[llvm] r269728 - [InstCombine] check vector elements before trying to transform LE/GE vector icmp (PR27756)
Mike Aizatsky via llvm-commits
llvm-commits at lists.llvm.org
Tue May 17 12:53:49 PDT 2016
Sanjay,
I think this change is breaking both ppc64 sanitizer build bots.
First breakage:
http://lab.llvm.org:8011/builders/sanitizer-ppc64be-linux/builds/2016
Not sure why is it PPC specific.
On Mon, May 16, 2016 at 6:04 PM Sanjay Patel via llvm-commits <
llvm-commits at lists.llvm.org> wrote:
> Author: spatel
> Date: Mon May 16 19:57:57 2016
> New Revision: 269728
>
> URL: http://llvm.org/viewvc/llvm-project?rev=269728&view=rev
> Log:
> [InstCombine] check vector elements before trying to transform LE/GE
> vector icmp (PR27756)
>
> Fix a bug introduced with rL269426 :
> [InstCombine] canonicalize* LE/GE vector integer comparisons to LT/GT
> (PR26701, PR26819)
>
> We were assuming that a ConstantDataVector / ConstantVector /
> ConstantAggregateZero operand of
> an ICMP was composed of ConstantInt elements, but it might have
> ConstantExpr or UndefValue
> elements. Handle those appropriately.
>
> Also, refactor this function to join the scalar and vector paths and
> eliminate the switches.
>
> Differential Revision: http://reviews.llvm.org/D20289
>
> Modified:
> llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
> llvm/trunk/test/Transforms/InstCombine/icmp-vec.ll
>
> Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp?rev=269728&r1=269727&r2=269728&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
> (original)
> +++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp Mon May
> 16 19:57:57 2016
> @@ -3102,90 +3102,54 @@ bool InstCombiner::replacedSelectWithOpe
> /// If we have an icmp le or icmp ge instruction with a constant operand,
> turn
> /// it into the appropriate icmp lt or icmp gt instruction. This transform
> /// allows them to be folded in visitICmpInst.
> -static ICmpInst *canonicalizeCmpWithConstant(ICmpInst &I,
> - InstCombiner::BuilderTy
> &Builder) {
> +static ICmpInst *canonicalizeCmpWithConstant(ICmpInst &I) {
> + ICmpInst::Predicate Pred = I.getPredicate();
> + if (Pred != ICmpInst::ICMP_SLE && Pred != ICmpInst::ICMP_SGE &&
> + Pred != ICmpInst::ICMP_ULE && Pred != ICmpInst::ICMP_UGE)
> + return nullptr;
> +
> Value *Op0 = I.getOperand(0);
> Value *Op1 = I.getOperand(1);
> -
> - if (auto *Op1C = dyn_cast<ConstantInt>(Op1)) {
> - // For scalars, SimplifyICmpInst has already handled the edge cases
> for us,
> - // so we just assert on them.
> - APInt Op1Val = Op1C->getValue();
> - switch (I.getPredicate()) {
> - case ICmpInst::ICMP_ULE:
> - assert(!Op1C->isMaxValue(false)); // A <=u MAX -> TRUE
> - return new ICmpInst(ICmpInst::ICMP_ULT, Op0, Builder.getInt(Op1Val
> + 1));
> - case ICmpInst::ICMP_SLE:
> - assert(!Op1C->isMaxValue(true)); // A <=s MAX -> TRUE
> - return new ICmpInst(ICmpInst::ICMP_SLT, Op0, Builder.getInt(Op1Val
> + 1));
> - case ICmpInst::ICMP_UGE:
> - assert(!Op1C->isMinValue(false)); // A >=u MIN -> TRUE
> - return new ICmpInst(ICmpInst::ICMP_UGT, Op0, Builder.getInt(Op1Val
> - 1));
> - case ICmpInst::ICMP_SGE:
> - assert(!Op1C->isMinValue(true)); // A >=s MIN -> TRUE
> - return new ICmpInst(ICmpInst::ICMP_SGT, Op0, Builder.getInt(Op1Val
> - 1));
> - default:
> - return nullptr;
> - }
> - }
> -
> - // The usual vector types are ConstantDataVector. Exotic vector types
> are
> - // ConstantVector. Zeros are special. They all derive from Constant.
