[KeyInstr] Enable Key Instructions support in LLVM #144324
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Set LLVM_EXPERIMENTAL_KEY_INSTRUCTIONS=ON by default. This enables support for Key Instructions in LLVM by default, it does not enable the feature by default. This does have an affect on compile time, which looks to have mostly been "paid for" (if that argument stands) by my PR llvm#143399. From compile-time-tracker: 1. this patch 2. PR llvm#143399 3. base ``` Commit stage1-O3 stage1-ReleaseThinLTO stage1-ReleaseLTO-g stage1-O0-g stage1-aarch64-O3 stage1-aarch64-O0-g stage2-O3 stage2-O0-g stage2-clang 1. 61213M (+0.02%) 77397M (+0.01%) 89413M (+0.08%) 18865M (+0.13%) 68670M (+0.01%) 23100M (+0.12%) 53409M (+0.00%) 16550M (+0.20%) 34060797M (+0.02%) 2. 61201M (-0.01%) 77389M (+0.00%) 89343M (-0.06%) 18841M (-0.16%) 68666M (+0.00%) 23073M (-0.16%) 53408M (-0.01%) 16518M (+0.01%) 34054978M (+0.00%) 3. 61207M (+0.00%) 77386M (-0.01%) 89396M (-0.02%) 18871M (-0.02%) 68665M (+0.01%) 23109M (+0.02%) 53415M (-0.02%) 16516M (-0.00%) 34054300M (-0.00%) ``` Compare 2-1: https://llvm-compile-time-tracker.com/compare.php?from=89490929c34f45842df1588cf78d836f51c2c222&to=7d00712c28bbcc8a8e00d672f2f7c109fb5823c9&stat=instructions%3Au Compare 3-2: https://llvm-compile-time-tracker.com/compare.php?from=2b7b0e178259a910355631d7d648c89052000872&to=89490929c34f45842df1588cf78d836f51c2c222&stat=instructions%3Au
jmorse
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Jul 8, 2025
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See Orlandos discourse post -- I believe we've rustled up sufficient memory-savings to justify landing this, overall users will see reduced max-rss for debug-info builds between LLVM20 and LLVM21.
Will land this shortly, after a final local-test passes. This is an easy revert if it causes any trouble.
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Set LLVM_EXPERIMENTAL_KEY_INSTRUCTIONS=ON by default. This enables support for Key Instructions in LLVM by default, it does not enable the feature by default.
This does have an affect on compile time, which looks to have mostly been "paid for" (if that argument stands) by my PR #143399.
From compile-time-tracker:
Compare 2-1: https://llvm-compile-time-tracker.com/compare.php?from=89490929c34f45842df1588cf78d836f51c2c222&to=7d00712c28bbcc8a8e00d672f2f7c109fb5823c9&stat=instructions%3Au
Compare 3-2: https://llvm-compile-time-tracker.com/compare.php?from=2b7b0e178259a910355631d7d648c89052000872&to=89490929c34f45842df1588cf78d836f51c2c222&stat=instructions%3Au