> -----Original Message----- > From: Richard Henderson [mailto:r...@redhat.com] > Sent: Sunday, October 12, 2014 12:52 PM > To: Zhenqiang Chen; gcc-patches@gcc.gnu.org > Subject: Re: [Ping] [PATCH, 7/10] aarch64: add function to output ccmp insn > > On 10/11/2014 09:11 AM, Richard Henderson wrote: > > On 09/22/2014 11:45 PM, Zhenqiang Chen wrote: > >> +static unsigned int > >> +aarch64_code_to_nzcv (enum rtx_code code, bool inverse) { > >> + switch (code) > >> + { > >> + case NE: /* NE, Z == 0. */ > >> + return inverse ? AARCH64_CC_Z : 0; > >> + case EQ: /* EQ, Z == 1. */ > >> + return inverse ? 0 : AARCH64_CC_Z; > >> + case LE: /* LE, !(Z == 0 && N == V). */ > >> + return inverse ? AARCH64_CC_N | AARCH64_CC_V : AARCH64_CC_Z; > >> + case GT: /* GT, Z == 0 && N == V. */ > >> + return inverse ? AARCH64_CC_Z : AARCH64_CC_N | AARCH64_CC_V; > >> + case LT: /* LT, N != V. */ > >> + return inverse ? AARCH64_CC_N | AARCH64_CC_V : AARCH64_CC_N; > >> + case GE: /* GE, N == V. */ > >> + return inverse ? AARCH64_CC_N : AARCH64_CC_N | AARCH64_CC_V; > >> + case LEU: /* LS, !(C == 1 && Z == 0). */ > >> + return inverse ? AARCH64_CC_C: AARCH64_CC_Z; > >> + case GTU: /* HI, C ==1 && Z == 0. */ > >> + return inverse ? AARCH64_CC_Z : AARCH64_CC_C; > >> + case LTU: /* CC, C == 0. */ > >> + return inverse ? AARCH64_CC_C : 0; > >> + case GEU: /* CS, C == 1. */ > >> + return inverse ? 0 : AARCH64_CC_C; > >> + default: > >> + gcc_unreachable (); > >> + return 0; > >> + } > >> +} > >> + > > > > I'm not overly fond of this, since "code" doesn't map 1-1. It needs > > the context of a mode to provide a unique mapping. > > > > I think it would be better to rearrange the existing aarch64_cond_code > > enum such that AARCH64_NE et al are meaningful wrt NZCV. Then you can > > use > > aarch64_get_condition_code_1 to get this mapping. > > Slight mistake in the advice here. I think you should use > aarch64_get_conditional_code_1 to get an aarch64_cond_code, and use that > to index an array to get the nzcv bits.
Thanks for the comments. Patch is updated. > Further, does it actually make sense to store both nzcv and its inverse, or > does it work to use nzcv and ~nzcv? Flag GE checks N == V and LT checks N != V. We can no distinguish them with nzcv and ~nzcv Since aarch64_output_ccmp is removed as your comments, the patch is combined with [PATCH, 8/10] aarch64: ccmp insn patterns. Please find the updated patch in later email. Thanks! -Zhenqiang
