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ConstantFolding: remove a wrong peephole optimization for signed "< 0" and ">= 0" comparisons #39938

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Merged
merged 1 commit into from
Oct 27, 2021
Merged

ConstantFolding: remove a wrong peephole optimization for signed "< 0" and ">= 0" comparisons #39938

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42 changes: 0 additions & 42 deletions lib/SILOptimizer/Utils/ConstantFolding.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -476,48 +476,6 @@ static SILValue constantFoldCompare(BuiltinInst *BI, BuiltinValueKind ID) {
return B.createIntegerLiteral(BI->getLoc(), BI->getType(), APInt());
}
}

// Fold x < 0 into false, if x is known to be a result of an unsigned
// operation with overflow checks enabled.
BuiltinInst *BIOp;
if (match(BI, m_BuiltinInst(BuiltinValueKind::ICMP_SLT,
m_TupleExtractOperation(m_BuiltinInst(BIOp), 0),
m_Zero()))) {
// Check if Other is a result of an unsigned operation with overflow.
switch (BIOp->getBuiltinInfo().ID) {
default:
break;
case BuiltinValueKind::UAddOver:
case BuiltinValueKind::USubOver:
case BuiltinValueKind::UMulOver:
// Was it an operation with an overflow check?
if (match(BIOp->getOperand(2), m_One())) {
SILBuilderWithScope B(BI);
return B.createIntegerLiteral(BI->getLoc(), BI->getType(), APInt());
}
}
}

// Fold x >= 0 into true, if x is known to be a result of an unsigned
// operation with overflow checks enabled.
if (match(BI, m_BuiltinInst(BuiltinValueKind::ICMP_SGE,
m_TupleExtractOperation(m_BuiltinInst(BIOp), 0),
m_Zero()))) {
// Check if Other is a result of an unsigned operation with overflow.
switch (BIOp->getBuiltinInfo().ID) {
default:
break;
case BuiltinValueKind::UAddOver:
case BuiltinValueKind::USubOver:
case BuiltinValueKind::UMulOver:
// Was it an operation with an overflow check?
if (match(BIOp->getOperand(2), m_One())) {
SILBuilderWithScope B(BI);
return B.createIntegerLiteral(BI->getLoc(), BI->getType(), APInt(1, 1));
}
}
}

return nullptr;
}

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18 changes: 4 additions & 14 deletions test/SILOptimizer/constant_propagation.sil
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Expand Up @@ -470,10 +470,7 @@ bb0:
// CHECK-NEXT: return %4 : $Builtin.Int64
}

// Fold x < 0 into false, if x is known to be a result of an unsigned
// operation with overflow checks enabled.
// At the same time x >= 0 is always true under the same conditions.
sil @fold_unsigned_op_with_overflow_lt_zero : $@convention(thin) (Builtin.Int64, Builtin.Int64) -> Builtin.Int64 {
sil @dont_fold_unsigned_op_with_overflow_lt_zero : $@convention(thin) (Builtin.Int64, Builtin.Int64) -> Builtin.Int64 {
bb0(%0 : $Builtin.Int64, %1 : $Builtin.Int64):
%zero = integer_literal $Builtin.Int64, 0
%2 = integer_literal $Builtin.Int1, -1
Expand Down Expand Up @@ -503,17 +500,10 @@ bb0(%0 : $Builtin.Int64, %1 : $Builtin.Int64):

return %uadd_with_overflow_result : $Builtin.Int64

// CHECK-LABEL: sil @fold_unsigned_op_with_overflow_lt_zero
// CHECK-LABEL: sil @dont_fold_unsigned_op_with_overflow_lt_zero
// CHECK: builtin "uadd_with_overflow_Int64"
// CHECK: integer_literal $Builtin.Int1, 0
// CHECK: integer_literal $Builtin.Int1, -1
// CHECK: builtin "usub_with_overflow_Int64"
// CHECK: integer_literal $Builtin.Int1, 0
// CHECK: integer_literal $Builtin.Int1, -1
// CHECK: builtin "umul_with_overflow_Int64"
// CHECK: integer_literal $Builtin.Int1, 0
// CHECK: integer_literal $Builtin.Int1, -1
// CHECK-NEXT: return {{.*}}$Builtin.Int64
// CHECK-NOT: integer_literal
// CHECK: } // end sil function 'dont_fold_unsigned_op_with_overflow_lt_zero'
}


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34 changes: 8 additions & 26 deletions test/SILOptimizer/constant_propagation_ownership.sil
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Expand Up @@ -539,22 +539,11 @@ bb0:
// CHECK-NEXT: return %4 : $Builtin.Int64
}

// Fold x < 0 into false, if x is known to be a result of an unsigned
// operation with overflow checks enabled.
// At the same time x >= 0 is always true under the same conditions.
//
// CHECK-LABEL: sil [ossa] @fold_unsigned_op_with_overflow_lt_zero :
// CHECK-LABEL: sil [ossa] @dont_fold_unsigned_op_with_overflow_lt_zero :
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Same here.

