[PATCH] Add TARGET_LOWER_LOCAL_DECL_ALIGNMENT [PR95237]
Sunil Pandey
skpgkp1@gmail.com
Tue Jul 21 23:04:35 GMT 2020
On Tue, Jul 21, 2020 at 12:50 AM Richard Biener
<richard.guenther@gmail.com> wrote:
>
> On Tue, Jul 21, 2020 at 7:16 AM Sunil Pandey <skpgkp1@gmail.com> wrote:
> >
> > On Mon, Jul 20, 2020 at 5:06 AM Richard Biener
> > <richard.guenther@gmail.com> wrote:
> > >
> > > On Sat, Jul 18, 2020 at 7:57 AM Sunil Pandey <skpgkp1@gmail.com> wrote:
> > > >
> > > > On Fri, Jul 17, 2020 at 1:22 AM Richard Biener
> > > > <richard.guenther@gmail.com> wrote:
> > > > >
> > > > > On Fri, Jul 17, 2020 at 7:15 AM Sunil Pandey <skpgkp1@gmail.com> wrote:
> > > > > >
> > > > > > Any comment on revised patch? At least, in finish_decl, decl global attributes are populated.
> > > > >
> > > > > +static void
> > > > > +ix86_lower_local_decl_alignment (tree decl)
> > > > > +{
> > > > > + unsigned new_align = LOCAL_DECL_ALIGNMENT (decl);
> > > > >
> > > > > please use the macro-expanded call here since we want to amend
> > > > > ix86_local_alignment to _not_ return a lower alignment when
> > > > > called as LOCAL_DECL_ALIGNMENT (by adding a new parameter
> > > > > to ix86_local_alignment). Can you also amend the patch in this
> > > > > way?
> > > > >
> > > > > + if (new_align < DECL_ALIGN (decl))
> > > > > + SET_DECL_ALIGN (decl, new_align);
> > > > >
> > > > > diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
> > > > > index 81bd2ee94f0..1ae99e30ed1 100644
> > > > > --- a/gcc/c/c-decl.c
> > > > > +++ b/gcc/c/c-decl.c
> > > > > @@ -5601,6 +5601,8 @@ finish_decl (tree decl, location_t init_loc, tree init,
> > > > > }
> > > > >
> > > > > invoke_plugin_callbacks (PLUGIN_FINISH_DECL, decl);
> > > > > + /* Lower local decl alignment. */
> > > > > + lower_decl_alignment (decl);
> > > > > }
> > > > >
> > > > > should come before plugin hook invocation, likewise for the cp_finish_decl case.
> > > > >
> > > > > +/* Lower DECL alignment. */
> > > > > +
> > > > > +void
> > > > > +lower_decl_alignment (tree decl)
> > > > > +{
> > > > > + if (VAR_P (decl)
> > > > > + && !is_global_var (decl)
> > > > > + && !DECL_HARD_REGISTER (decl))
> > > > > + targetm.lower_local_decl_alignment (decl);
> > > > > +}
> > > > >
> > > > > please avoid this function, it's name sounds too generic and it's not worth
> > > > > adding a public API for two calls.
> > > > >
> > > > > Alltogether this should avoid the x86 issue leaving left-overs (your identified
> > > > > inliner case) as missed optimization [for the linux kernel which appearantly
> > > > > decided that -mpreferred-stack-boundary=2 is a good ABI to use].
> > > > >
> > > > > Richard.
> > > > >
> > > > >
> > > > Revised patch attached.
> > >
> > > @@ -16776,7 +16783,7 @@ ix86_data_alignment (tree type, unsigned int
> > > align, bool opt)
> > >
> > > unsigned int
> > > ix86_local_alignment (tree exp, machine_mode mode,
> > > - unsigned int align)
> > > + unsigned int align, bool setalign)
> > > {
> > > tree type, decl;
> > >
> > > @@ -16801,6 +16808,10 @@ ix86_local_alignment (tree exp, machine_mode mode,
> > > && (!decl || !DECL_USER_ALIGN (decl)))
> > > align = 32;
> > >
> > > + /* Lower decl alignment. */
> > > + if (setalign && align < DECL_ALIGN (decl))
> > > + SET_DECL_ALIGN (decl, align);
> > > +
> > > /* If TYPE is NULL, we are allocating a stack slot for caller-save
> > > register in MODE. We will return the largest alignment of XF
> > > and DF. */
> > >
> > > sorry for not being clear - the parameter should indicate whether an
> > > alignment lower
> > > than natural alignment is OK to return thus sth like
> > >
> > > diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
> > > index 31757b044c8..19703cbceb9 100644
> > > --- a/gcc/config/i386/i386.c
> > > +++ b/gcc/config/i386/i386.c
> > > @@ -16641,7 +16641,7 @@ ix86_data_alignment (tree type, unsigned int
> > > align, bool opt)
> > >
> > > unsigned int
> > > ix86_local_alignment (tree exp, machine_mode mode,
> > > - unsigned int align)
> > > + unsigned int align, bool may_lower)
> > > {
> > > tree type, decl;
> > >
> > > @@ -16658,7 +16658,8 @@ ix86_local_alignment (tree exp, machine_mode mode,
> > >
> > > /* Don't do dynamic stack realignment for long long objects with
> > > -mpreferred-stack-boundary=2. */
> > > - if (!TARGET_64BIT
> > > + if (may_lower
> > > + && !TARGET_64BIT
> > > && align == 64
> > > && ix86_preferred_stack_boundary < 64
> > > && (mode == DImode || (type && TYPE_MODE (type) == DImode))
> > >
> > > I also believe that spill_slot_alignment () should be able to get the
> > > lower alignment
> > > for long long but not get_stack_local_alignment () (both use
> > > STACK_SLOT_ALIGNMENT).
