| Issue |
77158
|
| Summary |
Convert clamp into fmaxnum/fminnum pairs.
|
| Labels |
|
| Assignees |
|
| Reporter |
hiraditya
|
test case
```cpp
float clamp(float a)
{
const float b = 255.0;
const float c = 0.0;
if(b < a)
return b;
if(a < c)
return c;
return a;
}
```
clang compiles to
```asm
clamp: // @clamp
movi d1, #0000000000000000
fcmp s0, #0.0
mov w8, #1132396544 // =0x437f0000
fmov s2, w8
fcsel s1, s1, s0, mi
fcmp s0, s2
fcsel s0, s2, s1, gt
ret
```
but we could have something like
```asm
clamp: // @clamp
// BB#0: // %entry
adrp x8, .LCPI0_0
ldr s1, [x8, :lo12:.LCPI0_0]
fmov s2, wzr
fmaxnm s0, s0, s2
fminnm s0, s0, s1
ret
```
@sebpop had a patch a while back https://reviews.llvm.org/D24033 that would do this. Since phabricator is deprecated i'll move the patch here.
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