| Issue |
53006
|
| Summary |
Missed optimizations in conditionally selected constants
|
| Labels |
|
| Assignees |
|
| Reporter |
uncleasm
|
Compared to gcc, clang produces slightly more verbose code for a sequence
```
int test1(int a) { return a ? -1 : 1; }
xor eax, eax
test edi, edi
sete al
add eax, eax
add eax, -1
ret
```
AFAIK, the optimal sequence is
```
neg edi
sbb eax, eax
or eax, 1
```
which could be encoded from
```
int test0(int a) { return a ? -1 : 0; }
neg edi
sbb eax, eax
ret
int test1b(int a) { return test0(a) | 1; }
```
As a side note, gcc can produce the expected output from `test1b` but not from `test1`.
![]()
_______________________________________________
llvm-bugs mailing list
[email protected]
https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-bugs
