diff options
| -rw-r--r-- | lib/Analysis/InstructionSimplify.cpp | 162 | ||||
| -rw-r--r-- | lib/Transforms/InstCombine/InstCombineCompares.cpp | 43 | ||||
| -rw-r--r-- | test/Transforms/InstSimplify/2011-01-18-Compare.ll | 45 |
3 files changed, 218 insertions, 32 deletions
diff --git a/lib/Analysis/InstructionSimplify.cpp b/lib/Analysis/InstructionSimplify.cpp index 7935a2f..0cbaea3 100644 --- a/lib/Analysis/InstructionSimplify.cpp +++ b/lib/Analysis/InstructionSimplify.cpp @@ -1203,6 +1203,168 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS, // We already know that LHS != LHS. return ConstantInt::get(ITy, CmpInst::isFalseWhenEqual(Pred)); + // Compare of cast, for example (zext X) != 0 -> X != 0 + if (isa<CastInst>(LHS) && (isa<Constant>(RHS) || isa<CastInst>(RHS))) { + Instruction *LI = cast<CastInst>(LHS); + Value *SrcOp = LI->getOperand(0); + const Type *SrcTy = SrcOp->getType(); + const Type *DstTy = LI->getType(); + + // Turn icmp (ptrtoint x), (ptrtoint/constant) into a compare of the input + // if the integer type is the same size as the pointer type. + if (MaxRecurse && TD && isa<PtrToIntInst>(LI) && + TD->getPointerSizeInBits() == DstTy->getPrimitiveSizeInBits()) { + if (Constant *RHSC = dyn_cast<Constant>(RHS)) { + // Transfer the cast to the constant. + if (Value *V = SimplifyICmpInst(Pred, SrcOp, + ConstantExpr::getIntToPtr(RHSC, SrcTy), + TD, DT, MaxRecurse-1)) + return V; + } else if (PtrToIntInst *RI = dyn_cast<PtrToIntInst>(RHS)) { + if (RI->getOperand(0)->getType() == SrcTy) + // Compare without the cast. + if (Value *V = SimplifyICmpInst(Pred, SrcOp, RI->getOperand(0), + TD, DT, MaxRecurse-1)) + return V; + } + } + + if (isa<ZExtInst>(LHS)) { + // Turn icmp (zext X), (zext Y) into a compare of X and Y if they have the + // same type. + if (ZExtInst *RI = dyn_cast<ZExtInst>(RHS)) { + if (MaxRecurse && SrcTy == RI->getOperand(0)->getType()) + // Compare X and Y. Note that signed predicates become unsigned. + if (Value *V = SimplifyICmpInst(ICmpInst::getUnsignedPredicate(Pred), + SrcOp, RI->getOperand(0), TD, DT, + MaxRecurse-1)) + return V; + } + // Turn icmp (zext X), Cst into a compare of X and Cst if Cst is extended + // too. If not, then try to deduce the result of the comparison. + else if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) { + // Compute the constant that would happen if we truncated to SrcTy then + // reextended to DstTy. + Constant *Trunc = ConstantExpr::getTrunc(CI, SrcTy); + Constant *RExt = ConstantExpr::getCast(CastInst::ZExt, Trunc, DstTy); + + // If the re-extended constant didn't change then this is effectively + // also a case of comparing two zero-extended values. + if (RExt == CI && MaxRecurse) + if (Value *V = SimplifyICmpInst(ICmpInst::getUnsignedPredicate(Pred), + SrcOp, Trunc, TD, DT, MaxRecurse-1)) + return V; + + // Otherwise the upper bits of LHS are zero while RHS has a non-zero bit + // there. Use this to work out the result of the comparison. + if (RExt != CI) { + switch (Pred) { + default: + assert(false && "Unknown ICmp predicate!"); + // LHS <u RHS. + case ICmpInst::ICMP_EQ: + case ICmpInst::ICMP_UGT: + case ICmpInst::ICMP_UGE: + return ConstantInt::getFalse(CI->getContext()); + + case ICmpInst::ICMP_NE: + case ICmpInst::ICMP_ULT: + case ICmpInst::ICMP_ULE: + return ConstantInt::getTrue(CI->getContext()); + + // LHS is non-negative. If RHS is negative then LHS >s LHS. If RHS + // is non-negative then LHS <s RHS. + case ICmpInst::ICMP_SGT: + case ICmpInst::ICMP_SGE: + return CI->getValue().isNegative() ? + ConstantInt::getTrue(CI->getContext()) : + ConstantInt::getFalse(CI->getContext()); + + case ICmpInst::ICMP_SLT: + case ICmpInst::ICMP_SLE: + return CI->getValue().isNegative() ? + ConstantInt::getFalse(CI->getContext()) : + ConstantInt::getTrue(CI->getContext()); + } + } + } + } + + if (isa<SExtInst>(LHS)) { + // Turn icmp (sext X), (sext Y) into a compare of X and Y if they have the + // same type. + if (SExtInst *RI = dyn_cast<SExtInst>(RHS)) { + if (MaxRecurse && SrcTy == RI->getOperand(0)->getType()) + // Compare X and Y. Note that the predicate does not change. + if (Value *V = SimplifyICmpInst(Pred, SrcOp, RI->getOperand(0), + TD, DT, MaxRecurse-1)) + return V; + } + // Turn icmp (sext X), Cst into a compare of X and Cst if Cst is extended + // too. If not, then try to deduce the result of the comparison. + else if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) { + // Compute the constant that would happen if we truncated to SrcTy then + // reextended to DstTy. + Constant *Trunc = ConstantExpr::getTrunc(CI, SrcTy); + Constant *RExt = ConstantExpr::getCast(CastInst::SExt, Trunc, DstTy); + + // If the re-extended constant didn't change then this is effectively + // also a case of comparing two sign-extended values. + if (RExt == CI && MaxRecurse) + if (Value *V = SimplifyICmpInst(Pred, SrcOp, Trunc, TD, DT, + MaxRecurse-1)) + return V; + + // Otherwise the upper bits of LHS are all equal, while RHS has varying + // bits there. Use this to work out the result of the comparison. + if (RExt != CI) { + switch (Pred) { + default: + assert(false && "Unknown ICmp predicate!"); + case ICmpInst::ICMP_EQ: + return ConstantInt::getFalse(CI->getContext()); + case ICmpInst::ICMP_NE: + return ConstantInt::getTrue(CI->getContext()); + + // If RHS is non-negative then LHS <s RHS. If RHS is negative then + // LHS >s RHS. + case ICmpInst::ICMP_SGT: + case ICmpInst::ICMP_SGE: + return CI->getValue().isNegative() ? + ConstantInt::getTrue(CI->getContext()) : + ConstantInt::getFalse(CI->getContext()); + case ICmpInst::ICMP_SLT: + case ICmpInst::ICMP_SLE: + return CI->getValue().isNegative() ? + ConstantInt::getFalse(CI->getContext()) : + ConstantInt::getTrue(CI->getContext()); + + // If LHS is non-negative then LHS <u RHS. If LHS is negative then + // LHS >u RHS. + case ICmpInst::ICMP_UGT: + case ICmpInst::ICMP_UGE: + // Comparison is true iff the LHS <s 0. + if (MaxRecurse) + if (Value *V = SimplifyICmpInst(ICmpInst::ICMP_SLT, SrcOp, + Constant::getNullValue(SrcTy), + TD, DT, MaxRecurse-1)) + return V; + break; + case ICmpInst::ICMP_ULT: + case ICmpInst::ICMP_ULE: + // Comparison is true iff the LHS >=s 0. + if (MaxRecurse) + if (Value *V = SimplifyICmpInst(ICmpInst::ICMP_SGE, SrcOp, + Constant::getNullValue(SrcTy), + TD, DT, MaxRecurse-1)) + return V; + break; + } + } + } + } + } + // If the comparison is with the result of a select instruction, check whether // comparing with either branch of the select always yields the same value. if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS)) diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp index 73ae197..fe436bc 100644 --- a/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -1540,46 +1540,25 @@ Instruction *InstCombiner::visitICmpInstWithCastAndCast(ICmpInst &ICI) { // The re-extended constant changed so the constant cannot