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[SimplifyCFG] Delete the unnecessary range check for small mask operation #65835

Merged
merged 2 commits into from
Oct 26, 2023
Merged

[SimplifyCFG] Delete the unnecessary range check for small mask operation #65835

merged 2 commits into from
Oct 26, 2023

Commits on Oct 26, 2023

  1. [SimplifyCFG] Precommit tests for PR65835

    @vfdff
    vfdff committed Oct 26, 2023
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  2. [SimplifyCFG] Delete the unnecessary range check for small mask opera… 

    …tion

When the small mask value little than 64, we can eliminate the checking
for upper limit of the range by enlarge the lookup table size to the maximum
index value. (Then the final table size grows to the next pow2 value)
```
bool f(unsigned x) {
    switch (x % 8) {
        case 0: return 1;
        case 1: return 0;
        case 2: return 0;
        case 3: return 1;
        case 4: return 1;
        case 5: return 0;
        case 6: return 1;

        // This would remove the range check: case 7: return 0;
    }
    return 0;
}
```
Use WouldFitInRegister instead of fitsInLegalInteger to support
more result type beside bool.

Fixes llvm#65120
Reviewed By: zmodem, nikic, RKSimon
    @vfdff
    vfdff committed Oct 26, 2023
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