[llvm-branch-commits] [llvm] [ConstraintElim] Prove sadd/ssub.with.overflow cannot overflow from the exact sum (PR #235159)
Jon Roelofs via llvm-branch-commits
llvm-branch-commits at lists.llvm.org
Fri Oct 23 17:03:07 PDT 2026
https://github.com/jroelofs created https://github.com/llvm/llvm-project/pull/235159
Decompose the operands and show that the sum lies in the range of the type. This
handles patterns like A + (B - A), as well as sums involving signed min/max
results, which are split across their respective operands using monotonicity
(for example start + smax(end - start - 1, 0) <= end).
https://alive2.llvm.org/ce/z/ze8LCk
---
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>From c978fbb68aefd61a075e177520f85a81d4bae2e5 Mon Sep 17 00:00:00 2001
From: Jon Roelofs <jonathan_roelofs at apple.com>
Date: Fri, 23 Oct 2026 15:41:04 -0700
Subject: [PATCH] [ConstraintElim] Prove sadd/ssub.with.overflow cannot
overflow from the exact sum
Decompose the operands and show that the sum lies in the range of the type. This
handles patterns like A + (B - A), as well as sums involving signed min/max
results, which are split across their respective operands using monotonicity
(for example start + smax(end - start - 1, 0) <= end).
https://alive2.llvm.org/ce/z/ze8LCk
---
.../Scalar/ConstraintElimination.cpp | 163 +++++-
.../sadd-with-overflow.ll | 539 ++++++++++++++++++
2 files changed, 699 insertions(+), 3 deletions(-)
diff --git a/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp b/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
index 2c1323243cff02..33a4dfd8eb2d73 100644
--- a/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
@@ -13,6 +13,7 @@
#include "llvm/Transforms/Scalar/ConstraintElimination.h"
#include "ScalarOptions.h"
+#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/PointerIntPair.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/ScopeExit.h"
@@ -345,6 +346,30 @@ struct Decomposition {
return true;
return false;
}
+
+ /// Merge entries that refer to the same variable, and remove any whose
+ /// coefficient is zero. \returns true if any operation overflows, i.e. the
+ /// decomposition is invalid.
+ [[nodiscard]] bool canonicalize() {
+ // Sum the coefficients of each variable.
+ SmallMapVector<Value *, int64_t, 4> Coefficients;
+ for (const DecompEntry &E : Vars) {
+ int64_t &Sum = Coefficients[E.Variable];
+ if (AddOverflow(Sum, E.Coefficient, Sum))
+ return true;
+ }
+ Vars.clear();
+ for (const auto &[Variable, Coefficient] : Coefficients)
+ if (Coefficient != 0)
+ Vars.emplace_back(Coefficient, Variable);
+ return false;
+ }
+
+ /// Returns a new decomposition with \p Variable replaced by \p Replacement.
+ /// Returns std::nullopt if a coefficient overflows, i.e. the decomposition is
+ /// invalid.
+ [[nodiscard]] std::optional<Decomposition>
+ substitute(Value *Variable, Value *Replacement, ConstraintInfo &Info);
};
/// Wrapper encapsulating separate constraint systems and corresponding value
@@ -393,6 +418,8 @@ class ConstraintInfo {
return Signed ? SignedCS : UnsignedCS;
}
+ const DataLayout &getDataLayout() const { return DL; }
+
void popLastConstraint(bool Signed) {
assert(DecomposeCache.empty() && "Cache must be cleared");
getCS(Signed).popLastConstraint();
@@ -551,6 +578,129 @@ static bool doesHoldInRange(ConstraintInfo &Info, Value *Op,
return true;
}
+std::optional<Decomposition> Decomposition::substitute(Value *Variable,
+ Value *Replacement,
+ ConstraintInfo &Info) {
+ Decomposition Result(Offset);
+ int64_t Coefficient = 0;
+ for (const DecompEntry &E : Vars) {
+ if (E.Variable != Variable)
+ Result.Vars.push_back(E);
+ else if (AddOverflow(Coefficient, E.Coefficient, Coefficient))
+ return std::nullopt;
+ }
+ Decomposition ReplacementDec =
+ decompose(Replacement, Info, /*IsSigned=*/true, Info.getDataLayout());
+ if (ReplacementDec.mul(Coefficient) || Result.add(ReplacementDec))
+ return std::nullopt;
+ return Result;
+}
+
+enum class SignedBound { Upper, Lower };
+
+/// Returns true if \p Info implies that the value of \p D does not exceed the
+/// signed maximum of \p Ty (if \p Bound is Upper) or is not below the signed
+/// minimum of \p Ty (if \p Bound is Lower).
+///
+/// The constraint systems do not record that every variable is within the
+/// range of its type, so only decompositions that are trivially in range, or
+/// that reduce to a single variable plus an offset, are handled. A min/max
+/// intrinsic result in \p D is split across its respective operands, using the
+/// fact that the value of \p D is monotonic in it: for an upper bound on a
+/// maximum, both sides must be in range, while for a lower bound only one side
+/// must be.
