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.
- We do this when it is easy to determine that the backend will pass them on
the stack properly by itself.
Currently LLVM codegen is really bad in some cases with byval, for example, on
the test case here (which is derived from Sema code, which likes to pass
SourceLocations around)::
struct s47 { unsigned a; };
void f47(int,int,int,int,int,int,struct s47);
void test47(int a, struct s47 b) { f47(a, a, a, a, a, a, b); }
we used to emit code like this::
...
movl %esi, -8(%rbp)
movl -8(%rbp), %ecx
movl %ecx, (%rsp)
...
to handle moving the struct onto the stack, which is just appalling.
Now we generate::
movl %esi, (%rsp)
which seems better, no?
llvm-svn: 152462
Fangrui Song