JIT: Run profile repair after frontend phases #111915
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With this change, I'm seeing LSRA introduce more branches from critical edge splitting, which I wasn't expecting. I'll dig into this |
Profile synthesis currently isn't all that diligent in retaining the method's entry weight; if we are retaining likelihoods, it will use |
amanasifkhalid
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Jan 31, 2025
Part of #107749. Prerequisite to #111915. Regardless of the profile synthesis option used, we ought to maintain the method's entry weight, which is computed by summing all non-flow weight into the entry block. Ideally, we'd use fgCalledCount here, but this isn't computed until after morph, and we need to tolerate the existence of multiple entry blocks for methods with OSR pre-morph.
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Part of #107749. Introduce a repair phase that runs profile synthesis if the profile was marked inconsistent at some point, and call it at the end of the JIT frontend. LSRA and block layout are likely to benefit from profile consistency, and this is late enough in the JIT that the sources of diffs should be relatively obvious. We can save a bit of TP by precomputing a loop-aware DFS for profile repair to use, and then letting LSRA reuse this traversal to avoid redundant computations -- I'll save this for a follow-up PR.