> > > Some uses of STACK_SLOT_ALIGNMENT also look fishy with respect to mem attributes
> > > and alignment.
> > >
> > > Otherwise the patch looks reasonable to salvage a misguided optimization for
> > > a non-standard ABI. If it is sufficient to make the people using that ABI happy
> > > is of course another question. I'd rather see them stop using it ...
> > >
> > > That said, I'm hesitant to be the only one OKing this ugliness but I'd
> > > immediately
> > > OK a patch removing the questionable hunk from ix86_local_alignment ;)
> > >
> > > Jakub, Jeff - any opinion?
> > >
> > > Richard.
> > >
> >
> > Revised patch attached.
>
> You are now passing 'true' to ix86_local_alignment for all callers,
> that's not correct.
> I said at most STACK_SLOT_ALIGNMENT _might_ be able to take the lower alignment
> but some callers look suspicious so I wasn't sure.
>
> Which means - please pass false for LOCAL_ALIGNMENT, STACK_SLOT_ALIGNMENT
> and LOCAL_DECL_ALIGNMENT.
>
> + /* Lower local decl alignment. */
> +
> + if (VAR_P (decl)
> + && !is_global_var (decl)
> + && !DECL_HARD_REGISTER (decl))
> + targetm.lower_local_decl_alignment (decl);
>
> the comment is quite useless, just repeating what the code does.
> Please rephrase it
> as
>
> /* This is the last point we can lower alignment so give the target the
> chance to do so. */
>
> and remove the vertical space after the comment.
>
> OK with those changes.
> Richard.
>
Updated patch attached. I will ask H.J. to check it in for me.
--Sunil
> > > > > > On Tue, Jul 14, 2020 at 8:37 AM Sunil Pandey <skpgkp1@gmail.com> wrote:
> > > > > >>
> > > > > >> On Sat, Jul 4, 2020 at 9:11 AM Richard Biener
> > > > > >> <richard.guenther@gmail.com> wrote:
> > > > > >> >
> > > > > >> > On July 3, 2020 11:16:46 PM GMT+02:00, Jason Merrill <jason@redhat.com> wrote:
> > > > > >> > >On 6/29/20 5:00 AM, Richard Biener wrote:
> > > > > >> > >> On Fri, Jun 26, 2020 at 10:11 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> > > > > >> > >>>
> > > > > >> > >>> On Thu, Jun 25, 2020 at 1:10 AM Richard Biener
> > > > > >> > >>> <richard.guenther@gmail.com> wrote:
> > > > > >> > >>>>
> > > > > >> > >>>> On Thu, Jun 25, 2020 at 2:53 AM Sunil Pandey <skpgkp1@gmail.com>
> > > > > >> > >wrote:
> > > > > >> > >>>>>
> > > > > >> > >>>>> On Wed, Jun 24, 2020 at 12:30 AM Richard Biener
> > > > > >> > >>>>> <richard.guenther@gmail.com> wrote:
> > > > > >> > >>>>>>
> > > > > >> > >>>>>> On Tue, Jun 23, 2020 at 5:31 PM Sunil K Pandey via Gcc-patches
> > > > > >> > >>>>>> <gcc-patches@gcc.gnu.org> wrote:
> > > > > >> > >>>>>>>
> > > > > >> > >>>>>>> From: Sunil K Pandey <skpgkp1@gmail.com>
> > > > > >> > >>>>>>>
> > > > > >> > >>>>>>> Default for this hook is NOP. For x86, in 32 bit mode, this hook
> > > > > >> > >>>>>>> sets alignment of long long on stack to 32 bits if preferred
> > > > > >> > >stack
> > > > > >> > >>>>>>> boundary is 32 bits.
