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Add support for converting between integer types (#4753)

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Add a builtin `"int.convert"` supporting unchecked conversions between
different integer types. This performs a truncation, zero-extension, or
sign-extension, depending on the widths of the operands and the
signedness of the source type. Add explicit `As` support to the prelude.
No implicit conversions are supported yet as we don't have a way to
express the constraint that we can only implicitly convert to wider
types.
This commit is contained in:
Richard Smith
2025-01-08 08:25:20 +00:00
committed by GitHub
parent 96d836f965
commit 246ec785df
14 changed files with 545 additions and 98 deletions
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toolchain/check/eval.cpp
+26
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@@ -721,6 +721,26 @@ static auto ValidateFloatType(Context& context, SemIRLoc loc,
return ValidateFloatBitWidth(context, loc, result.bit_width_id);
}
// Performs a conversion between integer types, truncating if the value doesn't
// fit in the destination type.
static auto PerformIntConvert(Context& context, SemIR::InstId arg_id,
SemIR::TypeId dest_type_id) -> SemIR::ConstantId {
auto arg_val =
context.ints().Get(context.insts().GetAs<SemIR::IntValue>(arg_id).int_id);
auto [dest_is_signed, bit_width_id] =
context.sem_ir().types().GetIntTypeInfo(dest_type_id);
if (bit_width_id.is_valid()) {
// TODO: If the value fits in the destination type, reuse the existing
// int_id rather than recomputing it. This is probably the most common case.
bool src_is_signed = context.sem_ir().types().IsSignedInt(
context.insts().Get(arg_id).type_id());
unsigned width = context.ints().Get(bit_width_id).getZExtValue();
arg_val =
src_is_signed ? arg_val.sextOrTrunc(width) : arg_val.zextOrTrunc(width);
}
return MakeIntResult(context, dest_type_id, dest_is_signed, arg_val);
}
// Performs a conversion between integer types, diagnosing if the value doesn't
// fit in the destination type.
static auto PerformCheckedIntConvert(Context& context, SemIRLoc loc,
@@ -1284,6 +1304,12 @@ static auto MakeConstantForBuiltinCall(Context& context, SemIRLoc loc,
}
// Integer conversions.
case SemIR::BuiltinFunctionKind::IntConvert: {
if (phase == Phase::Symbolic) {
return MakeConstantResult(context, call, phase);
}
return PerformIntConvert(context, arg_ids[0], call.type_id);
}
case SemIR::BuiltinFunctionKind::IntConvertChecked: {
if (phase == Phase::Symbolic) {
return MakeConstantResult(context, call, phase);