| Issue |
55464
|
| Summary |
Missed optimization - suspect escape analysis
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
OfekShilon
|
[godbolt link](https://godbolt.org/z/fM5W96YjG)
In the following toy code:
```cpp
struct Arr { double* data; };
struct Scalar {
Scalar();
double val;
};
void func( const Arr* __restrict__ input, Arr* __restrict__ result ) {
const double* b = input->data;
Scalar sc;
for(int j = 0; j < 2; ++j ) {
sc.val += b[j];
result->data[j] += sc.val;
}
}
```
An optimization remark is visible in the line ` sc1.val += b[j];`, reading:
> Load of type double not eliminated because it is clobbered by call
The only suspected clobbering call (the only call for that matter) is the `Scalar` ctor. Indeed, adding a visible implementation like `Scalar() : val(0) {}` produces much better code. The godbolt link demonstrates both.
Not sure what the compiler is guarding against - it seems no address can escape through a ctor (or any) call with no arguments. The same remark is shown for a ctor taking an argument by value, and is equally surprising.
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