> > > > > >> > >>>>>>>
> > > > > >> > >>>>>>> - This patch fixes
> > > > > >> > >>>>>>> gcc.target/i386/pr69454-2.c
> > > > > >> > >>>>>>> gcc.target/i386/stackalign/longlong-1.c
> > > > > >> > >>>>>>> - Regression test on x86-64, no new fail introduced.
> > > > > >> > >>>>>>
> > > > > >> > >>>>>> I think the name is badly chosen,
> > > > > >> > >TARGET_LOWER_LOCAL_DECL_ALIGNMENT
> > > > > >> > >>>>>
> > > > > >> > >>>>> Yes, I can change the target hook name.
> > > > > >> > >>>>>
> > > > > >> > >>>>>> would be better suited (and then asks for LOCAL_DECL_ALIGNMENT to
> > > > > >> > >be
> > > > > >> > >>>>>> renamed to INCREASE_LOCAL_DECL_ALIGNMENT).
> > > > > >> > >>>>>
> > > > > >> > >>>>> It seems like LOCAL_DECL_ALIGNMENT macro documentation is
> > > > > >> > >incorrect.
> > > > > >> > >>>>> It increases as well as decreases alignment based on
> > > > > >> > >condition(-m32
> > > > > >> > >>>>> -mpreferred-stack-boundary=2)
> > > > > >> > >>>>> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95885
> > > > > >> > >>>>>
> > > > > >> > >>>>>>
> > > > > >> > >>>>>> You're calling it from do_type_align which IMHO is dangerous
> > > > > >> > >since that's
> > > > > >> > >>>>>> invoked from FIELD_DECL layout as well. Instead invoke it from
> > > > > >> > >>>>>> layout_decl itself where we do
> > > > > >> > >>>>>>
> > > > > >> > >>>>>> if (code != FIELD_DECL)
> > > > > >> > >>>>>> /* For non-fields, update the alignment from the type. */
> > > > > >> > >>>>>> do_type_align (type, decl);
> > > > > >> > >>>>>>
> > > > > >> > >>>>>> and invoke the hook _after_ do_type_align. Also avoid
> > > > > >> > >>>>>> invoking the hook on globals or hard regs and only
> > > > > >> > >>>>>> invoke it on VAR_DECLs, thus only
> > > > > >> > >>>>>>
> > > > > >> > >>>>>> if (VAR_P (decl) && !is_global_var (decl) &&
> > > > > >> > >!DECL_HARD_REGISTER (decl))
> > > > > >> > >>>>>
> > > > > >> > >>>>> It seems like decl property is not fully populated at this point
> > > > > >> > >call
> > > > > >> > >>>>> to is_global_var (decl) on global variable return false.
> > > > > >> > >>>>>
> > > > > >> > >>>>> $ cat foo.c
> > > > > >> > >>>>> long long x;
> > > > > >> > >>>>> int main()
> > > > > >> > >>>>> {
> > > > > >> > >>>>> if (__alignof__(x) != 8)
> > > > > >> > >>>>> __builtin_abort();
> > > > > >> > >>>>> return 0;
> > > > > >> > >>>>> }
> > > > > >> > >>>>>
> > > > > >> > >>>>> Breakpoint 1, layout_decl (decl=0x7ffff7ffbb40, known_align=0)
> > > > > >> > >>>>> at /local/skpandey/gccwork/gccwork/gcc/gcc/stor-layout.c:674
> > > > > >> > >>>>> 674 do_type_align (type, decl);
> > > > > >> > >>>>> Missing separate debuginfos, use: dnf debuginfo-install
> > > > > >> > >>>>> gmp-6.1.2-10.fc31.x86_64 isl-0.16.1-9.fc31.x86_64
> > > > > >> > >>>>> libmpc-1.1.0-4.fc31.x86_64 mpfr-3.1.6-5.fc31.x86_64
> > > > > >> > >>>>> zlib-1.2.11-20.fc31.x86_64
> > > > > >> > >>>>> (gdb) call debug_tree(decl)
> > > > > >> > >>>>> <var_decl 0x7ffff7ffbb40 x
> > > > > >> > >>>>> type <integer_type 0x7fffea801888 long long int DI
> > > > > >> > >>>>> size <integer_cst 0x7fffea7e8d38 constant 64>
> > > > > >> > >>>>> unit-size <integer_cst 0x7fffea7e8d50 constant 8>
> > > > > >> > >>>>> align:64 warn_if_not_align:0 symtab:0 alias-set -1
