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[InstSimplify] fold icmp based on range of abs/nabs (2nd try)
This is retrying the fold from rL345717 (reverted at rL347780) ...with a fix for the miscompile demonstrated by PR39510: https://bugs.llvm.org/show_bug.cgi?id=39510 Original commit message: This is a fix for PR39475: https://bugs.llvm.org/show_bug.cgi?id=39475 We managed to get some of these patterns using computeKnownBits in https://reviews.llvm.org/D47041, but that can't be used for nabs(). Instead, put in some range-based logic, so we can fold both abs/nabs with icmp with a constant value. Alive proofs: https://rise4fun.com/Alive/21r Name: abs_nsw_is_positive %cmp = icmp slt i32 %x, 0 %negx = sub nsw i32 0, %x %abs = select i1 %cmp, i32 %negx, i32 %x %r = icmp sgt i32 %abs, -1 => %r = i1 true Name: abs_nsw_is_not_negative %cmp = icmp slt i32 %x, 0 %negx = sub nsw i32 0, %x %abs = select i1 %cmp, i32 %negx, i32 %x %r = icmp slt i32 %abs, 0 => %r = i1 false Name: nabs_is_negative_or_0 %cmp = icmp slt i32 %x, 0 %negx = sub i32 0, %x %nabs = select i1 %cmp, i32 %x, i32 %negx %r = icmp slt i32 %nabs, 1 => %r = i1 true Name: nabs_is_not_over_0 %cmp = icmp slt i32 %x, 0 %negx = sub i32 0, %x %nabs = select i1 %cmp, i32 %x, i32 %negx %r = icmp sgt i32 %nabs, 0 => %r = i1 false Differential Revision: https://reviews.llvm.org/D53844 llvm-svn: 345832
This commit is contained in:
Sanjay Patel
parent
c44ecf6317
commit
f49b5e5933
@ -2996,6 +2996,44 @@ static Value *simplifyICmpWithBinOp(CmpInst::Predicate Pred, Value *LHS,
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return nullptr;
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}
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static Value *simplifyICmpWithAbsNabs(CmpInst::Predicate Pred, Value *Op0,
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Value *Op1) {
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// We need a comparison with a constant.
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const APInt *C;
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if (!match(Op1, m_APInt(C)))
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return nullptr;
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// matchSelectPattern returns the negation part of an abs pattern in SP1.
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// If the negate has an NSW flag, abs(INT_MIN) is undefined. Without that
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// constraint, we can't make a contiguous range for the result of abs.
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ICmpInst::Predicate AbsPred = ICmpInst::BAD_ICMP_PREDICATE;
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Value *SP0, *SP1;
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SelectPatternFlavor SPF = matchSelectPattern(Op0, SP0, SP1).Flavor;
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if (SPF == SelectPatternFlavor::SPF_ABS &&
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cast<Instruction>(SP1)->hasNoSignedWrap())
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// The result of abs(X) is >= 0 (with nsw).
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AbsPred = ICmpInst::ICMP_SGE;
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if (SPF == SelectPatternFlavor::SPF_NABS)
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// The result of -abs(X) is <= 0.
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AbsPred = ICmpInst::ICMP_SLE;
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if (AbsPred == ICmpInst::BAD_ICMP_PREDICATE)
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return nullptr;
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// If there is no intersection between abs/nabs and the range of this icmp,
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// the icmp must be false. If the abs/nabs range is a subset of the icmp
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// range, the icmp must be true.
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APInt Zero = APInt::getNullValue(C->getBitWidth());
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ConstantRange AbsRange = ConstantRange::makeExactICmpRegion(AbsPred, Zero);
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ConstantRange CmpRange = ConstantRange::makeExactICmpRegion(Pred, *C);
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if (AbsRange.intersectWith(CmpRange).isEmptySet())
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return getFalse(GetCompareTy(Op0));
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if (CmpRange.contains(AbsRange))
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return getTrue(GetCompareTy(Op0));
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return nullptr;
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}
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/// Simplify integer comparisons where at least one operand of the compare
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/// matches an integer min/max idiom.
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static Value *simplifyICmpWithMinMax(CmpInst::Predicate Pred, Value *LHS,
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@ -3427,6 +3465,9 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
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if (Value *V = simplifyICmpWithMinMax(Pred, LHS, RHS, Q, MaxRecurse))
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return V;
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if (Value *V = simplifyICmpWithAbsNabs(Pred, LHS, RHS))
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return V;
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// Simplify comparisons of related pointers using a powerful, recursive
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// GEP-walk when we have target data available..
