For a definition (of most linkage types), dso_local is set for ELF -fno-pic/-fpie
and COFF, but not for Mach-O. This nuance causes unneeded binary format differences.
This patch replaces (function) `define ` with `define{{.*}} `,
(variable/constant/alias) `= ` with `={{.*}} `, or inserts appropriate `{{.*}} `
if there is an explicit linkage.
* Clang will set dso_local for Mach-O, which is currently implied by TargetMachine.cpp. This will make COFF/Mach-O and executable ELF similar.
* Eventually I hope we can make dso_local the textual LLVM IR default (write explicit "dso_preemptable" when applicable) and -fpic ELF will be similar to everything else. This patch helps move toward that goal.
The objc_runtime_visible attribute deals with an odd corner case where
a particular Objective-C class is known to the Objective-C runtime
(and, therefore, accessible by name) but its symbol has been hidden
for some reason. For such classes, teach CodeGen to use
objc_lookUpClass to retrieve the Class object, rather than referencing
the class symbol directly.
Classes annotated with objc_runtime_visible have two major limitations
that fall out from places where Objective-C metadata needs to refer to
the class (or metaclass) symbol directly:
* One cannot implement a subclass of an objc_runtime_visible class.
* One cannot implement a category on an objc_runtime_visible class.
Implements rdar://problem/25494092.
llvm-svn: 265201
Fangrui Song