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[clang][CodeGen] Fix shift-exponent ubsan check for signed _BitInt #88004

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Merged
merged 1 commit into from
Apr 19, 2024
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[clang][CodeGen] Fix shift-exponent ubsan check for signed _BitInt #88004

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31 changes: 23 additions & 8 deletions clang/lib/CodeGen/CGExprScalar.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -146,6 +146,15 @@ struct BinOpInfo {
return UnOp->getSubExpr()->getType()->isFixedPointType();
return false;
}

/// Check if the RHS has a signed integer representation.
bool rhsHasSignedIntegerRepresentation() const {
if (const auto *BinOp = dyn_cast<BinaryOperator>(E)) {
QualType RHSType = BinOp->getRHS()->getType();
return RHSType->hasSignedIntegerRepresentation();
}
return false;
}
};

static bool MustVisitNullValue(const Expr *E) {
Expand Down Expand Up @@ -780,7 +789,7 @@ class ScalarExprEmitter
void EmitUndefinedBehaviorIntegerDivAndRemCheck(const BinOpInfo &Ops,
llvm::Value *Zero,bool isDiv);
// Common helper for getting how wide LHS of shift is.
static Value *GetMaximumShiftAmount(Value *LHS, Value *RHS);
static Value *GetMaximumShiftAmount(Value *LHS, Value *RHS, bool RHSIsSigned);

// Used for shifting constraints for OpenCL, do mask for powers of 2, URem for
// non powers of two.
Expand Down Expand Up @@ -4181,7 +4190,8 @@ Value *ScalarExprEmitter::EmitSub(const BinOpInfo &op) {
return Builder.CreateExactSDiv(diffInChars, divisor, "sub.ptr.div");
}

Value *ScalarExprEmitter::GetMaximumShiftAmount(Value *LHS, Value *RHS) {
Value *ScalarExprEmitter::GetMaximumShiftAmount(Value *LHS, Value *RHS,
bool RHSIsSigned) {
llvm::IntegerType *Ty;
if (llvm::VectorType *VT = dyn_cast<llvm::VectorType>(LHS->getType()))
Ty = cast<llvm::IntegerType>(VT->getElementType());
Expand All @@ -4192,7 +4202,9 @@ Value *ScalarExprEmitter::GetMaximumShiftAmount(Value *LHS, Value *RHS) {
// this in ConstantInt::get, this results in the value getting truncated.
// Constrain the return value to be max(RHS) in this case.
llvm::Type *RHSTy = RHS->getType();
llvm::APInt RHSMax = llvm::APInt::getMaxValue(RHSTy->getScalarSizeInBits());
llvm::APInt RHSMax =
RHSIsSigned ? llvm::APInt::getSignedMaxValue(RHSTy->getScalarSizeInBits())
: llvm::APInt::getMaxValue(RHSTy->getScalarSizeInBits());
if (RHSMax.ult(Ty->getBitWidth()))
return llvm::ConstantInt::get(RHSTy, RHSMax);
return llvm::ConstantInt::get(RHSTy, Ty->getBitWidth() - 1);
Expand All @@ -4207,7 +4219,7 @@ Value *ScalarExprEmitter::ConstrainShiftValue(Value *LHS, Value *RHS,
Ty = cast<llvm::IntegerType>(LHS->getType());

if (llvm::isPowerOf2_64(Ty->getBitWidth()))
return Builder.CreateAnd(RHS, GetMaximumShiftAmount(LHS, RHS), Name);
return Builder.CreateAnd(RHS, GetMaximumShiftAmount(LHS, RHS, false), Name);

return Builder.CreateURem(
RHS, llvm::ConstantInt::get(RHS->getType(), Ty->getBitWidth()), Name);
Expand Down Expand Up @@ -4240,7 +4252,9 @@ Value *ScalarExprEmitter::EmitShl(const BinOpInfo &Ops) {
isa<llvm::IntegerType>(Ops.LHS->getType())) {
CodeGenFunction::SanitizerScope SanScope(&CGF);
SmallVector<std::pair<Value *, SanitizerMask>, 2> Checks;
llvm::Value *WidthMinusOne = GetMaximumShiftAmount(Ops.LHS, Ops.RHS);
bool RHSIsSigned = Ops.rhsHasSignedIntegerRepresentation();
llvm::Value *WidthMinusOne =
GetMaximumShiftAmount(Ops.LHS, Ops.RHS, RHSIsSigned);
llvm::Value *ValidExponent = Builder.CreateICmpULE(Ops.RHS, WidthMinusOne);

