[clang][bytecode] Fix unsigned wraparound behavior with bitfields #164445
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
llvmbot
added
clang
|
@llvm/pr-subscribers-clang Author: Timm Baeder (tbaederr) Changesand inc/dec operations. We need to truncate the new value to the bitfield bitwidth. Full diff: https://github.com/llvm/llvm-project/pull/164445.diff 5 Files Affected:
diff --git a/clang/lib/AST/ByteCode/Compiler.cpp b/clang/lib/AST/ByteCode/Compiler.cpp
index f7731f06b664c..53e3c184ad081 100644
--- a/clang/lib/AST/ByteCode/Compiler.cpp
+++ b/clang/lib/AST/ByteCode/Compiler.cpp
@@ -6438,6 +6438,13 @@ bool Compiler<Emitter>::visitFunc(const FunctionDecl *F) {
return this->emitNoRet(SourceInfo{});
}
+static uint32_t getBitWidth(const Expr *E) {
+ assert(E->refersToBitField());
+ const auto *ME = cast<MemberExpr>(E);
+ const auto *FD = cast<FieldDecl>(ME->getMemberDecl());
+ return FD->getBitWidthValue();
+}
+
template <class Emitter>
bool Compiler<Emitter>::VisitUnaryOperator(const UnaryOperator *E) {
const Expr *SubExpr = E->getSubExpr();
@@ -6466,10 +6473,15 @@ bool Compiler<Emitter>::VisitUnaryOperator(const UnaryOperator *E) {
return DiscardResult ? this->emitPopPtr(E) : true;
}
- if (T == PT_Float) {
+ if (T == PT_Float)
return DiscardResult ? this->emitIncfPop(getFPOptions(E), E)
: this->emitIncf(getFPOptions(E), E);
- }
+
+ if (SubExpr->refersToBitField())
+ return DiscardResult ? this->emitIncPopBitfield(*T, E->canOverflow(),
+ getBitWidth(SubExpr), E)
+ : this->emitIncBitfield(*T, E->canOverflow(),
+ getBitWidth(SubExpr), E);
return DiscardResult ? this->emitIncPop(*T, E->canOverflow(), E)
: this->emitInc(*T, E->canOverflow(), E);
@@ -6490,9 +6502,15 @@ bool Compiler<Emitter>::VisitUnaryOperator(const UnaryOperator *E) {
return DiscardResult ? this->emitPopPtr(E) : true;
}
- if (T == PT_Float) {
+ if (T == PT_Float)
return DiscardResult ? this->emitDecfPop(getFPOptions(E), E)
: this->emitDecf(getFPOptions(E), E);
+
+ if (SubExpr->refersToBitField()) {
+ return DiscardResult ? this->emitDecPopBitfield(*T, E->canOverflow(),
+ getBitWidth(SubExpr), E)
+ : this->emitDecBitfield(*T, E->canOverflow(),
+ getBitWidth(SubExpr), E);
}
return DiscardResult ? this->emitDecPop(*T, E->canOverflow(), E)
@@ -6521,6 +6539,11 @@ bool Compiler<Emitter>::VisitUnaryOperator(const UnaryOperator *E) {
if (DiscardResult) {
if (T == PT_Float)
return this->emitIncfPop(getFPOptions(E), E);
+ if (SubExpr->refersToBitField())
+ return DiscardResult ? this->emitIncPopBitfield(*T, E->canOverflow(),
+ getBitWidth(SubExpr), E)
+ : this->emitIncBitfield(*T, E->canOverflow(),
+ getBitWidth(SubExpr), E);
return this->emitIncPop(*T, E->canOverflow(), E);
}
@@ -6536,6 +6559,11 @@ bool Compiler<Emitter>::VisitUnaryOperator(const UnaryOperator *E) {
return false;
if (!this->emitStoreFloat(E))
return false;
+ } else if (SubExpr->refersToBitField()) {
+ assert(isIntegralType(*T));
+ if (!this->emitPreIncBitfield(*T, E->canOverflow(), getBitWidth(SubExpr),
+ E))
+ return false;
} else {
assert(isIntegralType(*T));