+static bool isKnownWithinSignedRange(Decomposition D, SignedBound Bound,
+ Type *Ty, ConstraintInfo &Info,
+ unsigned Depth) {
+ if (D.canonicalize())
+ return false;
+
+ if (Depth != 0) {
+ for (const DecompEntry &E : D.Vars) {
+ auto *MM = dyn_cast<MinMaxIntrinsic>(E.Variable);
+ if (!MM || !MM->isSigned() || MM->getType() != Ty)
+ continue;
+ auto LHS = D.substitute(E.Variable, MM->getLHS(), Info);
+ auto RHS = D.substitute(E.Variable, MM->getRHS(), Info);
+ if (!LHS || !RHS)
+ return false;
+
+ // D is increasing in the min/max result iff its coefficient is positive.
+ // Then D is a max over the respective sides iff the intrinsic is a max.
+ bool IsMax =
+ (MM->getIntrinsicID() == Intrinsic::smax) == (E.Coefficient > 0);
+ bool L = isKnownWithinSignedRange(*LHS, Bound, Ty, Info, Depth - 1);
+ if ((Bound == SignedBound::Upper) == IsMax)
+ return L && isKnownWithinSignedRange(*RHS, Bound, Ty, Info, Depth - 1);
+ return L || isKnownWithinSignedRange(*RHS, Bound, Ty, Info, Depth - 1);
+ }
+ }
+
+ // Compare in a type wide enough for both the bounds of Ty and the int64_t
+ // offset, so this does not depend on the width of Ty.
+ unsigned BitWidth = Ty->getScalarSizeInBits();
+ unsigned WideBits = std::max(BitWidth, 64u);
+ APInt SMax = APInt::getSignedMaxValue(BitWidth).sext(WideBits);
+ APInt SMin = APInt::getSignedMinValue(BitWidth).sext(WideBits);
+ APInt Offset(WideBits, D.Offset, /*isSigned=*/true);
+ if (D.Vars.empty())
+ return Bound == SignedBound::Upper ? Offset.sle(SMax) : Offset.sge(SMin);
+
+ // V + C is at most the maximum if C <= 0 and at least the minimum if C >= 0,
+ // since V is itself in range.
+ if (D.Vars.size() != 1 || D.Vars[0].Coefficient != 1)
+ return false;
+
+ Value *V = D.Vars[0].Variable;
+ if (V->getType() != Ty)
+ return false;
+
+ if (Bound == SignedBound::Upper) {
+ if (D.Offset <= 0)
+ return true;
+
+ // V + C <= SMax iff V <= SMax - C, which is only satisfiable in range.
+ APInt Limit = SMax - Offset;
+ return Limit.sge(SMin) &&
+ Info.doesHold(CmpInst::ICMP_SLE, V,
+ ConstantInt::get(Ty, Limit.trunc(BitWidth)));
+ }
+
+ if (D.Offset >= 0)
+ return true;
+
+ // V + C >= SMin iff V >= SMin - C, which is only satisfiable in range.
+ APInt Limit = SMin - Offset;
+ return Limit.sle(SMax) &&
+ Info.doesHold(CmpInst::ICMP_SGE, V,
+ ConstantInt::get(Ty, Limit.trunc(BitWidth)));
+}
+
+/// Returns true if the signed \p Opcode (Add or Sub) of \p Op0 and \p Op1 is
+/// known to not overflow because the result is in the range of the type.
+/// For example, A + (B - A) is B and therefore cannot overflow.
+static bool isKnownNoSignedWrap(Instruction::BinaryOps Opcode, Value *Op0,
+ Value *Op1, ConstraintInfo &Info) {
+ if (Opcode != Instruction::Add && Opcode != Instruction::Sub)
+ return false;
+
+ Type *Ty = Op0->getType();
+ if (!Ty->isIntegerTy())
+ return false;
+
+ const DataLayout &DL = Info.getDataLayout();
+ Decomposition LHS = decompose(Op0, Info, /*IsSigned=*/true, DL);
+ Decomposition RHS = decompose(Op1, Info, /*IsSigned=*/true, DL);
+ if (Opcode == Instruction::Add ? LHS.add(RHS) : LHS.sub(RHS))
+ return false;
+
+ constexpr unsigned MaxDepth = 2;
+ return isKnownWithinSignedRange(LHS, SignedBound::Upper, Ty, Info,
+ MaxDepth) &&
+ isKnownWithinSignedRange(LHS, SignedBound::Lower, Ty, Info,
+ MaxDepth);
+}
+
/// Returns true if \p Opcode applied to \p Op0 and \p Op1 with \p NoWrapFlags
/// is known to not wrap in signed or unsigned, depending on \p Signed.
static bool isKnownNoWrap(Instruction::BinaryOps Opcode, Value *Op0, Value *Op1,
@@ -596,9 +746,16 @@ static bool isKnownNoWrap(Value *V, ConstraintInfo &Info, bool Signed) {
if (match(V, m_DisjointOr(m_Value(), m_Value())))
return true;
- if (auto *WO = dyn_cast<WithOverflowInst>(V))
- return isKnownNoWrap(WO->getBinaryOp(), WO->getLHS(), WO->getRHS(),
- /*NoWrapFlags=*/0, Info, Signed);
+ if (auto *WO = dyn_cast<WithOverflowInst>(V)) {
+ if (isKnownNoWrap(WO->getBinaryOp(), WO->getLHS(), WO->getRHS(),
+ /*NoWrapFlags=*/0, Info, Signed))
+ return true;
+ // Reasoning about the infinite precision sum is costlier than the checks
+ // above, so only do it for the overflow intrinsics themselves, not
+ // for the plain adds and subs that decompose() analyzes.
