| Issue |
58184
|
| Summary |
[clang++] Clang-15 vs Clang-14 local static init guards
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
eskimo-software
|
I'm using Clang++ to compile for a Cortex-M0+ target, and in moving from version 14 to version 15 I've found a difference in the code generated for guard variables for local statics.
So, for example:
```
int main()
{
static knl::QueueN<uint32_t, 8> valQueue;
...
}
```
Clang-14 generates the following:
```
ldr r0, .LCPI0_4
ldrb r0, [r0]
dmb sy
lsls r0, r0, #31
beq .LBB0_8
```
Clang-15 now generates:
```
ldr r0, .LCPI0_4
movs r1, #2
bl __atomic_load_1
lsls r0, r0, #31
beq .LBB0_8
```
An important consequence of this is that the second case actually requires an implementation of __atomic_load_1 to be provided from somewhere external to the compiler (e.g. -latomic?), whereas the first doesn't.
Note that the source code doesn't explicitly use atomics, only the implied usage by the statics (which can of course be disabled with `-fno-threadsafe-statics`).
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