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Unify the way we report overflow in increment/decrement operator. 

Summary:
Make sure signed overflow in "x--" is checked with
llvm.ssub.with.overflow intrinsic and is reported as:
  "-2147483648 - 1 cannot be represented in type 'int'"
instead of:
  "-2147483648 + -1 cannot be represented in type 'int'"
, like we do for unsigned overflow.

Test Plan: clang + compiler-rt regression test suite

Reviewers: rsmith

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D8236

llvm-svn: 235568
This commit is contained in:
Alexey Samsonov 2015-04-23 01:50:45 +00:00
parent 434984ef58
commit f624650354
2 changed files with 31 additions and 33 deletions
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60
clang/lib/CodeGen/CGExprScalar.cpp
View File

@ -349,10 +349,9 @@ public:
return EmitScalarPrePostIncDec(E, LV, true, true);
}
llvm::Value *EmitAddConsiderOverflowBehavior(const UnaryOperator *E,
llvm::Value *InVal,
llvm::Value *NextVal,
bool IsInc);
llvm::Value *EmitIncDecConsiderOverflowBehavior(const UnaryOperator *E,
llvm::Value *InVal,
bool IsInc);
llvm::Value *EmitScalarPrePostIncDec(const UnaryOperator *E, LValue LV,
bool isInc, bool isPre);
@ -1610,26 +1609,32 @@ Value *ScalarExprEmitter::VisitStmtExpr(const StmtExpr *E) {
// Unary Operators
//===----------------------------------------------------------------------===//
llvm::Value *ScalarExprEmitter::
EmitAddConsiderOverflowBehavior(const UnaryOperator *E,
llvm::Value *InVal,
llvm::Value *NextVal, bool IsInc) {
static BinOpInfo createBinOpInfoFromIncDec(const UnaryOperator *E,
llvm::Value *InVal, bool IsInc) {
BinOpInfo BinOp;
BinOp.LHS = InVal;
BinOp.RHS = llvm::ConstantInt::get(InVal->getType(), 1, false);
BinOp.Ty = E->getType();
BinOp.Opcode = IsInc ? BO_Add : BO_Sub;
BinOp.FPContractable = false;
BinOp.E = E;
return BinOp;
}
llvm::Value *ScalarExprEmitter::EmitIncDecConsiderOverflowBehavior(
const UnaryOperator *E, llvm::Value *InVal, bool IsInc) {
llvm::Value *Amount =
llvm::ConstantInt::get(InVal->getType(), IsInc ? 1 : -1, true);
StringRef Name = IsInc ? "inc" : "dec";
switch (CGF.getLangOpts().getSignedOverflowBehavior()) {
case LangOptions::SOB_Defined:
return Builder.CreateAdd(InVal, NextVal, IsInc ? "inc" : "dec");
return Builder.CreateAdd(InVal, Amount, Name);
case LangOptions::SOB_Undefined:
if (!CGF.SanOpts.has(SanitizerKind::SignedIntegerOverflow))
return Builder.CreateNSWAdd(InVal, NextVal, IsInc ? "inc" : "dec");
return Builder.CreateNSWAdd(InVal, Amount, Name);
// Fall through.
case LangOptions::SOB_Trapping:
BinOpInfo BinOp;
BinOp.LHS = InVal;
BinOp.RHS = NextVal;
BinOp.Ty = E->getType();
BinOp.Opcode = BO_Add;
BinOp.FPContractable = false;
BinOp.E = E;
return EmitOverflowCheckedBinOp(BinOp);
return EmitOverflowCheckedBinOp(createBinOpInfoFromIncDec(E, InVal, IsInc));
}
llvm_unreachable("Unknown SignedOverflowBehaviorTy");
}
@ -1707,27 +1712,20 @@ ScalarExprEmitter::EmitScalarPrePostIncDec(const UnaryOperator *E, LValue LV,
// Most common case by far: integer increment.
} else if (type->isIntegerType()) {
llvm::Value *amt = llvm::ConstantInt::get(value->getType(), amount, true);
// Note that signed integer inc/dec with width less than int can't
// overflow because of promotion rules; we're just eliding a few steps here.
bool CanOverflow = value->getType()->getIntegerBitWidth() >=
CGF.IntTy->getIntegerBitWidth();
if (CanOverflow && type->isSignedIntegerOrEnumerationType()) {
value = EmitAddConsiderOverflowBehavior(E, value, amt, isInc);
value = EmitIncDecConsiderOverflowBehavior(E, value, isInc);
} else if (CanOverflow && type->isUnsignedIntegerType() &&
CGF.SanOpts.has(SanitizerKind::UnsignedIntegerOverflow)) {
BinOpInfo BinOp;
BinOp.LHS = value;
BinOp.RHS = llvm::ConstantInt::get(value->getType(), 1, false);
BinOp.Ty = E->getType();
BinOp.Opcode = isInc ? BO_Add : BO_Sub;
BinOp.FPContractable = false;
BinOp.E = E;
value = EmitOverflowCheckedBinOp(BinOp);
} else
value =
EmitOverflowCheckedBinOp(createBinOpInfoFromIncDec(E, value, isInc));
} else {
llvm::Value *amt = llvm::ConstantInt::get(value->getType(), amount, true);
value = Builder.CreateAdd(value, amt, isInc ? "inc" : "dec");
}
// Next most common: pointer increment.
} else if (const PointerType *ptr = type->getAs<PointerType>()) {

4
clang/test/CodeGen/integer-overflow.c
View File

@ -52,8 +52,8 @@ void test1() {
// DEFAULT: add nsw i32 {{.*}}, -1
// WRAPV: add i32 {{.*}}, -1
// TRAPV: llvm.sadd.with.overflow.i32({{.*}}, i32 -1)
// CATCH_UB: llvm.sadd.with.overflow.i32({{.*}}, i32 -1)
// TRAPV: llvm.ssub.with.overflow.i32({{.*}}, i32 1)
// CATCH_UB: llvm.ssub.with.overflow.i32({{.*}}, i32 1)
// TRAPV_HANDLER: foo(
--a;