// CHECK: builtin "uadd_with_overflow_Int64"
// CHECK: integer_literal $Builtin.Int1, 0
// CHECK: integer_literal $Builtin.Int1, -1
// CHECK: builtin "usub_with_overflow_Int64"
// CHECK: integer_literal $Builtin.Int1, 0
// CHECK: integer_literal $Builtin.Int1, -1
// CHECK: builtin "umul_with_overflow_Int64"
// CHECK: integer_literal $Builtin.Int1, 0
// CHECK: integer_literal $Builtin.Int1, -1
// CHECK-NEXT: return {{.*}}$Builtin.Int64
sil [ossa] @fold_unsigned_op_with_overflow_lt_zero : $@convention(thin) (Builtin.Int64, Builtin.Int64) -> Builtin.Int64 {
// CHECK-NOT: integer_literal
// CHECK: } // end sil function 'dont_fold_unsigned_op_with_overflow_lt_zero'
sil [ossa] @dont_fold_unsigned_op_with_overflow_lt_zero : $@convention(thin) (Builtin.Int64, Builtin.Int64) -> Builtin.Int64 {
bb0(%0 : $Builtin.Int64, %1 : $Builtin.Int64):
%zero = integer_literal $Builtin.Int64, 0
%2 = integer_literal $Builtin.Int1, -1
Expand Down Expand Up @@ -585,18 +574,11 @@ bb0(%0 : $Builtin.Int64, %1 : $Builtin.Int64):
return %uadd_with_overflow_result : $Builtin.Int64
}

// CHECK-LABEL: sil [ossa] @fold_unsigned_op_with_overflow_lt_zero_destructure :
// CHECK-LABEL: sil [ossa] @dont_fold_unsigned_op_with_overflow_lt_zero_destructure :
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Can you just add a comment here (I am fine in a subsequent PR) that explains why we aren't doing this anymore.

// CHECK: builtin "uadd_with_overflow_Int64"
// CHECK: integer_literal $Builtin.Int1, 0
// CHECK: integer_literal $Builtin.Int1, -1
// CHECK: builtin "usub_with_overflow_Int64"
// CHECK: integer_literal $Builtin.Int1, 0
// CHECK: integer_literal $Builtin.Int1, -1
// CHECK: builtin "umul_with_overflow_Int64"
// CHECK: integer_literal $Builtin.Int1, 0
// CHECK: integer_literal $Builtin.Int1, -1
// CHECK-NEXT: return {{.*}}$Builtin.Int64
sil [ossa] @fold_unsigned_op_with_overflow_lt_zero_destructure : $@convention(thin) (Builtin.Int64, Builtin.Int64) -> Builtin.Int64 {
// CHECK-NOT: integer_literal
// CHECK: } // end sil function 'dont_fold_unsigned_op_with_overflow_lt_zero_destructure'
sil [ossa] @dont_fold_unsigned_op_with_overflow_lt_zero_destructure : $@convention(thin) (Builtin.Int64, Builtin.Int64) -> Builtin.Int64 {
bb0(%0 : $Builtin.Int64, %1 : $Builtin.Int64):
%zero = integer_literal $Builtin.Int64, 0
%2 = integer_literal $Builtin.Int1, -1
Expand Down
6 changes: 6 additions & 0 deletions test/stdlib/RangeTraps.swift
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Expand Up @@ -117,6 +117,12 @@ RangeTraps.test("throughNaN")
_ = ...Double.nan
}

RangeTraps.test("UIntOverflow")
.code {
expectCrashLater()
_blackHole((0 ..< UInt.max).count)
}

if #available(macOS 12.0, iOS 15.0, watchOS 8.0, tvOS 15.0, *) {
// Debug check was introduced in https://github.com/apple/swift/pull/34961
RangeTraps.test("UncheckedHalfOpen")
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