[webkit-changes] [WebKit/WebKit] cb49ec: REGRESSION(255736 at main): [JSC] Fix FP register off...

[Loïc Yhuel]

  Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: cb49ec55ee3b6f49db87dc9818732b462279188a
      https://github.com/WebKit/WebKit/commit/cb49ec55ee3b6f49db87dc9818732b462279188a
  Author: Loïc Yhuel <loic.yhuel at softathome.com>
  Date:   2023-08-24 (Thu, 24 Aug 2023)

  Changed paths:
    M Source/JavaScriptCore/jit/ScratchRegisterAllocator.cpp

  Log Message:
  -----------
  REGRESSION(255736 at main): [JSC] Fix FP register offsets in ScratchRegisterAllocator
https://bugs.webkit.org/show_bug.cgi?id=259778

Reviewed by Justin Michaud.

On 32-bit targets, count was multiplied by 4 bytes in GPR loop, then by 8 bytes in FPR loop,
using more than the computed stackOffset (so overwriting previous saved values on the stack).
In restoreRegistersFromStackForCall, the ignored FP registers didn't increase the count, so
the following registers wouln't be restored from the correct offset.

We now use an offset instead of a count, and the ASSERT checks it on all targets.
The roundUpToMultipleOf call matches the code in byteSizeOfSetRegisters (aligning the FP
registers save location).

* Source/JavaScriptCore/jit/ScratchRegisterAllocator.cpp:
(JSC::ScratchRegisterAllocator::preserveRegistersToStackForCall):
(JSC::ScratchRegisterAllocator::restoreRegistersFromStackForCall):

Canonical link: https://commits.webkit.org/267228@main