maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

Give the basic block variables here names based on the if-then-end 

structure being analyzed. No functionality changed.

llvm-svn: 173334
This commit is contained in:
Chandler Carruth 2013-01-24 09:59:39 +00:00
parent 56a3724cf1
commit e2a779f3a7
1 changed files with 33 additions and 32 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

65
llvm/lib/Transforms/Utils/SimplifyCFG.cpp
View File

@ -1369,17 +1369,29 @@ static bool SinkThenElseCodeToEnd(BranchInst *BI1) {
/// \endcode
///
/// \returns true if the conditional block is removed.
static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *BB1) {
static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *ThenBB) {
// Be conservative for now. FP select instruction can often be expensive.
Value *BrCond = BI->getCondition();
if (isa<FCmpInst>(BrCond))
return false;
BasicBlock *BB = BI->getParent();
BasicBlock *EndBB = ThenBB->getTerminator()->getSuccessor(0);
// If ThenBB is actually on the false edge of the conditional branch, remember
// to swap the select operands later.
bool Invert = false;
if (ThenBB != BI->getSuccessor(0)) {
assert(ThenBB == BI->getSuccessor(1) && "No edge from 'if' block?");
Invert = true;
}
assert(EndBB == BI->getSuccessor(!Invert) && "No edge from to end block");
// Only speculatively execution a single instruction (not counting the
// terminator) for now.
Instruction *HInst = NULL;
Instruction *Term = BB1->getTerminator();
for (BasicBlock::iterator BBI = BB1->begin(), BBE = BB1->end();
Instruction *Term = ThenBB->getTerminator();
for (BasicBlock::iterator BBI = ThenBB->begin(), BBE = ThenBB->end();
BBI != BBE; ++BBI) {
Instruction *I = BBI;
// Skip debug info.
@ -1391,8 +1403,6 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *BB1) {
HInst = I;
}
BasicBlock *BIParent = BI->getParent();
// Check the instruction to be hoisted, if there is one.
if (HInst) {
// Don't hoist the instruction if it's unsafe or expensive.
@ -1407,35 +1417,26 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *BB1) {
for (User::op_iterator i = HInst->op_begin(), e = HInst->op_end();
i != e; ++i) {
Instruction *OpI = dyn_cast<Instruction>(*i);
if (OpI && OpI->getParent() == BIParent &&
if (OpI && OpI->getParent() == BB &&
!OpI->mayHaveSideEffects() &&
!OpI->isUsedInBasicBlock(BIParent))
!OpI->isUsedInBasicBlock(BB))
return false;
}
}
// If BB1 is actually on the false edge of the conditional branch, remember
// to swap the select operands later.
bool Invert = false;
if (BB1 != BI->getSuccessor(0)) {
assert(BB1 == BI->getSuccessor(1) && "No edge from 'if' block?");
Invert = true;
}
// Collect interesting PHIs, and scan for hazards.
SmallSetVector<std::pair<Value *, Value *>, 4> PHIs;
BasicBlock *BB2 = BB1->getTerminator()->getSuccessor(0);
for (BasicBlock::iterator I = BB2->begin();
for (BasicBlock::iterator I = EndBB->begin();
PHINode *PN = dyn_cast<PHINode>(I); ++I) {
Value *BB1V = PN->getIncomingValueForBlock(BB1);
Value *BIParentV = PN->getIncomingValueForBlock(BIParent);
Value *OrigV = PN->getIncomingValueForBlock(BB);
Value *ThenV = PN->getIncomingValueForBlock(ThenBB);
// Skip PHIs which are trivial.
if (BB1V == BIParentV)
if (ThenV == OrigV)
continue;
// Check for safety.
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(BB1V)) {
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(ThenV)) {
// An unfolded ConstantExpr could end up getting expanded into
// Instructions. Don't speculate this and another instruction at
// the same time.
@ -1448,7 +1449,7 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *BB1) {
}
// Ok, we may insert a select for this PHI.
PHIs.insert(std::make_pair(BB1V, BIParentV));
PHIs.insert(std::make_pair(ThenV, OrigV));
}
// If there are no PHIs to process, bail early. This helps ensure idempotence
@ -1457,11 +1458,11 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *BB1) {
return false;
// If we get here, we can hoist the instruction and if-convert.
DEBUG(dbgs() << "SPECULATIVELY EXECUTING BB" << *BB1 << "\n";);
DEBUG(dbgs() << "SPECULATIVELY EXECUTING BB" << *ThenBB << "\n";);
// Hoist the instruction.
if (HInst)
BIParent->getInstList().splice(BI, BB1->getInstList(), HInst);
BB->getInstList().splice(BI, ThenBB->getInstList(), HInst);
// Insert selects and rewrite the PHI operands.
IRBuilder<true, NoFolder> Builder(BI);
@ -1483,15 +1484,15 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *BB1) {
// Make the PHI node use the select for all incoming values for "then" and
// "if" blocks.
for (BasicBlock::iterator I = BB2->begin();
for (BasicBlock::iterator I = EndBB->begin();
PHINode *PN = dyn_cast<PHINode>(I); ++I) {
unsigned BB1I = PN->getBasicBlockIndex(BB1);
unsigned BIParentI = PN->getBasicBlockIndex(BIParent);
Value *BB1V = PN->getIncomingValue(BB1I);
Value *BIParentV = PN->getIncomingValue(BIParentI);
if (TrueV == BB1V && FalseV == BIParentV) {
PN->setIncomingValue(BB1I, SI);
PN->setIncomingValue(BIParentI, SI);
unsigned ThenI = PN->getBasicBlockIndex(ThenBB);
unsigned OrigI = PN->getBasicBlockIndex(BB);
Value *ThenV = PN->getIncomingValue(ThenI);
Value *OrigV = PN->getIncomingValue(OrigI);
if (TrueV == ThenV && FalseV == OrigV) {
PN->setIncomingValue(ThenI, SI);
PN->setIncomingValue(OrigI, SI);
}
}
}