> - if (isa<ConstantDataVector>(Op1) || isa<ConstantVector>(Op1) ||
> - isa<ConstantAggregateZero>(Op1)) {
> - Constant *Op1C = cast<Constant>(Op1);
> - Type *Op1Type = Op1->getType();
> - unsigned NumElts = Op1Type->getVectorNumElements();
> -
> - // Set the new comparison predicate and splat a vector of 1 or -1 to
> - // increment or decrement the vector constants. But first, check that
> no
> - // elements of the constant vector would overflow/underflow when we
> - // increment/decrement the constants.
> - //
> + auto *Op1C = dyn_cast<Constant>(Op1);
> + if (!Op1C)
> + return nullptr;
> +
> + // Check if the constant operand can be safely incremented/decremented
> without
> + // overflowing/underflowing. For scalars, SimplifyICmpInst has already
> handled
> + // the edge cases for us, so we just assert on them. For vectors, we
> must
> + // handle the edge cases.
> + Type *Op1Type = Op1->getType();
> + bool IsSigned = I.isSigned();
> + bool IsLE = (Pred == ICmpInst::ICMP_SLE || Pred == ICmpInst::ICMP_ULE);
> + if (auto *CI = dyn_cast<ConstantInt>(Op1C)) {
> + // A <= MAX -> TRUE ; A >= MIN -> TRUE
> + assert(IsLE ? !CI->isMaxValue(IsSigned) : !CI->isMinValue(IsSigned));
> + } else if (Op1Type->isVectorTy()) {
> // TODO? If the edge cases for vectors were guaranteed to be handled
> as they
> - // are for scalar, we could remove the min/max checks here. However,
> to do
> - // that, we would have to use insertelement/shufflevector to replace
> edge
> - // values.
> -
> - CmpInst::Predicate NewPred;
> - Constant *OneOrNegOne = nullptr;
> - switch (I.getPredicate()) {
> - case ICmpInst::ICMP_ULE:
> - for (unsigned i = 0; i != NumElts; ++i)
> - if
> (cast<ConstantInt>(Op1C->getAggregateElement(i))->isMaxValue(false))
> - return nullptr;
> - NewPred = ICmpInst::ICMP_ULT;
> - OneOrNegOne = ConstantInt::get(Op1Type, 1);
> - break;
> - case ICmpInst::ICMP_SLE:
> - for (unsigned i = 0; i != NumElts; ++i)
> - if
> (cast<ConstantInt>(Op1C->getAggregateElement(i))->isMaxValue(true))
> - return nullptr;
> - NewPred = ICmpInst::ICMP_SLT;
> - OneOrNegOne = ConstantInt::get(Op1Type, 1);
> - break;
> - case ICmpInst::ICMP_UGE:
> - for (unsigned i = 0; i != NumElts; ++i)
> - if
> (cast<ConstantInt>(Op1C->getAggregateElement(i))->isMinValue(false))
> - return nullptr;
> - NewPred = ICmpInst::ICMP_UGT;
> - OneOrNegOne = ConstantInt::get(Op1Type, -1);
> - break;
> - case ICmpInst::ICMP_SGE:
> - for (unsigned i = 0; i != NumElts; ++i)
> - if
> (cast<ConstantInt>(Op1C->getAggregateElement(i))->isMinValue(true))
> - return nullptr;
> - NewPred = ICmpInst::ICMP_SGT;
> - OneOrNegOne = ConstantInt::get(Op1Type, -1);
> - break;
> - default:
> - return nullptr;
> - }
> -
> - return new ICmpInst(NewPred, Op0, ConstantExpr::getAdd(Op1C,
> OneOrNegOne));
> + // are for scalar, we could remove the min/max checks. However, to do
> that,
> + // we would have to use insertelement/shufflevector to replace edge
> values.