be represented // in the shorter type. Consequently, we cannot emit a simple comparison. + // All the cases that fold to true or false will have already been handled + // by SimplifyICmpInst, so only deal with the tricky case. - // First, handle some easy cases. We know the result cannot be equal at this - // point so handle the ICI.isEquality() cases - if (ICI.getPredicate() == ICmpInst::ICMP_EQ) - return ReplaceInstUsesWith(ICI, ConstantInt::getFalse(ICI.getContext())); - if (ICI.getPredicate() == ICmpInst::ICMP_NE) - return ReplaceInstUsesWith(ICI, ConstantInt::getTrue(ICI.getContext())); + if (isSignedCmp || !isSignedExt) + return 0; // Evaluate the comparison for LT (we invert for GT below). LE and GE cases // should have been folded away previously and not enter in here. - Value *Result; - if (isSignedCmp) { - // We're performing a signed comparison. - if (cast<ConstantInt>(CI)->getValue().isNegative()) - Result = ConstantInt::getFalse(ICI.getContext()); // X < (small) --> false - else - Result = ConstantInt::getTrue(ICI.getContext()); // X < (large) --> true - } else { - // We're performing an unsigned comparison. - if (isSignedExt) { - // We're performing an unsigned comp with a sign extended value. - // This is true if the input is >= 0. [aka >s -1] - Constant *NegOne = Constant::getAllOnesValue(SrcTy); - Result = Builder->CreateICmpSGT(LHSCIOp, NegOne, ICI.getName()); - } else { - // Unsigned extend & unsigned compare -> always true. - Result = ConstantInt::getTrue(ICI.getContext()); - } - } + + // We're performing an unsigned comp with a sign extended value. + // This is true if the input is >= 0. [aka >s -1] + Constant *NegOne = Constant::getAllOnesValue(SrcTy); + Value *Result = Builder->CreateICmpSGT(LHSCIOp, NegOne, ICI.getName()); // Finally, return the value computed. - if (ICI.getPredicate() == ICmpInst::ICMP_ULT || - ICI.getPredicate() == ICmpInst::ICMP_SLT) + if (ICI.getPredicate() == ICmpInst::ICMP_ULT) return ReplaceInstUsesWith(ICI, Result); - assert((ICI.getPredicate()==ICmpInst::ICMP_UGT || - ICI.getPredicate()==ICmpInst::ICMP_SGT) && - "ICmp should be folded!"); - if (Constant *CI = dyn_cast<Constant>(Result)) - return ReplaceInstUsesWith(ICI, ConstantExpr::getNot(CI)); + assert(ICI.getPredicate() == ICmpInst::ICMP_UGT && "ICmp should be folded!"); return BinaryOperator::CreateNot(Result); } diff --git a/test/Transforms/InstSimplify/2011-01-18-Compare.ll b/test/Transforms/InstSimplify/2011-01-18-Compare.ll new file mode 100644 index 0000000..1279579 --- /dev/null +++ b/test/Transforms/InstSimplify/2011-01-18-Compare.ll @@ -0,0 +1,45 @@ +; RUN: opt < %s -instsimplify -S | FileCheck %s +target datalayout = "p:32:32" + +define i1 @ptrtoint() { +; CHECK: @ptrtoint + %a = alloca i8 + %tmp = ptrtoint i8* %a to i32 + %r = icmp eq i32 %tmp, 0 + ret i1 %r +; CHECK: ret i1 false +} + +define i1 @zext(i32 %x) { +; CHECK: @zext + %e1 = zext i32 %x to i64 + %e2 = zext i32 %x to i64 + %r = icmp eq i64 %e1, %e2 + ret i1 %r +; CHECK: ret i1 true +} + +define i1 @zext2(i1 %x) { +; CHECK: @zext2 + %e = zext i1 %x to i32 + %c = icmp ne i32 %e, 0 + ret i1 %c +; CHECK: ret i1 %x +} + +define i1 @sext(i32 %x) { +; CHECK: @sext + %e1 = sext i32 %x to i64 + %e2 = sext i32 %x to i64 + %r = icmp eq i64 %e1, %e2 + ret i1 %r +; CHECK: ret i1 true +} + +define i1 @sext2(i1 %x) { +; CHECK: @sext2 + %e = sext i1 %x to i32 + %c = icmp ne i32 %e, 0 + ret i1 %c +; CHECK: ret i1 %x +} |