Messages in this thread | | | From | Andy Lutomirski <> | Date | Wed, 20 May 2015 13:53:45 -0700 | Subject | Re: Avoiding unnecessary jump relocations in gas? |
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On Mon, May 18, 2015 at 1:34 PM, H. Peter Anvin <hpa@zytor.com> wrote: > On 05/18/2015 01:28 PM, H. Peter Anvin wrote: >> >> OK, that is probably too recent. The simplest answer I think is just to >> .balign 16 each vector. This is init space... some extra padding really >> doesn't matter. >> >> Patch attached (still in compile test). >> > > Corrected.
Egads. Now I understand what that code is. I don't like the balign, since this has nothing to do with alignment -- we're creating an array of functions.
Can't we make it explicit?
#define EARLY_IDT_HANDLER_STRIDE 9
...
.rept NUM_EXCEPTION_VECTORS . = early_idt_handlers + i * EARLY_IDT_HANDLER_STRIDE .if (EXCEPTION_ERRCODE_MASK >> i) & 1 ASM_NOP2 .else pushl $0 # Dummy error code, to make stack frame uniform .endif pushl $i # 20(%esp) Vector number jmp early_idt_handler i = i + 1 .endr
gas will error out if we try to move . backwards, so this should be safe.
--Andy
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