+ return Signed && isKnownNoSignedWrap(WO->getBinaryOp(), WO->getLHS(),
+ WO->getRHS(), Info);
+ }
if (auto *Trunc = dyn_cast<TruncInst>(V)) {
if (Signed)
diff --git a/llvm/test/Transforms/ConstraintElimination/sadd-with-overflow.ll b/llvm/test/Transforms/ConstraintElimination/sadd-with-overflow.ll
index 4194797fa5ea05..e28610764f1b01 100644
--- a/llvm/test/Transforms/ConstraintElimination/sadd-with-overflow.ll
+++ b/llvm/test/Transforms/ConstraintElimination/sadd-with-overflow.ll
@@ -318,3 +318,542 @@ then:
else:
ret i8 0
}
+
+define void @sadd_sum_of_difference_assume(i8 %start, i8 %end) {
+; CHECK-LABEL: define void @sadd_sum_of_difference_assume(
+; CHECK-SAME: i8 [[START:%.*]], i8 [[END:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[NONNEG:%.*]] = icmp sge i8 [[START]], 0
+; CHECK-NEXT: call void @llvm.assume(i1 [[NONNEG]])
+; CHECK-NEXT: [[ORDERED:%.*]] = icmp sge i8 [[END]], [[START]]
+; CHECK-NEXT: call void @llvm.assume(i1 [[ORDERED]])
+; CHECK-NEXT: [[D:%.*]] = sub nuw nsw i8 [[END]], [[START]]
+; CHECK-NEXT: call void @use(i1 false)
+; CHECK-NEXT: ret void
+;
+entry:
+ %nonneg = icmp sge i8 %start, 0
+ call void @llvm.assume(i1 %nonneg)
+ %ordered = icmp sge i8 %end, %start
+ call void @llvm.assume(i1 %ordered)
+ %d = sub i8 %end, %start
+ %r = call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 %start, i8 %d)
+ %ov = extractvalue { i8, i1 } %r, 1
+ call void @use(i1 %ov)
+ ret void
+}
+
+define void @sadd_sum_of_difference_branch(i8 %start, i8 %end) {
+; CHECK-LABEL: define void @sadd_sum_of_difference_branch(
+; CHECK-SAME: i8 [[START:%.*]], i8 [[END:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[NONNEG:%.*]] = icmp sge i8 [[START]], 0
+; CHECK-NEXT: br i1 [[NONNEG]], label %[[B1:.*]], label %[[EXIT:.*]]
+; CHECK: [[B1]]:
+; CHECK-NEXT: [[ORDERED:%.*]] = icmp sge i8 [[END]], [[START]]
+; CHECK-NEXT: br i1 [[ORDERED]], label %[[BODY:.*]], label %[[EXIT]]
+; CHECK: [[BODY]]:
+; CHECK-NEXT: [[D:%.*]] = sub nuw nsw i8 [[END]], [[START]]
+; CHECK-NEXT: call void @use(i1 false)
+; CHECK-NEXT: br label %[[EXIT]]
+; CHECK: [[EXIT]]:
+; CHECK-NEXT: ret void
+;
+entry:
+ %nonneg = icmp sge i8 %start, 0
+ br i1 %nonneg, label %b1, label %exit
+b1:
+ %ordered = icmp sge i8 %end, %start
+ br i1 %ordered, label %body, label %exit
+body:
+ %d = sub i8 %end, %start
+ %r = call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 %start, i8 %d)
+ %ov = extractvalue { i8, i1 } %r, 1
+ call void @use(i1 %ov)
+ br label %exit
+exit:
+ ret void
+}
+
+define void @sadd_sum_of_difference_commuted(i8 %start, i8 %end) {
+; CHECK-LABEL: define void @sadd_sum_of_difference_commuted(
+; CHECK-SAME: i8 [[START:%.*]], i8 [[END:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[NONNEG:%.*]] = icmp sge i8 [[START]], 0
+; CHECK-NEXT: call void @llvm.assume(i1 [[NONNEG]])
+; CHECK-NEXT: [[ORDERED:%.*]] = icmp sge i8 [[END]], [[START]]
+; CHECK-NEXT: call void @llvm.assume(i1 [[ORDERED]])
+; CHECK-NEXT: [[D:%.*]] = sub nuw nsw i8 [[END]], [[START]]
+; CHECK-NEXT: call void @use(i1 false)
+; CHECK-NEXT: ret void
+;
+entry:
+ %nonneg = icmp sge i8 %start, 0
+ call void @llvm.assume(i1 %nonneg)
+ %ordered = icmp sge i8 %end, %start
+ call void @llvm.assume(i1 %ordered)
+ %d = sub i8 %end, %start
+ %r = call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 %d, i8 %start)
+ %ov = extractvalue { i8, i1 } %r, 1
+ call void @use(i1 %ov)
+ ret void
+}
+
+define void @sadd_sum_of_difference_nsw_any_sign(i8 %start, i8 %end) {
+; CHECK-LABEL: define void @sadd_sum_of_difference_nsw_any_sign(
