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Re: [RFD] MIPS/gas: Optimisation cannot be set to 0
"Maciej W. Rozycki" <email@example.com> writes:
> On Fri, 9 Nov 2007, Paul Koning wrote:
>> In other words, I thought that gcc now tells the assembler ".set
>> noreorder; .set nomacro; .set noat" so the assembler isn't going to do
>> ANY transformations.
> Not for inline asms (understandable) and (to my surprise!) not for MIPS16
Right. There's not really any point doing it for MIPS16 code. The only
kind of reordering you get is when GAS fills a delay slot that GCC didn't
know how to fill, so ".set noreorder" would mean "don't make this
function as small as you can". That'd be a bit perverse on a target
where size is really the only thing that matters. (In contrast,
GCC might have had good reasons to do what it did for non-MIPS16 code,
especially on targets like the VR413x.)
It would be quite hard for GCC to calculate precise (rather than
conversatively-correct) lengths for every MIPS16 instruction.
One of the problems is that the range of unextended PC-relative
instructions depends on the low bits of the instruction's address,
and GCC's length calculation code isn't yet ready for that kind of