RE: [PATCH, ARM] Backport fix for PR59593 (minipool of small values on big endian targets)

["Thomas Preud'homme" <thomas dot preudhomme at arm dot com>]

> From: Ramana Radhakrishnan [mailto:ramana.gcc@googlemail.com]
> Sent: Tuesday, February 17, 2015 4:08 PM
> To: Thomas Preud'homme
> Cc: gcc-patches; Richard Earnshaw; Ramana Radhakrishnan; Marcus
> Shawcroft; Richard Biener; Jakub Jelinek
> Subject: Re: [PATCH, ARM] Backport fix for PR59593 (minipool of small
> values on big endian targets)
> 
> On Tue, Jan 20, 2015 at 5:06 AM, Thomas Preud'homme
> <thomas.preudhomme@arm.com> wrote:
> > Currently on GCC 4.8 and 4.9, constant pool entries for QImode,
> HImode and SImode values are filled as 32-bit quantities. This works fine
> for little endian system but gives some incorrect results for big endian
> system when the value is accessed with a mode smaller than 32-bit in
> size. Suppose the case of the value 0x1234 that is accessed as an HImode
> value. It would be output as 0x0 0x0 0x12 0x34 in a constant pool entry
> and the 16-bit load that would be done would lead to the value 0x0 in
> register.
> >
> > This patch makes the consttable_1 and consttable_2 pattern available
> to ARM as well so that values are output according to their mode.
> >
> > This is a backport of commit r218118.
> >
> > *** gcc/ChangeLog ***
> >
> > 2015-01-14  Thomas Preud'homme  <thomas.preudhomme@arm.com>
> >
> >     Backport from mainline
> >     2014-11-27 Thomas Preud'homme <thomas.preudhomme@arm.com>
> >
> >     PR target/59593
> >     * config/arm/arm.c (dump_minipool): dispatch to consttable pattern
> >     based on mode size.
> >     * config/arm/arm.md (consttable_1): Make it TARGET_EITHER.
> >     (consttable_2): Make it TARGET_EITHER and move HFmode handling
> from
> >     consttable_4 to it.
> >     (consttable_4): Move HFmode handling to consttable_2 pattern.
> >
> >
> > *** gcc/testsuite/ChangeLog ***
> >
> > 2015-01-14  Thomas Preud'homme  <thomas.preudhomme@arm.com>
> >
> >     Backport from mainline
> >     2014-11-27 Thomas Preud'homme <thomas.preudhomme@arm.com>
> >
> >     PR target/59593
> >     * gcc.target/arm/constant-pool.c: New test.
> >
> >
> > diff --git a/gcc/ChangeLog b/gcc/ChangeLog
> > index 85372e5..eeaece8 100644
> > --- a/gcc/ChangeLog
> > +++ b/gcc/ChangeLog
> > @@ -1,3 +1,16 @@
> > +2015-01-14  Thomas Preud'homme
> <thomas.preudhomme@arm.com>
> > +
> > +       Backport from mainline
> > +       2014-11-27  Thomas Preud'homme
> <thomas.preudhomme@arm.com>
> > +
> > +       PR target/59593
> > +       * config/arm/arm.c (dump_minipool): dispatch to consttable
> pattern
> > +       based on mode size.
> > +       * config/arm/arm.md (consttable_1): Make it TARGET_EITHER.
> > +       (consttable_2): Make it TARGET_EITHER and move HFmode
> handling from
> > +       consttable_4 to it.
> > +       (consttable_4): Move HFmode handling to consttable_2 pattern.
> > +
> >  2015-01-14  Marek Polacek  <polacek@redhat.com>
> >
> >         Backport from mainline
> > diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
> > index 5e2571c..67ef80b 100644
> > --- a/gcc/config/arm/arm.c
> > +++ b/gcc/config/arm/arm.c
> > @@ -16274,7 +16274,7 @@ dump_minipool (rtx scan)
> >               fputc ('\n', dump_file);
> >             }
> >
> > -         switch (mp->fix_size)
> > +         switch (GET_MODE_SIZE (mp->mode))
> >             {
> >  #ifdef HAVE_consttable_1
> >             case 1:
> > diff --git a/gcc/config/arm/arm.md b/gcc/config/arm/arm.md