+; CHECK-SAME: i8 [[START:%.*]], i8 [[END:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[D:%.*]] = sub nsw i8 [[END]], [[START]]
+; CHECK-NEXT: call void @use(i1 false)
+; CHECK-NEXT: ret void
+;
+entry:
+ %d = sub nsw i8 %end, %start
+ %r = call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 %start, i8 %d)
+ %ov = extractvalue { i8, i1 } %r, 1
+ call void @use(i1 %ov)
+ ret void
+}
+
+define void @sadd_sum_of_difference_neg_start(i8 %start, i8 %end) {
+; CHECK-LABEL: define void @sadd_sum_of_difference_neg_start(
+; CHECK-SAME: i8 [[START:%.*]], i8 [[END:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[ORDERED:%.*]] = icmp sge i8 [[END]], [[START]]
+; CHECK-NEXT: call void @llvm.assume(i1 [[ORDERED]])
+; CHECK-NEXT: [[D:%.*]] = sub i8 [[END]], [[START]]
+; CHECK-NEXT: [[R:%.*]] = call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 [[START]], i8 [[D]])
+; CHECK-NEXT: [[OV:%.*]] = extractvalue { i8, i1 } [[R]], 1
+; CHECK-NEXT: call void @use(i1 [[OV]])
+; CHECK-NEXT: ret void
+;
+entry:
+ %ordered = icmp sge i8 %end, %start
+ call void @llvm.assume(i1 %ordered)
+ %d = sub i8 %end, %start
+ %r = call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 %start, i8 %d)
+ %ov = extractvalue { i8, i1 } %r, 1
+ call void @use(i1 %ov)
+ ret void
+}
+
+define void @sadd_sum_of_difference_unordered(i8 %start, i8 %end) {
+; CHECK-LABEL: define void @sadd_sum_of_difference_unordered(
+; CHECK-SAME: i8 [[START:%.*]], i8 [[END:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[NONNEG:%.*]] = icmp sge i8 [[START]], 0
+; CHECK-NEXT: call void @llvm.assume(i1 [[NONNEG]])
+; CHECK-NEXT: [[D:%.*]] = sub i8 [[END]], [[START]]
+; CHECK-NEXT: [[R:%.*]] = call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 [[START]], i8 [[D]])
+; CHECK-NEXT: [[OV:%.*]] = extractvalue { i8, i1 } [[R]], 1
+; CHECK-NEXT: call void @use(i1 [[OV]])
+; CHECK-NEXT: ret void
+;
+entry:
+ %nonneg = icmp sge i8 %start, 0
+ call void @llvm.assume(i1 %nonneg)
+ %d = sub i8 %end, %start
+ %r = call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 %start, i8 %d)
+ %ov = extractvalue { i8, i1 } %r, 1
+ call void @use(i1 %ov)
+ ret void
+}
+
+define void @sadd_smin_side(i8 %start, i8 %end) {
+; CHECK-LABEL: define void @sadd_smin_side(
+; CHECK-SAME: i8 [[START:%.*]], i8 [[END:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[NONNEG:%.*]] = icmp sge i8 [[START]], 0
+; CHECK-NEXT: call void @llvm.assume(i1 [[NONNEG]])
+; CHECK-NEXT: [[ORDERED:%.*]] = icmp sge i8 [[END]], [[START]]
+; CHECK-NEXT: call void @llvm.assume(i1 [[ORDERED]])
+; CHECK-NEXT: [[D:%.*]] = sub nuw nsw i8 [[END]], [[START]]
+; CHECK-NEXT: [[M:%.*]] = call i8 @llvm.smin.i8(i8 [[D]], i8 5)
+; CHECK-NEXT: call void @use(i1 false)
+; CHECK-NEXT: ret void
+;
+entry:
+ %nonneg = icmp sge i8 %start, 0
+ call void @llvm.assume(i1 %nonneg)
+ %ordered = icmp sge i8 %end, %start
+ call void @llvm.assume(i1 %ordered)
+ %d = sub i8 %end, %start
+ %m = call i8 @llvm.smin.i8(i8 %d, i8 5)
+ %r = call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 %start, i8 %m)
+ %ov = extractvalue { i8, i1 } %r, 1
+ call void @use(i1 %ov)
+ ret void
+}
+
+define void @sadd_smax_side_neg(i8 %start, i8 %end) {
+; CHECK-LABEL: define void @sadd_smax_side_neg(
+; CHECK-SAME: i8 [[START:%.*]], i8 [[END:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[NONNEG:%.*]] = icmp sge i8 [[START]], 0
+; CHECK-NEXT: call void @llvm.assume(i1 [[NONNEG]])
+; CHECK-NEXT: [[ORDERED:%.*]] = icmp sge i8 [[END]], [[START]]
