)]}'
{
  "commit": "1c21d5cb9b8e48ab928919a6f358eba8ffd3b49c",
  "tree": "35d713fa74a3900c43a5ff0b607ce504c0fd265c",
  "parents": [
    "6931bad36c0ddae441d115814022fd5d3cbc554b"
  ],
  "author": {
    "name": "David Green",
    "email": "david.green@arm.com",
    "time": "Mon Sep 15 07:32:00 2025 +0100"
  },
  "committer": {
    "name": "GitHub",
    "email": "noreply@github.com",
    "time": "Mon Sep 15 07:32:00 2025 +0100"
  },
  "message": "[GlobalISel] Remove GI known bits cache (#157352)\n\nThere is a cache on the known-bit computed by global-isel. It only works\ninside a single query to computeKnownBits, which limits its usefulness,\nand according to the tests can sometimes limit the effectiveness of\nknown-bits queries. (Although some AMD tests look longer). Keeping the\ncache valid and clearing it at the correct times can also require being\ncareful about the functions called inside known-bits queries.\n\nI measured compile-time of removing it and came up with:\n```\n7zip      2.06405E+11     2.06436E+11     0.015018992\nBullet    1.01298E+11     1.01186E+11     -0.110236169\nClamAV    57942466667     57848066667     -0.16292023\nSPASS     45444466667     45402966667     -0.091320249\nconsumer  35432466667     35381233333     -0.144594317\nkimwitu++ 40858833333     40927933333     0.169118877\nlencod    70022366667     69950633333     -0.102443457\nmafft     38439900000     38413233333     -0.069372362\nsqlite3   35822266667     35770033333     -0.145812474\ntramp3d   82083133333     82045600000     -0.045726\nAverage                                   -0.068828739\n```\nThe last column is % difference between with / without the cache. So in\ntotal it seems to be costing slightly more to keep the current\nknown-bits cache than if it was removed. (Measured in instruction count,\nsimilar to llvm-compile-time-tracker).\n\nThe hit rate wasn\u0027t terrible - higher than I expected. In the\nllvm-test-suite+external projects it was hit 4791030 times out of\n91107008 queries, slightly more than 5%.\n\nNote that as globalisel increases in complexity, more known bits calls\nmight be made and the numbers might shift. If that is the case it might\nbe better to have a cache that works across calls, providing it doesn\u0027t\nmake effectiveness worse.",
  "tree_diff": [
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