From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 6700 invoked by alias); 22 Oct 2012 07:36:11 -0000 Received: (qmail 6564 invoked by uid 22791); 22 Oct 2012 07:36:10 -0000 X-SWARE-Spam-Status: No, hits=-6.5 required=5.0 tests=AWL,BAYES_00,KHOP_RCVD_UNTRUST,KHOP_THREADED,RCVD_IN_DNSWL_HI,RP_MATCHES_RCVD,TW_SV X-Spam-Check-By: sourceware.org Received: from cantor2.suse.de (HELO mx2.suse.de) (195.135.220.15) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Mon, 22 Oct 2012 07:36:04 +0000 Received: from relay1.suse.de (unknown [195.135.220.254]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx2.suse.de (Postfix) with ESMTP id 2C2439A78E; Mon, 22 Oct 2012 09:36:01 +0200 (CEST) Date: Mon, 22 Oct 2012 08:00:00 -0000 From: Richard Biener To: Hans-Peter Nilsson Cc: gcc-patches@gcc.gnu.org, Jeffrey A Law , Roger Sayle , Ian Lance Taylor , dnovillo@google.com Subject: Re: Ping: [RFA:] Fix frame-pointer-clobbering in builtins.c:expand_builtin_setjmp_receiver In-Reply-To: Message-ID: References: <3114930.R4qRiBo81x@polaris> User-Agent: Alpine 2.00 (LNX 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org X-SW-Source: 2012-10/txt/msg01909.txt.bz2 On Sun, 21 Oct 2012, Hans-Peter Nilsson wrote: > CC:ing middle-end maintainers this time. I was a bit surprised > when Eric Botcazou wrote in his review, quoted below, that he's > not one of you. Maybe approve that too? If Eric is fine with the patch it is ok. Yes, he is not middle-end maintainer but RTL optimizer reviewer. Thanks, Richard. > On Mon, 15 Oct 2012, Hans-Peter Nilsson wrote: > > > On Fri, 12 Oct 2012, Eric Botcazou wrote: > > > > (insn 168 49 51 3 (set (reg/f:DI 253 $253) > > > > (plus:DI (reg/f:DI 253 $253) > > > > (const_int 24 [0x18]))) > > > > /tmp/mmiximp2/gcc/gcc/testsuite/gcc.c-torture/execute/built-in-setjmp.c:21 > > > > -1 (nil)) > > > > (insn 51 168 52 3 (clobber (reg/f:DI 253 $253)) > > ... > > > > > > Note that insn 168 deleted, which seems a logical optimization. The > > > > bug is to emit the clobber, not that the restoring insn is removed. > > > > > > Had that worked in the past for MMIX? > > > > Yes, for svn revision 106027 (20051030) 4.1.0-era (!) > > > > where the test must have passed, as > > gcc.c-torture/execute/built-in-setjmp.c is at least four years > > older than that. > > > > > If so, what changed recently? > > > > By "these days" I didn't mean "recent", just not "eons ago". :) > > I see in a gcc-test-results posting from Mike Stein (whom I'd > > like to thank for test-results posting over the years), matching > > FAILs for svn revision 126095 (20070628) 4.3.0-era > > . > > > > Sorry, I have nothing in between those reports, my bad. Though > > I see no point narrowing down the failing revision further here > > IMO; as mentioned the bug is not that the restoring insn is > > removed. > > > > > Agreed. However, I'd suggest rescuing the comment for the ELIMINABLE_REGS > > > block from expand_nl_goto_receiver as it still sounds valid to me. > > > > Oops, my bad; I see I removed all the good comments. Fixed. > > > > > > * stmt.c (expand_nl_goto_receiver): Remove almost-copy of > > > > expand_builtin_setjmp_receiver. > > > > (expand_label): Adjust, call expand_builtin_setjmp_receiver > > > > with NULL for the label parameter. > > > > * builtins.c (expand_builtin_setjmp_receiver): Don't clobber > > > > the frame-pointer. Adjust comments. > > > > [HAVE_builtin_setjmp_receiver]: Emit builtin_setjmp_receiver > > > > only if LABEL is non-NULL. > > > > > > I cannot formally approve, but this looks good to me modulo: > > > > > > + If RECEIVER_LABEL is NULL, instead the port-specific parts