+; CHECK-NEXT: call void @llvm.assume(i1 [[ORDERED]])
+; CHECK-NEXT: [[D:%.*]] = sub nuw nsw i8 [[END]], [[START]]
+; CHECK-NEXT: [[M:%.*]] = call i8 @llvm.smax.i8(i8 [[D]], i8 5)
+; CHECK-NEXT: [[R:%.*]] = call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 [[START]], i8 [[M]])
+; CHECK-NEXT: [[OV:%.*]] = extractvalue { i8, i1 } [[R]], 1
+; CHECK-NEXT: call void @use(i1 [[OV]])
+; CHECK-NEXT: ret void
+;
+entry:
+ %nonneg = icmp sge i8 %start, 0
+ call void @llvm.assume(i1 %nonneg)
+ %ordered = icmp sge i8 %end, %start
+ call void @llvm.assume(i1 %ordered)
+ %d = sub i8 %end, %start
+ %m = call i8 @llvm.smax.i8(i8 %d, i8 5)
+ %r = call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 %start, i8 %m)
+ %ov = extractvalue { i8, i1 } %r, 1
+ call void @use(i1 %ov)
+ ret void
+}
+
+define void @sadd_smax_clamp(i8 %start, i8 %end) {
+; CHECK-LABEL: define void @sadd_smax_clamp(
+; CHECK-SAME: i8 [[START:%.*]], i8 [[END:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[ORDERED:%.*]] = icmp sge i8 [[END]], [[START]]
+; CHECK-NEXT: call void @llvm.assume(i1 [[ORDERED]])
+; CHECK-NEXT: [[NOTSTART:%.*]] = xor i8 [[START]], -1
+; CHECK-NEXT: [[X:%.*]] = add nsw i8 [[END]], [[NOTSTART]]
+; CHECK-NEXT: [[M:%.*]] = call i8 @llvm.smax.i8(i8 [[X]], i8 0)
+; CHECK-NEXT: [[TMP0:%.*]] = add nsw i8 [[START]], [[M]]
+; CHECK-NEXT: call void @use(i1 false)
+; CHECK-NEXT: [[LT:%.*]] = icmp slt i8 [[TMP0]], [[START]]
+; CHECK-NEXT: call void @use(i1 [[LT]])
+; CHECK-NEXT: [[GT:%.*]] = icmp slt i8 [[END]], [[TMP0]]
+; CHECK-NEXT: call void @use(i1 [[GT]])
+; CHECK-NEXT: ret void
+;
+entry:
+ %ordered = icmp sge i8 %end, %start
+ call void @llvm.assume(i1 %ordered)
+ %notstart = xor i8 %start, -1
+ %x = add nsw i8 %end, %notstart
+ %m = call i8 @llvm.smax.i8(i8 %x, i8 0)
+ %r = call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 %start, i8 %m)
+ %ov = extractvalue { i8, i1 } %r, 1
+ call void @use(i1 %ov)
+ %new = extractvalue { i8, i1 } %r, 0
+ %lt = icmp slt i8 %new, %start
+ call void @use(i1 %lt)
+ %gt = icmp slt i8 %end, %new
+ call void @use(i1 %gt)
+ ret void
+}
+
+define void @sadd_smax_clamp_unordered(i8 %start, i8 %end) {
+; CHECK-LABEL: define void @sadd_smax_clamp_unordered(
+; CHECK-SAME: i8 [[START:%.*]], i8 [[END:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[NOTSTART:%.*]] = xor i8 [[START]], -1
+; CHECK-NEXT: [[X:%.*]] = add nsw i8 [[END]], [[NOTSTART]]
+; CHECK-NEXT: [[M:%.*]] = call i8 @llvm.smax.i8(i8 [[X]], i8 0)
+; CHECK-NEXT: [[TMP0:%.*]] = add nsw i8 [[START]], [[M]]
+; CHECK-NEXT: call void @use(i1 false)
+; CHECK-NEXT: [[LT:%.*]] = icmp slt i8 [[TMP0]], [[START]]
+; CHECK-NEXT: call void @use(i1 [[LT]])
+; CHECK-NEXT: [[GT:%.*]] = icmp slt i8 [[END]], [[TMP0]]
+; CHECK-NEXT: call void @use(i1 [[GT]])
+; CHECK-NEXT: ret void
+;
+entry:
+ %notstart = xor i8 %start, -1
+ %x = add nsw i8 %end, %notstart
+ %m = call i8 @llvm.smax.i8(i8 %x, i8 0)
+ %r = call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 %start, i8 %m)
+ %ov = extractvalue { i8, i1 } %r, 1
+ call void @use(i1 %ov)
+ %new = extractvalue { i8, i1 } %r, 0
+ %lt = icmp slt i8 %new, %start
+ call void @use(i1 %lt)
+ %gt = icmp slt i8 %end, %new
+ call void @use(i1 %gt)
+ ret void
+}
+
+define void @sadd_sum_of_difference_i128(i128 %start, i128 %end) {
+; CHECK-LABEL: define void @sadd_sum_of_difference_i128(
+; CHECK-SAME: i128 [[START:%.*]], i128 [[END:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[D:%.*]] = sub nsw i128 [[END]], [[START]]
