https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108642
Bug ID: 108642
Summary: ACLE function __arm_wsr missing when compiling in C++
mode for AArch64
Product: gcc
Version: 12.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: david.spickett at linaro dot org
Target Milestone: ---
This was found by a user trying to compile llvm's libc (which is largely
written in c++) using g++ 8.5.0 for AArch64. I then tried versions up to 12.2.0
and a recent trunk build.
https://godbolt.org/z/qxaYxdTcv, and I've copied the details below.
The following source:
```
#include <stdint.h>
#include <arm_acle.h>
void writeStatusWord(uint32_t fpsr) { __arm_wsr("fpsr", fpsr); }
```
When compiled with g++ gives the error:
```
<source>:4:39: error: '__arm_wsr' was not declared in this scope
4 | void writeStatusWord(uint32_t fpsr) { __arm_wsr("fpsr", fpsr); }
| ^~~~~~~~~
```
When compiled as C, there is instead a warning and it does compile:
```
<source>:4:39: warning: implicit declaration of function '__arm_wsr'
[-Wimplicit-function-declaration]
4 | void writeStatusWord(uint32_t fpsr) { __arm_wsr("fpsr", fpsr); }
| ^~~~~~~~~
```
The expected result would be that in either mode, we can compile without errors
or warnings.
This __arm_wsr function should be present after including arm_acle.h according
to https://github.com/ARM-software/acle/releases/tag/r2022Q4 (acle-2022Q4.pdf
). See "11.1 Special register intrinsics".
I looked in the arm_acle.h gcc/g++ is including and see no reference to it.
Which makes me wonder if it's a compiler builtin that somehow isn't present for
C++.
Over in clang there is a builtin for it, that is then #defined into the
__arm_wsr name in the header.
