Hi Richard,
Thanks a lot for your quick reply! Richard Biener <rguent...@suse.de> writes: > On Tue, 29 Aug 2023, Jiufu Guo wrote: > >> >> Hi All! >> >> "rguenth at gcc dot gnu.org" <gcc-bugzi...@gcc.gnu.org> writes: >> >> > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111166 >> ... >> > >> > >> > At RTL expansion time we store to D.2865 where it's DECL_RTL is r82:TI so >> > we can hardly fix it there. Only a later pass could figure each of the >> > insns fully define the reg. >> > >> > Jiufu Guo is working to improve what we choose for DECL_RTL, but for >> > incoming params / outgoing return. This is a case where we could, >> > with -fno-tree-vectorize, improve DECL_RTL for an automatic var and >> > choose not TImode but something like a (concat:TI reg:DI reg:DI). >> >> Here is the patch about improving the parameters and returns in >> registers. >> https://gcc.gnu.org/pipermail/gcc-patches/2023-August/628213.html >> >> I have a question about how to bind an RTL to a TREE expression. >> In this patch, a map TREE->RTL is used. But it would be better if >> there was a faster way. >> >> We have DECL_RTL/INCOMING_RTL, but they can only be bound to >> DECL(or PARM). In the above patch, the TREE can be an EXPR >> (e.g. COMPONENT_REF/ARRAY_REF). >> >> Is there a way to achieve this? Thanks for suggestions! > > No, but we don't need to bind RTL to COMPONENT_REF and friends, > what we want to change is the DECL_RTL of the underlying DECL. In the above patch, the scalarized rtx for the access of the parameter/returns are computed at the time when parameters are set up. And record "scalarized rtx" and "access expression". When expanding an expression, the patch queries the scalarized rtx. + rtx x = get_scalar_rtx_for_aggregate_expr (exp); + if (x) + return x; I'm reading "don't need to bind RTL to COMPONENT_REF and friends" and "change is the DECL_RTL of the underlying DECL." This may be doable. The method would be: 1. When the incoming/outgoing registers are determined, we can check if the parameter/return can be scalarized, **then bind the registers to DECL_RTL of the parm/ret**. 2. When expanding the expression (e.g. COMPONENT_REF), compute the scalarized rtx from DECL_RTL of the param/return. In expand_expr_real_1: case COMPONENT_REF: ... case ARRAY_REF: if base is parm... Is my understanding correct? BR, Jeff (Jiufu Guo) > > Richard.
