[SimplifyCFG] Delete the unnecessary range check for small mask operation #65835
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RKSimon
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Sep 9, 2023
nikic
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Sep 15, 2023
nikic
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Sep 18, 2023
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ping ? |
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sorry for ping |
zmodem
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zmodem
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This basically looks good to me. Just some minor comments.
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nikic
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…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
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It looks like this causes assertion failures on some build bots, for example https://lab.llvm.org/buildbot/#/builders/176/builds/6529:
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ok, I revert it soon, sorry |
This was referenced Oct 26, 2023
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…k operation (#70542) Fix the compile crash when the default result has no result for llvm/llvm-project#65835 Fixes llvm/llvm-project#65120 Reviewed By: zmodem, nikic
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…mall mask operation (#70542)" This caused llvm/llvm-project#71329 > Fix the compile crash when the default result has no result for > llvm/llvm-project#65835 > > Fixes llvm/llvm-project#65120 > Reviewed By: zmodem, nikic This reverts commit 7c4180a.
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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 its next pow2 value. Consider: https://godbolt.org/z/3qnE45YWj
Fixes #65120