On Fri, Jul 24, 2020 at 5:38 PM Andrew Stubbs <a...@codesourcery.com> wrote: > > Hi all, > > I want amdgcn to be able to support int128 types, partly because they > might come up in code offloaded from x86_64 code, and partly because > libgomp now requires at least some support (amdgcn builds have been > failing since yesterday). > > But, amdgcn has 32-bit registers, and therefore defines BITS_PER_WORD to > 32, which means that TImode doesn't Just Work, at least not for all > operators. It already has TImode moves, for internal uses, so I can > enable TImode and fix the libgomp build, but now libgfortran tries to > use operators that don't exist, so I'm no better off. > > The expand pass won't emit libgcc calls, like it does for DImode, and > libgcc doesn't have the routines for it anyway. Neither does it support > synthesized shifts or rotates for more than double-word types. > (Multiple-word add and subtract appear to work fine, however.) > > What would be the best (least effort) way to implement this? > > I think I need shift, rotate, multiply, divide, and modulus, but there's > probably more.
You've figured out that TImode support for SImode word_mode targets is not implemented in generic code. So what you need to do is either provide patterns for all of the operations you need or implement generic support for libgcc fallbacks (which isn't there). Joseph might have an idea what's missing and how difficult it would be (I suppose we do not want divti3 to end up calling divdi3, thus "stage" TImode support ontop of DImode ops eventually provided by libgcc only). libgcc2.c uses LIBGCC2_UNITS_PER_WORD so it _might_ be possible to somehow do this "staging" by providing two different values here. I guess you'd have to try. Richard. > Thanks, any advise will be appreciated. > > Andrew