+; CHECK-NEXT: [[R:%.*]] = call { i128, i1 } @llvm.sadd.with.overflow.i128(i128 [[START]], i128 [[D]])
+; CHECK-NEXT: [[OV:%.*]] = extractvalue { i128, i1 } [[R]], 1
+; CHECK-NEXT: call void @use(i1 [[OV]])
+; CHECK-NEXT: ret void
+;
+entry:
+ %d = sub nsw i128 %end, %start
+ %r = call { i128, i1 } @llvm.sadd.with.overflow.i128(i128 %start, i128 %d)
+ %ov = extractvalue { i128, i1 } %r, 1
+ call void @use(i1 %ov)
+ ret void
+}
+
+define void @sadd_smax_clamp_i256(i256 %start, i256 %end) {
+; CHECK-LABEL: define void @sadd_smax_clamp_i256(
+; CHECK-SAME: i256 [[START:%.*]], i256 [[END:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[ORDERED:%.*]] = icmp sge i256 [[END]], [[START]]
+; CHECK-NEXT: call void @llvm.assume(i1 [[ORDERED]])
+; CHECK-NEXT: [[NOTSTART:%.*]] = xor i256 [[START]], -1
+; CHECK-NEXT: [[X:%.*]] = add nsw i256 [[END]], [[NOTSTART]]
+; CHECK-NEXT: [[M:%.*]] = call i256 @llvm.smax.i256(i256 [[X]], i256 0)
+; CHECK-NEXT: [[R:%.*]] = call { i256, i1 } @llvm.sadd.with.overflow.i256(i256 [[START]], i256 [[M]])
+; CHECK-NEXT: [[OV:%.*]] = extractvalue { i256, i1 } [[R]], 1
+; CHECK-NEXT: call void @use(i1 [[OV]])
+; CHECK-NEXT: ret void
+;
+entry:
+ %ordered = icmp sge i256 %end, %start
+ call void @llvm.assume(i1 %ordered)
+ %notstart = xor i256 %start, -1
+ %x = add nsw i256 %end, %notstart
+ %m = call i256 @llvm.smax.i256(i256 %x, i256 0)
+ %r = call { i256, i1 } @llvm.sadd.with.overflow.i256(i256 %start, i256 %m)
+ %ov = extractvalue { i256, i1 } %r, 1
+ call void @use(i1 %ov)
+ ret void
+}
+
+define void @sadd_repeated_variable_cancels(i8 %start, i8 %end) {
+; CHECK-LABEL: define void @sadd_repeated_variable_cancels(
+; CHECK-SAME: i8 [[START:%.*]], i8 [[END:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[D:%.*]] = sub nsw i8 [[END]], [[START]]
+; CHECK-NEXT: [[E:%.*]] = add nsw i8 [[D]], [[START]]
+; CHECK-NEXT: [[F:%.*]] = sub nsw i8 [[E]], [[START]]
+; CHECK-NEXT: call void @use(i1 false)
+; CHECK-NEXT: ret void
+;
+entry:
+ %d = sub nsw i8 %end, %start
+ %e = add nsw i8 %d, %start
+ %f = sub nsw i8 %e, %start
+ %r = call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 %start, i8 %f)
+ %ov = extractvalue { i8, i1 } %r, 1
+ call void @use(i1 %ov)
+ ret void
+}
+
+define void @sadd_repeated_variable_nonzero(i8 %start) {
+; CHECK-LABEL: define void @sadd_repeated_variable_nonzero(
+; CHECK-SAME: i8 [[START:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[A:%.*]] = add nsw i8 [[START]], [[START]]
+; CHECK-NEXT: [[R:%.*]] = call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 [[A]], i8 [[START]])
+; CHECK-NEXT: [[OV:%.*]] = extractvalue { i8, i1 } [[R]], 1
+; CHECK-NEXT: call void @use(i1 [[OV]])
+; CHECK-NEXT: ret void
+;
+entry:
+ %a = add nsw i8 %start, %start
+ %r = call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 %a, i8 %start)
+ %ov = extractvalue { i8, i1 } %r, 1
+ call void @use(i1 %ov)
+ ret void
+}
+
+define void @sadd_cancels_to_constant(i8 %x) {
+; CHECK-LABEL: define void @sadd_cancels_to_constant(
+; CHECK-SAME: i8 [[X:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[N:%.*]] = sub nsw i8 0, [[X]]
+; CHECK-NEXT: call void @use(i1 false)
+; CHECK-NEXT: ret void
+;
+entry:
+ %n = sub nsw i8 0, %x
+ %r = call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 %x, i8 %n)
+ %ov = extractvalue { i8, i1 } %r, 1
+ call void @use(i1 %ov)
+ ret void
+}
+
+define void @sadd_smin_second_operand(i8 %start, i8 %end) {
+; CHECK-LABEL: define void @sadd_smin_second_operand(
+; CHECK-SAME: i8 [[START:%.*]], i8 [[END:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[NONNEG:%.*]] = icmp sge i8 [[START]], 0