> > > > > >> > >>>>> canonical-type 0x7fffea801888 precision:64 min <integer_cst
> > > > > >> > >>>>> 0x7fffea7e8fd8 -9223372036854775808> max <integer_cst
> > > > > >> > >0x7fffea806000
> > > > > >> > >>>>> 9223372036854775807>
> > > > > >> > >>>>> pointer_to_this <pointer_type 0x7fffea8110a8>>
> > > > > >> > >>>>> DI foo.c:1:11 size <integer_cst 0x7fffea7e8d38 64> unit-size
> > > > > >> > >>>>> <integer_cst 0x7fffea7e8d50 8>
> > > > > >> > >>>>> align:1 warn_if_not_align:0>
> > > > > >> > >>>>>
> > > > > >> > >>>>> (gdb) p is_global_var(decl)
> > > > > >> > >>>>> $1 = false
> > > > > >> > >>>>> (gdb)
> > > > > >> > >>>>>
> > > > > >> > >>>>>
> > > > > >> > >>>>> What about calling hook here
> > > > > >> > >>>>>
> > > > > >> > >>>>> 603 do_type_align (tree type, tree decl)
> > > > > >> > >>>>> 604 {
> > > > > >> > >>>>> 605 if (TYPE_ALIGN (type) > DECL_ALIGN (decl))
> > > > > >> > >>>>> 606 {
> > > > > >> > >>>>> 607 SET_DECL_ALIGN (decl, TYPE_ALIGN (type));
> > > > > >> > >>>>> 608 if (TREE_CODE (decl) == FIELD_DECL)
> > > > > >> > >>>>> 609 DECL_USER_ALIGN (decl) = TYPE_USER_ALIGN (type);
> > > > > >> > >>>>> 610 else
> > > > > >> > >>>>> 611 /* Lower local decl alignment */
> > > > > >> > >>>>> 612 if (VAR_P (decl)
> > > > > >> > >>>>> 613 && !is_global_var (decl)
> > > > > >> > >>>>> 614 && !DECL_HARD_REGISTER (decl)
> > > > > >> > >>>>> 615 && cfun != NULL)
> > > > > >> > >>>>> 616 targetm.lower_local_decl_alignment (decl);
> > > > > >> > >>>>> 617 }
> > > > > >> > >>>>
> > > > > >> > >>>> But that doesn't change anything (obviously). layout_decl
> > > > > >> > >>>> is called quite early, too early it looks like.
> > > > > >> > >>>>
> > > > > >> > >>>> Now there doesn't seem to be any other good place where
> > > > > >> > >>>> we are sure to catch the decl before we evaluate things
> > > > > >> > >>>> like __alignof__
> > > > > >> > >>>>
> > > > > >> > >>>> void __attribute__((noipa))
> > > > > >> > >>>> foo (__SIZE_TYPE__ align, long long *p)
> > > > > >> > >>>> {
> > > > > >> > >>>> if ((__SIZE_TYPE__)p & (align-1))
> > > > > >> > >>>> __builtin_abort ();
> > > > > >> > >>>> }
> > > > > >> > >>>> int main()
> > > > > >> > >>>> {
> > > > > >> > >>>> long long y;
> > > > > >> > >>>> foo (_Alignof y, &y);
> > > > > >> > >>>> return 0;
> > > > > >> > >>>> }
> > > > > >> > >>>>
> > > > > >> > >>>> Joseph/Jason - do you have a good recommendation
> > > > > >> > >>>> how to deal with targets where natural alignment
> > > > > >> > >>>> is supposed to be lowered for optimization purposes?
> > > > > >> > >>>> (this case is for i?86 to avoid dynamic stack re-alignment
> > > > > >> > >>>> to align long long to 8 bytes with -mpreferred-stack-boundary=2)
> > > > > >> > >>>>
> > > > > >> > >>>> I note that for -mincoming-stack-boundary=2 we do perform
> > > > > >> > >>>> dynamic stack re-alignment already.
> > > > > >> > >>>>
> > > > > >> > >>>> I can't find a suitable existing target macro/hook for this,
> > > > > >> > >>>> but my gut feeling is that the default alignment should
> > > > > >> > >>>> instead be the lower one and instead the alignment for
> > > > > >> > >>>> globals should be raised as optimization?
> > > > > >> > >>>>
> > > > > >> > >>>
> > > > > >> > >>> Here is the updated patch from Sunil.