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if (LHS->getType()->isPointerTy())
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@ -5,11 +5,7 @@
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define i1 @abs_nsw_is_positive(i32 %x) {
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; CHECK-LABEL: @abs_nsw_is_positive(
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; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[X:%.*]], 0
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; CHECK-NEXT: [[NEGX:%.*]] = sub nsw i32 0, [[X]]
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; CHECK-NEXT: [[ABS:%.*]] = select i1 [[CMP]], i32 [[NEGX]], i32 [[X]]
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; CHECK-NEXT: [[R:%.*]] = icmp sgt i32 [[ABS]], -1
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; CHECK-NEXT: ret i1 [[R]]
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; CHECK-NEXT: ret i1 true
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;
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%cmp = icmp slt i32 %x, 0
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%negx = sub nsw i32 0, %x
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@ -35,11 +31,7 @@ define i1 @abs_nsw_is_positive_sge(i32 %x) {
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define i1 @abs_nsw_is_positive_reduced_range(i32 %x) {
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; CHECK-LABEL: @abs_nsw_is_positive_reduced_range(
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; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[X:%.*]], 0
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; CHECK-NEXT: [[NEGX:%.*]] = sub nsw i32 0, [[X]]
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; CHECK-NEXT: [[ABS:%.*]] = select i1 [[CMP]], i32 [[NEGX]], i32 [[X]]
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; CHECK-NEXT: [[R:%.*]] = icmp sgt i32 [[ABS]], -42
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; CHECK-NEXT: ret i1 [[R]]
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; CHECK-NEXT: ret i1 true
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;
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%cmp = icmp slt i32 %x, 0
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%negx = sub nsw i32 0, %x
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@ -99,11 +91,7 @@ define i1 @abs_nsw_is_not_negative(i32 %x) {
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define i1 @abs_nsw_is_not_negative_sle(i32 %x) {
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; CHECK-LABEL: @abs_nsw_is_not_negative_sle(
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; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[X:%.*]], 1
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; CHECK-NEXT: [[NEGX:%.*]] = sub nsw i32 0, [[X]]
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; CHECK-NEXT: [[ABS:%.*]] = select i1 [[CMP]], i32 [[NEGX]], i32 [[X]]
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; CHECK-NEXT: [[R:%.*]] = icmp sle i32 [[ABS]], -1
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; CHECK-NEXT: ret i1 [[R]]
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; CHECK-NEXT: ret i1 false
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;
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%cmp = icmp slt i32 %x, 1
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%negx = sub nsw i32 0, %x
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@ -116,11 +104,7 @@ define i1 @abs_nsw_is_not_negative_sle(i32 %x) {
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define i1 @abs_nsw_is_not_negative_reduced_range(i32 %x) {
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; CHECK-LABEL: @abs_nsw_is_not_negative_reduced_range(
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; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[X:%.*]], 0
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; CHECK-NEXT: [[NEGX:%.*]] = sub nsw i32 0, [[X]]
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; CHECK-NEXT: [[ABS:%.*]] = select i1 [[CMP]], i32 [[NEGX]], i32 [[X]]
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; CHECK-NEXT: [[R:%.*]] = icmp slt i32 [[ABS]], -24
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; CHECK-NEXT: ret i1 [[R]]
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; CHECK-NEXT: ret i1 false
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;
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%cmp = icmp slt i32 %x, 0
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%negx = sub nsw i32 0, %x
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@ -167,11 +151,7 @@ define i1 @abs_nsw_is_not_negative_wrong_range(i32 %x) {
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define i1 @nabs_is_negative_or_0(i32 %x) {
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; CHECK-LABEL: @nabs_is_negative_or_0(
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; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[X:%.*]], 0
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; CHECK-NEXT: [[NEGX:%.*]] = sub i32 0, [[X]]
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; CHECK-NEXT: [[NABS:%.*]] = select i1 [[CMP]], i32 [[X]], i32 [[NEGX]]
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; CHECK-NEXT: [[R:%.*]] = icmp slt i32 [[NABS]], 1
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; CHECK-NEXT: ret i1 [[R]]
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; CHECK-NEXT: ret i1 true
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;
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%cmp = icmp slt i32 %x, 0
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%negx = sub i32 0, %x
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@ -184,11 +164,7 @@ define i1 @nabs_is_negative_or_0(i32 %x) {