> > index 8119387..93b25e9 100644
> > --- a/gcc/config/arm/arm.md
> > +++ b/gcc/config/arm/arm.md
> > @@ -12224,7 +12224,7 @@
> >
> >  (define_insn "consttable_1"
> >    [(unspec_volatile [(match_operand 0 "" "")] VUNSPEC_POOL_1)]
> > -  "TARGET_THUMB1"
> > +  "TARGET_EITHER"
> >    "*
> >    making_const_table = TRUE;
> >    assemble_integer (operands[0], 1, BITS_PER_WORD, 1);
> > @@ -12237,14 +12237,23 @@
> >
> >  (define_insn "consttable_2"
> >    [(unspec_volatile [(match_operand 0 "" "")] VUNSPEC_POOL_2)]
> > -  "TARGET_THUMB1"
> > +  "TARGET_EITHER"
> >    "*
> > -  making_const_table = TRUE;
> > -  gcc_assert (GET_MODE_CLASS (GET_MODE (operands[0])) !=
> MODE_FLOAT);
> > -  assemble_integer (operands[0], 2, BITS_PER_WORD, 1);
> > -  assemble_zeros (2);
> > -  return \"\";
> > -  "
> > +  {
> > +    rtx x = operands[0];
> > +    making_const_table = TRUE;
> > +    switch (GET_MODE_CLASS (GET_MODE (x)))
> > +      {
> > +      case MODE_FLOAT:
> > +       arm_emit_fp16_const (x);
> > +       break;
> > +      default:
> > +       assemble_integer (operands[0], 2, BITS_PER_WORD, 1);
> > +       assemble_zeros (2);
> > +       break;
> > +      }
> > +    return \"\";
> > +  }"
> >    [(set_attr "length" "4")
> >     (set_attr "type" "no_insn")]
> >  )
> > @@ -12259,15 +12268,12 @@
> >      switch (GET_MODE_CLASS (GET_MODE (x)))
> >        {
> >        case MODE_FLOAT:
> > -       if (GET_MODE (x) == HFmode)
> > -         arm_emit_fp16_const (x);
> > -       else
> > -         {
> > -           REAL_VALUE_TYPE r;
> > -           REAL_VALUE_FROM_CONST_DOUBLE (r, x);
> > -           assemble_real (r, GET_MODE (x), BITS_PER_WORD);
> > -         }
> > -       break;
> > +       {
> > +         REAL_VALUE_TYPE r;
> > +         REAL_VALUE_FROM_CONST_DOUBLE (r, x);
> > +         assemble_real (r, GET_MODE (x), BITS_PER_WORD);
> > +         break;
> > +       }
> >        default:
> >         /* XXX: Sometimes gcc does something really dumb and ends up
> with
> >            a HIGH in a constant pool entry, usually because it's trying to
> > diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
> > index 222716d..49d1a73 100644
> > --- a/gcc/testsuite/ChangeLog
> > +++ b/gcc/testsuite/ChangeLog
> > @@ -1,3 +1,11 @@
> > +2015-01-14  Thomas Preud'homme
> <thomas.preudhomme@arm.com>
> > +
> > +       Backport from mainline
> > +       2014-11-27  Thomas Preud'homme
> <thomas.preudhomme@arm.com>
> > +
> > +       PR target/59593
> > +       * gcc.target/arm/constant-pool.c: New test.
> > +
> >  2015-01-14  Marek Polacek  <polacek@redhat.com>
> >
> >         Backport from mainline
> > diff --git a/gcc/testsuite/gcc.target/arm/constant-pool.c
> b/gcc/testsuite/gcc.target/arm/constant-pool.c
> > new file mode 100644
> > index 0000000..8427dfb
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/arm/constant-pool.c
> > @@ -0,0 +1,27 @@
> > +/* { dg-do run } */
> > +/* { dg-options "-O1" } */
> > +
> > +unsigned short v = 0x5678;
> > +int i;
> > +int j = 0;
> > +int *ptr = &j;
> > +
> > +int
> > +func (void)
> > +{
> > +  for (i = 0; i < 1; ++i)
> > +    {
> > +      *ptr = -1;
> > +      v = 0x1234;
> > +    }
> > +  return v;
> > +}
> > +
> > +int
> > +main (void)
> > +{
> > +  func ();
> > +  if (v != 0x1234)
> > +    __builtin_abort ();
> > +  return 0;
> > +}
> >
> >
> > Is this ok for 4.8 and 4.9 branches?
> 
> Ok if no regressions and no RM objects to this in 24 hours. I think
> it's baked sufficiently on trunk to backport now.

Done.

Best regards,

Thomas