> > > > > >> > >>
> > > > > >> > >> It does not address the fundamental issue that during
> > > > > >> > >> do_type_align the is_global_var predicate is not
> > > > > >> > >> reliable. This means that for
> > > > > >> > >>
> > > > > >> > >> int main()
> > > > > >> > >> {
> > > > > >> > >> extern long z;
> > > > > >> > >> }
> > > > > >> > >>
> > > > > >> > >> the new hook (with -m32 -mpreferred-stack-boundary=2)
> > > > > >> > >> will lower the alignment of 'z' which looks wrong. During
> > > > > >> > >> layout_decl we can unfortunately not distinguish between
> > > > > >> > >> locals and globals. We need to find another spot to adjust
> > > > > >> > >> alignment of locals. For C that might be in finish_decl,
> > > > > >> > >> for C++ there's probably another suitable place.
> > > > > >> > >
> > > > > >> > >cp_finish_decl could work, but layout_decl seems like the right spot;
> > > > > >> > >if
> > > > > >> > >the problem is that the appropriate flags currently aren't being set in
> > > > > >> > >
> > > > > >> > >time, can't we fix that?
> > > > > >> >
> > > > > >> > The first and usually only call to layout_decl is from build_decl which gets nothing more than the type... But yes, I also initially thought that's the correct spot but it turns out it isn't.
> > > > > >>
> > > > > >> I added a new function lower_decl_alignment and invoked from
> > > > > >> cp_decl_finish/decl_finish. Attached is revised patch.
> > > > > >> >
> > > > > >> > >> Note it needs to be a place before the frontends possibly
> > > > > >> > >> inspect the alignment of the decl
> > > > > >> > >> In C++ constexpr evalualtion might also expose alignment
> > > > > >> > >> "early" so we really need a frontend solution here.
> > > > > >> > >
> > > > > >> > >Yes, we need to know the alignment right after the declaration.
> > > > > >> > >
> > > > > >> > >Jason
> > > > > >> >
-------------- next part --------------
From c4f601c0f6ebfa2a417a76aedcfa5fcf112f318d Mon Sep 17 00:00:00 2001
From: Sunil K Pandey <skpgkp2@gmail.com>
Date: Fri, 17 Jul 2020 19:42:09 -0700
Subject: [PATCH] Add TARGET_LOWER_LOCAL_DECL_ALIGNMENT [PR95237]
Default for this hook is NOP. For x86, in 32 bit mode, this hook
sets alignment of long long on stack to 32 bits if preferred stack
boundary is 32 bits.
- This patch prevents lowering of alignment from following macros.
LOCAL_ALIGNMENT
STACK_SLOT_ALIGNMENT
LOCAL_DECL_ALIGNMENT
- This patch fixes
gcc.target/i386/pr69454-2.c
gcc.target/i386/stackalign/longlong-1.c
- Regression test on x86-64, no new fail introduced.
Tested on x86-64.
gcc/c/ChangeLog:
PR target/95237
* c-decl.c (finish_decl): Call target hook
lower_local_decl_alignment to lower local decl alignment.
gcc/ChangeLog:
PR target/95237
* config/i386/i386-protos.h (ix86_local_alignment): Add
another function parameter may_lower alignment. Default is
false.
* config/i386/i386.c (ix86_lower_local_decl_alignment): New
function.
(ix86_local_alignment): Amend ix86_local_alignment to accept
another parameter may_lower. If may_lower is true, new align
may be lower than incoming alignment. If may_lower is false,
new align will be greater or equal to incoming alignment.
(TARGET_LOWER_LOCAL_DECL_ALIGNMENT): Define.
* doc/tm.texi: Regenerate.
* doc/tm.texi.in (TARGET_LOWER_LOCAL_DECL_ALIGNMENT): New
hook.
* target.def (lower_local_decl_alignment): New hook.
gcc/cp/ChangeLog:
PR target/95237
* decl.c (cp_finish_decl): Call target hook
lower_local_decl_alignment to lower local decl alignment.
gcc/testsuite/ChangeLog:
PR target/95237
* c-c++-common/pr95237-1.c: New test.
* c-c++-common/pr95237-2.c: New test.
* c-c++-common/pr95237-3.c: New test.
* c-c++-common/pr95237-4.c: New test.
* c-c++-common/pr95237-5.c: New test.
* c-c++-common/pr95237-6.c: New test.
* c-c++-common/pr95237-7.c: New test.
* c-c++-common/pr95237-8.c: New test.
* c-c++-common/pr95237-9.c: New test.
