Re: [PATCH] Sanitizing the middle-end interface to the back-end for strict alignment

[Christophe Lyon <christophe.lyon@linaro.org>]

On Wed, 28 Aug 2019 at 11:42, Kyrill Tkachov
<kyrylo.tkachov@foss.arm.com> wrote:
>
>
> On 8/28/19 10:38 AM, Bernd Edlinger wrote:
> > On 8/27/19 11:25 AM, Kyrill Tkachov wrote:
> >> Hi Bernd,
> >>
> >> On 8/15/19 8:47 PM, Bernd Edlinger wrote:
> >>> Hi,
> >>>
> >>> this is the split out part from the "Fix not 8-byte aligned ldrd/strd on ARMv5 (PR 89544)"
> >>> which is sanitizing the middle-end interface to the back-end for strict alignment,
> >>> and a couple of bug-fixes that are necessary to survive boot-strap.
> >>> It is intended to be applied after the PR 89544 fix.
> >>>
> >>> I think it would be possible to change the default implementation of STACK_SLOT_ALIGNMENT
> >>> to make all stack variables always naturally aligned instead of doing that only
> >>> in assign_parm_setup_stack, but would still like to avoid changing too many things
> >>> that do not seem to have a problem.  Since this would affect many targets, and more
> >>> kinds of variables that may probably not have a strict alignment problem.
> >>> But I am ready to take your advice though.
> >>>
> >>>
> >>> Boot-strapped and reg-tested on x86_64-pc-linux-gnu and arm-linux-gnueabihf
> >>> Is it OK for trunk?
> >> I'm not opposed to the checks but...
> >>
> >>
> >>> Thanks
> >>> Bernd.
> >>>
> >> Index: gcc/config/arm/vec-common.md
> >> ===================================================================
> >> --- gcc/config/arm/vec-common.md    (Revision 274531)
> >> +++ gcc/config/arm/vec-common.md    (Arbeitskopie)
> >> @@ -26,6 +26,12 @@
> >>     "TARGET_NEON
> >>      || (TARGET_REALLY_IWMMXT && VALID_IWMMXT_REG_MODE (<MODE>mode))"
> >>   {
> >> +  gcc_checking_assert (!MEM_P (operands[0])
> >> +               || MEM_ALIGN (operands[0])
> >> +              >= GET_MODE_ALIGNMENT (<MODE>mode));
> >> +  gcc_checking_assert (!MEM_P (operands[1])
> >> +               || MEM_ALIGN (operands[1])
> >> +              >= GET_MODE_ALIGNMENT (<MODE>mode));
> >>     if (can_create_pseudo_p ())
> >>       {
> >>         if (!REG_P (operands[0]))
> >>
> >> ... can we please factor the (!MEM_P (operands[0]) || MEM_ALIGN (operands[0]) >= GET_MODE_ALIGNMENT (<MODE>mode)) checks into a common function and use that?
> >>
> > Sure, good idea.  How about converting it to a predicate?
> > This creates 1:1 equivalent code to the open coded assertions.
> >
> > Is it OK for trunk?
> >
> >
> > Thanks
> > Bernd.
>
>
> patch-strict-align.diff
>
> 2019-08-15  Bernd Edlinger<bernd.edlinger@hotmail.de>
>             Richard Biener<rguenther@suse.de>
>
>         * expr.c (expand_assignment): Handle misaligned DECLs.
>         (expand_expr_real_1): Handle FUNCTION_DECL as unaligned.
>         * function.c (assign_parm_adjust_stack_rtl): Check movmisalign optab
>         too.
>         (assign_parm_setup_stack): Allocate properly aligned stack slots.
>         * varasm.c (build_constant_desc): Align constants of misaligned types.
>         * config/arm/predicates.md (aligned_operand): New predicate.
>         * config/arm/arm.md (movdi, movsi, movhi, movhf, movsf, movdf): Use
>         sligned_operand to check restrictions on memory addresses.
>
> typo in "aligned_operand"
>
>          * config/arm/neon.md (movti, mov<VSTRUCT>, mov<VH>): Likewise.
>         * config/arm/vec-common.md (mov<VALL>): Likewise.
>
>
> Looks good now.
>