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define i1 @nabs_is_negative_or_0_sle(i32 %x) {
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; CHECK-LABEL: @nabs_is_negative_or_0_sle(
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; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[X:%.*]], 1
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; CHECK-NEXT: [[NEGX:%.*]] = sub i32 0, [[X]]
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; CHECK-NEXT: [[NABS:%.*]] = select i1 [[CMP]], i32 [[X]], i32 [[NEGX]]
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; CHECK-NEXT: [[R:%.*]] = icmp sle i32 [[NABS]], 0
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; CHECK-NEXT: ret i1 [[R]]
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; CHECK-NEXT: ret i1 true
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;
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%cmp = icmp slt i32 %x, 1
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%negx = sub i32 0, %x
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@ -201,11 +177,7 @@ define i1 @nabs_is_negative_or_0_sle(i32 %x) {
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define i1 @nabs_is_negative_or_0_reduced_range(i32 %x) {
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; CHECK-LABEL: @nabs_is_negative_or_0_reduced_range(
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; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[X:%.*]], 1
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; CHECK-NEXT: [[NEGX:%.*]] = sub i32 0, [[X]]
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; CHECK-NEXT: [[NABS:%.*]] = select i1 [[CMP]], i32 [[X]], i32 [[NEGX]]
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; CHECK-NEXT: [[R:%.*]] = icmp slt i32 [[NABS]], 421
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; CHECK-NEXT: ret i1 [[R]]
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; CHECK-NEXT: ret i1 true
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;
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%cmp = icmp slt i32 %x, 1
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%negx = sub i32 0, %x
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@ -235,11 +207,7 @@ define i1 @nabs_is_negative_or_0_wrong_range(i32 %x) {
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define i1 @nabs_is_not_over_0(i32 %x) {
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; CHECK-LABEL: @nabs_is_not_over_0(
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; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[X:%.*]], 0
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; CHECK-NEXT: [[NEGX:%.*]] = sub i32 0, [[X]]
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; CHECK-NEXT: [[NABS:%.*]] = select i1 [[CMP]], i32 [[X]], i32 [[NEGX]]
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; CHECK-NEXT: [[R:%.*]] = icmp sgt i32 [[NABS]], 0
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; CHECK-NEXT: ret i1 [[R]]
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; CHECK-NEXT: ret i1 false
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;
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%cmp = icmp slt i32 %x, 0
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%negx = sub i32 0, %x
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@ -252,11 +220,7 @@ define i1 @nabs_is_not_over_0(i32 %x) {
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define i1 @nabs_is_not_over_0_sle(i32 %x) {
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; CHECK-LABEL: @nabs_is_not_over_0_sle(
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; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[X:%.*]], 1
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; CHECK-NEXT: [[NEGX:%.*]] = sub i32 0, [[X]]
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; CHECK-NEXT: [[NABS:%.*]] = select i1 [[CMP]], i32 [[X]], i32 [[NEGX]]
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; CHECK-NEXT: [[R:%.*]] = icmp sge i32 [[NABS]], 1
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; CHECK-NEXT: ret i1 [[R]]
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; CHECK-NEXT: ret i1 false
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;
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%cmp = icmp slt i32 %x, 1
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%negx = sub i32 0, %x
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@ -269,11 +233,7 @@ define i1 @nabs_is_not_over_0_sle(i32 %x) {
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define i1 @nabs_is_not_over_0_reduced_range(i32 %x) {
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; CHECK-LABEL: @nabs_is_not_over_0_reduced_range(
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; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[X:%.*]], 1
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; CHECK-NEXT: [[NEGX:%.*]] = sub i32 0, [[X]]
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; CHECK-NEXT: [[NABS:%.*]] = select i1 [[CMP]], i32 [[X]], i32 [[NEGX]]
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; CHECK-NEXT: [[R:%.*]] = icmp sgt i32 [[NABS]], 4223
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; CHECK-NEXT: ret i1 [[R]]
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; CHECK-NEXT: ret i1 false
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;
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%cmp = icmp slt i32 %x, 1
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%negx = sub i32 0, %x
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@ -318,11 +278,7 @@ define i1 @abs_nsw_is_positive_eq(i32 %x) {
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define i1 @abs_nsw_is_positive_ult(i8 %x) {