---
gcc/c/c-decl.c | 7 +++++++
gcc/config/i386/i386-protos.h | 2 +-
gcc/config/i386/i386.c | 18 ++++++++++++++++--
gcc/cp/decl.c | 7 +++++++
gcc/doc/tm.texi | 5 +++++
gcc/doc/tm.texi.in | 2 ++
gcc/target.def | 7 +++++++
gcc/testsuite/c-c++-common/pr95237-1.c | 16 ++++++++++++++++
gcc/testsuite/c-c++-common/pr95237-2.c | 10 ++++++++++
gcc/testsuite/c-c++-common/pr95237-3.c | 10 ++++++++++
gcc/testsuite/c-c++-common/pr95237-4.c | 10 ++++++++++
gcc/testsuite/c-c++-common/pr95237-5.c | 16 ++++++++++++++++
gcc/testsuite/c-c++-common/pr95237-6.c | 24 ++++++++++++++++++++++++
gcc/testsuite/c-c++-common/pr95237-7.c | 19 +++++++++++++++++++
gcc/testsuite/c-c++-common/pr95237-8.c | 10 ++++++++++
gcc/testsuite/c-c++-common/pr95237-9.c | 10 ++++++++++
16 files changed, 170 insertions(+), 3 deletions(-)
create mode 100644 gcc/testsuite/c-c++-common/pr95237-1.c
create mode 100644 gcc/testsuite/c-c++-common/pr95237-2.c
create mode 100644 gcc/testsuite/c-c++-common/pr95237-3.c
create mode 100644 gcc/testsuite/c-c++-common/pr95237-4.c
create mode 100644 gcc/testsuite/c-c++-common/pr95237-5.c
create mode 100644 gcc/testsuite/c-c++-common/pr95237-6.c
create mode 100644 gcc/testsuite/c-c++-common/pr95237-7.c
create mode 100644 gcc/testsuite/c-c++-common/pr95237-8.c
create mode 100644 gcc/testsuite/c-c++-common/pr95237-9.c
diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
index 81bd2ee94f0..5d6b504fe78 100644
--- a/gcc/c/c-decl.c
+++ b/gcc/c/c-decl.c
@@ -5600,6 +5600,13 @@ finish_decl (tree decl, location_t init_loc, tree init,
NULL_TREE, DECL_ATTRIBUTES (decl));
}
+ /* This is the last point we can lower alignment so give the target the
+ chance to do so. */
+ if (VAR_P (decl)
+ && !is_global_var (decl)
+ && !DECL_HARD_REGISTER (decl))
+ targetm.lower_local_decl_alignment (decl);
+
invoke_plugin_callbacks (PLUGIN_FINISH_DECL, decl);
}
diff --git a/gcc/config/i386/i386-protos.h b/gcc/config/i386/i386-protos.h
index 7c2ce618f3f..0b95c57b1a0 100644
--- a/gcc/config/i386/i386-protos.h
+++ b/gcc/config/i386/i386-protos.h
@@ -223,7 +223,7 @@ extern void init_cumulative_args (CUMULATIVE_ARGS *, tree, rtx, tree, int);
#ifdef TREE_CODE
extern int ix86_data_alignment (tree, unsigned int, bool);
extern unsigned int ix86_local_alignment (tree, machine_mode,
- unsigned int);
+ unsigned int, bool = false);
extern unsigned int ix86_minimum_alignment (tree, machine_mode,
unsigned int);
extern tree ix86_handle_shared_attribute (tree *, tree, tree, int, bool *);
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 5c373c091ce..45e85dd13de 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -16768,6 +16768,16 @@ ix86_data_alignment (tree type, unsigned int align, bool opt)
return align;
}
+/* Implememnt TARGET_LOWER_LOCAL_DECL_ALIGNMENT. */
+static void
+ix86_lower_local_decl_alignment (tree decl)
+{
+ unsigned int new_align = ix86_local_alignment (decl, VOIDmode,
+ DECL_ALIGN (decl), true);
+ if (new_align < DECL_ALIGN (decl))
+ SET_DECL_ALIGN (decl, new_align);
+}
+
/* Compute the alignment for a local variable or a stack slot. EXP is
the data type or decl itself, MODE is the widest mode available and
ALIGN is the alignment that the object would ordinarily have. The
@@ -16776,7 +16786,7 @@ ix86_data_alignment (tree type, unsigned int align, bool opt)
unsigned int
ix86_local_alignment (tree exp, machine_mode mode,
- unsigned int align)
+ unsigned int align, bool may_lower)
{
tree type, decl;
@@ -16793,7 +16803,8 @@ ix86_local_alignment (tree exp, machine_mode mode,
/* Don't do dynamic stack realignment for long long objects with
-mpreferred-stack-boundary=2. */
- if (!TARGET_64BIT
+ if (may_lower
+ && !TARGET_64BIT
&& align == 64
&& ix86_preferred_stack_boundary < 64
&& (mode == DImode || (type && TYPE_MODE (type) == DImode))
