https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109414
Bug ID: 109414
Summary: RISC-V: unnecessary sext.w in rv64
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: sinan.lin at linux dot alibaba.com
Target Milestone: ---
I recently encountered several suboptimal cases with unnecessary sext.w in
not/and/xor/or in rv64i.
e.g.
```
int xor_2 (int x, int n) {
return (x + 1) ^ n;
}
int not_2 (int x, int n) {
return ~(x + n);
}
```
gcc:
```
xor_2:
addiw a0,a0,1
xor a0,a1,a0
sext.w a0,a0
ret
not_2:
addw a0,a0,a1
not a0,a0
sext.w a0,a0
ret
```
clang:
```
xor_2:
addw a0, a0, a1
xor a0, a0, a1
ret
not_2:
addw a0, a0, a1
not a0, a0
ret
```
This case looks a bit similar to
https://gcc.gnu.org/bugzilla//show_bug.cgi?id=106585 , where the X iterator is
used in insn pattern.
