[Bug target/45335] Use ldrd to load two consecutive words

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=45335

Andrew Pinski  changed:

   What|Removed |Added

  Known to work||14.0, 7.3.0
 Status|NEW |RESOLVED
 Resolution|--- |FIXED
  Known to fail||4.6.4, 5.4.0
   Target Milestone|--- |7.0

--- Comment #2 from Andrew Pinski  ---
6.3.0 produced:

sub r1, r4, #16
ldr r4, [r4, #-4]
ldr r0, .L3+4
ldm r1, {r1, r2, r3}

5.4.0 produced:

sub r1, r4, #16
ldr r4, [r4, #-4]
ldr r0, .L3+4
ldmia   r1, {r1, r2, r3}

7.40 produced:

ldrdr2, r3, [r4, #-12]
ldr r1, [r4, #-16]
ldrdr4, r5, [r4, #-4]
ldr r0, .L4+4
strdr4, r5, [sp]

Which was changed by r7-4653-g2fe3721128b991 or r7-991-g37923729c5ab01 .

The ldrd support was added originally with r0-122648-g4542a38a21fea5 (for GCC
4.9.0).

So closing as fixed.

[Bug target/45335] Use ldrd to load two consecutive words

[ramana at gcc dot gnu dot org]

-- 

ramana at gcc dot gnu dot org changed:

   What|Removed |Added

 Status|UNCONFIRMED |NEW
 Ever Confirmed|0   |1
   Keywords||missed-optimization
   Last reconfirmed|-00-00 00:00:00 |2010-08-23 08:23:52
   date||


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45335

[Bug target/45335] Use ldrd to load two consecutive words

[carrot at google dot com]

--- Comment #1 from carrot at google dot com  2010-08-20 03:13 ---
By simply define the following pattern

(define_insn *thumb2_ldrd
  [(parallel [(set (match_operand:SI 0 s_register_operand )
   (mem:SI (match_operand:SI 2  )))
  (set (match_operand:SI 1 s_register_operand )
   (mem:SI (match_operand:SI 3  )))])]
  TARGET_THUMB2  thumb2_ldrd_addr (operands[2], operands[3])
  *
  {
rtx ldrd_addr = thumb2_ldrd_addr (operands[2], operands[3]);
operands[4] = gen_rtx_MEM (SImode, ldrd_addr);
if (ldrd_addr == operands[3])
  return \ldrd\\t%1, %0, %4\;
else
  return \ldrd\\t%0, %1, %4\;
  }
)

The combine pass can't handle it. The instructions handled by combine should
have some def-use relation. There is no such relation in this case. So another
peephole2 rule is needed to catch the opportunity.

Even though there are chances missed. After register renumbering and
instruction scheduling, more chances are revealed. Change the option -O2 to -Os
can show such an example. So a peephole rule is needed to deal with this case.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45335