| Issue |
76460
|
| Summary |
[AArch64] Suboptimal comparison against certain immediates
|
| Labels |
backend:AArch64,
missed-optimization
|
| Assignees |
|
| Reporter |
Kmeakin
|
LLVM canonicalizes non-strict comparisons against constants to strict comparisons (eg `ule x, c` => `ult x, c+1`. This results in less optimal AArch64 assembly if `c` can be encoded in a single `mov` instruction but `c+1` or `c-1` takes a `mov+movk` pair to encode:
[godbolt](https://godbolt.org/z/KxoWeYK3d)
```c
#include <stdbool.h>
#include <stdint.h>
#define u32 uint32_t
#define s32 int32_t
bool ule_11111111(u32 x) { return x <= 0x11111111; }
bool ule_22222222(u32 x) { return x <= 0x22222222; }
bool ule_33333333(u32 x) { return x <= 0x33333333; }
bool ule_44444444(u32 x) { return x <= 0x44444444; }
bool ule_55555555(u32 x) { return x <= 0x55555555; }
bool ule_66666666(u32 x) { return x <= 0x66666666; }
bool ule_77777777(u32 x) { return x <= 0x77777777; }
bool ule_88888888(u32 x) { return x <= 0x88888888; }
bool ule_99999999(u32 x) { return x <= 0x99999999; }
bool uge_11111111(u32 x) { return x >= 0x11111111; }
bool uge_22222222(u32 x) { return x >= 0x22222222; }
bool uge_33333333(u32 x) { return x >= 0x33333333; }
bool uge_44444444(u32 x) { return x >= 0x44444444; }
bool uge_55555555(u32 x) { return x >= 0x55555555; }
bool uge_66666666(u32 x) { return x >= 0x66666666; }
bool uge_77777777(u32 x) { return x >= 0x77777777; }
bool uge_88888888(u32 x) { return x >= 0x88888888; }
bool uge_99999999(u32 x) { return x >= 0x99999999; }
bool sle_11111111(s32 x) { return x <= 0x11111111; }
bool sle_22222222(s32 x) { return x <= 0x22222222; }
bool sle_33333333(s32 x) { return x <= 0x33333333; }
bool sle_44444444(s32 x) { return x <= 0x44444444; }
bool sle_55555555(s32 x) { return x <= 0x55555555; }
bool sle_66666666(s32 x) { return x <= 0x66666666; }
bool sle_77777777(s32 x) { return x <= 0x77777777; }
bool sle_88888888(s32 x) { return x <= 0x88888888; }
bool sle_99999999(s32 x) { return x <= 0x99999999; }
bool sge_11111111(s32 x) { return x >= 0x11111111; }
bool sge_22222222(s32 x) { return x >= 0x22222222; }
bool sge_33333333(s32 x) { return x >= 0x33333333; }
bool sge_44444444(s32 x) { return x >= 0x44444444; }
bool sge_55555555(s32 x) { return x >= 0x55555555; }
bool sge_66666666(s32 x) { return x >= 0x66666666; }
bool sge_77777777(s32 x) { return x >= 0x77777777; }
bool sge_88888888(s32 x) { return x >= 0x88888888; }
bool sge_99999999(s32 x) { return x >= 0x99999999; }
```
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