On Thu 31 Mar 2016 at 21:24:04 -0700, Jake Hamby wrote: > On VAX, you might be able to do the same thing if there's a > particularly long instruction that's an effective nop and is faster to > execute than the number of bytes it is. Is there any mechanism in gcc to jump into the middle of an instruction which is (effectively) a nop when executed from the start, but which can be mostly any (shorter) instruction when entered somewhere in the middle? It's a common technique on 8-bitters such as the 6502, to avoid extra branches: cmp #42 beq label lda #1 .byte $2C ; opcode for a 3-byte instruction that doesn't do much, ; usually the BIT abs instruction that only changes ; condition codes label: lda #2 ; a 2-byte instruction ... -Olaf. -- ___ Olaf 'Rhialto' Seibert -- The Doctor: No, 'eureka' is Greek for \X/ rhialto/at/xs4all.nl -- 'this bath is too hot.'
Attachment:
signature.asc
Description: PGP signature