| Issue |
117332
|
| Summary |
Possible missed optimization when calling memcpy or memmove in a loop
|
| Labels |
missed-optimization
|
| Assignees |
|
| Reporter |
ldionne
|
I noticed that the following code did not optimize to a single memcpy, unlike I would expect:
```c++
template <class T>
void relocate_1(T *first, T *last, T *dest) {
for ( ; first != last; ++first, ++dest) {
std::memcpy((void*)dest, first, sizeof(T));
}
}
```
I would expect this to be equivalent to roughly:
```c++
template <class T>
void relocate_2(T *first, T *last, T *dest) {
auto n = last - first;
std::memcpy((void*)dest, first, n);
}
```
Is this a problem with e.g. the lack of knowledge that the `[first, last)` range is all valid? Note that both GCC and Clang fail to perform this optimization.
Godbolt: https://godbolt.org/z/zzdhcKPh4
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