From: Duncan Sands Date: Thu, 17 Feb 2011 07:46:37 +0000 (+0000) Subject: Transform "A + B >= A + C" into "B >= C" if the adds do not wrap. Likewise for some X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=a77243300ba1a40c80c0f8417ba74bb76e7de279;p=oota-llvm.git Transform "A + B >= A + C" into "B >= C" if the adds do not wrap. Likewise for some variations (some of these were already present so I unified the code). Spotted by my auto-simplifier as occurring a lot. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@125734 91177308-0d34-0410-b5e6-96231b3b80d8 --- diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp index 67c97d24cc8..f1533ce9fe5 100644 --- a/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -698,13 +698,6 @@ Instruction *InstCombiner::FoldICmpAddOpCst(ICmpInst &ICI, if (Pred == ICmpInst::ICMP_NE) return ReplaceInstUsesWith(ICI, ConstantInt::getTrue(X->getContext())); - // If this is an instruction (as opposed to constantexpr) get NUW/NSW info. - bool isNUW = false, isNSW = false; - if (BinaryOperator *Add = dyn_cast(TheAdd)) { - isNUW = Add->hasNoUnsignedWrap(); - isNSW = Add->hasNoSignedWrap(); - } - // From this point on, we know that (X+C <= X) --> (X+C < X) because C != 0, // so the values can never be equal. Similiarly for all other "or equals" // operators. @@ -713,10 +706,6 @@ Instruction *InstCombiner::FoldICmpAddOpCst(ICmpInst &ICI, // (X+2) X >u (MAXUINT-2) --> X > 253 // (X+MAXUINT) X >u (MAXUINT-MAXUINT) --> X != 0 if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE) { - // If this is an NUW add, then this is always false. - if (isNUW) - return ReplaceInstUsesWith(ICI, ConstantInt::getFalse(X->getContext())); - Value *R = ConstantExpr::getSub(ConstantInt::getAllOnesValue(CI->getType()), CI); return new ICmpInst(ICmpInst::ICMP_UGT, X, R); @@ -725,12 +714,8 @@ Instruction *InstCombiner::FoldICmpAddOpCst(ICmpInst &ICI, // (X+1) >u X --> X X != 255 // (X+2) >u X --> X X u X --> X X X == 0 - if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE) { - // If this is an NUW add, then this is always true. - if (isNUW) - return ReplaceInstUsesWith(ICI, ConstantInt::getTrue(X->getContext())); + if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE) return new ICmpInst(ICmpInst::ICMP_ULT, X, ConstantExpr::getNeg(CI)); - } unsigned BitWidth = CI->getType()->getPrimitiveSizeInBits(); ConstantInt *SMax = ConstantInt::get(X->getContext(), @@ -742,16 +727,8 @@ Instruction *InstCombiner::FoldICmpAddOpCst(ICmpInst &ICI, // (X+MINSINT) X >s (MAXSINT-MINSINT) --> X >s -1 // (X+ -2) X >s (MAXSINT- -2) --> X >s 126 // (X+ -1) X >s (MAXSINT- -1) --> X != 127 - if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE) { - // If this is an NSW add, then we have two cases: if the constant is - // positive, then this is always false, if negative, this is always true. - if (isNSW) { - bool isTrue = CI->getValue().isNegative(); - return ReplaceInstUsesWith(ICI, ConstantInt::get(ICI.getType(), isTrue)); - } - + if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE) return new ICmpInst(ICmpInst::ICMP_SGT, X, ConstantExpr::getSub(SMax, CI)); - } // (X+ 1) >s X --> X X != 127 // (X+ 2) >s X --> X X s X --> X X s X --> X X == -128 - // If this is an NSW add, then we have two cases: if the constant is - // positive, then this is always true, if negative, this is always false. - if (isNSW) { - bool isTrue = !CI->getValue().isNegative(); - return ReplaceInstUsesWith(ICI, ConstantInt::get(ICI.getType(), isTrue)); - } - assert(Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE); Constant *C = ConstantInt::get(X->getContext(), CI->getValue()-1); return new ICmpInst(ICmpInst::ICMP_SLT, X, ConstantExpr::getSub(SMax, C)); @@ -2263,60 +2233,115 