[webkit-dev] want to port JIT to MIPS - stack/code segment alignment

x yz lastguy at yahoo.com
Fri Feb 27 09:34:19 PST 2009 

Zoltan,
you are right, thanks a lot!
joe


--- On Fri, 2/27/09, Zoltan Herczeg <zherczeg at inf.u-szeged.hu> wrote:

> From: Zoltan Herczeg <zherczeg at inf.u-szeged.hu>
> Subject: Re: [webkit-dev] want to port JIT to MIPS - stack/code segment alignment
> To: webkit-dev at lists.webkit.org
> Date: Friday, February 27, 2009, 3:41 PM
> Hi,
> 
> in ARM, we have a rule set called EABI (Embedded
> Application Binary
> Interface). It says the stack must always be word aligned,
> and must be 2
> words (8 bytes) aligned if you call other functions. The
> WebKit
> interpreter callbacks returns either a single pointer
> (sometimes an int
> contains a boolean value) or double pointers. These return
> values can be
> passed through registers, no need to pre-allocate stack
> space for them.
> The functions generated by g++ are also EABI compilant, so
> we don't need
> worry about the stack at all.
> 
> I think AssemblerBuffer is only temporary hold the
> generated machine
> instructions. When the compilation phase is done, you need
> to call
> AssemblerBuffer::executableCopy, which allocates a new
> executable memory
> space and that space is aligned by ExecutableAllocator.
> 
> Cheers,
> Zoltan
> 
> > Zoltan,
> > thanks a lot! yeah the issue is just JIT related.
> > Do I need to take care of stack in JIT code, say
> before emit asm call I
> > align the stack? I guess no need because Mips always
> aligned to 32bits,
> > and the only double functions in webkit return result
> in registers not
> > memory.
> > For AssemblerBuffer.h I think it is different because
> the initial 256bytes
> > buffer may be not aligned to 32bit. I'll add
> __attribute__ ((aligned (4)))
> > or 8.
> > rgds
> > joe
> >
> >
> > --- On Fri, 2/27/09, Zoltan Herczeg
> <zherczeg at inf.u-szeged.hu> wrote:
> >
> >> From: Zoltan Herczeg
> <zherczeg at inf.u-szeged.hu>
> >> Subject: Re: [webkit-dev] want to port JIT to MIPS
> - stack/code segment
> >> alignment
> >> To: webkit-dev at lists.webkit.org
> >> Date: Friday, February 27, 2009, 6:16 AM
> >> Hi,
> >>
> >> I am not sure I understand your questions. The
> code blocks
> >> are allocated
> >> by mmap() or VirtualAlloc(), thus they are aligned
> to 4K.
> >> Smaller chunks
> >> are aligned by roundUpAllocationSize() function.
> Now the
> >> alignemt is
> >> sizeof(void*) in both x86 and ARM. See
> >> ExecutableAllocator.h
> >>
> >> The current jit implementations don't store
> temporary
> >> variables on the
> >> stack, they allocate a fixed size buffer after the
> entry,
> >> and only free
> >> that when you leave the jit. This approach is much
> easier
> >> than keep
> >> tracking of the stack.
> >>
> >> Cheers,
> >> Zoltan
> >>
> >> > gcc handles it well for X86. now on Mips I
> need to do
> >> followings right?
> >> > 1. make sure (re)allocated code buffer
> aligned to
> >> 64bits and gcc malloc()
> >> > only guarantee 32bits
> >> > 2. before any call instruction in JIT code,
> make sure
> >> stack is aligned to
> >> > 64bit also.
> >> > PPC no JIT thus no problem right?
> >> > rgds
> >> > joe
> >> >
> >> >
> >> > --- On Sun, 2/22/09, x yz
> <lastguy at yahoo.com>
> >> wrote:
> >> >
> >> >> From: x yz <lastguy at yahoo.com>
> >> >> Subject: Re: [webkit-dev] want to port
> JIT to MIPS
> >> >> To: "WebKit Development"
> >> <webkit-dev at lists.webkit.org>, "Gavin
> >> >> Barraclough"
> <barraclough at apple.com>
> >> >> Date: Sunday, February 22, 2009, 4:34 PM
> >> >> Thanks a lot otherwise I have
> misunderstanding.
> >> Yes I'll
> >> >> do wrec first. I just want to clean up
> possible
> >> blocking
> >> >> issues.
> >> >>
> >> >> I see wrec uses regparm(3) and jit always
> use
> >> fastcall for
> >> >> X86?
> >> >> In JIT.cpp ctiTrampoline put CallFrame in
> edi, but
> >> how
> >> >> about other arguments - where are they be
> >> fetched/poped from
> >> >> stack?
> >> >>
> >> >> when deal with caller/callee saved regs,
> gcc MIPS
> >> just
> >> >> preserves them when necesasary. The
> problem is
> >> after JIT
> >> >> used gcc may not have enough knowledge on
> >> >> "necessary", do we have a way
> to force
> >> gcc always
> >> >> preserve
> >> >> them?
