The linkage/visibility of `__profn_*` variables are derived
from the profiled functions.
extern_weak => linkonce
available_externally => linkonce_odr
internal => private
extern => private
_ => unchanged
The linkage/visibility of `__profc_*`/`__profd_*` variables are derived from
`__profn_*` with linkage/visibility wrestling for Windows.
The changes can be folded to the following without changing semantics.
```
if (TT.isOSBinFormatCOFF() && !NeedComdat) {
Linkage = GlobalValue::InternalLinkage;
Visibility = GlobalValue::DefaultVisibility;
}
```
That said, I think we can just delete the code block.
An extern/internal function will now use private `__profc_*`/`__profd_*`
variables, instead of internal ones. This saves some symbol table entries.
A non-comdat {linkonce,weak}_odr function will now use hidden external
`__profc_*`/`__profd_*` variables instead of internal ones. There is potential
object file size increase because such symbols need `/INCLUDE:` directives.
However such non-comdat functions are rare (note that non-comdat weak
definitions don't prevent duplicate definition error).
The behavior changes match ELF.
Reviewed By: rnk
Differential Revision: https://reviews.llvm.org/D103355
See PR43425:
https://bugs.llvm.org/show_bug.cgi?id=43425
When writing profile data on Windows we were opening profile file with
exclusive read/write access.
In case we are trying to write to the file from multiple processes
simultaneously, subsequent calls to CreateFileA would return
INVALID_HANDLE_VALUE.
To fix this, I changed to open without exclusive access and then take a
lock.
Patch by Michael Holman!
Differential revision: https://reviews.llvm.org/D70330
Fangrui Song