@@ -23521,6 +23532,9 @@ ix86_run_selftests (void)
#undef TARGET_CAN_CHANGE_MODE_CLASS
#define TARGET_CAN_CHANGE_MODE_CLASS ix86_can_change_mode_class
+#undef TARGET_LOWER_LOCAL_DECL_ALIGNMENT
+#define TARGET_LOWER_LOCAL_DECL_ALIGNMENT ix86_lower_local_decl_alignment
+
#undef TARGET_STATIC_RTX_ALIGNMENT
#define TARGET_STATIC_RTX_ALIGNMENT ix86_static_rtx_alignment
#undef TARGET_CONSTANT_ALIGNMENT
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 6e4d546d55e..d72abc1a111 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -8012,6 +8012,13 @@ cp_finish_decl (tree decl, tree init, bool init_const_expr_p,
NULL_TREE, DECL_ATTRIBUTES (decl));
}
+ /* This is the last point we can lower alignment so give the target the
+ chance to do so. */
+ if (VAR_P (decl)
+ && !is_global_var (decl)
+ && !DECL_HARD_REGISTER (decl))
+ targetm.lower_local_decl_alignment (decl);
+
invoke_plugin_callbacks (PLUGIN_FINISH_DECL, decl);
}
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index 6e7d9dc54a9..1058221842d 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -1086,6 +1086,11 @@ On 32-bit ELF the largest supported section alignment in bits is
@samp{(0x80000000 * 8)}, but this is not representable on 32-bit hosts.
@end defmac
+@deftypefn {Target Hook} void TARGET_LOWER_LOCAL_DECL_ALIGNMENT (tree @var{decl})
+Define this hook to lower alignment of local, parm or result
+decl @samp{(@var{decl})}.
+@end deftypefn
+
@deftypefn {Target Hook} HOST_WIDE_INT TARGET_STATIC_RTX_ALIGNMENT (machine_mode @var{mode})
This hook returns the preferred alignment in bits for a
statically-allocated rtx, such as a constant pool entry. @var{mode}
diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index 3be984bbd5c..d76c85d5800 100644
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -1036,6 +1036,8 @@ On 32-bit ELF the largest supported section alignment in bits is
@samp{(0x80000000 * 8)}, but this is not representable on 32-bit hosts.
@end defmac
+@hook TARGET_LOWER_LOCAL_DECL_ALIGNMENT
+
@hook TARGET_STATIC_RTX_ALIGNMENT
@defmac DATA_ALIGNMENT (@var{type}, @var{basic-align})
diff --git a/gcc/target.def b/gcc/target.def
index 07059a87caf..e122d3c32c2 100644
--- a/gcc/target.def
+++ b/gcc/target.def
@@ -3348,6 +3348,13 @@ HOOK_VECTOR_END (addr_space)
#undef HOOK_PREFIX
#define HOOK_PREFIX "TARGET_"
+DEFHOOK
+(lower_local_decl_alignment,
+ "Define this hook to lower alignment of local, parm or result\n\
+decl @samp{(@var{decl})}.",
+ void, (tree decl),
+ hook_void_tree)
+
DEFHOOK
(static_rtx_alignment,
"This hook returns the preferred alignment in bits for a\n\
diff --git a/gcc/testsuite/c-c++-common/pr95237-1.c b/gcc/testsuite/c-c++-common/pr95237-1.c
new file mode 100644
index 00000000000..8947a9fed26
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr95237-1.c
@@ -0,0 +1,16 @@
+/* { dg-do run } */
+/* { dg-require-effective-target ia32 } */
+/* { dg-options "-mpreferred-stack-boundary=2" { target { i?86-*-* x86_64-*-* } } } */
+typedef __UINTPTR_TYPE__ uintptr_t;
+void __attribute__((noipa)) foo (long long *p, uintptr_t a)
+{
+ if ((uintptr_t)p & (a-1))
+ __builtin_abort ();
+}
+int main()
+{
+ long long x;
+ uintptr_t a = __alignof__(x);
+ foo(&x, a);
+ return 0;
+}
diff --git a/gcc/testsuite/c-c++-common/pr95237-2.c b/gcc/testsuite/c-c++-common/pr95237-2.c
new file mode 100644
index 00000000000..87949a9e122
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr95237-2.c
@@ -0,0 +1,10 @@
+/* { dg-do run } */
+/* { dg-require-effective-target ia32 } */
+/* { dg-options "-mpreferred-stack-boundary=2" { target { i?86-*-* x86_64-*-* } } } */
+long long x;
+int main()
+{
+ if (__alignof__(x) != 8)
+ __builtin_abort();
+ return 0;
+}