Hi,

This patch causes an ICE when building libgcc's unwind-arm.o
when configuring GCC:
--target  arm-none-linux-gnueabihf --with-mode thumb --with-cpu
cortex-a15 --with-fpu neon-vfpv4:

The build works for the same target, but --with-mode arm --with-cpu
cortex a9 --with-fpu vfp

In file included from
/tmp/6852788_4.tmpdir/aci-gcc-fsf/sources/gcc-fsf/gccsrc/libgcc/config/arm/unwind-arm.c:144:
/tmp/6852788_4.tmpdir/aci-gcc-fsf/sources/gcc-fsf/gccsrc/libgcc/unwind-arm-common.inc:
In function 'get_eit_entry':
/tmp/6852788_4.tmpdir/aci-gcc-fsf/sources/gcc-fsf/gccsrc/libgcc/unwind-arm-common.inc:245:29:
warning: cast discards 'const' qualifier from pointer target type
[-Wcast-qual]
  245 |       ucbp->pr_cache.ehtp = (_Unwind_EHT_Header *)&eitp->content;
      |                             ^
during RTL pass: expand
/tmp/6852788_4.tmpdir/aci-gcc-fsf/sources/gcc-fsf/gccsrc/libgcc/unwind-arm-common.inc:
In function 'unwind_phase2_forced':
/tmp/6852788_4.tmpdir/aci-gcc-fsf/sources/gcc-fsf/gccsrc/libgcc/unwind-arm-common.inc:319:18:
internal compiler error: in gen_movdi, at config/arm/arm.md:5235
  319 |   saved_vrs.core = entry_vrs->core;
      |   ~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~
0x126530f gen_movdi(rtx_def*, rtx_def*)
        /tmp/6852788_4.tmpdir/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/config/arm/arm.md:5235
0x896d92 insn_gen_fn::operator()(rtx_def*, rtx_def*) const
        /tmp/6852788_4.tmpdir/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/recog.h:318
0x896d92 emit_move_insn_1(rtx_def*, rtx_def*)
        /tmp/6852788_4.tmpdir/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/expr.c:3694
0x897083 emit_move_insn(rtx_def*, rtx_def*)
        /tmp/6852788_4.tmpdir/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/expr.c:3790
0xfc25d6 gen_cpymem_ldrd_strd(rtx_def**)
        /tmp/6852788_4.tmpdir/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/config/arm/arm.c:14582
0x126a1f1 gen_cpymemqi(rtx_def*, rtx_def*, rtx_def*, rtx_def*)
        /tmp/6852788_4.tmpdir/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/config/arm/arm.md:6688
0xb0bc08 maybe_expand_insn(insn_code, unsigned int, expand_operand*)
        /tmp/6852788_4.tmpdir/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/optabs.c:7440
0x89ba1e emit_block_move_via_cpymem
        /tmp/6852788_4.tmpdir/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/expr.c:1808
0x89ba1e emit_block_move_hints(rtx_def*, rtx_def*, rtx_def*,
block_op_methods, unsigned int, long, unsigned long, unsigned long,
unsigned long, bool, bool*)
        /tmp/6852788_4.tmpdir/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/expr.c:1627
0x89c383 emit_block_move(rtx_def*, rtx_def*, rtx_def*, block_op_methods)
        /tmp/6852788_4.tmpdir/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/expr.c:1667
0x89fb4e store_expr(tree_node*, rtx_def*, int, bool, bool)
        /tmp/6852788_4.tmpdir/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/expr.c:5845
0x88c1f9 store_field
        /tmp/6852788_4.tmpdir/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/expr.c:7149
0x8a0c22 expand_assignment(tree_node*, tree_node*, bool)
        /tmp/6852788_4.tmpdir/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/expr.c:5304
0x761964 expand_gimple_stmt_1
        /tmp/6852788_4.tmpdir/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/cfgexpand.c:3779
0x761964 expand_gimple_stmt
        /tmp/6852788_4.tmpdir/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/cfgexpand.c:3875
0x768583 expand_gimple_basic_block
        /tmp/6852788_4.tmpdir/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/cfgexpand.c:5915
0x76abc6 execute
        /tmp/6852788_4.tmpdir/aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/cfgexpand.c:6538

Christophe

> Ok, thanks!
>
> Kyrill
>