https://github.com/el-ev updated
https://github.com/llvm/llvm-project/pull/135785
>From c5328e2075b5f98311eb9c9657da79d800cf28f4 Mon Sep 17 00:00:00 2001
From: Iris Shi <0...@owo.li>
Date: Tue, 15 Apr 2025 20:20:45 +0800
Subject: [PATCH 1/2] [ConstraintElim] Simplify `usub_with_overflow` when A uge
B
---
.../Scalar/ConstraintElimination.cpp | 10 ++++++
.../usub-with-overflow.ll | 33 +++++++------------
2 files changed, 21 insertions(+), 22 deletions(-)
diff --git a/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
b/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
index 6d17b36b7d9ea..e030f0fac4c0d 100644
--- a/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
@@ -1123,6 +1123,7 @@ void State::addInfoFor(BasicBlock &BB) {
// Enqueue overflow intrinsics for simplification.
case Intrinsic::sadd_with_overflow:
case Intrinsic::ssub_with_overflow:
+ case Intrinsic::usub_with_overflow:
case Intrinsic::ucmp:
case Intrinsic::scmp:
WorkList.push_back(
@@ -1785,6 +1786,15 @@ tryToSimplifyOverflowMath(IntrinsicInst *II,
ConstraintInfo &Info,
Changed = replaceSubOverflowUses(II, A, B, ToRemove);
break;
}
+ case Intrinsic::usub_with_overflow: {
+ // usub overflows iff A < B
+ // TODO: If the operation is guaranteed to overflow, we could
+ // also apply some simplifications.
+ if (DoesConditionHold(CmpInst::ICMP_UGE, A, B, Info)) {
+ Changed = replaceSubOverflowUses(II, A, B, ToRemove);
+ }
+ break;
+ }
}
return Changed;
diff --git a/llvm/test/Transforms/ConstraintElimination/usub-with-overflow.ll
b/llvm/test/Transforms/ConstraintElimination/usub-with-overflow.ll
index 06bfd8269d97d..0a3c4eb00fd25 100644
--- a/llvm/test/Transforms/ConstraintElimination/usub-with-overflow.ll
+++ b/llvm/test/Transforms/ConstraintElimination/usub-with-overflow.ll
@@ -9,11 +9,9 @@ define i8 @usub_no_overflow_due_to_cmp_condition(i8 %a, i8 %b)
{
; CHECK-NEXT: [[C_1:%.*]] = icmp uge i8 [[B:%.*]], [[A:%.*]]
; CHECK-NEXT: br i1 [[C_1]], label [[MATH:%.*]], label [[EXIT_FAIL:%.*]]
; CHECK: math:
-; CHECK-NEXT: [[OP:%.*]] = tail call { i8, i1 }
@llvm.usub.with.overflow.i8(i8 [[B]], i8 [[A]])
-; CHECK-NEXT: [[STATUS:%.*]] = extractvalue { i8, i1 } [[OP]], 1
-; CHECK-NEXT: br i1 [[STATUS]], label [[EXIT_FAIL]], label [[EXIT_OK:%.*]]
+; CHECK-NEXT: [[RES:%.*]] = sub i8 [[B]], [[A]]
+; CHECK-NEXT: br i1 false, label [[EXIT_FAIL]], label [[EXIT_OK:%.*]]
; CHECK: exit.ok:
-; CHECK-NEXT: [[RES:%.*]] = extractvalue { i8, i1 } [[OP]], 0
; CHECK-NEXT: ret i8 [[RES]]
; CHECK: exit.fail:
; CHECK-NEXT: ret i8 0
@@ -41,11 +39,9 @@ define i8 @usub_no_overflow_due_to_cmp_condition2(i8 %a, i8
%b) {
; CHECK-NEXT: [[C_1:%.*]] = icmp ule i8 [[B:%.*]], [[A:%.*]]
; CHECK-NEXT: br i1 [[C_1]], label [[EXIT_FAIL:%.*]], label [[MATH:%.*]]
; CHECK: math:
-; CHECK-NEXT: [[OP:%.*]] = tail call { i8, i1 }
@llvm.usub.with.overflow.i8(i8 [[B]], i8 [[A]])
-; CHECK-NEXT: [[STATUS:%.*]] = extractvalue { i8, i1 } [[OP]], 1
-; CHECK-NEXT: br i1 [[STATUS]], label [[EXIT_FAIL]], label [[EXIT_OK:%.*]]
+; CHECK-NEXT: [[RES:%.*]] = sub i8 [[B]], [[A]]
+; CHECK-NEXT: br i1 false, label [[EXIT_FAIL]], label [[EXIT_OK:%.*]]
; CHECK: exit.ok:
-; CHECK-NEXT: [[RES:%.*]] = extractvalue { i8, i1 } [[OP]], 0
; CHECK-NEXT: ret i8 [[RES]]
; CHECK: exit.fail:
; CHECK-NEXT: ret i8 0
@@ -75,12 +71,11 @@ define i8