diff --git a/gcc/testsuite/c-c++-common/pr95237-3.c b/gcc/testsuite/c-c++-common/pr95237-3.c
new file mode 100644
index 00000000000..6941b6f154b
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr95237-3.c
@@ -0,0 +1,10 @@
+/* { dg-do run } */
+/* { dg-require-effective-target ia32 } */
+/* { dg-options "-mpreferred-stack-boundary=2" { target { i?86-*-* x86_64-*-* } } } */
+int main()
+{
+ long long x;
+ if (__alignof__(x) != 4)
+ __builtin_abort();
+ return 0;
+}
diff --git a/gcc/testsuite/c-c++-common/pr95237-4.c b/gcc/testsuite/c-c++-common/pr95237-4.c
new file mode 100644
index 00000000000..deace53cc26
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr95237-4.c
@@ -0,0 +1,10 @@
+/* { dg-do run } */
+/* { dg-require-effective-target ia32 } */
+/* { dg-options "-mpreferred-stack-boundary=4" { target { i?86-*-* x86_64-*-* } } } */
+int main()
+{
+ long long x;
+ if (__alignof__(x) != 8)
+ __builtin_abort();
+ return 0;
+}
diff --git a/gcc/testsuite/c-c++-common/pr95237-5.c b/gcc/testsuite/c-c++-common/pr95237-5.c
new file mode 100644
index 00000000000..9dc5cfcd739
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr95237-5.c
@@ -0,0 +1,16 @@
+/* { dg-do compile { target ia32 } } */
+/* { dg-options "-mpreferred-stack-boundary=2 -Os -w" { target { i?86-*-* x86_64-*-* } } } */
+
+int a;
+
+long long __attribute__((noinline))
+b (void)
+{
+}
+
+void
+c (void)
+{
+ if (b())
+ a = 1;
+}
diff --git a/gcc/testsuite/c-c++-common/pr95237-6.c b/gcc/testsuite/c-c++-common/pr95237-6.c
new file mode 100644
index 00000000000..ce1568fa282
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr95237-6.c
@@ -0,0 +1,24 @@
+/* { dg-do run } */
+/* { dg-options "-O2" { target { i?86-*-* x86_64-*-* } } } */
+#include <stddef.h>
+#ifdef __x86_64__
+# define EXP_ALIGN 8
+#else
+# define EXP_ALIGN 4
+#endif
+
+struct test
+{
+ char a;
+ long long b;
+};
+struct test global_var;
+int main()
+{
+ struct test local_var;
+ if (__alignof__(global_var) != EXP_ALIGN
+ || __alignof__(local_var) != EXP_ALIGN
+ || offsetof(struct test, b) != EXP_ALIGN)
+ __builtin_abort();
+ return 0;
+}
diff --git a/gcc/testsuite/c-c++-common/pr95237-7.c b/gcc/testsuite/c-c++-common/pr95237-7.c
new file mode 100644
index 00000000000..8410009d00e
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr95237-7.c
@@ -0,0 +1,19 @@
+/* { dg-do run } */
+/* { dg-require-effective-target ia32 } */
+/* { dg-options "-mpreferred-stack-boundary=2" { target { i?86-*-* x86_64-*-* } } } */
+#include <stddef.h>
+struct test
+{
+ char a;
+ long long b;
+};
+struct test global_var;
+int main()
+{
+ struct test local_var;
+ if (__alignof__(global_var) != 4
+ || __alignof__(local_var) != 4
+ || offsetof(struct test, b) != 4)
+ __builtin_abort();
+ return 0;
+}
diff --git a/gcc/testsuite/c-c++-common/pr95237-8.c b/gcc/testsuite/c-c++-common/pr95237-8.c
new file mode 100644
index 00000000000..8ba98abafc9
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr95237-8.c
@@ -0,0 +1,10 @@
+/* { dg-do run } */
+/* { dg-require-effective-target ia32 } */
+/* { dg-options "-mpreferred-stack-boundary=2" { target { i?86-*-* x86_64-*-* } } } */
+int main()
+{
+ extern long long x;
+ if (__alignof__(x) != 8)
+ __builtin_abort();
+ return 0;
+}
diff --git a/gcc/testsuite/c-c++-common/pr95237-9.c b/gcc/testsuite/c-c++-common/pr95237-9.c
new file mode 100644
index 00000000000..687517cbc0a
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr95237-9.c
@@ -0,0 +1,10 @@
+/* { dg-do run } */
+/* { dg-require-effective-target ia32 } */
+/* { dg-options "-mpreferred-stack-boundary=2" { target { i?86-*-* x86_64-*-* } } } */
+int main()
+{
+ static long long x;
+ if (__alignof__(x) != 8)
+ __builtin_abort();
+ return 0;
+}
--
2.25.4
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