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Move Sub simplifications and additional Add simplifications out of 

instcombine and into InstructionSimplify.

llvm-svn: 121861
This commit is contained in:
Duncan Sands 2010-12-15 14:07:39 +00:00
parent 019a418808
commit 0a2c416894
4 changed files with 77 additions and 39 deletions
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5
llvm/include/llvm/Analysis/InstructionSimplify.h
View File

@ -29,6 +29,11 @@ namespace llvm {
Value *SimplifyAddInst(Value *LHS, Value *RHS, bool isNSW, bool isNUW,
const TargetData *TD = 0, const DominatorTree *DT = 0);
/// SimplifySubInst - Given operands for a Sub, see if we can
/// fold the result. If not, this returns null.
Value *SimplifySubInst(Value *LHS, Value *RHS, bool isNSW, bool isNUW,
const TargetData *TD = 0, const DominatorTree *DT = 0);
/// SimplifyAndInst - Given operands for an And, see if we can
/// fold the result. If not, this returns null.
Value *SimplifyAndInst(Value *LHS, Value *RHS, const TargetData *TD = 0,

75
llvm/lib/Analysis/InstructionSimplify.cpp
View File

@ -242,17 +242,25 @@ Value *llvm::SimplifyAddInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
std::swap(Op0, Op1);
}
if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
// X + undef -> undef
if (isa<UndefValue>(Op1C))
return Op1C;
// X + undef -> undef
if (isa<UndefValue>(Op1))
return Op1;
// X + 0 --> X
if (Op1C->isNullValue())
return Op0;
}
// X + 0 -> X
if (match(Op1, m_Zero()))
return Op0;
// FIXME: Could pull several more out of instcombine.
// X + (Y - X) -> Y
// (Y - X) + X -> Y
Value *Y = 0;
if (match(Op1, m_Sub(m_Value(Y), m_Specific(Op0))) ||
match(Op0, m_Sub(m_Value(Y), m_Specific(Op1))))
return Y;
// X + ~X -> -1 since ~X = -X-1
if (match(Op0, m_Not(m_Specific(Op1))) ||
match(Op1, m_Not(m_Specific(Op0))))
return Constant::getAllOnesValue(Op0->getType());
// Threading Add over selects and phi nodes is pointless, so don't bother.
// Threading over the select in "A + select(cond, B, C)" means evaluating
@ -266,6 +274,49 @@ Value *llvm::SimplifyAddInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
return 0;
}
/// SimplifySubInst - Given operands for a Sub, see if we can
/// fold the result. If not, this returns null.
Value *llvm::SimplifySubInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
const TargetData *TD, const DominatorTree *) {
if (Constant *CLHS = dyn_cast<Constant>(Op0))
if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
Constant *Ops[] = { CLHS, CRHS };
return ConstantFoldInstOperands(Instruction::Sub, CLHS->getType(),
Ops, 2, TD);
}
// X - undef -> undef
// undef - X -> undef
if (isa<UndefValue>(Op0) || isa<UndefValue>(Op1))
return UndefValue::get(Op0->getType());
// X - 0 -> X
if (match(Op1, m_Zero()))
return Op0;
// X - X -> 0
if (Op0 == Op1)
return Constant::getNullValue(Op0->getType());
// (X + Y) - Y -> X
// (Y + X) - Y -> X
Value *X = 0;
if (match(Op0, m_Add(m_Value(X), m_Specific(Op1))) ||
match(Op0, m_Add(m_Specific(Op1), m_Value(X))))
return X;
// Threading Sub over selects and phi nodes is pointless, so don't bother.
// Threading over the select in "A - select(cond, B, C)" means evaluating
// "A-B" and "A-C" and seeing if they are equal; but they are equal if and
// only if B and C are equal. If B and C are equal then (since we assume
// that operands have already been simplified) "select(cond, B, C)" should
// have been simplified to the common value of B and C already. Analysing
// "A-B" and "A-C" thus gains nothing, but costs compile time. Similarly
// for threading over phi nodes.
return 0;
}
/// SimplifyAndInst - Given operands for an And, see if we can
/// fold the result. If not, this returns null.
static Value *SimplifyAndInst(Value *Op0, Value *Op1, const TargetData *TD,
@ -835,6 +886,12 @@ Value *llvm::SimplifyInstruction(Instruction *I, const TargetData *TD,
cast<BinaryOperator>(I)->hasNoUnsignedWrap(),
TD, DT);
break;
case Instruction::Sub:
Result = SimplifySubInst(I->getOperand(0), I->getOperand(1),
cast<BinaryOperator>(I)->hasNoSignedWrap(),
cast<BinaryOperator>(I)->hasNoUnsignedWrap(),
TD, DT);
break;
case Instruction::And:
Result = SimplifyAndInst(I->getOperand(0), I->getOperand(1), TD, DT);
break;