if (SanitizeExponent) {
Expand All @@ -4258,7 +4272,7 @@ Value *ScalarExprEmitter::EmitShl(const BinOpInfo &Ops) {
Builder.CreateCondBr(ValidExponent, CheckShiftBase, Cont);
llvm::Value *PromotedWidthMinusOne =
(RHS == Ops.RHS) ? WidthMinusOne
: GetMaximumShiftAmount(Ops.LHS, RHS);
: GetMaximumShiftAmount(Ops.LHS, RHS, RHSIsSigned);
CGF.EmitBlock(CheckShiftBase);
llvm::Value *BitsShiftedOff = Builder.CreateLShr(
Ops.LHS, Builder.CreateSub(PromotedWidthMinusOne, RHS, "shl.zeros",
Expand Down Expand Up @@ -4308,8 +4322,9 @@ Value *ScalarExprEmitter::EmitShr(const BinOpInfo &Ops) {
else if (CGF.SanOpts.has(SanitizerKind::ShiftExponent) &&
isa<llvm::IntegerType>(Ops.LHS->getType())) {
CodeGenFunction::SanitizerScope SanScope(&CGF);
llvm::Value *Valid =
Builder.CreateICmpULE(Ops.RHS, GetMaximumShiftAmount(Ops.LHS, Ops.RHS));
bool RHSIsSigned = Ops.rhsHasSignedIntegerRepresentation();
llvm::Value *Valid = Builder.CreateICmpULE(
Ops.RHS, GetMaximumShiftAmount(Ops.LHS, Ops.RHS, RHSIsSigned));
EmitBinOpCheck(std::make_pair(Valid, SanitizerKind::ShiftExponent), Ops);
}

Expand Down
33 changes: 31 additions & 2 deletions clang/test/CodeGen/ubsan-shift-bitint.c
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Original file line number Diff line number Diff line change
Expand Up @@ -6,14 +6,14 @@
// CHECK-LABEL: define{{.*}} i32 @test_left_variable
int test_left_variable(unsigned _BitInt(5) b, unsigned _BitInt(2) e) {
// CHECK: [[E_REG:%.+]] = load [[E_SIZE:i2]]
// CHECK: icmp ule [[E_SIZE]] [[E_REG]], -1
// CHECK: icmp ule [[E_SIZE]] [[E_REG]], -1,
return b << e;
}

// CHECK-LABEL: define{{.*}} i32 @test_right_variable
int test_right_variable(unsigned _BitInt(2) b, unsigned _BitInt(3) e) {
// CHECK: [[E_REG:%.+]] = load [[E_SIZE:i3]]
// CHECK: icmp ule [[E_SIZE]] [[E_REG]], 1
// CHECK: icmp ule [[E_SIZE]] [[E_REG]], 1,
return b >> e;
}

Expand All @@ -34,3 +34,32 @@ int test_right_literal(unsigned _BitInt(2) b) {
// CHECK: br i1 false, label %cont, label %handler.shift_out_of_bounds
return b >> 4uwb;
}

// CHECK-LABEL: define{{.*}} i32 @test_signed_left_variable
int test_signed_left_variable(unsigned _BitInt(15) b, _BitInt(2) e) {
// CHECK: [[E_REG:%.+]] = load [[E_SIZE:i2]]
// CHECK: icmp ule [[E_SIZE]] [[E_REG]], 1,
return b << e;
}

// CHECK-LABEL: define{{.*}} i32 @test_signed_right_variable
int test_signed_right_variable(unsigned _BitInt(32) b, _BitInt(4) e) {
// CHECK: [[E_REG:%.+]] = load [[E_SIZE:i4]]
// CHECK: icmp ule [[E_SIZE]] [[E_REG]], 7,
return b >> e;
}

// CHECK-LABEL: define{{.*}} i32 @test_signed_left_literal
int test_signed_left_literal(unsigned _BitInt(16) b) {
// CHECK-NOT: br i1 true, label %cont, label %handler.shift_out_of_bounds
// CHECK: br i1 false, label %cont, label %handler.shift_out_of_bounds
return b << (_BitInt(4))-2wb;
}

// CHECK-LABEL: define{{.*}} i32 @test_signed_right_literal
int test_signed_right_literal(unsigned _BitInt(16) b) {
// CHECK-NOT: br i1 true, label %cont, label %handler.shift_out_of_bounds
// CHECK: br i1 false, label %cont, label %handler.shift_out_of_bounds
return b >> (_BitInt(4))-8wb;
}