@sub_no_overflow_due_to_cmp_condition_result_used(i8 %a, i8 %b) {
; CHECK-NEXT: [[C_1:%.*]] = icmp ule i8 [[B:%.*]], [[A:%.*]]
; CHECK-NEXT: br i1 [[C_1]], label [[EXIT_FAIL:%.*]], label [[MATH:%.*]]
; CHECK: math:
+; CHECK-NEXT: [[RES:%.*]] = sub i8 [[B]], [[A]]
; CHECK-NEXT: [[OP:%.*]] = tail call { i8, i1 }
@llvm.usub.with.overflow.i8(i8 [[B]], i8 [[A]])
; CHECK-NEXT: call void @use_res({ i8, i1 } [[OP]])
-; CHECK-NEXT: [[STATUS:%.*]] = extractvalue { i8, i1 } [[OP]], 1
-; CHECK-NEXT: br i1 [[STATUS]], label [[EXIT_FAIL]], label [[EXIT_OK:%.*]]
+; CHECK-NEXT: br i1 false, label [[EXIT_FAIL]], label [[EXIT_OK:%.*]]
; CHECK: exit.ok:
-; CHECK-NEXT: [[RES:%.*]] = extractvalue { i8, i1 } [[OP]], 0
; CHECK-NEXT: ret i8 [[RES]]
; CHECK: exit.fail:
; CHECK-NEXT: ret i8 0
@@ -111,11 +106,9 @@ define i8 @usub_no_overflow_due_to_or_conds(i8 %a, i8 %b) {
; CHECK-NEXT: [[OR:%.*]] = or i1 [[C_2]], [[C_1]]
; CHECK-NEXT: br i1 [[OR]], label [[EXIT_FAIL:%.*]], label [[MATH:%.*]]
; CHECK: math:
-; CHECK-NEXT: [[OP:%.*]] = tail call { i8, i1 }
@llvm.usub.with.overflow.i8(i8 [[B]], i8 [[A]])
-; CHECK-NEXT: [[STATUS:%.*]] = extractvalue { i8, i1 } [[OP]], 1
-; CHECK-NEXT: br i1 [[STATUS]], label [[EXIT_FAIL]], label [[EXIT_OK:%.*]]
+; CHECK-NEXT: [[RES:%.*]] = sub i8 [[B]], [[A]]
+; CHECK-NEXT: br i1 false, label [[EXIT_FAIL]], label [[EXIT_OK:%.*]]
; CHECK: exit.ok:
-; CHECK-NEXT: [[RES:%.*]] = extractvalue { i8, i1 } [[OP]], 0
; CHECK-NEXT: ret i8 [[RES]]
; CHECK: exit.fail:
; CHECK-NEXT: ret i8 0
@@ -147,9 +140,7 @@ define i8
@usub_no_overflow_due_to_or_conds_sub_result_not_used(i8 %a, i8 %b) {
; CHECK-NEXT: [[OR:%.*]] = or i1 [[C_2]], [[C_1]]
; CHECK-NEXT: br i1 [[OR]], label [[EXIT_FAIL:%.*]], label [[MATH:%.*]]
; CHECK: math:
-; CHECK-NEXT: [[OP:%.*]] = tail call { i8, i1 }
@llvm.usub.with.overflow.i8(i8 [[B]], i8 [[A]])
-; CHECK-NEXT: [[STATUS:%.*]] = extractvalue { i8, i1 } [[OP]], 1
-; CHECK-NEXT: br i1 [[STATUS]], label [[EXIT_FAIL]], label [[EXIT_OK:%.*]]
+; CHECK-NEXT: br i1 false, label [[EXIT_FAIL]], label [[EXIT_OK:%.*]]
; CHECK: exit.ok:
; CHECK-NEXT: ret i8 20
; CHECK: exit.fail:
@@ -181,11 +172,9 @@ define i8 @usub_no_overflow_due_to_and_conds(i8 %a, i8 %b)
{
; CHECK-NEXT: [[AND:%.*]] = and i1 [[C_2]], [[C_1]]
; CHECK-NEXT: br i1 [[AND]], label [[MATH:%.*]], label [[EXIT_FAIL:%.*]]
; CHECK: math:
-; CHECK-NEXT: [[OP:%.*]] = tail call { i8, i1 }
@llvm.usub.with.overflow.i8(i8 [[B]], i8 [[A]])
-; CHECK-NEXT: [[STATUS:%.*]] = extractvalue { i8, i1 } [[OP]], 1
-; CHECK-NEXT: br i1 [[STATUS]], label [[EXIT_FAIL]], label [[EXIT_OK:%.*]]
+; CHECK-NEXT: [[RES:%.*]] = sub i8 [[B]], [[A]]
+; CHECK-NEXT: br i1 false, label [[EXIT_FAIL]], label [[EXIT_OK:%.*]]
; CHECK: exit.ok:
-; CHECK-NEXT: [[RES:%.*]] = extractvalue { i8, i1 } [[OP]], 0
; CHECK-NEXT: ret i8 [[RES]]
; CHECK: exit.fail:
; CHECK-NEXT: ret i8 0
>From 398a45d417a8e9f2880c6b967fe8b44806030abe Mon Sep 17 00:00:00 2001
From: Iris Shi <0...@owo.li>
Date: Wed, 30 Apr 2025 18:16:40 +0800
Subject: [PATCH 2/2] apply suggestions
---
.../Scalar/ConstraintElimination.cpp | 61 +++++--------------
1 file changed, 15 insertions(+), 46 deletions(-)
diff --git a/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
b/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
index ac8aff442b6c4..cc1a29cebbd56 100644