> >> >>
> >> >> how to identify a patch
> >> (patchimm/patchptr/patchaddr)
> >> >> relates to a data field in an instruction
> or
> >> relates to an
> >> >> element in a data array? In Mips the
> former means
> >> the 32bit
> >> >> needs to be separated into two 16bits and
> patched
> >> into two
> >> >> instructions. But if a 32bit is a pointer
> in a
> >> pointer
> >> >> array, we can save it directly.
> >> >>
> >> >> rgds
> >> >> joe
> >> >>
> >> >>
> >> >> --- On Fri, 2/20/09, Gavin Barraclough
> >> >> <barraclough at apple.com> wrote:
> >> >>
> >> >> > From: Gavin Barraclough
> >> <barraclough at apple.com>
> >> >> > Subject: Re: [webkit-dev] want to
> port JIT to
> >> MIPS
> >> >> > To: "WebKit Development"
> >> >> <webkit-dev at lists.webkit.org>
> >> >> > Date: Friday, February 20, 2009,
> 2:01 PM
> >> >> > On Feb 19, 2009, at 8:27 PM, x yz
> wrote:
> >> >> >
> >> >> > > I'd appreaciate your help
> to clarify
> >> the
> >> >> problem I
> >> >> > faced:
> >> >> > >
> >> >> > > 1.In JIT.cpp I roughly
> understand
> >> ctiTrampoline()
> >> >> > except for sp-0x1C, I guess the 1C
> includes 6
> >> argument
> >> >> yet
> >> >> > the 7th or 1st may be the hidden C++
> pointer?
> >> And the
> >> >> > reserved 1C stack space seems not
> used? why
> >> esi is
> >> >> forced to
> >> >> > be 512 rather than use input
> argument?
> >> >> >
> >> >> > The JIT allocates a fixed frame on
> the stack
> >> which is
> >> >> used
> >> >> > to pass arguments into stub
> functions.  The
> >> 0x1C
> >> >> contains a
> >> >> > spare word or two to maintain stack
> >> alignment.  %esi
> >> >> is used
> >> >> > in the timeout check mechanism.
> >> >> >
> >> >> > > 2.How to understand the stack
> balance in
> >> >> > ctiVMThrowTrampoline()? why after
> calling we
> >> still add
> >> >> 1C
> >> >> > w/o sub 1C before calling? where
> comes
> >> >> >
> _ZN3JSC11Interpreter12cti_vm_throwEPPv and
> >> how do I
> >> >> know
> >> >> > which name for Mips? does this one
> relates to
> >> variable
> >> >> > argument function call?
> >> >> >
> >> >> > ctiVMThrowTrampoline is never called
> as a
> >> function (it
> >> >> is
> >> >> > declared as a function only to
> provide a
> >> symbol that
> >> >> can be
> >> >> > manipulated from C code).
> >> ctiVMThrowTrampoline is
> >> >> used in
> >> >> > returning back from JIT generated
> code, in
> >> the case of
> >> >> an
> >> >> > exception.
> >> >> >
> >> >> > > 3.I know how to handle jump in
> Mips, but
> >> not sure
> >> >> > how/when to handle
> >> patchAddress/patchImm/patchPointer
> >> >> > because I'm not sure the
> instructions
> >> related. I
> >> >> guess
> >> >> > all patches are for last 32bit IMM
> field of
> >> >> instructions.
> >> >> > > Mips can't load 32bit in
> one
> >> instruction,
> >> >> thus I
> >> >> > need to know the instruction before
> I can
> >> patch/add in
> >> >> the
> >> >> > 32bit data.
> >> >> > >
> >> >> > > 4.I'm kind of want no asm
> code
> >> outside
> >> >> > <assembler> folder, any plan
> for that?
> >> >> >
> >> >> > No.  The assembler is intended to be
> >> independent of
> >> >> > JavaScript types - it's just an
> >> assembler.  The
> >> >> asm
> >> >> > trampolines are specific to the JIT.
>  It is
> >> currently
> >> >> the
> >> >> > intention that architecture specific
> parts of
> >> the JIT
> >> >> > implementation will remain in the
> jit folder.
> >> >> >
> >> >> > I'd suggest that in attempting
> to port
> >> the jit,
> >> >> WREC
> >> >> > would be a good place to start.
> >> >> >
> >> >> > cheers,
> >> >> > G.
> >> >> >
> >> >> > >
> >> >> > > rgds
> >> >> > > joe
> >> >> > >
> >> >> > > --- On Mon, 2/16/09, x yz
> >> >> <lastguy at yahoo.com>
> >> >> > wrote:
> >> >> > >
> >> >> > >> From: x yz
> <lastguy at yahoo.com>
> >> >> > >> Subject: Re: [webkit-dev]
> want to
> >> port JIT to
> >> >> MIPS
> >> >> > - when WREC/JIT enabled?
> >> >> > >> To: "Gavin
> Barraclough"
> >> >> > <barraclough at apple.com>
> >> >> > >> Cc: "WebKit
> Development"
> >> >> > <webkit-dev at lists.webkit.org>
> >> >> > >> Date: Monday, February 16,
> 2009,
> >> 5:25 AM
> >> >> > >> Hi,
> >> >> > >> from paltform.h it is
> enabled only
> >> on X86
> >> >> MAC/WIN;
> >> >> > from
> >> >> > >> javaScriptCore.pri it is
> also
> >> enabled for
> >> >> > (QT_ARCH,i386).