> + unsigned NumElts = Op1Type->getVectorNumElements();
> + for (unsigned i = 0; i != NumElts; ++i) {
> + Constant *Elt = Op1C->getAggregateElement(i);
> + if (isa<UndefValue>(Elt))
> + continue;
> + // Bail out if we can't determine if this constant is min/max or if
> we
> + // know that this constant is min/max.
> + auto *CI = dyn_cast<ConstantInt>(Elt);
> + if (!CI || (IsLE ? CI->isMaxValue(IsSigned) :
> CI->isMinValue(IsSigned)))
> + return nullptr;
> + }
> + } else {
> + // ConstantExpr?
> + return nullptr;
> }
>
> - return nullptr;
> + // Increment or decrement the constant and set the new comparison
> predicate:
> + // ULE -> ULT ; UGE -> UGT ; SLE -> SLT ; SGE -> SGT
> + Constant *OneOrNegOne = ConstantInt::get(Op1Type, IsLE ? 1 : -1);
> + CmpInst::Predicate NewPred = IsLE ? ICmpInst::ICMP_ULT:
> ICmpInst::ICMP_UGT;
> + NewPred = IsSigned ? ICmpInst::getSignedPredicate(NewPred) : NewPred;
> + return new ICmpInst(NewPred, Op0, ConstantExpr::getAdd(Op1C,
> OneOrNegOne));
> }
>
> Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
> @@ -3271,7 +3235,7 @@ Instruction *InstCombiner::visitICmpInst
> }
> }
>
> - if (ICmpInst *NewICmp = canonicalizeCmpWithConstant(I, *Builder))
> + if (ICmpInst *NewICmp = canonicalizeCmpWithConstant(I))
> return NewICmp;
>
> unsigned BitWidth = 0;
>
> Modified: llvm/trunk/test/Transforms/InstCombine/icmp-vec.ll
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/icmp-vec.ll?rev=269728&r1=269727&r2=269728&view=diff
>
> ==============================================================================
> --- llvm/trunk/test/Transforms/InstCombine/icmp-vec.ll (original)
> +++ llvm/trunk/test/Transforms/InstCombine/icmp-vec.ll Mon May 16 19:57:57
> 2016
> @@ -159,3 +159,25 @@ define <2 x i1> @ule_max(<2 x i3> %x) {
> ret <2 x i1> %cmp
> }
>
> +; If we can't determine if a constant element is min/max (eg, it's a
> ConstantExpr), do nothing.
> +
> +define <2 x i1> @PR27756_1(<2 x i8> %a) {
> +; CHECK-LABEL: @PR27756_1(
> +; CHECK-NEXT: [[CMP:%.*]] = icmp sle <2 x i8> %a, <i8 bitcast (<2 x
> i4> <i4 1, i4 2> to i8), i8 0>
> +; CHECK-NEXT: ret <2 x i1> [[CMP]]
> +;
> + %cmp = icmp sle <2 x i8> %a, <i8 bitcast (<2 x i4> <i4 1, i4 2> to i8),
> i8 0>
> + ret <2 x i1> %cmp
> +}
> +
> +; Undef elements don't prevent the transform of the comparison.
> +
> +define <2 x i1> @PR27756_2(<2 x i8> %a) {
> +; CHECK-LABEL: @PR27756_2(
> +; CHECK-NEXT: [[CMP:%.*]] = icmp slt <2 x i8> %a, <i8 undef, i8 1>
> +; CHECK-NEXT: ret <2 x i1> [[CMP]]
> +;
> + %cmp = icmp sle <2 x i8> %a, <i8 undef, i8 0>
> + ret <2 x i1> %cmp
> +}
> +
>
>
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--
Mike
Sent from phone
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