if (!this->emitPreInc(*T, E->canOverflow(), E))
@@ -6566,6 +6594,11 @@ bool Compiler<Emitter>::VisitUnaryOperator(const UnaryOperator *E) {
if (DiscardResult) {
if (T == PT_Float)
return this->emitDecfPop(getFPOptions(E), E);
+ if (SubExpr->refersToBitField())
+ return DiscardResult ? this->emitDecPopBitfield(*T, E->canOverflow(),
+ getBitWidth(SubExpr), E)
+ : this->emitDecBitfield(*T, E->canOverflow(),
+ getBitWidth(SubExpr), E);
return this->emitDecPop(*T, E->canOverflow(), E);
}
@@ -6581,6 +6614,11 @@ bool Compiler<Emitter>::VisitUnaryOperator(const UnaryOperator *E) {
return false;
if (!this->emitStoreFloat(E))
return false;
+ } else if (SubExpr->refersToBitField()) {
+ assert(isIntegralType(*T));
+ if (!this->emitPreDecBitfield(*T, E->canOverflow(), getBitWidth(SubExpr),
+ E))
+ return false;
} else {
assert(isIntegralType(*T));
if (!this->emitPreDec(*T, E->canOverflow(), E))
diff --git a/clang/lib/AST/ByteCode/Interp.cpp b/clang/lib/AST/ByteCode/Interp.cpp
index a72282caf5e73..805ce6d698aae 100644
--- a/clang/lib/AST/ByteCode/Interp.cpp
+++ b/clang/lib/AST/ByteCode/Interp.cpp
@@ -1610,6 +1610,8 @@ bool Call(InterpState &S, CodePtr OpPC, const Function *Func,
if (!CheckCallDepth(S, OpPC))
return cleanup();
+ // Func->dump();
+
auto NewFrame = std::make_unique<InterpFrame>(S, Func, OpPC, VarArgSize);
InterpFrame *FrameBefore = S.Current;
S.Current = NewFrame.get();
diff --git a/clang/lib/AST/ByteCode/Interp.h b/clang/lib/AST/ByteCode/Interp.h
index d8529daf591ee..89f6fbefb1907 100644
--- a/clang/lib/AST/ByteCode/Interp.h
+++ b/clang/lib/AST/ByteCode/Interp.h
@@ -702,7 +702,7 @@ enum class IncDecOp {
template <typename T, IncDecOp Op, PushVal DoPush>
bool IncDecHelper(InterpState &S, CodePtr OpPC, const Pointer &Ptr,
- bool CanOverflow) {
+ bool CanOverflow, UnsignedOrNone BitWidth = std::nullopt) {
assert(!Ptr.isDummy());
if (!S.inConstantContext()) {
@@ -725,12 +725,18 @@ bool IncDecHelper(InterpState &S, CodePtr OpPC, const Pointer &Ptr,
if constexpr (Op == IncDecOp::Inc) {
if (!T::increment(Value, &Result) || !CanOverflow) {
- Ptr.deref<T>() = Result;
+ if (BitWidth)
+ Ptr.deref<T>() = Result.truncate(*BitWidth);
+ else
+ Ptr.deref<T>() = Result;
return true;
}
} else {
if (!T::decrement(Value, &Result) || !CanOverflow) {
- Ptr.deref<T>() = Result;
+ if (BitWidth)
+ Ptr.deref<T>() = Result.truncate(*BitWidth);
+ else
+ Ptr.deref<T>() = Result;
return true;
}
}
@@ -774,6 +780,17 @@ bool Inc(InterpState &S, CodePtr OpPC, bool CanOverflow) {
CanOverflow);
}
+template <PrimType Name, class T = typename PrimConv<Name>::T>
+bool IncBitfield(InterpState &S, CodePtr OpPC, bool CanOverflow,
+ unsigned BitWidth) {
+ const Pointer &Ptr = S.Stk.pop<Pointer>();
+ if (!CheckLoad(S, OpPC, Ptr, AK_Increment))
+ return false;
+
+ return IncDecHelper<T, IncDecOp::Inc, PushVal::Yes>(S, OpPC, Ptr, CanOverflow,
+ BitWidth);
+}
+
/// 1) Pops a pointer from the stack
/// 2) Load the value from the pointer
/// 3) Writes the value increased by one back to the pointer
@@ -786,6 +803,17 @@ bool IncPop(InterpState &S, CodePtr OpPC, bool CanOverflow) {
