Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: 00eff83b64f0a5eee31b293a86656c8e61b96a14
https://github.com/WebKit/WebKit/commit/00eff83b64f0a5eee31b293a86656c8e61b96a14
Author: Dan Hecht <[email protected]>
Date: 2025-09-15 (Mon, 15 Sep 2025)
Changed paths:
M Source/JavaScriptCore/offlineasm/x86.rb
Log Message:
-----------
[JSC] Fix x86 offlineasm lowering of shift
https://bugs.webkit.org/show_bug.cgi?id=298882
rdar://160625576
Reviewed by Yusuke Suzuki.
On x86, when the shift-by is in a register, the register must be %cl.
The shift lowering code handled this with the following transformation:
When %rA != %ecx:
shift %rA, %rB
=>
xchg %rA, %rcx
shift %cl, %rB
xchg %rA, %rcx
But this is incorrect when %rB is %rcx since the shift value/destination
lives in %rA for the duration of the shift instruction.
So, when %rB is %rcx, we should use %rA as the shift value/dest
operand of the shift instruction.
This bug appeared in IPInt _simd_*_bitmask but apparently does not
occur in any other offlineasm code.
Manually tested this by inspecting the resulting bitmask code and also
verifying that this fixes the IPInt SIMD bitmask
instructions on x86 using simd-instructions-bitwise.js.
Canonical link: https://commits.webkit.org/299994@main
To unsubscribe from these emails, change your notification settings at
https://github.com/WebKit/WebKit/settings/notifications
_______________________________________________
webkit-changes mailing list
[email protected]
https://lists.webkit.org/mailman/listinfo/webkit-changes
