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Mar 1, 2025
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[InstSimplify] Fold X * C >= X to true #129352

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066e78c
Add Test
veera-sivarajan Feb 28, 2025
5fd5aa3
[InstSimplify] Fold `X * C >= X` to `true`
veera-sivarajan Mar 1, 2025
9007445
Add Commuted Test
veera-sivarajan Mar 1, 2025
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34 changes: 22 additions & 12 deletions llvm/lib/Analysis/InstructionSimplify.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3031,7 +3031,9 @@ enum class MonotonicType { GreaterEq, LowerEq };

/// Get values V_i such that V uge V_i (GreaterEq) or V ule V_i (LowerEq).
static void getUnsignedMonotonicValues(SmallPtrSetImpl<Value *> &Res, Value *V,
MonotonicType Type, unsigned Depth = 0) {
MonotonicType Type,
const SimplifyQuery &Q,
unsigned Depth = 0) {
if (!Res.insert(V).second)
return;

Expand All @@ -3047,24 +3049,31 @@ static void getUnsignedMonotonicValues(SmallPtrSetImpl<Value *> &Res, Value *V,
if (Type == MonotonicType::GreaterEq) {
if (match(I, m_Or(m_Value(X), m_Value(Y))) ||
match(I, m_Intrinsic<Intrinsic::uadd_sat>(m_Value(X), m_Value(Y)))) {
getUnsignedMonotonicValues(Res, X, Type, Depth);
getUnsignedMonotonicValues(Res, Y, Type, Depth);
getUnsignedMonotonicValues(Res, X, Type, Q, Depth);
getUnsignedMonotonicValues(Res, Y, Type, Q, Depth);
}
// X * Y >= X --> true
if (match(I, m_NUWMul(m_Value(X), m_Value(Y)))) {
if (isKnownNonZero(X, Q))
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@nikic nikic Mar 1, 2025

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Do we need the non-constant support?

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@dtcxzyw dtcxzyw Mar 1, 2025

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It is needed by assimp:
https://github.com/assimp/assimp/blob/2bce77f909b9f56c8c67cff33cc73a244505aa46/code/AssetLib/glTF2/glTF2Asset.inl#L897-L903

  %switch.gep = getelementptr inbounds nuw [7 x i64], ptr @switch.table._ZN5glTF28Accessor6Sparse9PatchDataEj, i64 0, i64 %307
  %switch.load = load i64, ptr %switch.gep, align 8
  %308 = mul nuw nsw i64 %switch.load, %202
  store i64 %308, ptr %20, align 8
  %309 = icmp samesign ult i64 %308, %202

getUnsignedMonotonicValues(Res, Y, Type, Q, Depth);
if (isKnownNonZero(Y, Q))
getUnsignedMonotonicValues(Res, X, Type, Q, Depth);
}
} else {
assert(Type == MonotonicType::LowerEq);
switch (I->getOpcode()) {
case Instruction::And:
getUnsignedMonotonicValues(Res, I->getOperand(0), Type, Depth);
getUnsignedMonotonicValues(Res, I->getOperand(1), Type, Depth);
getUnsignedMonotonicValues(Res, I->getOperand(0), Type, Q, Depth);
getUnsignedMonotonicValues(Res, I->getOperand(1), Type, Q, Depth);
break;
case Instruction::URem:
case Instruction::UDiv:
case Instruction::LShr:
getUnsignedMonotonicValues(Res, I->getOperand(0), Type, Depth);
getUnsignedMonotonicValues(Res, I->getOperand(0), Type, Q, Depth);
break;
case Instruction::Call:
if (match(I, m_Intrinsic<Intrinsic::usub_sat>(m_Value(X))))
getUnsignedMonotonicValues(Res, X, Type, Depth);
getUnsignedMonotonicValues(Res, X, Type, Q, Depth);
break;
default:
break;
Expand All @@ -3073,16 +3082,17 @@ static void getUnsignedMonotonicValues(SmallPtrSetImpl<Value *> &Res, Value *V,
}

static Value *simplifyICmpUsingMonotonicValues(CmpPredicate Pred, Value *LHS,
Value *RHS) {
Value *RHS,
const SimplifyQuery &Q) {
if (Pred != ICmpInst::ICMP_UGE && Pred != ICmpInst::ICMP_ULT)
return nullptr;

