+), 64 deletions(-)
Index: llvm/lib/CodeGen/IfConversion.cpp
diff -u llvm/lib/CodeGen/IfConversion.cpp:1.4 llvm/lib/CodeGen/IfConversion.cpp:1.5
--- llvm/lib/CodeGen/IfConversion.cpp:1.4 Wed May 16 16:54:37 2007
+++ llvm/lib/CodeGen/IfConversion.cpp Thu May 17 19:20:58 2007
@@ -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 @@
/// 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 @@
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 @@
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 @@
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 @@
}
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 @@
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!");
-
- // 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)
+ if (!BBI.FalseBB)
+ BBI.FalseBB = findFalseBlock(BB, BBI.TrueBB);
+ assert(BBI.FalseBB && "Expected to find the fallthrough block!");
+
+ // 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 @@
// | /
// 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 @@
}
}
+/// 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 @@
/// 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 @@
}
// 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);
+
+ // Remove the conditional branch from entry to the blocks.
+ BBI.Size -= TII->RemoveBranch(*BBI.BB);
- // 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);
+ // 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 @@
/// 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 @@
}
}
-/// 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;
}
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