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Fix broken optimization disabled by a logic bug.

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Analyze GEPs. If the indices are all zero, transfer whether the pointer is
known to be not null through the GEP.

Add a few more cases for xor and shift instructions.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35257 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nick Lewycky 2007-03-22 02:02:51 +00:00
parent 67606125f6
commit 27e4da93b6
1 changed files with 51 additions and 10 deletions
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61
lib/Transforms/Scalar/PredicateSimplifier.cpp
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@ -1516,13 +1516,27 @@ namespace {
add(SI->getCondition(), ConstantInt::getFalse(),
ICmpInst::ICMP_EQ, NewContext);
}
} else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
for (GetElementPtrInst::op_iterator OI = GEPI->idx_begin(),
OE = GEPI->idx_end(); OI != OE; ++OI) {
ConstantInt *Op = dyn_cast<ConstantInt>(IG.canonicalize(*OI, Top));
if (!Op || !Op->isZero()) return;
}
// TODO: The GEPI indices are all zero. Copy from definition to operand,
// jumping the type plane as needed.
if (isRelatedBy(GEPI, Constant::getNullValue(GEPI->getType()),
ICmpInst::ICMP_NE)) {
Value *Ptr = GEPI->getPointerOperand();
add(Ptr, Constant::getNullValue(Ptr->getType()), ICmpInst::ICMP_NE,
NewContext);
}
}
// TODO: CastInst "%a = cast ... %b" where %a is EQ or NE a constant.
}
/// opsToDef - A new relationship was discovered involving one of this
/// instruction's operands. Find any new relationship involving the
/// definition.
/// definition, or another operand.
void opsToDef(Instruction *I) {
Instruction *NewContext = below(I) ? I : TopInst;
@ -1551,6 +1565,9 @@ namespace {
switch (Opcode) {
default: break;
case Instruction::LShr:
case Instruction::AShr:
case Instruction::Shl:
case Instruction::Sub:
if (Op1 == Zero) {
add(BO, Op0, ICmpInst::ICMP_EQ, NewContext);
@ -1562,6 +1579,7 @@ namespace {
add(BO, AllOnes, ICmpInst::ICMP_EQ, NewContext);
return;
} // fall-through
case Instruction::Xor:
case Instruction::Add:
if (Op0 == Zero) {
add(BO, Op1, ICmpInst::ICMP_EQ, NewContext);
@ -1589,25 +1607,32 @@ namespace {
}
// "%x = add i32 %y, %z" and %x EQ %y then %z EQ 0
// "%x = mul i32 %y, %z" and %x EQ %y then %z EQ 1
// 1. Repeat all of the above, with order of operands reversed.
// "%x = add i32 %y, %z" and %x EQ %z then %y EQ 0
// "%x = shl i32 %y, %z" and %x EQ %y and %y NE 0 then %z EQ 0
// "%x = udiv i32 %y, %z" and %x EQ %y then %z EQ 1
Value *Known = Op0, *Unknown = Op1;
if (Known != BO) std::swap(Known, Unknown);
if (Known == BO) {
Value *Known = Op0, *Unknown = Op1,
*TheBO = IG.canonicalize(BO, Top);
if (Known != TheBO) std::swap(Known, Unknown);
if (Known == TheBO) {
switch (Opcode) {
default: break;
case Instruction::LShr:
case Instruction::AShr:
case Instruction::Shl:
if (!isRelatedBy(Known, Zero, ICmpInst::ICMP_NE)) break;
// otherwise, fall-through.
case Instruction::Sub:
if (Unknown == Op1) break;
// otherwise, fall-through.
case Instruction::Xor:
case Instruction::Add:
case Instruction::Sub:
add(Unknown, Zero, ICmpInst::ICMP_EQ, NewContext);
break;
case Instruction::UDiv:
case Instruction::SDiv:
if (Unknown == Op0) break; // otherwise, fallthrough
case Instruction::Mul:
if (isa<ConstantInt>(Unknown)) {
if (Unknown == Op1) break;
if (isRelatedBy(Known, Zero, ICmpInst::ICMP_NE)) {
Constant *One = ConstantInt::get(Ty, 1);
add(Unknown, One, ICmpInst::ICMP_EQ, NewContext);
}
@ -1633,6 +1658,8 @@ namespace {
}
} else if (SelectInst *SI = dyn_cast<SelectInst>(I)) {
if (I->getType()->isFPOrFPVector()) return;
// Given: "%a = select i1 %x, i32 %b, i32 %c"
// %x EQ true then %a EQ %b
// %x EQ false then %a EQ %c
@ -1658,6 +1685,20 @@ namespace {
}
// TODO: "%a = cast ... %b" where %b is NE/LT/GT a constant.
} else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
for (GetElementPtrInst::op_iterator OI = GEPI->idx_begin(),
OE = GEPI->idx_end(); OI != OE; ++OI) {
ConstantInt *Op = dyn_cast<ConstantInt>(IG.canonicalize(*OI, Top));
if (!Op || !Op->isZero()) return;
}
// TODO: The GEPI indices are all zero. Copy from operand to definition,
// jumping the type plane as needed.
Value *Ptr = GEPI->getPointerOperand();
if (isRelatedBy(Ptr, Constant::getNullValue(Ptr->getType()),
ICmpInst::ICMP_NE)) {
add(GEPI, Constant::getNullValue(GEPI->getType()), ICmpInst::ICMP_NE,
NewContext);
}
}
}