| Issue |
160441
|
| Summary |
[Clang] const objects can be assumed to be immutable
|
| Labels |
clang
|
| Assignees |
|
| Reporter |
xcpky
|
According to both C and C++ standards, object defined with const is not allowed to be modified in any way(UB), thus can be assumed to be immutable.
However, currently clang/llvm doens't utilize it for optimization unless the initializer of the object is constant _expression_:
```c
// https://godbolt.org/z/6qe8vEK15
void f(const int *p);
int t1()
{
const int x = 5;
f(&x);
return x;
}
int t2(int y)
{
const int x = y;
f(&x);
return x;
}
```
For t1, clang optimizes the load away.
For t2, clang doesn't.
There are a similar GCC bug report: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80794, from which I copy the title.
#59694 may be related.
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