> >> >> > >> But, from config.log I see
> them are
> >> enabled!
> >> >> > >>
> >> >> > >> how can I run WREC/JIT test
> so I can
> >> trace in
> >> >> X86
> >> >> > asm coce
> >> >> > >> generated?
> >> >> > >> thanks a lot.
> >> >> > >> joe
> >> >> > >>
> >> >> > >>
> >> >> > >>
> >> >> > >> --- On Sat, 2/7/09, Gavin
> >> Barraclough
> >> >> > >>
> <barraclough at apple.com> wrote:
> >> >> > >>
> >> >> > >>> From: Gavin Barraclough
> >> >> > <barraclough at apple.com>
> >> >> > >>> Subject: Re:
> [webkit-dev] want
> >> to port
> >> >> JIT to
> >> >> > MIPS -
> >> >> > >> using X86::ecx as base
> >> >> > >>> To: lastguy at yahoo.com
> >> >> > >>> Cc: "WebKit
> >> Development"
> >> >> > >>
> <webkit-dev at lists.webkit.org>
> >> >> > >>> Date: Saturday,
> February 7,
> >> 2009, 7:08 AM
> >> >> > >>> On Feb 6, 2009, at 2:52
> PM, x yz
> >> wrote:
> >> >> > >>>
> >> >> > >>>> 1.what's the
> meaning of
> >> >> > ALTERNATE_JSIMMEDIATE
> >> >> > >> and
> >> >> > >>> slow case?
> >> >> > >>>
> >> >> > >>> On x86-64 we use a
> different
> >> >> implementation of
> >> >> > the
> >> >> > >> class
> >> >> > >>> JSImmediate.  See
> JSImmediate.h.
> >> >> > >>> Re 'slow case',
> in the
> >> JIT code
> >> >> > generation is
> >> >> > >>> performed as two passes
> over the
> >> bytecode
> >> >> –
> >> >> > see
> >> >> > >>>
> JIT::privateCompileMainPass and
> >> >> > >>>
> JIT::privateCompileSlowCases.
> >> >> > >>>
> >> >> > >>>> 2.how come the
> following
> >> code can use
> >> >> ECX
> >> >> > as base
> >> >> > >>> register?
> >> >> > >>>>
> load32(Address(X86::ecx,
> >> >> > FIELD_OFFSET(Structure,
> >> >> > >>> m_typeInfo.m_flags)),
> X86::ecx);
> >> >> > >>>> if the X86::ecx
> just means
> >> its value
> >> >> 1 in
> >> >> > ModR/M,
> >> >> > >> does
> >> >> > >>> it means [BX+DI]?
> >> >> > >>>
> >> >> > >>> I think you're
> looking at
> >> the old
> >> >> 16-bit
> >> >> > >> addressing
> >> >> > >>> mode tables; 32/64-bit
> x86 can
> >> happily
> >> >> encode
> >> >> > ecx as a
> >> >> > >> base
> >> >> > >>> register.  If
> you're looking
> >> at the
> >> >> Intel
> >> >> > IA-32
> >> >> > >> manual
> >> >> > >>> volume 2, see table 2-2
> on the
> >> next page.
> >> >> > >>>
> >> >> > >>>> 3. can anybody help
> me on my
> >> previous
> >> >> > questions?
> >> >> > >> does
> >> >> > >>> JIT support floating
> point?
> >> >> > >>>
> >> >> > >>> Yes, some.  See
> >> JITArithmetic.cpp.
> >> >> > >>>
> >> >> > >>> cheers,
> >> >> > >>> G.
> >> >> > >>
> >> >> > >>
> >> >> > >>
> >> >> > >>
> >> >>
> _______________________________________________
> >> >> > >> webkit-dev mailing list
> >> >> > >> webkit-dev at lists.webkit.org
> >> >> > >>
> >> >> >
> >> >>
> >>
> http://lists.webkit.org/mailman/listinfo.cgi/webkit-dev
> >> >> > >
> >> >> > >
> >> >> > >
> >> >> >
> >> >> >
> >> _______________________________________________
> >> >> > webkit-dev mailing list
> >> >> > webkit-dev at lists.webkit.org
> >> >> >
> >> >>
> >>
> http://lists.webkit.org/mailman/listinfo.cgi/webkit-dev
> >> >>
> >> >>
> >> >>
> >> >>
> _______________________________________________
> >> >> webkit-dev mailing list
> >> >> webkit-dev at lists.webkit.org
> >> >>
> >>
> http://lists.webkit.org/mailman/listinfo.cgi/webkit-dev
> >> >
> >> >
> >> >
> >> >
> _______________________________________________
> >> > webkit-dev mailing list
> >> > webkit-dev at lists.webkit.org
> >> >
> >>
> http://lists.webkit.org/mailman/listinfo.cgi/webkit-dev
> >> >
> >>
> >> _______________________________________________
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> >>
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> >
> >
> >
> >
> 
> 
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