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While hoisting instruction to speculatively execute simple bb, ignore dbg intrinsics.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@66255 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Devang Patel
2009-03-06 06:00:17 +00:00
parent f957436254
commit 06b1e67d44
2 changed files with 138 additions and 18 deletions
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48
lib/Transforms/Utils/SimplifyCFG.cpp
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@ -943,11 +943,22 @@ HoistTerminator:
static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *BB1) {
// Only speculatively execution a single instruction (not counting the
// terminator) for now.
BasicBlock::iterator BBI = BB1->begin();
++BBI; // must have at least a terminator
if (BBI == BB1->end()) return false; // only one inst
++BBI;
if (BBI != BB1->end()) return false; // more than 2 insts.
Instruction *HInst = NULL;
Instruction *Term = BB1->getTerminator();
for (BasicBlock::iterator BBI = BB1->begin(), BBE = BB1->end();
BBI != BBE; ++BBI) {
Instruction *I = BBI;
// Skip debug info.
if (isa<DbgInfoIntrinsic>(I)) continue;
if (I == Term) break;
if (!HInst)
HInst = I;
else
return false;
}
if (!HInst)
return false;
// Be conservative for now. FP select instruction can often be expensive.
Value *BrCond = BI->getCondition();
@ -976,13 +987,13 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *BB1) {
// %t1 = icmp
// %t4 = add %t2, c
// %t3 = select i1 %t1, %t2, %t3
Instruction *I = BB1->begin();
switch (I->getOpcode()) {
switch (HInst->getOpcode()) {
default: return false; // Not safe / profitable to hoist.
case Instruction::Add:
case Instruction::Sub:
// FP arithmetic might trap. Not worth doing for vector ops.
if (I->getType()->isFloatingPoint() || isa<VectorType>(I->getType()))
if (HInst->getType()->isFloatingPoint()
|| isa<VectorType>(HInst->getType()))
return false;
break;
case Instruction::And:
@ -992,14 +1003,14 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *BB1) {
case Instruction::LShr:
case Instruction::AShr:
// Don't mess with vector operations.
if (isa<VectorType>(I->getType()))
if (isa<VectorType>(HInst->getType()))
return false;
break; // These are all cheap and non-trapping instructions.
}
// If the instruction is obviously dead, don't try to predicate it.
if (I->use_empty()) {
I->eraseFromParent();
if (HInst->use_empty()) {
HInst->eraseFromParent();
return true;
}
@ -1012,7 +1023,7 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *BB1) {
Value *FalseV = NULL;
BasicBlock *BB2 = BB1->getTerminator()->getSuccessor(0);
for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
for (Value::use_iterator UI = HInst->use_begin(), E = HInst->use_end();
UI != E; ++UI) {
// Ignore any user that is not a PHI node in BB2. These can only occur in
// unreachable blocks, because they would not be dominated by the instr.
@ -1033,7 +1044,8 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *BB1) {
// Do not hoist the instruction if any of its operands are defined but not
// used in this BB. The transformation will prevent the operand from
// being sunk into the use block.
for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i) {
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 &&
!OpI->isUsedInBasicBlock(BIParent))
@ -1062,17 +1074,17 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *BB1) {
}
} else
InsertPos = BI;
BIParent->getInstList().splice(InsertPos, BB1->getInstList(), I);
BIParent->getInstList().splice(InsertPos, BB1->getInstList(), HInst);
// Create a select whose true value is the speculatively executed value and
// false value is the previously determined FalseV.
SelectInst *SI;
if (Invert)
SI = SelectInst::Create(BrCond, FalseV, I,
FalseV->getName() + "." + I->getName(), BI);
SI = SelectInst::Create(BrCond, FalseV, HInst,
FalseV->getName() + "." + HInst->getName(), BI);
else
SI = SelectInst::Create(BrCond, I, FalseV,
I->getName() + "." + FalseV->getName(), BI);
SI = SelectInst::Create(BrCond, HInst, FalseV,
HInst->getName() + "." + FalseV->getName(), BI);
// Make the PHI node use the select for all incoming values for "then" and
// "if" blocks.