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- ZScript: fixed integer type promotion for shift operator

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* the first operand must never be sign-changed.
* the second operand should always be made unsigned. Shift by negative values is undefined and may produce undefined behavior on some systems.
This commit is contained in:
Christoph Oelckers 2022-08-03 09:03:03 +02:00
parent 8eabaf61c9
commit 388a5cb481
2 changed files with 7 additions and 6 deletions
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11
src/common/scripting/backend/codegen.cpp
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@ -2678,21 +2678,22 @@ FxBinary::~FxBinary()
//
//==========================================================================
bool FxBinary::Promote(FCompileContext &ctx, bool forceint)
bool FxBinary::Promote(FCompileContext &ctx, bool forceint, bool shiftop)
{
// math operations of unsigned ints results in an unsigned int. (16 and 8 bit values never get here, they get promoted to regular ints elsewhere already.)
if (left->ValueType == TypeUInt32 && right->ValueType == TypeUInt32)
{
ValueType = TypeUInt32;
}
// If one side is an unsigned 32-bit int and the other side is a signed 32-bit int, the signed side is implicitly converted to unsigned.
else if (!ctx.FromDecorate && left->ValueType == TypeUInt32 && right->ValueType == TypeSInt32 && ctx.Version >= MakeVersion(4, 9, 0))
// If one side is an unsigned 32-bit int and the other side is a signed 32-bit int, the signed side is implicitly converted to unsigned,
// unless this is a shift operator where different rules must apply.
else if (((!ctx.FromDecorate && left->ValueType == TypeUInt32 && right->ValueType == TypeSInt32) || !shiftop) && ctx.Version >= MakeVersion(4, 9, 0))
{
right = new FxIntCast(right, false, false, true);
right = right->Resolve(ctx);
ValueType = TypeUInt32;
}
else if (!ctx.FromDecorate && left->ValueType == TypeSInt32 && right->ValueType == TypeUInt32 && ctx.Version >= MakeVersion(4, 9, 0))
else if (!ctx.FromDecorate && left->ValueType == TypeSInt32 && right->ValueType == TypeUInt32 && !shiftop && ctx.Version >= MakeVersion(4, 9, 0))
{
left = new FxIntCast(left, false, false, true);
left = left->Resolve(ctx);
@ -3942,7 +3943,7 @@ FxExpression *FxShift::Resolve(FCompileContext& ctx)
if (left->IsNumeric() && right->IsNumeric())
{
if (!Promote(ctx, true)) return nullptr;
if (!Promote(ctx, true, true)) return nullptr;
if ((left->ValueType == TypeUInt32 && ctx.Version >= MakeVersion(3, 7)) && Operator == TK_RShift) Operator = TK_URShift;
}
else

2
src/common/scripting/backend/codegen.h
View file

@ -910,7 +910,7 @@ public:
FxBinary(int, FxExpression*, FxExpression*);
~FxBinary();
bool Promote(FCompileContext &ctx, bool forceint = false);
bool Promote(FCompileContext &ctx, bool forceint = false, bool shiftop = false);
};
//==========================================================================