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Re: Scheduling x86 dispatch windows
On Thu, Jun 10, 2010 at 09:48:24PM -0500, Quentin Neill wrote:
> > On the other hand, I'm not going to argue that it's a lot of work.
Missing "not" !
> When you say "put assertions in the assembler output" I understood it
> to mean "in the assembly source code output by the compiler", not "the
> output produced by the assembler".
Yes.
> Does this qualify as a form of what you are suggesting? Because this
> is exactly what is being proposed:
>
> .balign 8 # start window
> insn op, op # 67 67 XX YY ZZ - padded with 2 prefixes to make 8
> insn2 op, op # AA BB CC
> .padalign 8 # window boundary
> insn4 op
> . . .
No, this is quite different. These are directives that tell the
assembler to make changes. I'm talking about assertions, not
directives. Something like this:
mov r0, r1 @ [length 2]
add ip, lr, ip @ [length 4]
mov r0, r1 @ [length 4] <-- assembler error 'insn has length 2'
GCC can output length information, but it is never exact, and it is
not in a form recognized by the assembler.
On x86, I have no idea how this would work.
--
Daniel Jacobowitz
CodeSourcery