> -----Original Message----- > From: Richard Henderson [mailto:r...@redhat.com] > Sent: Monday, October 27, 2014 11:20 PM > To: Zhenqiang Chen > Cc: gcc-patches@gcc.gnu.org > Subject: Re: [Ping] [PATCH, 6/10] aarch64: add ccmp CC mode > > On 10/27/2014 12:48 AM, Zhenqiang Chen wrote: > > > >> -----Original Message----- > >> From: Richard Henderson [mailto:r...@redhat.com] > >> Sent: Saturday, October 11, 2014 11:32 PM > >> To: Zhenqiang Chen; gcc-patches@gcc.gnu.org > >> Subject: Re: [Ping] [PATCH, 6/10] aarch64: add ccmp CC mode > >> > >> On 09/22/2014 11:44 PM, Zhenqiang Chen wrote: > >>> + case CC_DNEmode: > >>> + return comp_code == NE ? AARCH64_NE : AARCH64_EQ; > >>> + case CC_DEQmode: > >>> + return comp_code == NE ? AARCH64_EQ : AARCH64_NE; > >>> + case CC_DGEmode: > >>> + return comp_code == NE ? AARCH64_GE : AARCH64_LT; > >>> + case CC_DLTmode: > >>> + return comp_code == NE ? AARCH64_LT : AARCH64_GE; > >>> + case CC_DGTmode: > >>> + return comp_code == NE ? AARCH64_GT : AARCH64_LE; > >>> + case CC_DLEmode: > >>> + return comp_code == NE ? AARCH64_LE : AARCH64_GT; > >>> + case CC_DGEUmode: > >>> + return comp_code == NE ? AARCH64_CS : AARCH64_CC; > >>> + case CC_DLTUmode: > >>> + return comp_code == NE ? AARCH64_CC : AARCH64_CS; > >>> + case CC_DGTUmode: > >>> + return comp_code == NE ? AARCH64_HI : AARCH64_LS; > >>> + case CC_DLEUmode: > >>> + return comp_code == NE ? AARCH64_LS : AARCH64_HI; > >> > >> I think these should return -1 if comp_code is not EQ. Like the > >> CC_Zmode case below. > > > > Since the code can not guarantee that the CC is used in cbranchcc > > insns when expand, it maybe in a tmp register. After some > > optimizations the CC is forwarded in cbranchcc insn. So the comp_code > might be any legal COMPARE. > > Um, no. The point of returning -1 is to avoid combining with comparisons for > which we cannot produce the proper result.
Patch is updated. > E.g. the existing CC_Zmode, where only the Z bit is valid. We want to reject > combination with LTU, which checks the C bit. > > Are you honestly suggesting that using CC_DNEmode with GE can be made > to make sense in any way? No. I misuse the function in previous patch. Now it returns -1. Thanks! -Zhenqiang
6-ccmp-cc-mode.patch
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