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) { if (Instruction *R = visitICmpInstWithCastAndCast(I)) return R; } - - // See if it's the same type of instruction on the left and right. - if (BinaryOperator *Op0I = dyn_cast(Op0)) { - if (BinaryOperator *Op1I = dyn_cast(Op1)) { - if (Op0I->getOpcode() == Op1I->getOpcode() && Op0I->hasOneUse() && - Op1I->hasOneUse() && Op0I->getOperand(1) == Op1I->getOperand(1)) { - switch (Op0I->getOpcode()) { - default: break; - case Instruction::Add: - case Instruction::Sub: - case Instruction::Xor: - if (I.isEquality()) // a+x icmp eq/ne b+x --> a icmp b - return new ICmpInst(I.getPredicate(), Op0I->getOperand(0), - Op1I->getOperand(0)); - // icmp u/s (a ^ signbit), (b ^ signbit) --> icmp s/u a, b - if (ConstantInt *CI = dyn_cast(Op0I->getOperand(1))) { - if (CI->getValue().isSignBit()) { - ICmpInst::Predicate Pred = I.isSigned() - ? I.getUnsignedPredicate() - : I.getSignedPredicate(); - return new ICmpInst(Pred, Op0I->getOperand(0), - Op1I->getOperand(0)); - } - - if (CI->getValue().isMaxSignedValue()) { - ICmpInst::Predicate Pred = I.isSigned() - ? I.getUnsignedPredicate() - : I.getSignedPredicate(); - Pred = I.getSwappedPredicate(Pred); - return new ICmpInst(Pred, Op0I->getOperand(0), - Op1I->getOperand(0)); - } + + // Special logic for binary operators. + BinaryOperator *BO0 = dyn_cast(Op0); + BinaryOperator *BO1 = dyn_cast(Op1); + if (BO0 || BO1) { + CmpInst::Predicate Pred = I.getPredicate(); + bool NoOp0WrapProblem = false, NoOp1WrapProblem = false; + if (BO0 && isa(BO0)) + NoOp0WrapProblem = ICmpInst::isEquality(Pred) || + (CmpInst::isUnsigned(Pred) && BO0->hasNoUnsignedWrap()) || + (CmpInst::isSigned(Pred) && BO0->hasNoSignedWrap()); + if (BO1 && isa(BO1)) + NoOp1WrapProblem = ICmpInst::isEquality(Pred) || + (CmpInst::isUnsigned(Pred) && BO1->hasNoUnsignedWrap()) || + (CmpInst::isSigned(Pred) && BO1->hasNoSignedWrap()); + + // Analyze the case when either Op0 or Op1 is an add instruction. + // Op0 = A + B (or A and B are null); Op1 = C + D (or C and D are null). + Value *A = 0, *B = 0, *C = 0, *D = 0; + if (BO0 && BO0->getOpcode() == Instruction::Add) + A = BO0->getOperand(0), B = BO0->getOperand(1); + if (BO1 && BO1->getOpcode() == Instruction::Add) + C = BO1->getOperand(0), D = BO1->getOperand(1); + + // icmp (X+Y), X -> icmp Y, 0 for equalities or if there is no overflow. + if ((A == Op1 || B == Op1) && NoOp0WrapProblem) + return new ICmpInst(Pred, A == Op1 ? B : A, + Constant::getNullValue(Op1->getType())); + + // icmp X, (X+Y) -> icmp 0, Y for equalities or if there is no overflow. + if ((C == Op0 || D == Op0) && NoOp1WrapProblem) + return new ICmpInst(Pred, Constant::getNullValue(Op0->getType()), + C == Op0 ? D : C); + + // icmp (X+Y), (X+Z) -> icmp Y,Z for equalities or if there is no overflow. + if (A && C && (A == C || A == D || B == C || B == D) && + NoOp0WrapProblem && NoOp1WrapProblem && + // Try not to increase register pressure. + BO0->hasOneUse() && BO1->hasOneUse()) { + // Determine Y and Z in the form icmp (X+Y), (X+Z). + Value *Y = (A == C || A == D) ? B : A; + Value *Z = (C == A || C == B) ? D : C; + return new ICmpInst(Pred, Y, Z); + } + + // Analyze the case when either Op0 or Op1 is a sub instruction. + // Op0 = A - B (or A and B are null); Op1 = C - D (or C and D are null). + A = 0; B = 0; C = 0; D = 0; + if (BO0 && BO0->getOpcode() == Instruction::Sub) + A = BO0->getOperand(0), B = BO0->getOperand(1); + if (BO1 && BO1->getOpcode() == Instruction::Sub) + C = BO1->getOperand(0), D = BO1->getOperand(1); + + // icmp (Y-X), (Z-X) -> icmp Y,Z for equalities or if there is no overflow. + if (B && D && B == D && NoOp0WrapProblem && NoOp1WrapProblem && + // Try not to increase register pressure. + BO0->hasOneUse() && BO1->hasOneUse()) + return