Hi, Xi Ruoyao <xry...@xry111.site> writes:
> On Tue, 2023-06-13 at 20:23 +0800, Jiufu Guo via Gcc-patches wrote: > >> Compare with previous version, this addes ChangeLog and removes >> const_anchor parts. >> https://gcc.gnu.org/pipermail/gcc-patches/2023-June/621356.html. > > [Off topic] > > const_anchor is just broken now. See > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104843 and the thread > beginning at > https://gcc.gnu.org/pipermail/gcc-patches/2022-March/591470.html. If > you want to use it for rs6000 I guess you need to fix it first... Thanks so much for pointing out this. It seems about supporting negative value, right? As you say: for 1. "g(0x8123ffff, 0x81240001)", it would be fine. The generated insns are: (insn 5 2 6 2 (set (reg:DI 117) (const_int -2128347135 [0xffffffff81240001])) "negative.c":5:3 681 {*movdi_internal64} (nil)) (insn 6 5 7 2 (set (reg:DI 118) (plus:DI (reg:DI 117) (const_int -2 [0xfffffffffffffffe]))) "negative.c":5:3 66 {*adddi3} (expr_list:REG_EQUAL (const_int -2128347137 [0xffffffff8123ffff]) (nil))) While for 2. "g (0x7fffffff, 0x80000001)", the generated rtl insns: (insn 5 2 6 2 (set (reg:DI 117) (const_int -2147483647 [0xffffffff80000001])) "negative.c":5:3 681 {*movdi_internal64} (nil)) (insn 7 6 8 2 (set (reg:DI 3 3) (const_int 2147483647 [0x7fffffff])) "negative.c":5:3 681 {*movdi_internal64} (nil)) The current const_anchor does not generate sth like: "r3 = r117 - 2" But I would lean to say it is the limitation of current implementation: "0xffffffff80000001" and "0x7fffffff" hit different anchors(even these two values are 'close' on some aspect.) BR, Jeff (Jiufu Guo) > > To me const_anchor needs a complete rework but I don't want to spend my > time on it.
