Graham Stott <graham.st...@btinternet.com> writes: > Hi Richard, > > This patch attemps to elimate the TEQ instruction div DIV/MOD instructions > if possible (i.e the numerator is known to be non-zero) > > I have introduced and seperated UNSPEC UNSPEC_SET_HILO_NOTRAP > which is generation by a peephole2 when the trap is known not to be required. > > The peephole's work by checking for a REG_EQUAL or/REG_EQUIV on the > instruction which sets the numerator for the DIV/MOD this doesn't catch all > possible cases but does catch the common cases where ths numerator is > set set in a insn immediately preceeding the DIV/MOD.
Nice idea, but TBH, I think I'd prefer to expose the trap code at expand time and let the rtl optimisers try to remove it. I can't remember any correctness reason why that wouldn't work. I think the only reason we don't do it yet is because (before gimple) there was a preference for keeping the division as a unit during early rtl optimisations. Thanks, Richard
