[PATCH v2] PR target/96759 - Handle global variable assignment from misaligned structure/PARALLEL return values.

[Kito Cheng]

ping^2

Hi Eric:

Do you mind having a review for that?

thanks :)

On Mon, Oct 5, 2020 at 5:24 PM Kito Cheng <kito.cheng@sifive.com> wrote:

> ping.
>
>
> On Fri, Sep 25, 2020 at 2:33 PM Richard Biener <rguenther@suse.de> wrote:
>
>> On Fri, 25 Sep 2020, Kito Cheng wrote:
>>
>> > In g:70cdb21e579191fe9f0f1d45e328908e59c0179e, DECL/global variable has
>> handled
>> > misaligned stores, but it didn't handle PARALLEL values, and I refer the
>> > other part of this function, I found the PARALLEL need handled by
>> > emit_group_* functions, so I add a check, and using emit_group_store if
>> > storing a PARALLEL value, also checked this change didn't break the
>> > testcase(gcc.target/arm/unaligned-argument-3.c) added by the orginal
>> changes.
>> >
>> > For riscv64 target, struct S {int a; double b;} will pack into a
>> parallel
>> > value to return and it has TImode when misaligned access is supported,
>> > however TImode required 16-byte align, but it only 8-byte align, so it
>> go to
>> > the misaligned stores handling, then it will try to generate move
>> > instruction from a PARALLEL value.
>> >
>> > Tested on following target without introduced new reguression:
>> >   - riscv32/riscv64 elf
>> >   - x86_64-linux
>> >   - arm-eabi
>>
>> OK if Eric says so.
>>
>> Thanks,
>> Richard.
>>
>> > v2 changes:
>> >   - Use maybe_emit_group_store instead of emit_group_store.
>> >   - Remove push_temp_slots/pop_temp_slots, emit_group_store only require
>> >     stack temp slot when dst is CONCAT or PARALLEL, however
>> >     maybe_emit_group_store will always use REG for dst if needed.
>> >
>> > gcc/ChangeLog:
>> >
>> >       PR target/96759
>> >       * expr.c (expand_assignment): Handle misaligned stores with
>> PARALLEL
>> >       value.
>> >
>> > gcc/testsuite/ChangeLog:
>> >
>> >       PR target/96759
>> >       * g++.target/riscv/pr96759.C: New.
>> >       * gcc.target/riscv/pr96759.c: New.
>> > ---
>> >  gcc/expr.c                               |  2 ++
>> >  gcc/testsuite/g++.target/riscv/pr96759.C |  8 ++++++++
>> >  gcc/testsuite/gcc.target/riscv/pr96759.c | 13 +++++++++++++
>> >  3 files changed, 23 insertions(+)
>> >  create mode 100644 gcc/testsuite/g++.target/riscv/pr96759.C
>> >  create mode 100644 gcc/testsuite/gcc.target/riscv/pr96759.c
>> >
>> > diff --git a/gcc/expr.c b/gcc/expr.c
>> > index 1a15f24b3979..6eb13a12c8c5 100644
>> > --- a/gcc/expr.c
>> > +++ b/gcc/expr.c
>> > @@ -5168,6 +5168,8 @@ expand_assignment (tree to, tree from, bool
>> nontemporal)
>> >        rtx reg, mem;
>> >
>> >        reg = expand_expr (from, NULL_RTX, VOIDmode, EXPAND_NORMAL);
>> > +      /* Handle PARALLEL.  */
>> > +      reg = maybe_emit_group_store (reg, TREE_TYPE (from));
>> >        reg = force_not_mem (reg);
>> >        mem = expand_expr (to, NULL_RTX, VOIDmode, EXPAND_WRITE);
>> >        if (TREE_CODE (to) == MEM_REF && REF_REVERSE_STORAGE_ORDER (to))
>> > diff --git a/gcc/testsuite/g++.target/riscv/pr96759.C
>> b/gcc/testsuite/g++.target/riscv/pr96759.C
>> > new file mode 100644
>> > index 000000000000..673999a4baf7
>> > --- /dev/null
>> > +++ b/gcc/testsuite/g++.target/riscv/pr96759.C
>> > @@ -0,0 +1,8 @@
>> > +/* { dg-options "-mno-strict-align -std=gnu++17" } */
>> > +/* { dg-do compile } */
>> > +struct S {
>> > +  int a;
>> > +  double b;
>> > +};
>> > +S GetNumbers();
>> > +auto [globalC, globalD] = GetNumbers();
>> > diff --git a/gcc/testsuite/gcc.target/riscv/pr96759.c
>> b/gcc/testsuite/gcc.target/riscv/pr96759.c
>> > new file mode 100644
>> > index 000000000000..621c39196fca
>> > --- /dev/null
>> > +++ b/gcc/testsuite/gcc.target/riscv/pr96759.c
>> > @@ -0,0 +1,13 @@
>> > +/* { dg-options "-mno-strict-align" } */
>> > +/* { dg-do compile } */
>> > +
>> > +struct S {
>> > +  int a;
>> > +  double b;
>> > +};
>> > +struct S GetNumbers();
>> > +struct S g;
>> > +
>> > +void foo(){
>> > +  g = GetNumbers();
>> > +}
>> >
>>
>> --
>> Richard Biener <rguenther@suse.de>
>> SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
>> Germany; GF: Felix Imend
>>
>