[Webkit-unassigned] [Bug 231159] [JSC][ARMv7] Improve instruction selection in MacroAssembler

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=231159

--- Comment #1 from Guillaume Emont <guijemont at igalia.com> ---
(In reply to Geza Lore from comment #0)
> I have spotted some improvement opportunities in MacroAssemblerARMv7 for
> better instruction selection for some macros. What shows up most often in
> the disassembly ('ip' is 'r12'):
> 
> mvn ip, #8
> and r0, r0, ip
> 
> This is an 8-byte sequence which is equivalent to the following 2-byte
> instruction:
> 
> bic r0, #8
> 
> 
> similarly:
> 
> mvn ip, #7
> add r0, r0, ip
> 
> should be:
> 
> sub r0, r0, #8
> 
> A review of the disassembly would likely yield more examples of similar
> sequences where an immediate can be encoded cheaper using an alternative
> instruction.

Would any of this change the minimal version of the instruction set that we support? (not that I have it very clear in my mind what is our minimum currently).

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