return IncDecHelper<T, IncDecOp::Inc, PushVal::No>(S, OpPC, Ptr, CanOverflow);
}
+template <PrimType Name, class T = typename PrimConv<Name>::T>
+bool IncPopBitfield(InterpState &S, CodePtr OpPC, bool CanOverflow,
+ uint32_t BitWidth) {
+ const Pointer &Ptr = S.Stk.pop<Pointer>();
+ if (!CheckLoad(S, OpPC, Ptr, AK_Increment))
+ return false;
+
+ return IncDecHelper<T, IncDecOp::Inc, PushVal::No>(S, OpPC, Ptr, CanOverflow,
+ BitWidth);
+}
+
template <PrimType Name, class T = typename PrimConv<Name>::T>
bool PreInc(InterpState &S, CodePtr OpPC, bool CanOverflow) {
const Pointer &Ptr = S.Stk.peek<Pointer>();
@@ -795,6 +823,17 @@ bool PreInc(InterpState &S, CodePtr OpPC, bool CanOverflow) {
return IncDecHelper<T, IncDecOp::Inc, PushVal::No>(S, OpPC, Ptr, CanOverflow);
}
+template <PrimType Name, class T = typename PrimConv<Name>::T>
+bool PreIncBitfield(InterpState &S, CodePtr OpPC, bool CanOverflow,
+ uint32_t BitWidth) {
+ const Pointer &Ptr = S.Stk.peek<Pointer>();
+ if (!CheckLoad(S, OpPC, Ptr, AK_Increment))
+ return false;
+
+ return IncDecHelper<T, IncDecOp::Inc, PushVal::No>(S, OpPC, Ptr, CanOverflow,
+ BitWidth);
+}
+
/// 1) Pops a pointer from the stack
/// 2) Load the value from the pointer
/// 3) Writes the value decreased by one back to the pointer
@@ -808,6 +847,16 @@ bool Dec(InterpState &S, CodePtr OpPC, bool CanOverflow) {
return IncDecHelper<T, IncDecOp::Dec, PushVal::Yes>(S, OpPC, Ptr,
CanOverflow);
}
+template <PrimType Name, class T = typename PrimConv<Name>::T>
+bool DecBitfield(InterpState &S, CodePtr OpPC, bool CanOverflow,
+ uint32_t BitWidth) {
+ const Pointer &Ptr = S.Stk.pop<Pointer>();
+ if (!CheckLoad(S, OpPC, Ptr, AK_Decrement))
+ return false;
+
+ return IncDecHelper<T, IncDecOp::Dec, PushVal::Yes>(S, OpPC, Ptr, CanOverflow,
+ BitWidth);
+}
/// 1) Pops a pointer from the stack
/// 2) Load the value from the pointer
@@ -821,6 +870,17 @@ bool DecPop(InterpState &S, CodePtr OpPC, bool CanOverflow) {
return IncDecHelper<T, IncDecOp::Dec, PushVal::No>(S, OpPC, Ptr, CanOverflow);
}
+template <PrimType Name, class T = typename PrimConv<Name>::T>
+bool DecPopBitfield(InterpState &S, CodePtr OpPC, bool CanOverflow,
+ uint32_t BitWidth) {
+ const Pointer &Ptr = S.Stk.pop<Pointer>();
+ if (!CheckLoad(S, OpPC, Ptr, AK_Decrement))
+ return false;
+
+ return IncDecHelper<T, IncDecOp::Dec, PushVal::No>(S, OpPC, Ptr, CanOverflow,
+ BitWidth);
+}
+
template <PrimType Name, class T = typename PrimConv<Name>::T>
bool PreDec(InterpState &S, CodePtr OpPC, bool CanOverflow) {
const Pointer &Ptr = S.Stk.peek<Pointer>();
@@ -829,6 +889,16 @@ bool PreDec(InterpState &S, CodePtr OpPC, bool CanOverflow) {
return IncDecHelper<T, IncDecOp::Dec, PushVal::No>(S, OpPC, Ptr, CanOverflow);
}
+template <PrimType Name, class T = typename PrimConv<Name>::T>
+bool PreDecBitfield(InterpState &S, CodePtr OpPC, bool CanOverflow,
+ uint32_t BitWidth) {
+ const Pointer &Ptr = S.Stk.peek<Pointer>();
+ if (!CheckLoad(S, OpPC, Ptr, AK_Decrement))
+ return false;
+ return IncDecHelper<T, IncDecOp::Dec, PushVal::No>(S, OpPC, Ptr, CanOverflow,
