[llvm-commits] [llvm] r40960 - /llvm/trunk/lib/Transforms/Scalar/LoopIndexSplit.cpp
Devang Patel
dpatel at apple.com
Wed Aug 8 18:39:01 PDT 2007
Author: dpatel
Date: Wed Aug 8 20:39:01 2007
New Revision: 40960
URL: http://llvm.org/viewvc/llvm-project?rev=40960&view=rev
Log:
Traverse loop blocks' terminators to find split candidates.
Modified:
llvm/trunk/lib/Transforms/Scalar/LoopIndexSplit.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/LoopIndexSplit.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopIndexSplit.cpp?rev=40960&r1=40959&r2=40960&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopIndexSplit.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopIndexSplit.cpp Wed Aug 8 20:39:01 2007
@@ -54,7 +54,9 @@
class SplitInfo {
public:
SplitInfo() : IndVar(NULL), SplitValue(NULL), ExitValue(NULL),
- SplitCondition(NULL), ExitCondition(NULL) {}
+ SplitCondition(NULL), ExitCondition(NULL),
+ IndVarIncrement(NULL) {}
+
// Induction variable whose range is being split by this transformation.
PHINode *IndVar;
@@ -70,6 +72,8 @@
// Loop exit condition.
ICmpInst *ExitCondition;
+ Instruction *IndVarIncrement;
+
// Clear split info.
void clear() {
IndVar = NULL;
@@ -77,7 +81,12 @@
ExitValue = NULL;
SplitCondition = NULL;
ExitCondition = NULL;
+ IndVarIncrement = NULL;
}
+
+ /// Return true if V is a induction variable or induction variable's
+ /// increment for loop L.
+ bool findIndVar(Value *V, Loop *L);
};
private:
@@ -172,52 +181,93 @@
return Changed;
}
+/// Return true if V is a induction variable or induction variable's
+/// increment for loop L.
+bool LoopIndexSplit::SplitInfo::findIndVar(Value *V, Loop *L) {
+
+ Instruction *I = dyn_cast<Instruction>(V);
+ if (!I)
+ return false;
+
+ // Check if I is a phi node from loop header or not.
+ if (PHINode *PN = dyn_cast<PHINode>(V)) {
+ if (PN->getParent() == L->getHeader()) {
+ IndVar = PN;
+ return true;
+ }
+ }
+
+ // Check if I is a add instruction whose one operand is
+ // phi node from loop header and second operand is constant.
+ if (I->getOpcode() != Instruction::Add)
+ return false;
+
+ Value *Op0 = I->getOperand(0);
+ Value *Op1 = I->getOperand(1);
+
+ if (PHINode *PN = dyn_cast<PHINode>(Op0)) {
+ if (PN->getParent() == L->getHeader()
+ && isa<ConstantInt>(Op1)) {
+ IndVar = PN;
+ IndVarIncrement = I;
+ return true;
+ }
+ }
+
+ if (PHINode *PN = dyn_cast<PHINode>(Op1)) {
+ if (PN->getParent() == L->getHeader()
+ && isa<ConstantInt>(Op0)) {
+ IndVar = PN;
+ IndVarIncrement = I;
+ return true;
+ }
+ }
+
+ return false;
+}
+
/// Find condition inside a loop that is suitable candidate for index split.
void LoopIndexSplit::findSplitCondition() {
SplitInfo SD;
- BasicBlock *Header = L->getHeader();
+ // Check all basic block's terminators.
- for (BasicBlock::iterator I = Header->begin(); isa<PHINode>(I); ++I) {
- PHINode *PN = cast<PHINode>(I);
+ for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
+ I != E; ++I) {
+ BasicBlock *BB = *I;
- if (!PN->getType()->isInteger())
+ // If this basic block does not terminate in a conditional branch
+ // then terminator is not a suitable split condition.
+ BranchInst *BR = dyn_cast<BranchInst>(BB->getTerminator());
+ if (!BR)
continue;
-
- SCEVHandle SCEV = SE->getSCEV(PN);
- if (!isa<SCEVAddRecExpr>(SCEV))
+
+ if (BR->isUnconditional())
continue;
- // If this phi node is used in a compare instruction then it is a
- // split condition candidate.
- for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end();
- UI != E; ++UI) {
- if (ICmpInst *CI = dyn_cast<ICmpInst>(*UI)) {
- SD.SplitCondition = CI;
- break;
- }
- }
-
- // Valid SplitCondition's one operand is phi node and the other operand
- // is loop invariant.