// We have LHS uge GreaterValues and LowerValues uge RHS. If any of the
// GreaterValues and LowerValues are the same, it follows that LHS uge RHS.
SmallPtrSet<Value *, 4> GreaterValues;
SmallPtrSet<Value *, 4> LowerValues;
getUnsignedMonotonicValues(GreaterValues, LHS, MonotonicType::GreaterEq);
getUnsignedMonotonicValues(LowerValues, RHS, MonotonicType::LowerEq);
getUnsignedMonotonicValues(GreaterValues, LHS, MonotonicType::GreaterEq, Q);
getUnsignedMonotonicValues(LowerValues, RHS, MonotonicType::LowerEq, Q);
for (Value *GV : GreaterValues)
if (LowerValues.contains(GV))
return ConstantInt::getBool(getCompareTy(LHS),
Expand Down Expand Up @@ -3998,10 +4008,10 @@ static Value *simplifyICmpInst(CmpPredicate Pred, Value *LHS, Value *RHS,
ICmpInst::getSwappedPredicate(Pred), RHS, LHS))
return V;

if (Value *V = simplifyICmpUsingMonotonicValues(Pred, LHS, RHS))
if (Value *V = simplifyICmpUsingMonotonicValues(Pred, LHS, RHS, Q))
return V;
if (Value *V = simplifyICmpUsingMonotonicValues(
ICmpInst::getSwappedPredicate(Pred), RHS, LHS))
ICmpInst::getSwappedPredicate(Pred), RHS, LHS, Q))
return V;

if (Value *V = simplifyICmpWithDominatingAssume(Pred, LHS, RHS, Q))
Expand Down
144 changes: 144 additions & 0 deletions llvm/test/Transforms/InstSimplify/icmp-monotonic.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -216,3 +216,147 @@ define i1 @lshr_add_ule_non_monotonic(i32 %x, i32 %y, i32 %z) {
%cmp = icmp ule i32 %op1, %op2
ret i1 %cmp
}

define i1 @mul_nuw_nonzero_rhs_monotonic(i8 %x, i8 %c) {
; CHECK-LABEL: define i1 @mul_nuw_nonzero_rhs_monotonic(
; CHECK-SAME: i8 [[X:%.*]], i8 [[C:%.*]]) {
; CHECK-NEXT: [[C_NONZERO:%.*]] = icmp ne i8 [[C]], 0
; CHECK-NEXT: call void @llvm.assume(i1 [[C_NONZERO]])
; CHECK-NEXT: ret i1 true
;
%c_nonzero = icmp ne i8 %c, 0
call void @llvm.assume(i1 %c_nonzero)

%prod = mul nuw i8 %x, %c
%cmp = icmp uge i8 %prod, %x
ret i1 %cmp
}

define i1 @mul_nuw_nonzero_rhs_commuted_monotonic(i8 %x, i8 %c) {
; CHECK-LABEL: define i1 @mul_nuw_nonzero_rhs_commuted_monotonic(
; CHECK-SAME: i8 [[X:%.*]], i8 [[C:%.*]]) {
; CHECK-NEXT: [[C_NONZERO:%.*]] = icmp ne i8 [[C]], 0
; CHECK-NEXT: call void @llvm.assume(i1 [[C_NONZERO]])
; CHECK-NEXT: ret i1 true
;
%c_nonzero = icmp ne i8 %c, 0
call void @llvm.assume(i1 %c_nonzero)

%prod = mul nuw i8 %c, %x
%cmp = icmp uge i8 %prod, %x
ret i1 %cmp
}

define i1 @mul_nuw_nonzero_rhs_monotonic_inverse_predicate(i8 %x, i8 %c) {
; CHECK-LABEL: define i1 @mul_nuw_nonzero_rhs_monotonic_inverse_predicate(
; CHECK-SAME: i8 [[X:%.*]], i8 [[C:%.*]]) {
; CHECK-NEXT: [[C_NONZERO:%.*]] = icmp ne i8 [[C]], 0
; CHECK-NEXT: call void @llvm.assume(i1 [[C_NONZERO]])
; CHECK-NEXT: ret i1 false
;
%c_nonzero = icmp ne i8 %c, 0
call void @llvm.assume(i1 %c_nonzero)

%prod = mul nuw i8 %x, %c
%cmp = icmp ult i8 %prod, %x
ret i1 %cmp
}

define i1 @mul_nuw_nonzero_lhs_monotonic(i8 %x, i8 %c) {
; CHECK-LABEL: define i1 @mul_nuw_nonzero_lhs_monotonic(
; CHECK-SAME: i8 [[X:%.*]], i8 [[C:%.*]]) {
; CHECK-NEXT: [[C_NONZERO:%.*]] = icmp ne i8 [[X]], 0
; CHECK-NEXT: call void @llvm.assume(i1 [[C_NONZERO]])
; CHECK-NEXT: ret i1 true
;
%c_nonzero = icmp ne i8 %x, 0
call void @llvm.assume(i1 %c_nonzero)

