Bug 115144 – Special thunks for math functions should work on ARMv7

• Status: RESOLVED
• Resolution: FIXED
• Component: JavaScriptCore

[Filip Pizlo]

Patch forthcoming.

[Filip Pizlo]

Created attachment 199572 [details]
the patch

[Filip Pizlo]

Landed in http://trac.webkit.org/changeset/149082

[Benjamin Poulain]

Comment on attachment 199572 [details]
the patch

View in context: https://bugs.webkit.org/attachment.cgi?id=199572&action=review

nice :)

> Source/JavaScriptCore/jit/ThunkGenerators.cpp:559
> +        "str lr, [sp, #0]\n" \

push {lr}?

> Source/JavaScriptCore/jit/ThunkGenerators.cpp:563
> +        "ldr lr, [sp, #0]\n" \

pop {lr}?

[Michael Saboff]

Comment on attachment 199572 [details]
the patch

View in context: https://bugs.webkit.org/attachment.cgi?id=199572&action=review

> Source/JavaScriptCore/jit/ThunkGenerators.cpp:558
> +        "sub sp, sp, #16\n" \

Why a frame size of 16 bytes?

[Filip Pizlo]

(In reply to comment #4)
> (From update of attachment 199572 [details])
> View in context: https://bugs.webkit.org/attachment.cgi?id=199572&action=review
> 
> > Source/JavaScriptCore/jit/ThunkGenerators.cpp:558
> > +        "sub sp, sp, #16\n" \
> 
> Why a frame size of 16 bytes?

Stack pointer has to be 16-byte aligned.

[Filip Pizlo]

(In reply to comment #3)
> (From update of attachment 199572 [details])
> View in context: https://bugs.webkit.org/attachment.cgi?id=199572&action=review
> 
> nice :)
> 
> > Source/JavaScriptCore/jit/ThunkGenerators.cpp:559
> > +        "str lr, [sp, #0]\n" \
> 
> push {lr}?
> 
> > Source/JavaScriptCore/jit/ThunkGenerators.cpp:563
> > +        "ldr lr, [sp, #0]\n" \
> 
> pop {lr}?

What do those magical push/pop thingies do? ;-)

[Michael Saboff]

(In reply to comment #6)
> (In reply to comment #3)
> > (From update of attachment 199572 [details] [details])
> > View in context: https://bugs.webkit.org/attachment.cgi?id=199572&action=review
> > 
> > nice :)
> > 
> > > Source/JavaScriptCore/jit/ThunkGenerators.cpp:559
> > > +        "str lr, [sp, #0]\n" \
> > 
> > push {lr}?
> > 
> > > Source/JavaScriptCore/jit/ThunkGenerators.cpp:563
> > > +        "ldr lr, [sp, #0]\n" \
> > 
> > pop {lr}?
> 
> What do those magical push/pop thingies do? ;-)

Push / pop multiple registers.  The registers in the curly braces will be pushed / popped.  Note these instructions also post dec/inc SP.  That was the reason for asking about 16 byte aligned.  I only find the requirements for being 8 byte (double) aligned in any of the runtime architecture documents.

Is we use push/pop {lr} then the 16 will need to be change to 12.