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; CHECK-LABEL: @abs_nsw_is_positive_ult(
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; CHECK-NEXT: [[CMP:%.*]] = icmp slt i8 [[X:%.*]], 0
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; CHECK-NEXT: [[NEGX:%.*]] = sub nsw i8 0, [[X]]
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; CHECK-NEXT: [[ABS:%.*]] = select i1 [[CMP]], i8 [[NEGX]], i8 [[X]]
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; CHECK-NEXT: [[R:%.*]] = icmp ult i8 [[ABS]], -117
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; CHECK-NEXT: ret i1 [[R]]
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; CHECK-NEXT: ret i1 true
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;
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%cmp = icmp slt i8 %x, 0
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%negx = sub nsw i8 0, %x
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@ -335,11 +291,7 @@ define i1 @abs_nsw_is_positive_ult(i8 %x) {
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define i1 @abs_nsw_is_not_negative_ugt(i8 %x) {
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; CHECK-LABEL: @abs_nsw_is_not_negative_ugt(
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; CHECK-NEXT: [[CMP:%.*]] = icmp slt i8 [[X:%.*]], 0
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; CHECK-NEXT: [[NEGX:%.*]] = sub nsw i8 0, [[X]]
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; CHECK-NEXT: [[ABS:%.*]] = select i1 [[CMP]], i8 [[NEGX]], i8 [[X]]
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; CHECK-NEXT: [[R:%.*]] = icmp ugt i8 [[ABS]], 127
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; CHECK-NEXT: ret i1 [[R]]
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; CHECK-NEXT: ret i1 false
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;
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%cmp = icmp slt i8 %x, 0
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%negx = sub nsw i8 0, %x
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@ -352,11 +304,7 @@ define i1 @abs_nsw_is_not_negative_ugt(i8 %x) {
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define <2 x i1> @abs_nsw_is_not_negative_vec_splat(<2 x i32> %x) {
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; CHECK-LABEL: @abs_nsw_is_not_negative_vec_splat(
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; CHECK-NEXT: [[CMP:%.*]] = icmp slt <2 x i32> [[X:%.*]], zeroinitializer
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; CHECK-NEXT: [[NEGX:%.*]] = sub nsw <2 x i32> zeroinitializer, [[X]]
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; CHECK-NEXT: [[ABS:%.*]] = select <2 x i1> [[CMP]], <2 x i32> [[NEGX]], <2 x i32> [[X]]
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; CHECK-NEXT: [[R:%.*]] = icmp slt <2 x i32> [[ABS]], <i32 -8, i32 -8>
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; CHECK-NEXT: ret <2 x i1> [[R]]
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; CHECK-NEXT: ret <2 x i1> zeroinitializer
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;
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%cmp = icmp slt <2 x i32> %x, zeroinitializer
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%negx = sub nsw <2 x i32> zeroinitializer, %x
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@ -369,11 +317,7 @@ define <2 x i1> @abs_nsw_is_not_negative_vec_splat(<2 x i32> %x) {
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define i1 @nabs_is_negative_or_0_ne(i8 %x) {
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; CHECK-LABEL: @nabs_is_negative_or_0_ne(
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; CHECK-NEXT: [[CMP:%.*]] = icmp slt i8 [[X:%.*]], 0
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; CHECK-NEXT: [[NEGX:%.*]] = sub i8 0, [[X]]
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; CHECK-NEXT: [[NABS:%.*]] = select i1 [[CMP]], i8 [[X]], i8 [[NEGX]]
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; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[NABS]], 12
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; CHECK-NEXT: ret i1 [[R]]
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; CHECK-NEXT: ret i1 true
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;
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%cmp = icmp slt i8 %x, 0
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%negx = sub i8 0, %x
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@ -386,11 +330,7 @@ define i1 @nabs_is_negative_or_0_ne(i8 %x) {
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define <3 x i1> @nabs_is_not_over_0_sle_vec_splat(<3 x i33> %x) {
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; CHECK-LABEL: @nabs_is_not_over_0_sle_vec_splat(
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; CHECK-NEXT: [[CMP:%.*]] = icmp slt <3 x i33> [[X:%.*]], <i33 1, i33 1, i33 1>
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; CHECK-NEXT: [[NEGX:%.*]] = sub <3 x i33> zeroinitializer, [[X]]
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; CHECK-NEXT: [[NABS:%.*]] = select <3 x i1> [[CMP]], <3 x i33> [[X]], <3 x i33> [[NEGX]]
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; CHECK-NEXT: [[R:%.*]] = icmp sge <3 x i33> [[NABS]], <i33 1, i33 1, i33 1>
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; CHECK-NEXT: ret <3 x i1> [[R]]
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; CHECK-NEXT: ret <3 x i1> zeroinitializer
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;
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%cmp = icmp slt <3 x i33> %x, <i33 1, i33 1, i33 1>
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%negx = sub <3 x i33> zeroinitializer, %x
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