+; CHECK-NEXT: call void @llvm.assume(i1 [[NONNEG]])
+; CHECK-NEXT: [[ORDERED:%.*]] = icmp sge i8 [[END]], [[START]]
+; CHECK-NEXT: call void @llvm.assume(i1 [[ORDERED]])
+; CHECK-NEXT: [[D:%.*]] = sub nuw nsw i8 [[END]], [[START]]
+; CHECK-NEXT: [[M:%.*]] = call i8 @llvm.smin.i8(i8 5, i8 [[D]])
+; CHECK-NEXT: call void @use(i1 false)
+; CHECK-NEXT: ret void
+;
+entry:
+ %nonneg = icmp sge i8 %start, 0
+ call void @llvm.assume(i1 %nonneg)
+ %ordered = icmp sge i8 %end, %start
+ call void @llvm.assume(i1 %ordered)
+ %d = sub nsw i8 %end, %start
+ %m = call i8 @llvm.smin.i8(i8 5, i8 %d)
+ %r = call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 %start, i8 %m)
+ %ov = extractvalue { i8, i1 } %r, 1
+ call void @use(i1 %ov)
+ ret void
+}
+
+define void @sadd_vector_not_folded(<2 x i8> %start, <2 x i8> %end) {
+; CHECK-LABEL: define void @sadd_vector_not_folded(
+; CHECK-SAME: <2 x i8> [[START:%.*]], <2 x i8> [[END:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[D:%.*]] = sub nsw <2 x i8> [[END]], [[START]]
+; CHECK-NEXT: [[R:%.*]] = call { <2 x i8>, <2 x i1> } @llvm.sadd.with.overflow.v2i8(<2 x i8> [[START]], <2 x i8> [[D]])
+; CHECK-NEXT: [[OV:%.*]] = extractvalue { <2 x i8>, <2 x i1> } [[R]], 1
+; CHECK-NEXT: call void @use.vec(<2 x i1> [[OV]])
+; CHECK-NEXT: ret void
+;
+entry:
+ %d = sub nsw <2 x i8> %end, %start
+ %r = call { <2 x i8>, <2 x i1> } @llvm.sadd.with.overflow.v2i8(<2 x i8> %start, <2 x i8> %d)
+ %ov = extractvalue { <2 x i8>, <2 x i1> } %r, 1
+ call void @use.vec(<2 x i1> %ov)
+ ret void
+}
+
+; Negative: the coefficients of %x add up to 4 * 2^61 = 2^63, which does not fit
+; the 64-bit coefficients, so the decomposition is given up on.
+define void @sadd_coefficient_overflow(i64 %x, i64 %y) {
+; CHECK-LABEL: define void @sadd_coefficient_overflow(
+; CHECK-SAME: i64 [[X:%.*]], i64 [[Y:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[A:%.*]] = mul nsw i64 [[X]], 2305843009213693952
+; CHECK-NEXT: [[B:%.*]] = add nsw i64 [[A]], [[A]]
+; CHECK-NEXT: [[C:%.*]] = add nsw i64 [[B]], [[A]]
+; CHECK-NEXT: [[D:%.*]] = add nsw i64 [[C]], [[A]]
+; CHECK-NEXT: [[R:%.*]] = call { i64, i1 } @llvm.sadd.with.overflow.i64(i64 [[D]], i64 [[Y]])
+; CHECK-NEXT: [[OV:%.*]] = extractvalue { i64, i1 } [[R]], 1
+; CHECK-NEXT: call void @use(i1 [[OV]])
+; CHECK-NEXT: ret void
+;
+entry:
+ %a = mul nsw i64 %x, 2305843009213693952
+ %b = add nsw i64 %a, %a
+ %c = add nsw i64 %b, %a
+ %d = add nsw i64 %c, %a
+ %r = call { i64, i1 } @llvm.sadd.with.overflow.i64(i64 %d, i64 %y)
+ %ov = extractvalue { i64, i1 } %r, 1
+ call void @use(i1 %ov)
+ ret void
+}
+
+define void @sadd_umax_not_split(i8 %start, i8 %end) {
+; CHECK-LABEL: define void @sadd_umax_not_split(
+; CHECK-SAME: i8 [[START:%.*]], i8 [[END:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[NONNEG:%.*]] = icmp sge i8 [[START]], 0
+; CHECK-NEXT: call void @llvm.assume(i1 [[NONNEG]])
+; CHECK-NEXT: [[R:%.*]] = call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 [[START]], i8 [[END]])
+; CHECK-NEXT: [[OV:%.*]] = extractvalue { i8, i1 } [[R]], 1
+; CHECK-NEXT: call void @use(i1 [[OV]])
+; CHECK-NEXT: ret void
+;
+entry:
+ %nonneg = icmp sge i8 %start, 0
+ call void @llvm.assume(i1 %nonneg)
+ %m = call i8 @llvm.umax.i8(i8 %end, i8 0)
+ %r = call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 %start, i8 %m)
+ %ov = extractvalue { i8, i1 } %r, 1
+ call void @use(i1 %ov)
+ ret void
+}
+
+define void @slt_coefficient_overflow(i64 %x, i64 %y) {