new ICmpInst(Pred, A, C); + + if (BO0 && BO1 && BO0->getOpcode() == BO1->getOpcode() && + BO0->hasOneUse() && BO1->hasOneUse() && + BO0->getOperand(1) == BO1->getOperand(1)) { + switch (BO0->getOpcode()) { + default: break; + case Instruction::Add: + case Instruction::Sub: + case Instruction::Xor: + if (I.isEquality()) // a+x icmp eq/ne b+x --> a icmp b + return new ICmpInst(I.getPredicate(), BO0->getOperand(0), + BO1->getOperand(0)); + // icmp u/s (a ^ signbit), (b ^ signbit) --> icmp s/u a, b + if (ConstantInt *CI = dyn_cast(BO0->getOperand(1))) { + if (CI->getValue().isSignBit()) { + ICmpInst::Predicate Pred = I.isSigned() + ? I.getUnsignedPredicate() + : I.getSignedPredicate(); + return new ICmpInst(Pred, BO0->getOperand(0), + BO1->getOperand(0)); + } + + if (CI->getValue().isMaxSignedValue()) { + ICmpInst::Predicate Pred = I.isSigned() + ? I.getUnsignedPredicate() + : I.getSignedPredicate(); + Pred = I.getSwappedPredicate(Pred); + return new ICmpInst(Pred, BO0->getOperand(0), + BO1->getOperand(0)); } + } + break; + case Instruction::Mul: + if (!I.isEquality()) break; - case Instruction::Mul: - if (!I.isEquality()) - break; - if (ConstantInt *CI = dyn_cast(Op0I->getOperand(1))) { - // a * Cst icmp eq/ne b * Cst --> a & Mask icmp b & Mask - // Mask = -1 >> count-trailing-zeros(Cst). - if (!CI->isZero() && !CI->isOne()) { - const APInt &AP = CI->getValue(); - ConstantInt *Mask = ConstantInt::get(I.getContext(), - APInt::getLowBitsSet(AP.getBitWidth(), - AP.getBitWidth() - - AP.countTrailingZeros())); - Value *And1 = Builder->CreateAnd(Op0I->getOperand(0), Mask); - Value *And2 = Builder->CreateAnd(Op1I->getOperand(0), Mask); - return new ICmpInst(I.getPredicate(), And1, And2); - } + if (ConstantInt *CI = dyn_cast(BO0->getOperand(1))) { + // a * Cst icmp eq/ne b * Cst --> a & Mask icmp b & Mask + // Mask = -1 >> count-trailing-zeros(Cst). + if (!CI->isZero() && !CI->isOne()) { + const APInt &AP = CI->getValue(); + ConstantInt *Mask = ConstantInt::get(I.getContext(), + APInt::getLowBitsSet(AP.getBitWidth(), + AP.getBitWidth() - + AP.countTrailingZeros())); + Value *And1 = Builder->CreateAnd(BO0->getOperand(0), Mask); + Value *And2 = Builder->CreateAnd(BO1->getOperand(0), Mask); + return new ICmpInst(I.getPredicate(), And1, And2); } - break; } + break; } } } @@ -2400,18 +2425,6 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) { return new ICmpInst(I.getPredicate(), B, Constant::getNullValue(B->getType())); - // (A+B) == A -> B == 0 - if (match(Op0, m_Add(m_Specific(Op1), m_Value(B))) || - match(Op0, m_Add(m_Value(B), m_Specific(Op1)))) - return new ICmpInst(I.getPredicate(), B, - Constant::getNullValue(B->getType())); - - // A == (A+B) -> B == 0 - if (match(Op1, m_Add(m_Specific(Op0), m_Value(B))) || - match(Op1, m_Add(m_Value(B), m_Specific(Op0)))) - return new ICmpInst(I.getPredicate(), B, - Constant::getNullValue(B->getType())); - // (X&Z) == (Y&Z) -> (X^Y) & Z == 0 if (Op0->hasOneUse() && Op1->hasOneUse() && match(Op0, m_And(m_Value(A), m_Value(B))) && diff --git a/test/Transforms/InstCombine/icmp.ll b/test/Transforms/InstCombine/icmp.ll index 72ada2476fd..08718affa02 100644 --- a/test/Transforms/InstCombine/icmp.ll +++ b/test/Transforms/InstCombine/icmp.ll @@ -234,3 +234,22 @@ define i1 @test24(i64 %i) { ret i1 %cmp } +; CHECK: @test25 +; CHECK: %c = icmp sgt i32 %x, %y +; CHECK: ret i1 %c +define i1 @test25(i32 %x, i32 %y, i32 %z) { + %lhs = add nsw i32 %x, %z + %rhs = add nsw i32 %y, %z + %c = icmp sgt i32 %lhs, %rhs + ret i1 %c +} + +; CHECK: @test26 +; CHECK: %c = icmp sgt i32 %x, %y +; CHECK: ret i1 %c +define i1 @test26(i32 %x, i32 %y, i32 %z) { + %lhs = sub nsw i32 %x, %z + %rhs = sub nsw i32 %y, %z + %c = icmp sgt i32 %lhs, %rhs + ret i1 %c +}