On 26/05/11 17:45, Julian Brown wrote: > On Fri, 13 May 2011 17:31:18 +0100 > Julian Brown <jul...@codesourcery.com> wrote: > >> On Fri, 13 May 2011 14:54:47 +0000 (UTC) >> "Joseph S. Myers" <jos...@codesourcery.com> wrote: >> >>> On Fri, 13 May 2011, Julian Brown wrote: >>> >>>> although Joseph's comments have (hopefully) all been addressed. >>>> One must now configure with "--enable-fixed-point" to enable the >>>> fixed-point support. >>> >>> No, that's not how this configure logic works; it enables fixed >>> point by default for the given targets. The bit that enables it by >>> default for MIPS (and that you're changing to cover ARM as well) is >>> the code that is called if the user *doesn't* pass >>> --enable-fixed-point or --disable-fixed-point. >> >> Yes, you're quite right: I had forgotten to run autoconf after >> changing configure.ac whilst testing. Sorry for the misinformation! > > This is a new version of the patch, which fixes a couple of issues > discovered on our internal branch since the last version was posted. > This version handles "long long" fixed point types in the same way as > 32-bit MIPS: basically the sizes of those types are clamped to 64 bits. > > This means the testsuite changes in: > > http://gcc.gnu.org/ml/gcc-patches/2011-05/msg00969.html > > are no longer required. > > Another couple of problems have also been fixed, relating to big-endian > mode. One was the use of simplify_gen_subreg with a hard-wired offset in > a several of the insn expanders, where I should have just used > gen_highpart -- which works in either endianness, and makes the intent > clearer anyway. > > The other issue is ABI-related. My previous assertion that fixed-point > types (smaller than word size) should be passed to and returned from > functions "like integers" doesn't really work out very well after all > in big-endian mode, so needs re-thinking. The problem is basically that > such fixed-point types are incorrectly padded in big-endian mode, so > the data ends up in a different part of the passed word than expected. > > The way chars and shorts is handled is as follows: when those types are > passed to a function, they are promoted to word-size ints, which is a > nop-op: the values can simply be reinterpreted as ints, and that works > fine in either endianness. We might hope to be able to do the same thing > for smaller-than-word-size fixed-point types, but unfortunately we > can't: e.g. a "short fract" or "fract" can't just be reinterpreted as a > "long fract" (the 32-bit fractional type), because the fixed-point is > in a different place for the wider type (and performing conversions > would itself require libcalls at present). It also doesn't work to > promote small fixed-point types to SImode: as well as being > conceptually messy, we hit ICEs very quickly attempting that. > > So instead, I think that small fixed-point types should be handled the > same way as small aggregates or small complex-valued types. This means > effectively no change in little-endian mode, but in big-endian mode: > > * for register arguments, fixed-point types are passed in the > most-significant end of the register. > > * for stack arguments, fixed-point types are passed in lower memory > addresses. > > * for return values, fixed-point types are again in the > most-significant end of the return register (r0). > > This is quite easy to set up in the backend code, but unfortunately I > hit a snag in libcall expansion in calls.c: padding of arguments and > return values is not properly supported, as it is for regular function > calls. I've implemented that, and will post it as a separate patch. > > OK to apply? Tested alongside the rest of the patch series, in both big > & little-endian mode. > > Julian > > ChangeLog > > gcc/ > * configure.ac (fixed-point): Add ARM support. > * configure: Regenerate. > * config/arm/arm.c (arm_fixed_mode_set): New struct. > (arm_set_fixed_optab_libfunc): New. > (arm_set_fixed_conv_libfunc): New. > (arm_init_libfuncs): Initialise fixed-point helper libfuncs with > ARM-specific names. > (aapcs_libcall_value): Return sub-word-size fixed-point libcall > return values in SImode. > (arm_return_in_msb): Return fixed-point types in the msb. > (arm_pad_reg_upwards, arm_pad_arg_upwards): Pad fixed-point types > upwards. > (arm_scalar_mode_supported_p): Support fixed-point modes. > (arm_vector_mode_supported_p): Support vector fixed-point modes. > * config/arm/arm.h (SHORT_FRACT_TYPE_SIZE, FRACT_TYPE_SIZE) > (LONG_FRACT_TYPE_SIZE, LONG_LONG_FRACT_TYPE_SIZE) > (SHORT_ACCUM_TYPE_SIZE, ACCUM_TYPE_SIZE, LONG_ACCUM_TYPE_SIZE) > (LONG_LONG_ACCUM_TYPE_SIZE, MAX_FIXED_MODE_SIZE): Define. > * config/arm/arm-modes.def (FRACT, UFRACT, ACCUM, UACCUM): Declare > vector modes. > * config/arm/predicates.md (sat_shift_operator): New predicate. > * config/arm/arm-fixed.md: New. > * config/arm/arm.md: Include arm-fixed.md. > * config/arm/t-arm (MD_INCLUDES): Add arm-fixed.md. > * config/arm/fixed-bit-machine.h: New. > > libgcc/ > * config.host (arm*-*-linux*, arm*-*-uclinux*, arm*-*-eabi*) > (arm*-*-symbianelf*): Add arm/t-fixed-point makefile fragment. > target-specific or generic fixed_bit_machine_header to decorate the > names of fixed-point helper functions. > * config/arm/t-fixed-point: New. > > gcc/testsuite/ > * gcc.target/arm/fixed-point-exec.c: New test. > >
Please put the iterator definitions in iterators.md Otherwise OK. R.
