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when result loc is a slice, avoid evaluating lazy start..end

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This prevents lazy values from being unnecessarily evaluated.
This commit is contained in:
Andrew Kelley 2020-03-18 12:22:39 -04:00
parent e947f0c740
commit 8688c43745
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GPG Key ID: 7C5F548F728501A9
1 changed files with 18 additions and 3 deletions
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21
src/ir.cpp
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@ -26191,6 +26191,16 @@ static IrInstGen *ir_analyze_instruction_memcpy(IrAnalyze *ira, IrInstSrcMemcpy
return ir_build_memcpy_gen(ira, &instruction->base.base, casted_dest_ptr, casted_src_ptr, casted_count);
}
static ZigType *get_result_loc_type(IrAnalyze *ira, ResultLoc *result_loc) {
if (result_loc == nullptr) return nullptr;
if (result_loc->id == ResultLocIdCast) {
return ir_resolve_type(ira, result_loc->source_instruction->child);
}
return nullptr;
}
static IrInstGen *ir_analyze_instruction_slice(IrAnalyze *ira, IrInstSrcSlice *instruction) {
Error err;
@ -26297,11 +26307,16 @@ static IrInstGen *ir_analyze_instruction_slice(IrAnalyze *ira, IrInstSrcSlice *i
ZigType *child_array_type = (array_type->id == ZigTypeIdPointer &&
array_type->data.pointer.ptr_len == PtrLenSingle) ? array_type->data.pointer.child_type : array_type;
// If start index and end index are both comptime known, then the result type is a pointer to array
// not a slice.
ZigType *return_type;
if (value_is_comptime(casted_start->value) &&
// If start index and end index are both comptime known, then the result type is a pointer to array
// not a slice. However, if the start or end index is a lazy value, and the result location is a slice,
// then the pointer-to-array would be casted to a slice anyway. So, we preserve the laziness of these
// values by making the return type a slice.
ZigType *res_loc_type = get_result_loc_type(ira, instruction->result_loc);
if ((res_loc_type == nullptr || !is_slice(res_loc_type)) &&
value_is_comptime(casted_start->value) &&
((end != nullptr && value_is_comptime(end->value)) ||
(end == nullptr && child_array_type->id == ZigTypeIdArray)))
{