Messages in this thread | | | Date | Fri, 18 Jul 2014 09:43:20 +0100 | From | Will Deacon <> | Subject | Re: [PATCH RFCv3 08/14] arm64: introduce aarch64_insn_gen_movewide() |
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On Fri, Jul 18, 2014 at 06:47:22AM +0100, Z Lim wrote: > (resending this email in case the first one got caught in your spam > filter. sorry.) > > On Thu, Jul 17, 2014 at 10:41:02AM +0100, Will Deacon wrote: > > On Wed, Jul 16, 2014 at 11:04:22PM +0100, Zi Shen Lim wrote: > > > On Wed, Jul 16, 2014 at 05:17:15PM +0100, Will Deacon wrote: > > > > On Tue, Jul 15, 2014 at 07:25:06AM +0100, Zi Shen Lim wrote: > > > > > Introduce function to generate move wide (immediate) instructions. > [...] > > > > > + switch (variant) { > > > > > + case AARCH64_INSN_VARIANT_32BIT: > > > > > + BUG_ON(shift != 0 && shift != 16); > > > > > + break; > > > > > + case AARCH64_INSN_VARIANT_64BIT: > > > > > + insn |= BIT(31); > > > > > + BUG_ON(shift != 0 && shift != 16 && shift != 32 && > > > > > + shift != 48); > > > > > > > > Would be neater as a nested switch, perhaps? If you reorder the > > > > outer-switch, you could probably fall-through too and combine the shift > > > > checks. > > > > > > Not sure I picture what you had in mind... I couldn't come up with a > > > neater version with the properties you described. > > > > > > The alternative I had was using masks instead of integer values, but > > > one could argue that while neater, it could also be harder to read: > > > > > > switch (variant) { > > > case AARCH64_INSN_VARIANT_32BIT: > > > BUG_ON(shift & ~BIT(4)); > > > break; > > > case AARCH64_INSN_VARIANT_64BIT: > > > insn |= BIT(31); > > > BUG_ON(shift & ~GENMASK(5, 4)); > > > ... > > > > I was thinking of using nested switches, but that doesn't fall out like I > > hoped. How about: > > > > switch (variant) { > > case AARCH64_INSN_VARIANT_64BIT: > > BUG_ON(shift != 32 && shift != 48); > > Sorry this won't work. For example, on the valid case of shift==0, > we'll barf right here - no fallthrough. > > Shall we just leave the code as is? :)
Yeah, I'm an idiot ;)
Cheers,
Will
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