On Mon, Jul 19, 2010 at 11:12 AM, Ian Lance Taylor <i...@google.com> wrote: > "Amker.Cheng" <amker.ch...@gmail.com> writes: > >> I found although there are standard pattern names such as "ceilm2/floorm2", >> there is no insn pattern in mips.md for such float insns on mips target. >> further more, there is no ceil/floor rtl code in rtl.def either. >> >> based on these facts, I assuming those float insns are not supported by gcc, >> but don't know why, seems not difficult to add such insns. > > You're right that gcc does not currently have a way to represent those > instructions directly in RTL. In current gcc it would have to be done > using an unspec. E.g., see ceildf2 and ceildf2_fpr in rs6000.md. > > You're also right that it would not be difficult to add direct RTL > support. I'm not sure how useful that would be, since I don't see a lot > of additional optimization opportunity. An unspec will handle > scheduling correctly, the only benefit I see of direct RTL exposure > would be that you could do optimizations like floor(ceil(x)) => ceil(x), > but that seems unlikely to occur in real code.
And we'd be doing that at the tree level anyway. Richard. > Ian >