- if (SD.SplitCondition) {
- if (SD.SplitCondition->getOperand(0) != PN)
- SD.SplitValue = SD.SplitCondition->getOperand(0);
- else
- SD.SplitValue = SD.SplitCondition->getOperand(1);
- SCEVHandle ValueSCEV = SE->getSCEV(SD.SplitValue);
-
- // If SplitValue is not invariant then SplitCondition is not appropriate.
- if (!ValueSCEV->isLoopInvariant(L))
- SD.SplitCondition = NULL;
+ ICmpInst *CI = dyn_cast<ICmpInst>(BR->getCondition());
+ if (!CI)
+ return;
+
+ // If one operand is loop invariant and second operand is SCEVAddRecExpr
+ // based on induction variable then CI is a candidate split condition.
+ Value *V0 = CI->getOperand(0);
+ Value *V1 = CI->getOperand(1);
+
+ SCEVHandle SH0 = SE->getSCEV(V0);
+ SCEVHandle SH1 = SE->getSCEV(V1);
+
+ if (SH0->isLoopInvariant(L) && isa<SCEVAddRecExpr>(SH1)) {
+ SD.SplitValue = V0;
+ SD.SplitCondition = CI;
+ if (SD.findIndVar(V1, L))
+ SplitData.push_back(SD);
}
-
- // We are looking for only one split condition.
- if (SD.SplitCondition) {
- SD.IndVar = PN;
- SplitData.push_back(SD);
- // Before reusing SD for next split condition clear its content.
- SD.clear();
+ else if (SH1->isLoopInvariant(L) && isa<SCEVAddRecExpr>(SH0)) {
+ SD.SplitValue = V1;
+ SD.SplitCondition = CI;
+ if (SD.findIndVar(V0, L))
+ SplitData.push_back(SD);
}
}
}
@@ -362,6 +412,14 @@
if (I == SD.SplitCondition)
continue;
+ // Induction variable is OK.
+ if (I == SD.IndVar)
+ continue;
+
+ // Induction variable increment is OK.
+ if (I == SD.IndVarIncrement)
+ continue;
+
// Terminator is also harmless.
if (I == Terminator)
continue;
@@ -377,8 +435,6 @@
// loop may not be eliminated. This is used by processOneIterationLoop().
bool LoopIndexSplit::safeExitBlock(SplitInfo &SD, BasicBlock *ExitBlock) {
- Instruction *IndVarIncrement = NULL;
-
for (BasicBlock::iterator BI = ExitBlock->begin(), BE = ExitBlock->end();
BI != BE; ++BI) {
Instruction *I = BI;
@@ -387,26 +443,28 @@
if (isa<PHINode>(I))
continue;
+ // Induction variable increment is OK.
+ if (SD.IndVarIncrement && SD.IndVarIncrement == I)
+ continue;
+
// Check if I is induction variable increment instruction.
- if (BinaryOperator *BOp = dyn_cast<BinaryOperator>(I)) {
- if (BOp->getOpcode() != Instruction::Add)
- return false;
+ if (!SD.IndVarIncrement && I->getOpcode() == Instruction::Add) {
- Value *Op0 = BOp->getOperand(0);
- Value *Op1 = BOp->getOperand(1);
+ Value *Op0 = I->getOperand(0);
+ Value *Op1 = I->getOperand(1);
PHINode *PN = NULL;
ConstantInt *CI = NULL;
if ((PN = dyn_cast<PHINode>(Op0))) {
if ((CI = dyn_cast<ConstantInt>(Op1)))
- IndVarIncrement = I;
+ SD.IndVarIncrement = I;
} else
if ((PN = dyn_cast<PHINode>(Op1))) {
if ((CI = dyn_cast<ConstantInt>(Op0)))
- IndVarIncrement = I;
+ SD.IndVarIncrement = I;
}
- if (IndVarIncrement && PN == SD.IndVar && CI->isOne())
+ if (SD.IndVarIncrement && PN == SD.IndVar && CI->isOne())
continue;
}
@@ -436,9 +494,9 @@
Instruction *Insn0 = dyn_cast<Instruction>(Op0);
Instruction *Insn1 = dyn_cast<Instruction>(Op1);
- if (Insn0 && Insn0 == IndVarIncrement)
+ if (Insn0 && Insn0 == SD.IndVarIncrement)
SD.ExitValue = Op1;
- else if (Insn1 && Insn1 == IndVarIncrement)
+ else if (Insn1 && Insn1 == SD.IndVarIncrement)
SD.ExitValue = Op0;
SCEVHandle ValueSCEV = SE->getSCEV(SD.ExitValue);
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