Re: [RFC][PATCH] Remove SLOW_BYTE_ACCESS

[Palmer Dabbelt <palmer at sifive dot com>]

On Fri, 17 Nov 2017 11:01:21 PST (-0800), Wilco.Dijkstra@arm.com wrote:
> Remove SLOW_BYTE_ACCESS given it's confusing, badly named,
> badly documented and used incorrectly.  Although most targets
> define it as 1, there are several targets which confuse it
> (based on comments next to it) and set it to 0 since the name 
> obviously implies it should be 0 when byte accesses are not slow.
>
> It's hard to tell whether there are targets which actually have
> slow *WORD* accesses, where it may be preferable to use narrow
> accesses for bitfields.  If this is the case (maybe an old 8-bit
> target?) then we should consider improving the narrow_volatile_bitfield
> callback. That way you could pass the size/alignment/volatile and
> decide per bitfield access.
>
> What do people think?

FWIW, this tripped us up.  I don't know about the other targets, but it 
certainly would have saved us a few hours had things been this way a year ago 
:).

> ChangeLog:
> 2017-11-17  Wilco Dijkstra  <wdijkstr@arm.com>
>
> 	* config/aarch64/aarch64.h: Remove SLOW_BYTE_ACCESS.
> 	* config/alpha/alpha.h: Likewise.
> 	* config/arc/arc.h: Likewise.
> 	* config/arm/arm.h: Likewise.
> 	* config/avr/avr.h: Likewise.
> 	* config/bfin/bfin.h: Likewise.
> 	* config/c6x/c6x.h: Likewise.
> 	* config/cr16/cr16.h: Likewise.
> 	* config/cris/cris.h: Likewise.
> 	* config/epiphany/epiphany.h: Likewise.
> 	* config/fr30/fr30.h: Likewise.
> 	* config/frv/frv.h: Likewise.
> 	* config/ft32/ft32.h: Likewise.
> 	* config/h8300/h8300.h: Likewise.
> 	* config/i386/i386.h: Likewise.
> 	* config/ia64/ia64.h: Likewise.
> 	* config/iq2000/iq2000.h: Likewise.
> 	* config/lm32/lm32.h: Likewise.
> 	* config/m32c/m32c.h: Likewise.
> 	* config/m32r/m32r.h: Likewise.
> 	* config/m68k/m68k.h: Likewise.
> 	* config/mcore/mcore.h: Likewise.
> 	* config/microblaze/microblaze.h: Likewise.
> 	* config/mips/mips.h: Likewise.
> 	* config/mmix/mmix.h: Likewise.
> 	* config/mn10300/mn10300.h: Likewise.
> 	* config/moxie/moxie.h: Likewise.
> 	* config/msp430/msp430.h: Likewise.
> 	* config/nds32/nds32.h: Likewise.
> 	* config/nios2/nios2.h: Likewise.
> 	* config/nvptx/nvptx.h: Likewise.
> 	* config/pa/pa.h: Likewise.
> 	* config/pdp11/pdp11.h: Likewise.
> 	* config/powerpcspe/powerpcspe.h: Likewise.
> 	* config/riscv/riscv.h: Likewise.
> 	* config/rl78/rl78.h: Likewise.
> 	* config/rs6000/rs6000.h: Likewise.
> 	* config/rx/rx.h: Likewise.
> 	* config/s390/s390.h: Likewise.
> 	* config/sh/sh.h: Likewise.
> 	* config/sparc/sparc.h: Likewise.
> 	* config/spu/spu.h: Likewise.
> 	* config/stormy16/stormy16.h: Likewise.
> 	* config/tilegx/tilegx.h: Likewise.
> 	* config/tilepro/tilepro.h: Likewise.
> 	* config/v850/v850.h: Likewise.
> 	* config/vax/vax.h: Likewise.
> 	* config/visium/visium.h: Likewise.
> 	* config/xtensa/xtensa.h: Likewise.
> 	* doc/tm.texi: Likewise.
> 	* doc/tm.texi.in: Likewise.
> 	* dojump.c: Likewise.
> 	* stor-layout.c: Likewise.