From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 8665 invoked by alias); 10 Mar 2002 17:00:44 -0000 Mailing-List: contact gdb-patches-help@sources.redhat.com; run by ezmlm Precedence: bulk List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sources.redhat.com Received: (qmail 8557 invoked from network); 10 Mar 2002 17:00:38 -0000 Received: from unknown (HELO nevyn.them.org) (128.2.145.6) by sources.redhat.com with SMTP; 10 Mar 2002 17:00:38 -0000 Received: from drow by nevyn.them.org with local (Exim 3.35 #1 (Debian)) id 16k6gX-0007tC-00; Sun, 10 Mar 2002 12:00:37 -0500 Date: Sun, 10 Mar 2002 09:00:00 -0000 From: Daniel Jacobowitz To: Andrew Cagney Cc: Don Howard , gdb-patches@sources.redhat.com Subject: Re: [RFA] mips: Fix "info registers" output Message-ID: <20020310120037.A29124@nevyn.them.org> Mail-Followup-To: Andrew Cagney , Don Howard , gdb-patches@sources.redhat.com References: <20010619225007.A10141@nevyn.them.org> <20020307165956.A22042@nevyn.them.org> <3C8ABF59.7080908@cygnus.com> <20020310015637.A13373@nevyn.them.org> <3C8B8A11.8070609@cygnus.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3C8B8A11.8070609@cygnus.com> User-Agent: Mutt/1.3.23i X-SW-Source: 2002-03/txt/msg00136.txt.bz2 On Sun, Mar 10, 2002 at 11:30:09AM -0500, Andrew Cagney wrote: > > > >FP_REGISTER_DOUBLE describes a property of the ABI. I don't really > >think it's the appropriate check when printing floating-point > >registers; we always take care to print the single-precision value even > >if FP_REGISTER_DOUBLE, because they might be used in single-precision > >anyway. > > True, sort of. The decision is a function of that FP bit, > FP_REGISTER_DOUBLE and the user typing ``(gdb) set mips > fp-register-double on, damit!'' (the user is always right :-). (said `set' does not exist, of course) > If the FP register bit is used by just this code, other parts of GDB are > going to be inconsistent since they are still using FP_REGISTER_DOUBLE > when [un]packing FP registers. Can I suggest using FP_REGISTER_DOUBLE > initially (#if 0 #else #endif the code in mips2_fp_compat()) and bug > report the need to change everyting to use mips2_fp_compat() as a > separate change. But there is nowhere else that we really unpack FP registers... well, I suppose there is actually. A fixme and PR it is. The PR will include a question about what to do with the displayed types of these registers. I have a few ideas, involving gdbarch, on how to solve this properly. I'll get back to it in a few months, thus the PR :) > Apart from that, I think the code is brilliant. Just suggest a few > comment tweaks before the commit. > > + if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG) > + > { > + > mips_read_fp_register_single (regno, rare_buffer + 4); > + > mips_read_fp_register_single (regno + 1, rare_buffer); > + > } > + else > + > { > + > mips_read_fp_register_single (regno, rare_buffer); > + > mips_read_fp_register_single (regno + 1, rare_buffer + 4); > + > } > > Suggest mentioning that mips_read_fp_register_single() handles the > problem of extracting the correct four bytes from from each register. OK, will do. > >- /* use HI and LO to control the order of combining two flt regs */ > >- int HI = (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG); > >- int LO = (TARGET_BYTE_ORDER != BFD_ENDIAN_BIG); > > Yes! In 20:20 hindsight that was a very confusing idea. > > >+ /* 4-byte registers: we can fit two registers per row. */ > >+ /* Also print every pair of 4-byte regs as an 8-byte double. */ > >+ mips_read_fp_register_single (regnum, raw_buffer); > >+ flt1 = unpack_double (builtin_type_float, raw_buffer, &inv1); > >+ > >+ mips_read_fp_register_single (regnum + 1, raw_buffer); > >+ flt2 = unpack_double (builtin_type_float, raw_buffer, &inv2); > > > >+ mips_read_fp_register_double (regnum, raw_buffer); > >+ doub = unpack_double (builtin_type_double, raw_buffer, &inv3); > >+ > > printf_filtered (" %-5s", REGISTER_NAME (regnum)); > > Suggest a FIXME and bug report here. It isn't safe to assume things > like builtin_type_double is 64 bit. The code should use the ABI > independant builtin_type_ieee_BLAH. But this is a separate bug and not > your problem :-) builtin_type_double = init_type (TYPE_CODE_FLT, TARGET_DOUBLE_BIT / TARGET_CHAR_BIT, 0, "double", (struct objfile *) NULL); set_gdbarch_double_bit (gdbarch, 64); Why isn't it safe to assume that a double is 64-bit when we explicitly set it that way? I assume that the builtin types get swapped out when we change gdbarch... yes, they do. Besides, is MIPS FP actually IEEE? Oh, I suppose the values probably are and only some of the math isn't. Committed without that last FIXME; I'll add it if it's really necessary. -- Daniel Jacobowitz Carnegie Mellon University MontaVista Software Debian GNU/Linux Developer