%prod = mul nuw i8 %x, %c
%cmp = icmp uge i8 %prod, %c
ret i1 %cmp
}

define i1 @mul_nuw_nonzero_lhs_rhs_monotonic(i8 %x, i8 %c) {
; CHECK-LABEL: define i1 @mul_nuw_nonzero_lhs_rhs_monotonic(
; CHECK-SAME: i8 [[X:%.*]], i8 [[C:%.*]]) {
; CHECK-NEXT: [[C_NONZERO:%.*]] = icmp ne i8 [[C]], 0
; CHECK-NEXT: call void @llvm.assume(i1 [[C_NONZERO]])
; CHECK-NEXT: [[X_NONZERO:%.*]] = icmp ne i8 [[X]], 0
; CHECK-NEXT: call void @llvm.assume(i1 [[X_NONZERO]])
; CHECK-NEXT: ret i1 true
;
%c_nonzero = icmp ne i8 %c, 0
call void @llvm.assume(i1 %c_nonzero)

%x_nonzero = icmp ne i8 %x, 0
call void @llvm.assume(i1 %x_nonzero)

%prod = mul nuw i8 %x, %c
%cmp = icmp uge i8 %prod, %x
ret i1 %cmp
}


define i1 @negative_mul_non_nsw(i8 %x, i8 %c) {
; CHECK-LABEL: define i1 @negative_mul_non_nsw(
; CHECK-SAME: i8 [[X:%.*]], i8 [[C:%.*]]) {
; CHECK-NEXT: [[C_NONZERO:%.*]] = icmp ne i8 [[C]], 0
; CHECK-NEXT: call void @llvm.assume(i1 [[C_NONZERO]])
; CHECK-NEXT: [[X3:%.*]] = mul i8 [[X]], [[C]]
; CHECK-NEXT: [[CMP:%.*]] = icmp uge i8 [[X3]], [[X]]
; CHECK-NEXT: ret i1 [[CMP]]
;
%c_nonzero = icmp ne i8 %c, 0
call void @llvm.assume(i1 %c_nonzero)

%prod = mul i8 %x, %c
%cmp = icmp uge i8 %prod, %x
ret i1 %cmp
}

define i1 @negative_mul_no_nonzero(i8 %x, i8 %c) {
; CHECK-LABEL: define i1 @negative_mul_no_nonzero(
; CHECK-SAME: i8 [[X:%.*]], i8 [[C:%.*]]) {
; CHECK-NEXT: [[X3:%.*]] = mul nsw i8 [[X]], [[C]]
; CHECK-NEXT: [[CMP:%.*]] = icmp uge i8 [[X3]], [[X]]
; CHECK-NEXT: ret i1 [[CMP]]
;
%prod = mul nsw i8 %x, %c
%cmp = icmp uge i8 %prod, %x
ret i1 %cmp
}

define i1 @negative_mul_lhs_maybe_zero(i8 %x, i8 %c) {
; CHECK-LABEL: define i1 @negative_mul_lhs_maybe_zero(
; CHECK-SAME: i8 [[X:%.*]], i8 [[C:%.*]]) {
; CHECK-NEXT: [[C_NONZERO:%.*]] = icmp ne i8 [[C]], 0
; CHECK-NEXT: call void @llvm.assume(i1 [[C_NONZERO]])
; CHECK-NEXT: [[X3:%.*]] = mul nuw i8 [[X]], [[C]]
; CHECK-NEXT: [[CMP:%.*]] = icmp uge i8 [[X3]], [[C]]
; CHECK-NEXT: ret i1 [[CMP]]
;
%c_nonzero = icmp ne i8 %c, 0
call void @llvm.assume(i1 %c_nonzero)

%prod = mul nuw i8 %x, %c
%cmp = icmp uge i8 %prod, %c
ret i1 %cmp
}

define i1 @negative_mul_rhs_maybe_zero(i8 %x, i8 %c) {
; CHECK-LABEL: define i1 @negative_mul_rhs_maybe_zero(
; CHECK-SAME: i8 [[X:%.*]], i8 [[C:%.*]]) {
; CHECK-NEXT: [[C_NONZERO:%.*]] = icmp ne i8 [[X]], 0
; CHECK-NEXT: call void @llvm.assume(i1 [[C_NONZERO]])
; CHECK-NEXT: [[X3:%.*]] = mul nuw i8 [[X]], [[C]]
; CHECK-NEXT: [[CMP:%.*]] = icmp uge i8 [[X3]], [[X]]
; CHECK-NEXT: ret i1 [[CMP]]
;
%c_nonzero = icmp ne i8 %x, 0
call void @llvm.assume(i1 %c_nonzero)

%prod = mul nuw i8 %x, %c
%cmp = icmp uge i8 %prod, %x
ret i1 %cmp
}