release/19.x: [compiler-rt] Stop using x86 builtin on AArch64 with GCC (#93890) #115006
Conversation
|
@statham-arm What do you think about merging this PR to the release branch? |
|
|
|
Looking at the patch it looks sane to me. Is there any risk that this breaks something if we merge it as is now? |
|
Despite the force-push, I think the current patch looks the same as the one I clicked approve on (maybe it was just rebased?). I can't see a problem – it's the same patch that hasn't been causing trouble on |
|
The force push was just a rebase to get it on the latest code. |
tru
force-pushed
the
issue114720
branch
2 times, most recently
from
04e2bbe to
19026a4
Compare
Previously, building `multc3.c` on A64 with GCC 7 or up but 9 and lower
will attempt to reference `__builtin_copysignq`, an [x86-specific
intrinsic][1]:
```
$ gcc -c multc3.c
In file included from fp_lib.h:24,
from multc3.c:14:
multc3.c: In function '__multc3':
int_math.h:71:32: warning: implicit declaration of function '__builtin_copysignq'; did you mean '__builtin_copysign'? [-Wimplicit-function-declaration]
#define crt_copysignf128(x, y) __builtin_copysignq((x), (y))
^~~~~~~~~~~~~~~~~~~
```
This is because `__has_builtin` is from GCC 10, and defined to 0 at the
top of int_math.h for affected GCC versions, so the fallback definition
is used. But `__builtin_copysignq` is unavailable on A64.
Use version detection to find `__builtin_copysignf128` instead. It's
available since GCC 7 and [available][2] on both x86 and A64, given this
macro is only used when `CRT_HAS_IEEE_TF`.
---
I realize this is fixing a problem for an out-of-tree build
configuration, but help would be greatly appreciated. Rust
[builds](https://github.com/rust-lang/compiler-builtins) `multc3.c` with
GCC 8 and this mis-selection is causing [build
issues](rust-lang/rust#125619) way downstream.
ref: d2ce3e9
[1]: https://gcc.gnu.org/onlinedocs/gcc/x86-Built-in-Functions.html
[2]: https://gcc.gnu.org/gcc-7/changes.html
(cherry picked from commit 8aa9d62)
|
@XrXr (or anyone else). If you would like to add a note about this fix in the release notes (completely optional). Please reply to this comment with a one or two sentence description of the fix. When you are done, please add the release:note label to this PR. |
Backport 8aa9d62
Requested by: @XrXr