[webkit-changes] [WebKit/WebKit] c83189: Do not coalesce unspillable tmps

[Justin Michaud]

  Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: c83189eceb5f1ef951785251158eb26173c62563
      https://github.com/WebKit/WebKit/commit/c83189eceb5f1ef951785251158eb26173c62563
  Author: Justin Michaud <justin at justinmichaud.com>
  Date:   2023-02-28 (Tue, 28 Feb 2023)

  Changed paths:
    A JSTests/wasm/stress/simd-regalloc-stress-2-export-mutable-v128.wasm
    A JSTests/wasm/stress/simd-regalloc-stress-2-module0.wasm
    A JSTests/wasm/stress/simd-regalloc-stress-2-module1.wasm
    A JSTests/wasm/stress/simd-regalloc-stress-2.js
    M Source/JavaScriptCore/b3/air/AirAllocateRegistersByGraphColoring.cpp

  Log Message:
  -----------
  Do not coalesce unspillable tmps
https://bugs.webkit.org/show_bug.cgi?id=253006
rdar://105878987

Reviewed by Yusuke Suzuki.

We have been encountering multiple test cases where we make a graph
uncolourable by coalescing too aggressively. If a tmp is marked as unspillable
because its live range is too small, it will never be un-marked if it gets
coalesced. Let's try not coalescing these registers ever.

* Source/JavaScriptCore/b3/air/AirAllocateRegistersByGraphColoring.cpp:

Canonical link: https://commits.webkit.org/260969@main