32
llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
View File

@ -154,17 +154,6 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
// X + X --> X << 1
if (LHS == RHS)
return BinaryOperator::CreateShl(LHS, ConstantInt::get(I.getType(), 1));
if (Instruction *RHSI = dyn_cast<Instruction>(RHS)) {
if (RHSI->getOpcode() == Instruction::Sub)
if (LHS == RHSI->getOperand(1)) // A + (B - A) --> B
return ReplaceInstUsesWith(I, RHSI->getOperand(0));
}
if (Instruction *LHSI = dyn_cast<Instruction>(LHS)) {
if (LHSI->getOpcode() == Instruction::Sub)
if (RHS == LHSI->getOperand(1)) // (B - A) + A --> B
return ReplaceInstUsesWith(I, LHSI->getOperand(0));
}
}
// -A + B --> B - A
@ -201,11 +190,6 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
if (dyn_castFoldableMul(RHS, C2) == LHS)
return BinaryOperator::CreateMul(LHS, AddOne(C2));
// X + ~X --> -1 since ~X = -X-1
if (match(LHS, m_Not(m_Specific(RHS))) ||
match(RHS, m_Not(m_Specific(LHS))))
return ReplaceInstUsesWith(I, Constant::getAllOnesValue(I.getType()));
// A+B --> A|B iff A and B have no bits set in common.
if (const IntegerType *IT = dyn_cast<IntegerType>(I.getType())) {
APInt Mask = APInt::getAllOnesValue(IT->getBitWidth());
@ -547,8 +531,9 @@ Value *InstCombiner::OptimizePointerDifference(Value *LHS, Value *RHS,
Instruction *InstCombiner::visitSub(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (Op0 == Op1) // sub X, X -> 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
if (Value *V = SimplifySubInst(Op0, Op1, I.hasNoSignedWrap(),
I.hasNoUnsignedWrap(), TD))
return ReplaceInstUsesWith(I, V);
if (Instruction *NV = SimplifyByFactorizing(I)) // (A*B)-(A*C) -> A*(B-C)
return NV;
@ -561,10 +546,6 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) {
return Res;
}
if (isa<UndefValue>(Op0))
return ReplaceInstUsesWith(I, Op0); // undef - X -> undef
if (isa<UndefValue>(Op1))
return ReplaceInstUsesWith(I, Op1); // X - undef -> undef
if (I.getType()->isIntegerTy(1))
return BinaryOperator::CreateXor(Op0, Op1);
@ -693,12 +674,7 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) {
}
if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
if (Op0I->getOpcode() == Instruction::Add) {
if (Op0I->getOperand(0) == Op1) // (Y+X)-Y == X
return ReplaceInstUsesWith(I, Op0I->getOperand(1));
else if (Op0I->getOperand(1) == Op1) // (X+Y)-Y == X
return ReplaceInstUsesWith(I, Op0I->getOperand(0));
} else if (Op0I->getOpcode() == Instruction::Sub) {
if (Op0I->getOpcode() == Instruction::Sub) {
if (Op0I->getOperand(0) == Op1) // (X-Y)-X == -Y
return BinaryOperator::CreateNeg(Op0I->getOperand(1),
I.getName());

4
llvm/test/Analysis/BasicAA/modref.ll
View File

@ -105,7 +105,7 @@ define i32 @test4(i8* %P) {
; CHECK: load i32* @G
; CHECK: memset.p0i8.i32
; CHECK-NOT: load
; CHECK: sub i32 %tmp, %tmp
; CHECK: ret i32 0
}
; Verify that basicaa is handling variable length memcpy, knowing it doesn't
@ -120,7 +120,7 @@ define i32 @test5(i8* %P, i32 %Len) {
; CHECK: load i32* @G
; CHECK: memcpy.p0i8.p0i8.i32
; CHECK-NOT: load
; CHECK: sub i32 %tmp, %tmp
; CHECK: ret i32 0
}
define i8 @test6(i8* %p, i8* noalias %a) {