[PATCH] D122539: [SelectionDAG][DAGCombiner] Reuse exist node by reassociate

Wed Jun 22 19:52:13 PDT 2022

kripken added subscribers: tlively, kripken.
kripken added a comment.

This somehow caused a regression in the wasm targets, which I bisected to here. Certain files when compiled with `-O1` appear to hang for a very long time (maybe forever). This happened on the Bullet physics engine codebase in the Emscripten test suite, but affects all wasm targets (wasm32-unknown-unknown, -wasi, and -emscripten).

This doesn't affect other targets, which I guess is why it wasn't noticed before it reached our CI. So maybe this uncovered an existing wasm bug.

@tlively is reducing this atm. Posting the original testcase here for future reference.F23552133: bug.cpp <https://reviews.llvm.org/F23552133>
STR: `clang++ -target wasm32-unknown-unknown  -O1 -c bug.cpp`. That should take less than a second normally, but from this change landing it hangs a very long time (I measured at least 10 seconds during bisection).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D122539/new/

https://reviews.llvm.org/D122539