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Fold binary expressions and casts into PHI nodes that have all constant inputs.

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This takes something like this:

%A = phi int [ 3, %cond_false.0 ], [ 2, %endif.0.i ], [ 2, %endif.1.i ]
%B = div int %tmp.243, 4

and turns it into:

%A = phi int [ 3/4, %cond_false.0 ], [ 2/4, %endif.0.i ], [ 2/4, %endif.1.i ]

which is later simplified (in this case) into %A = 0.

This triggers thousands of times in spec, for example, 269 times in 176.gcc.

This is tested by InstCombine/add.ll:test23 and set.ll:test18.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@16582 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-09-29 05:07:12 +00:00
parent e14a9a71d3
commit 4e998b2fea
1 changed files with 86 additions and 1 deletions
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87
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -198,9 +198,15 @@ namespace {
Instruction *InsertBefore);
// SimplifyCommutative - This performs a few simplifications for commutative
// operators...
// operators.
bool SimplifyCommutative(BinaryOperator &I);
// FoldOpIntoPhi - Given a binary operator or cast instruction which has a
// PHI node as operand #0, see if we can fold the instruction into the PHI
// (which is only possible if all operands to the PHI are constants).
Instruction *FoldOpIntoPhi(Instruction &I);
Instruction *OptAndOp(Instruction *Op, ConstantIntegral *OpRHS,
ConstantIntegral *AndRHS, BinaryOperator &TheAnd);
};
@ -485,6 +491,46 @@ static Value *FoldOperationIntoSelectOperand(Instruction &BI, Value *SO,
return IC->InsertNewInstBefore(New, BI);
}
/// FoldOpIntoPhi - Given a binary operator or cast instruction which has a PHI
/// node as operand #0, see if we can fold the instruction into the PHI (which
/// is only possible if all operands to the PHI are constants).
Instruction *InstCombiner::FoldOpIntoPhi(Instruction &I) {
PHINode *PN = cast<PHINode>(I.getOperand(0));
if (!PN->hasOneUse()) return 0;
// Check to see if all of the operands of the PHI are constants. If not, we
// cannot do the transformation.
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
if (!isa<Constant>(PN->getIncomingValue(i)))
return 0;
// Okay, we can do the transformation: create the new PHI node.
PHINode *NewPN = new PHINode(I.getType(), I.getName());
I.setName("");
NewPN->op_reserve(PN->getNumOperands());
InsertNewInstBefore(NewPN, *PN);
// Next, add all of the operands to the PHI.
if (I.getNumOperands() == 2) {
Constant *C = cast<Constant>(I.getOperand(1));
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
Constant *InV = cast<Constant>(PN->getIncomingValue(i));
NewPN->addIncoming(ConstantExpr::get(I.getOpcode(), InV, C),
PN->getIncomingBlock(i));
}
} else {
assert(isa<CastInst>(I) && "Unary op should be a cast!");
const Type *RetTy = I.getType();
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
Constant *InV = cast<Constant>(PN->getIncomingValue(i));
NewPN->addIncoming(ConstantExpr::getCast(InV, RetTy),
PN->getIncomingBlock(i));
}
}
return ReplaceInstUsesWith(I, NewPN);
}
// FoldBinOpIntoSelect - Given an instruction with a select as one operand and a
// constant as the other operand, try to fold the binary operator into the
// select arguments.
@ -522,6 +568,10 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
if (Val == (1ULL << NumBits-1))
return BinaryOperator::createXor(LHS, RHS);
}
if (isa<PHINode>(LHS))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
}
// X + X --> X << 1
@ -658,6 +708,10 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) {
if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
return R;
if (isa<PHINode>(Op0))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
}
if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1))
@ -769,6 +823,10 @@ Instruction *InstCombiner::visitMul(BinaryOperator &I) {
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
return R;
if (isa<PHINode>(Op0))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
}
if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
@ -849,6 +907,10 @@ Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
if (uint64_t C = Log2(Val))
return new ShiftInst(Instruction::Shr, I.getOperand(0),
ConstantUInt::get(Type::UByteTy, C));
if (isa<PHINode>(I.getOperand(0)) && !RHS->isNullValue())
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
}
// 0 / X == 0, we don't need to preserve faults!
@ -882,6 +944,9 @@ Instruction *InstCombiner::visitRem(BinaryOperator &I) {
if (!(Val & (Val-1))) // Power of 2
return BinaryOperator::createAnd(I.getOperand(0),
ConstantUInt::get(I.getType(), Val-1));
if (isa<PHINode>(I.getOperand(0)) && !RHS->isNullValue())
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
}
// 0 % X == 0, we don't need to preserve faults!
@ -1202,6 +1267,9 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
return R;
if (isa<PHINode>(Op0))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
}
Value *Op0NotVal = dyn_castNotVal(Op0);
@ -1365,6 +1433,9 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
return R;
if (isa<PHINode>(Op0))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
}
// (A & C1)|(A & C2) == A & (C1|C2)
@ -1587,6 +1658,9 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) {
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
return R;
if (isa<PHINode>(Op0))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
}
if (Value *X = dyn_castNotVal(Op0)) // ~A ^ A == -1
@ -1698,6 +1772,10 @@ Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
switch (LHSI->getOpcode()) {
case Instruction::PHI:
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
break;
case Instruction::And:
if (LHSI->hasOneUse() && isa<ConstantInt>(LHSI->getOperand(1)) &&
LHSI->getOperand(0)->hasOneUse()) {
@ -2259,6 +2337,9 @@ Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
return R;
if (isa<PHINode>(Op0))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
// If the operand is an bitwise operator with a constant RHS, and the
// shift is the only use, we can pull it out of the shift.
@ -2552,6 +2633,10 @@ Instruction *InstCombiner::visitCastInst(CastInst &CI) {
}
}
if (isa<PHINode>(Src))
if (Instruction *NV = FoldOpIntoPhi(CI))
return NV;
// If the source value is an instruction with only this use, we can attempt to
// propagate the cast into the instruction. Also, only handle integral types
// for now.