Avoid copying const string constants to the stack. #674
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jaykrell
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chamons,
dalexsoto,
rolfbjarne and
spouliot
as code owners
| @@ -74,7 +74,7 @@ public void WriteMethodLookup () | |||
| implementation.Indent++; | |||
| implementation.WriteLine ($"__method = mono_get_method (__{AssemblySafeName}_image, 0x{MetadataToken:X8}, {ObjCTypeName}_class);"); | |||
| implementation.WriteLineUnindented ("#else"); | |||
| implementation.WriteLine ($"const char __method_name [] = \"{ManagedTypeName}:{MonoSignature}\";"); | |||
| implementation.WriteLine ($"static const char __method_name [] = \"{ManagedTypeName}:{MonoSignature}\";"); | |||
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Will this generate the same native code as if the string constant had been passed directly to the method call?
i.e.:
implementation.WriteLine ($"__method = mono_embeddinator_lookup_method (\"{ManagedTypeName}:{MonoSignature}\", {ObjCTypeName}_class);");There was a problem hiding this comment.
Another way is to pass the literal directly.
There are tradeoffs either way.
With msvc:
Literals can be writable or not, depending on version/flags.
Literals can be single-instanced or not, depending on version/flags.
static const will be not writable and not single-instanced.
Ideal is readonly and single instanced.
Non-static const at least with msvc will copy to stack.
Though I have seen clang optimize similar, kinda surprising.
Perhaps literals w/o temporary are best.
Sometimes people will also assign the literal to a pointer.
That is a wasted assignment but only of a pointer, so minor.
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