From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 30929 invoked by alias); 21 Oct 2012 04:07:00 -0000 Received: (qmail 30916 invoked by uid 22791); 21 Oct 2012 04:06:58 -0000 X-SWARE-Spam-Status: No, hits=-2.8 required=5.0 tests=AWL,BAYES_00,KHOP_THREADED,TW_SV,TW_TJ X-Spam-Check-By: sourceware.org Received: from dair.pair.com (HELO dair.pair.com) (209.68.1.49) by sourceware.org (qpsmtpd/0.43rc1) with SMTP; Sun, 21 Oct 2012 04:06:49 +0000 Received: (qmail 60873 invoked by uid 20157); 21 Oct 2012 04:06:48 -0000 Received: from localhost (sendmail-bs@127.0.0.1) by localhost with SMTP; 21 Oct 2012 04:06:48 -0000 Date: Sun, 21 Oct 2012 06:09:00 -0000 From: Hans-Peter Nilsson To: gcc-patches@gcc.gnu.org cc: Jeffrey A Law , Roger Sayle , Ian Lance Taylor , dnovillo@google.com, rguenther@suse.de Subject: 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 (BSF 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-IsSubscribed: yes 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/msg01874.txt.bz2 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? 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 >