+ BitWidth);
+}
+
template <IncDecOp Op, PushVal DoPush>
bool IncDecFloatHelper(InterpState &S, CodePtr OpPC, const Pointer &Ptr,
uint32_t FPOI) {
diff --git a/clang/lib/AST/ByteCode/Opcodes.td b/clang/lib/AST/ByteCode/Opcodes.td
index 532c4448e6f40..406feb57418fa 100644
--- a/clang/lib/AST/ByteCode/Opcodes.td
+++ b/clang/lib/AST/ByteCode/Opcodes.td
@@ -612,12 +612,25 @@ class OverflowOpcode : Opcode {
let HasGroup = 1;
}
+class OverflowBitfieldOpcode : Opcode {
+ let Types = [AluTypeClass];
+ let Args = [ArgBool, ArgUint32];
+ let HasGroup = 1;
+}
+
def Inc : OverflowOpcode;
+def IncBitfield : OverflowBitfieldOpcode;
def IncPop : OverflowOpcode;
+def IncPopBitfield : OverflowBitfieldOpcode;
def PreInc : OverflowOpcode;
+def PreIncBitfield : OverflowBitfieldOpcode;
+
def Dec : OverflowOpcode;
+def DecBitfield : OverflowBitfieldOpcode;
def DecPop : OverflowOpcode;
+def DecPopBitfield : OverflowBitfieldOpcode;
def PreDec : OverflowOpcode;
+def PreDecBitfield : OverflowBitfieldOpcode;
// Float increment and decrement.
def Incf: FloatOpcode;
diff --git a/clang/test/AST/ByteCode/bitfields.cpp b/clang/test/AST/ByteCode/bitfields.cpp
index df8d5678287d3..a58328286bd9a 100644
--- a/clang/test/AST/ByteCode/bitfields.cpp
+++ b/clang/test/AST/ByteCode/bitfields.cpp
@@ -128,3 +128,82 @@ namespace NonConstBitWidth {
// both-note {{read of non-const variable}}
};
}
+
+namespace IncDecOverflow {
+ constexpr bool test1() {
+ struct {unsigned u: 5; } a {};
+ a.u--;
+ return a.u == 31;
+ }
+ static_assert(test1(), "");
+
+ constexpr bool test2() {
+ struct {unsigned u: 5; } a {};
+ --a.u;
+ return a.u == 31;
+ }
+ static_assert(test2(), "");
+
+ constexpr bool test3() {
+ int x = 0;
+ struct {unsigned u: 5; } a {};
+ x = a.u--;
+ return a.u == 31;
+ }
+ static_assert(test3(), "");
+
+ constexpr bool test4() {
+ int x = 0;
+ struct {unsigned u: 5; } a {};
+ x = --a.u;
+ return a.u == 31;
+ }
+ static_assert(test4(), "");
+
+ constexpr bool test5() {
+ struct {unsigned u: 5; } a {};
+ a.u = 31;
+ ++a.u;
+
+ return a.u == 0;
+ }
+ static_assert(test5(), "");
+
+ constexpr bool test6() {
+ struct {unsigned u: 5; } a {};
+ a.u = 31;
+ ++a.u;
+
+ return a.u == 0;
+ }
+ static_assert(test6(), "");
+
+ constexpr bool test7() {
+ struct {unsigned u: 5; } a {};
+ a.u = 31;
+ a.u++;
+
+ return a.u == 0;
+ }
+ static_assert(test7(), "");
+
+ constexpr bool test8() {
+ int x = 0;
+ struct {unsigned u: 5; } a {};
+ a.u = 31;
+ x = a.u++;
+
+ return a.u == 0;
+ }
+ static_assert(test8(), "");
+
+ constexpr bool test9() {
+ int x = 0;
+ struct {unsigned u: 5; } a {};
+ a.u = 31;
+ x = ++a.u;
+
+ return a.u == 0;
+ }
+ static_assert(test9(), "");
+}
|
tbaederr
force-pushed
the
bitfield-wraparound
branch
from
90e3bc9 to
f1d2184
Compare
and inc/dec operations. We need to truncate the new value to the bitfield bitwidth.
tbaederr
force-pushed
the
bitfield-wraparound
branch
from
f1d2184 to
0970b22
Compare
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
and inc/dec operations. We need to truncate the new value to the bitfield bitwidth.