https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121559
Bug ID: 121559
Summary: ccp does not do copy prop when there is bit info
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Keywords: compile-time-hog
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: pinskia at gcc dot gnu.org
Target Milestone: ---
Take:
```
int a[1024];
int f(int n)
{
int *b = &a[n];
int *c = b;
int *d = c;
return *d;
}
int f1(int n)
{
int b = a[n];
b&=0x2;
int c = b;
int d = c;
return d;
}
```
In both cases ccp does not do the copy prop as the bit info takes over:
For f we have:
```
Visiting statement:
c_3 = b_2;
which is likely CONSTANT
Lattice value changed to CONSTANT 0x0 (0xfffffffffffffffc). Adding SSA edges
to worklist.
marking stmt to be not simulated again
```
For f1 we have:
```
Visiting statement:
c_5 = b_4;
which is likely CONSTANT
Lattice value changed to CONSTANT 0x0 (0x2). Adding SSA edges to worklist.
marking stmt to be not simulated again
```
if we comment out the `b&=2;` statement in f1 we get:
```
Visiting statement:
c_4 = b_3;
which is likely CONSTANT
Lattice value changed to CONSTANT b_3. Adding SSA edges to worklist.
marking stmt to be not simulated again
```
And then b_3 is prop'ed the rest of the way.
I noticed this while looking PR 91901 and trying to see why something is
missing now compared to when I did backwards walk rather than a forward walk.