+; CHECK-LABEL: define void @slt_coefficient_overflow(
+; CHECK-SAME: i64 [[X:%.*]], i64 [[Y:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[A:%.*]] = mul nsw i64 [[X]], 2305843009213693952
+; CHECK-NEXT: [[B:%.*]] = add nsw i64 [[A]], [[A]]
+; CHECK-NEXT: [[C:%.*]] = add nsw i64 [[B]], [[A]]
+; CHECK-NEXT: [[D:%.*]] = add nsw i64 [[C]], [[A]]
+; CHECK-NEXT: [[CMP:%.*]] = icmp slt i64 [[D]], [[Y]]
+; CHECK-NEXT: call void @use(i1 [[CMP]])
+; CHECK-NEXT: ret void
+;
+entry:
+ %a = mul nsw i64 %x, 2305843009213693952
+ %b = add nsw i64 %a, %a
+ %c = add nsw i64 %b, %a
+ %d = add nsw i64 %c, %a
+ %cmp = icmp slt i64 %d, %y
+ call void @use(i1 %cmp)
+ ret void
+}
+
+define void @sadd_smax_three_levels(i8 %start, i8 %end) {
+; CHECK-LABEL: define void @sadd_smax_three_levels(
+; CHECK-SAME: i8 [[START:%.*]], i8 [[END:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[NONNEG:%.*]] = icmp sge i8 [[START]], 0
+; CHECK-NEXT: call void @llvm.assume(i1 [[NONNEG]])
+; CHECK-NEXT: [[M1:%.*]] = call i8 @llvm.smax.i8(i8 [[END]], i8 0)
+; CHECK-NEXT: [[M2:%.*]] = call i8 @llvm.smax.i8(i8 [[M1]], i8 1)
+; CHECK-NEXT: [[M3:%.*]] = call i8 @llvm.smax.i8(i8 [[M2]], i8 2)
+; CHECK-NEXT: [[R:%.*]] = call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 [[START]], i8 [[M3]])
+; CHECK-NEXT: [[OV:%.*]] = extractvalue { i8, i1 } [[R]], 1
+; CHECK-NEXT: call void @use(i1 [[OV]])
+; CHECK-NEXT: ret void
+;
+entry:
+ %nonneg = icmp sge i8 %start, 0
+ call void @llvm.assume(i1 %nonneg)
+ %m1 = call i8 @llvm.smax.i8(i8 %end, i8 0)
+ %m2 = call i8 @llvm.smax.i8(i8 %m1, i8 1)
+ %m3 = call i8 @llvm.smax.i8(i8 %m2, i8 2)
+ %r = call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 %start, i8 %m3)
+ %ov = extractvalue { i8, i1 } %r, 1
+ call void @use(i1 %ov)
+ ret void
+}
+
+define void @sadd_offset_overflow(i64 %x, i64 %y) {
+; CHECK-LABEL: define void @sadd_offset_overflow(
+; CHECK-SAME: i64 [[X:%.*]], i64 [[Y:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[A:%.*]] = add nsw i64 [[X]], 9223372036854775806
+; CHECK-NEXT: [[B:%.*]] = add nsw i64 [[Y]], 5
+; CHECK-NEXT: [[R:%.*]] = call { i64, i1 } @llvm.sadd.with.overflow.i64(i64 [[A]], i64 [[B]])
+; CHECK-NEXT: [[OV:%.*]] = extractvalue { i64, i1 } [[R]], 1
+; CHECK-NEXT: call void @use(i1 [[OV]])
+; CHECK-NEXT: ret void
+;
+entry:
+ %a = add nsw i64 %x, 9223372036854775806
+ %b = add nsw i64 %y, 5
+ %r = call { i64, i1 } @llvm.sadd.with.overflow.i64(i64 %a, i64 %b)
+ %ov = extractvalue { i64, i1 } %r, 1
+ call void @use(i1 %ov)
+ ret void
+}
+
+define void @sadd_smax_substitute_overflow(i64 %x, i64 %z, i64 %y) {
+; CHECK-LABEL: define void @sadd_smax_substitute_overflow(
+; CHECK-SAME: i64 [[X:%.*]], i64 [[Z:%.*]], i64 [[Y:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[A:%.*]] = mul nsw i64 [[X]], 1099511627776
+; CHECK-NEXT: [[M:%.*]] = call i64 @llvm.smax.i64(i64 [[A]], i64 [[Z]])
+; CHECK-NEXT: [[D:%.*]] = mul nsw i64 [[M]], 1073741824
+; CHECK-NEXT: [[R:%.*]] = call { i64, i1 } @llvm.sadd.with.overflow.i64(i64 [[D]], i64 [[Y]])
+; CHECK-NEXT: [[OV:%.*]] = extractvalue { i64, i1 } [[R]], 1
+; CHECK-NEXT: call void @use(i1 [[OV]])
+; CHECK-NEXT: ret void
+;
+entry:
+ %a = mul nsw i64 %x, 1099511627776
+ %m = call i64 @llvm.smax.i64(i64 %a, i64 %z)
+ %d = mul nsw i64 %m, 1073741824
+ %r = call { i64, i1 } @llvm.sadd.with.overflow.i64(i64 %d, i64 %y)
+ %ov = extractvalue { i64, i1 } %r, 1
+ call void @use(i1 %ov)
+ ret void
+}
+
+declare void @use.vec(<2 x i1>)
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