I have a beefy section of code that makes significant use of the constant pool. I am aware that by doing this, I must LTORG at least every 511 instructions (PC relative addressing is limited to 4k, instructions are 4 byte, and addressing is signed so absolute distance is one less than half) to ensure the constant pools are close enough to their use.
I could, of course, keep track of this myself, but this is manual and a bit of a pain (especially in the presence of macros). Are there any special features of gcc/gas (or macro tricks, etc.) that will automatically LTORG every 511 instructions for me? Ideally I'd like it to insert:
b lxxx
.ltorg
lxxx:
(Where lxxx is some unique label)
Bonus points if it only LTORGs after 510 instructions following the last instruction that uses an expression literal (that isn't in a constant pool). As an example, if there are 1024 sequential instructions that don't use expression literals, it shouldn't place an LTORG after them. But if immediately after that there is one instruction that uses an expression literal, then it will LTORG after 510 instructions (and after that the counter reset until the next instruction that uses an expression literal is reached).
Bonus bonus points if the above but it doesn't reset the counter unless the constant pool is actually used (ie. =1 doesn't use it, so it doesn't reset the counter, but =1234567689 does so an instruction using that expression literal would start/continue the countdown from 510).
edit: My initial thinking is if you wrapped every instruction in a macro that subtracts one from a global arithmetic variable (starting at 510). Once it reaches 0, an LTORG is omitted (it's unclear if you can get the assembler to give you a unique label to branch around the LTORG). You can get the "bonus points" with this solution by special casing the wrapper for LDR such that only it can restart the counter if it's negative. If there was a way of inspecting expression literals (to see if they need the constant pool), then you could special case the reset to only apply when the constant pool is used.
edit: edit: It's unclear if you can do what I've proposed generically, because label-expressions may be resolved at link time (after the assembler has run all the macros). But, I'd still be interested in a solution that works for just expressions (eg. ldr r0, =12345678).
