Use compiler-specific WINRT_IMPL_NOINLINE macro for noinline functions #893
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Different toolchains use different ways of marking a function as not inlinable. Wrap it inside a macro so we can accommodate the differences.
kennykerr
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Mar 17, 2021
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| #if defined(_MSC_VER) | ||
| #define WINRT_IMPL_NOINLINE __declspec(noinline) | ||
| #elif defined(__GNUC__) | ||
| #define WINRT_IMPL_NOINLINE __attribute__((noinline)) | ||
| #else | ||
| #define WINRT_IMPL_NOINLINE | ||
| #endif |
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How does this cover Clang? I believe clang already know how to interpret __declspec(noinline). I wouldn't want to degrade Clang inadvertently.
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Clang defines __GNUC__ and supports GNU-style __attribute__((noinline)). Clang has a (non-default) option to support MSVC-style __declspec(noinline) as well. This version removes the need to add the -fdeclspec flag when compiling with clang.
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The breakdown is
| Toolchain | Special macros | __declspec(noinline) |
__attribute__((noinline)) |
|---|---|---|---|
| MSVC | _MSC_VER |
☑ | |
| Clang (default) | __GNUC____clang__ |
☑ | |
Clang (-fdeclspec) |
__GNUC____clang__ |
☑ | ☑ |
| gcc | __GNUC__ |
☑ | |
| icc | __GNUC____INTEL_COMPILER |
☑ | |
| icx | __GNUC____INTEL_LLVM_COMPILER |
☑ | ☑ |
djgpp, ellcc and zapcc are based on one of the above toolchains.
So sniffing for _MSC_VER and __GNUC__ covers all the major toolchains.
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Different toolchains use different ways of marking a function as not inlinable. Wrap it inside a macro so we can accommodate the differences.
Fortunately, all of them insert the marker at the same place (between the "inline" keyword and the return type).