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[ubsan] Detect signed overflow UB in remainder operations 

Teach ubsan to diagnose remainder operations which have undefined
behavior due to signed overflow (e.g INT_MIN % -1).

Differential Revision: https://reviews.llvm.org/D29437

llvm-svn: 296214
This commit is contained in:
Vedant Kumar 2017-02-25 00:43:39 +00:00
parent 82ee16beb8
commit 42de380765
2 changed files with 14 additions and 7 deletions
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8
clang/lib/CodeGen/CGExprScalar.cpp
View File

@ -2403,12 +2403,12 @@ Value *ScalarExprEmitter::EmitDiv(const BinOpInfo &Ops) {
Value *ScalarExprEmitter::EmitRem(const BinOpInfo &Ops) {
// Rem in C can't be a floating point type: C99 6.5.5p2.
if (CGF.SanOpts.has(SanitizerKind::IntegerDivideByZero)) {
if ((CGF.SanOpts.has(SanitizerKind::IntegerDivideByZero) ||
CGF.SanOpts.has(SanitizerKind::SignedIntegerOverflow)) &&
Ops.Ty->isIntegerType()) {
CodeGenFunction::SanitizerScope SanScope(&CGF);
llvm::Value *Zero = llvm::Constant::getNullValue(ConvertType(Ops.Ty));
if (Ops.Ty->isIntegerType())
EmitUndefinedBehaviorIntegerDivAndRemCheck(Ops, Zero, false);
EmitUndefinedBehaviorIntegerDivAndRemCheck(Ops, Zero, false);
}
if (Ops.Ty->hasUnsignedIntegerRepresentation())

13
clang/test/CodeGen/ubsan-promoted-arith.cpp
View File

@ -2,6 +2,7 @@
typedef unsigned char uchar;
typedef unsigned short ushort;
typedef int int4 __attribute__((ext_vector_type(4)));
enum E1 : int {
a
@ -101,12 +102,14 @@ char rem1(char c) { return c % c; }
// CHECK-NOT: ubsan_handle_divrem_overflow
uchar rem2(uchar uc) { return uc % uc; }
// FIXME: This is a long-standing false negative.
//
// CHECK-LABEL: define signext i8 @_Z4rem3
// rdar30301609: ubsan_handle_divrem_overflow
// CHECK: ubsan_handle_divrem_overflow
char rem3(int i, char c) { return i % c; }
// CHECK-LABEL: define signext i8 @_Z4rem4
// CHECK-NOT: ubsan_handle_divrem_overflow
char rem4(char c, int i) { return c % i; }
// CHECK-LABEL: define signext i8 @_Z4inc1
// CHECK-NOT: sadd.with.overflow
char inc1(char c) { return c++ + (char)0; }
@ -122,3 +125,7 @@ void inc3(char c) { c++; }
// CHECK-LABEL: define void @_Z4inc4
// CHECK-NOT: uadd.with.overflow
void inc4(uchar uc) { uc++; }
// CHECK-LABEL: define <4 x i32> @_Z4vremDv4_iS_
// CHECK-NOT: ubsan_handle_divrem_overflow
int4 vrem(int4 a, int4 b) { return a % b; }