llvm

d27cbc5f - [DSE] Introduce `eliminateRedundantStoresViaDominatingConditions` (#181709)

[DSE] Introduce `eliminateRedundantStoresViaDominatingConditions` (#181709) While optimizing tautological assignments, if there exists a dominating condition that implies the value being stored in a pointer, and such a condition appears in a node that dominates the store via equality edge, then subsequent stores may be redundant, if no write occurs in between. This is achieved via a DFS top-down walk of the dom-tree, collecting dominating conditions and propagating them to each subtree, popping them upon backtracking. This also generalizes `dominatingConditionImpliesValue` transform, which was previously taking into account only the immediate dominator. Compile-time: https://llvm-compile-time-tracker.com/compare.php?from=f8906704104e446a7482aeca32d058b91867e05c&to=24c5d61f1e28acbe6a59ea4e9a5da0ffcee3bf1a&stat=instructions:u. Compile-time w/ limit on recursion: https://llvm-compile-time-tracker.com/compare.php?from=24c5d61f1e28acbe6a59ea4e9a5da0ffcee3bf1a&to=9889567fe8a0515ab895b22003c93fabfd9ac4e5&stat=instructions:u. Seems to alleviate the small regression in stage2-O3, but seemingly adds one in stage2-O0-g.