--- a/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
@@ -1674,48 +1674,19 @@ void ConstraintInfo::addFactImpl(CmpInst::Predicate
Pred, Value *A, Value *B,
}
}
-static bool replaceAddOverflowUses(IntrinsicInst *II, Value *A, Value *B,
- SmallVectorImpl<Instruction *> &ToRemove) {
- bool Changed = false;
- IRBuilder<> Builder(II->getParent(), II->getIterator());
- Value *Add = nullptr;
- for (User *U : make_early_inc_range(II->users())) {
- if (match(U, m_ExtractValue<0>(m_Value()))) {
- if (!Add)
- Add = Builder.CreateAdd(A, B);
- U->replaceAllUsesWith(Add);
- Changed = true;
- } else if (match(U, m_ExtractValue<1>(m_Value()))) {
- U->replaceAllUsesWith(Builder.getFalse());
- Changed = true;
- } else
- continue;
-
- if (U->use_empty()) {
- auto *I = cast<Instruction>(U);
- ToRemove.push_back(I);
- I->setOperand(0, PoisonValue::get(II->getType()));
- Changed = true;
- }
- }
-
- if (II->use_empty()) {
- II->eraseFromParent();
- Changed = true;
- }
- return Changed;
-}
-
-static bool replaceSubOverflowUses(IntrinsicInst *II, Value *A, Value *B,
- SmallVectorImpl<Instruction *> &ToRemove) {
+static bool
+replaceAddOrSubOverflowUses(IntrinsicInst *II, Value *A, Value *B,
+ SmallVectorImpl<Instruction *> &ToRemove) {
+ bool IsAdd = II->getIntrinsicID() == Intrinsic::sadd_with_overflow ||
+ II->getIntrinsicID() == Intrinsic::uadd_with_overflow;
bool Changed = false;
IRBuilder<> Builder(II->getParent(), II->getIterator());
- Value *Sub = nullptr;
+ Value *AddOrSub = nullptr;
for (User *U : make_early_inc_range(II->users())) {
if (match(U, m_ExtractValue<0>(m_Value()))) {
- if (!Sub)
- Sub = Builder.CreateSub(A, B);
- U->replaceAllUsesWith(Sub);
+ if (!AddOrSub)
+ AddOrSub = IsAdd ? Builder.CreateAdd(A, B) : Builder.CreateSub(A, B);
+ U->replaceAllUsesWith(AddOrSub);
Changed = true;
} else if (match(U, m_ExtractValue<1>(m_Value()))) {
U->replaceAllUsesWith(Builder.getFalse());
@@ -1761,15 +1732,13 @@ tryToSimplifyOverflowMath(IntrinsicInst *II,
ConstraintInfo &Info,
default:
llvm_unreachable("Unexpected intrinsic.");
case Intrinsic::sadd_with_overflow: {
- bool ASgeZero = DoesConditionHold(CmpInst::ICMP_SGE, A, Zero, Info);
- bool BSgeZero = DoesConditionHold(CmpInst::ICMP_SGE, B, Zero, Info);
- bool ASleZero = DoesConditionHold(CmpInst::ICMP_SLE, A, Zero, Info);
- bool BSleZero = DoesConditionHold(CmpInst::ICMP_SLE, B, Zero, Info);
-
// If A and B have different signs, sadd.with.overflow(a, b) should not
// overflow.
- if ((ASgeZero && BSleZero) || (ASleZero && BSgeZero)) {
- Changed = replaceAddOverflowUses(II, A, B, ToRemove);
+ if ((DoesConditionHold(CmpInst::ICMP_SGE, A, Zero, Info) &&
+ DoesConditionHold(CmpInst::ICMP_SLE, B, Zero, Info)) ||
+ (DoesConditionHold(CmpInst::ICMP_SLE, A, Zero, Info) &&
+ DoesConditionHold(CmpInst::ICMP_SGE, B, Zero, Info))) {
+ Changed = replaceAddOrSubOverflowUses(II, A, B, ToRemove);
break;
}
break;
@@ -1780,7 +1749,7 @@ tryToSimplifyOverflowMath(IntrinsicInst *II,
ConstraintInfo &Info,
if (!DoesConditionHold(CmpInst::ICMP_SGE, A, B, Info) ||
!DoesConditionHold(CmpInst::ICMP_SGE, B, Zero, Info))
return false;
- Changed = replaceSubOverflowUses(II, A, B, ToRemove);
+ Changed = replaceAddOrSubOverflowUses(II, A, B, ToRemove);
break;
}
}
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