of a > > > > + nonlocal goto handler are emitted. */ > > > > > > The "port-specific parts" wording is a bit confusing I think. I'd just write: > > > > > > If RECEIVER_LABEL is NULL, instead contruct a nonlocal goto handler. > > > > Sure. Thanks for the review. Updated patch below. As nothing > > was changed from the previous post but comments as per the > > review (mostly moving / reviving, fixing one grammo), already > > covered by the changelog quoted above, the previous testing is > > still valid. > > > > Ok for trunk, approvers? > > > > Index: gcc/builtins.c > > =================================================================== > > --- gcc/builtins.c (revision 192353) > > +++ gcc/builtins.c (working copy) > > @@ -885,14 +885,15 @@ expand_builtin_setjmp_setup (rtx buf_add > > } > > > > /* Construct the trailing part of a __builtin_setjmp call. This is > > - also called directly by the SJLJ exception handling code. */ > > + also called directly by the SJLJ exception handling code. > > + If RECEIVER_LABEL is NULL, instead contruct a nonlocal goto handler. */ > > > > void > > expand_builtin_setjmp_receiver (rtx receiver_label ATTRIBUTE_UNUSED) > > { > > rtx chain; > > > > - /* Clobber the FP when we get here, so we have to make sure it's > > + /* Mark the FP as used when we get here, so we have to make sure it's > > marked as used by this function. */ > > emit_use (hard_frame_pointer_rtx); > > > > @@ -907,17 +908,28 @@ expand_builtin_setjmp_receiver (rtx rece > > #ifdef HAVE_nonlocal_goto > > if (! HAVE_nonlocal_goto) > > #endif > > - { > > - emit_move_insn (virtual_stack_vars_rtx, hard_frame_pointer_rtx); > > - /* This might change the hard frame pointer in ways that aren't > > - apparent to early optimization passes, so force a clobber. */ > > - emit_clobber (hard_frame_pointer_rtx); > > - } > > + /* First adjust our frame pointer to its actual value. It was > > + previously set to the start of the virtual area corresponding to > > + the stacked variables when we branched here and now needs to be > > + adjusted to the actual hardware fp value. > > + > > + Assignments to virtual registers are converted by > > + instantiate_virtual_regs into the corresponding assignment > > + to the underlying register (fp in this case) that makes > > + the original assignment true. > > + So the following insn will actually be decrementing fp by > > + STARTING_FRAME_OFFSET. */ > > + emit_move_insn (virtual_stack_vars_rtx, hard_frame_pointer_rtx); > > > > #if !HARD_FRAME_POINTER_IS_ARG_POINTER > > if (fixed_regs[ARG_POINTER_REGNUM]) > > { > > #ifdef ELIMINABLE_REGS > > + /* If the argument pointer can be eliminated in favor of the > > + frame pointer, we don't need to restore it. We assume here > > + that if such an elimination is present, it can always be used. > > + This is the case on all known machines; if we don't make this > > + assumption, we do unnecessary saving on many machines. */ > > size_t i; > > static const struct elims {const int from, to;} elim_regs[] = ELIMINABLE_REGS; > > > > @@ -938,7 +950,7 @@ expand_builtin_setjmp_receiver (rtx rece > > #endif > > > > #ifdef HAVE_builtin_setjmp_receiver > > - if (HAVE_builtin_setjmp_receiver) > > + if (receiver_label != NULL && HAVE_builtin_setjmp_receiver) > > emit_insn (gen_builtin_setjmp_receiver (receiver_label)); > > else > > #endif > > Index: gcc/stmt.c > > =================================================================== > > --- gcc/stmt.c (revision 192353) > > +++ gcc/stmt.c (working copy) > > @@ -102,7 +102,6 @@ typedef struct case_node *case_node_ptr; > > > > static int n_occurrences (int, const char *); > > static bool tree_conflicts_with_clobbers_p (tree, HARD_REG_SET *); > > -static void expand_nl_goto_receiver (void); > > static bool check_operand_nalternatives (tree, tree); > > static bool check_unique_operand_names (tree, tree, tree); > > static char *resolve_operand_name_1 (char *, tree, tree, tree); > > @@ -196,7 +195,7 @@ expand_label (tree label) > > > > if (DECL_NONLOCAL (label)) > > { > > - expand_nl_goto_receiver (); > > + expand_builtin_setjmp_receiver (NULL); > > nonlocal_goto_handler_labels > > = gen_rtx_EXPR_LIST (VOIDmode, label_r, > > nonlocal_goto_handler_labels); > > @@ -1552,77 +1551,6 @@ expand_return (tree retval) > > } > > } > > > > -/* Emit code to restore vital registers at the beginning of a nonlocal goto > > - handler. */ > > -static void > > -expand_nl_goto_receiver (void) > > -{ > > - rtx chain; > > - > > - /* Clobber the FP when we get here, so we have to make sure it's > > - marked as used by this function. */ > > - emit_use (hard_frame_pointer_rtx); > > - > > - /* Mark the static chain as clobbered here so life information > > - doesn't get messed up for it. */ > > - chain = targetm.calls.static_chain (current_function_decl, true); > > - if (chain && REG_P (chain)) > > - emit_clobber (chain); > > - > > -#ifdef HAVE_nonlocal_goto > > - if (! HAVE_nonlocal_goto) > > -#endif > > - /* First adjust our frame pointer to its actual value. It was > > - previously set to the start of the virtual area corresponding to > > - the stacked variables when we branched here and now needs to be > > - adjusted to the actual hardware fp value. > > - > > - Assignments are to virtual registers are converted by > > - instantiate_virtual_regs into the corresponding assignment > > - to the underlying register (fp in this case) that makes > > - the original assignment true. > > - So the following insn will actually be > > - decrementing fp by STARTING_FRAME_OFFSET. */ > > - emit_move_insn (virtual_stack_vars_rtx, hard_frame_pointer_rtx); > > - > > -#if !HARD_FRAME_POINTER_IS_ARG_POINTER > > - if (fixed_regs[ARG_POINTER_REGNUM]) > > - { > > -#ifdef ELIMINABLE_REGS > > - /* If the argument pointer can be eliminated in favor of the > > - frame pointer, we don't need to restore it. We assume here > > - that if such an elimination is present, it can always be used. > > - This is the case on all known machines; if we don't make this > > - assumption, we do unnecessary saving on many machines. */ > > - static const struct elims {const int from, to;} elim_regs[] = ELIMINABLE_REGS; > > - size_t i; > > - > > - for (i = 0; i < ARRAY_SIZE (elim_regs); i++) > > - if (elim_regs[i].from == ARG_POINTER_REGNUM > > - && elim_regs[i].to == HARD_FRAME_POINTER_REGNUM) > > - break; > > - > > - if (i == ARRAY_SIZE (elim_regs)) > > -#endif > > - { > > - /* Now restore our arg pointer from the address at which it > > - was saved in our stack frame. */ > > - emit_move_insn (crtl->args.internal_arg_pointer, > > - copy_to_reg (get_arg_pointer_save_area ())); > > - } > > - } > > -#endif > > - > > -#ifdef HAVE_nonlocal_goto_receiver > > - if (HAVE_nonlocal_goto_receiver) > > - emit_insn (gen_nonlocal_goto_receiver ()); > > -#endif > > - > > - /* We must not allow the code we just generated to be reordered by > > - scheduling. Specifically, the update of the frame pointer must > > - happen immediately, not later. */ > > - emit_insn (gen_blockage ()); > > -} > > > > /* Emit code to save the current value of stack. */ > > rtx > > brgds, H-P > > > > -- Richard Biener SUSE / SUSE Labs SUSE LINUX Products GmbH - Nuernberg - AG Nuernberg - HRB 16746 GF: Jeff Hawn, Jennifer Guild, Felix Imend