Make consume methods more amenable to optimization #1462
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dmachaj
approved these changes
Dec 12, 2024
| @@ -1137,7 +1137,8 @@ namespace cppwinrt | |||
| {% | |||
| if constexpr (!std::is_same_v<D, %>) | |||
| { | |||
| auto const [_winrt_casted_result, _winrt_cast_result_code] = impl::try_as_with_reason<%, D const*>(static_cast<D const*>(this)); | |||
| winrt::hresult _winrt_cast_result_code; | |||
| auto const _winrt_casted_result = impl::try_as_with_reason<%, D const*>(static_cast<D const*>(this), _winrt_cast_result_code); | |||
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I'm not sure if it is still the recommended coding standard, but for a long time non-const references were disallowed and passing a pointer was preferred. That way the call site is clearly mutating the variable because the & is visible. In this case it is generated code so I guess it is [shrug].
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The temporary std::pair introduced with
try_as_with_reasonsometimes causes spurious temporary dtor calls, depending on the optimization flags used and/or the version of the compiler. This didn't result in an extra refcount bump/release, but it still resulted in generating spurious destructor calls towinrt::Foundation::~IUnknown()as a result of that temporary.The temporary had already been moved-from into the local variables, so was always zero, but this code bloat, extra function call and branch, when multiplied over thousands of projected methods can still add up.