[Bug tree-optimization/45144] New: SRA optimization issue of bit-field

[Bug tree-optimization/45144] New: SRA optimization issue of bit-field

[jiez at gcc dot gnu dot org]

For the following code:

void baz (unsigned);

extern unsigned buf[];

struct A
{
  unsigned a1:10;
  unsigned a2:3;
  unsigned:19;
};

union TMP
{
  struct A a;
  unsigned int b;
};

static unsigned
foo (struct A *p)
{
  union TMP t;
  struct A x;

  x = *p;
  t.a = x;
  return t.b;
}

void
bar (unsigned orig, unsigned *new)
{
  struct A a;
  union TMP s;

  s.b = orig;
  a = s.a;
  if (a.a1)
    baz (a.a2);
  *new = foo (&a);
}

"arm-none-eabi-gcc -O2" generates:

bar:
        @ Function supports interworking.
        @ args = 0, pretend = 0, frame = 0
        @ frame_needed = 0, uses_anonymous_args = 0
        stmfd   sp!, {r3, r4, r5, r6, r7, lr}
        mov     r4, r0, asl #22
        mov     r5, r0, lsr #10
        movs    r4, r4, lsr #22
        mov     r6, r1
        and     r5, r5, #7
        mov     r7, r0, lsr #13
        movne   r0, r5
        blne    baz
.L2:
        orr     r4, r4, r5, asl #10
        orr     r7, r4, r7, asl #13
        str     r7, [r6, #0]
        ldmfd   sp!, {r3, r4, r5, r6, r7, lr}
        bx      lr

while "arm-none-eabi-gcc -O2 -fno-tree-sra" generates:

bar:
        @ Function supports interworking.
        @ args = 0, pretend = 0, frame = 0
        @ frame_needed = 0, uses_anonymous_args = 0
        stmfd   sp!, {r3, r4, r5, lr}
        movs    r3, r0, asl #22
        mov     r4, r0
        mov     r5, r1
        movne   r0, r0, lsr #10
        andne   r0, r0, #7
        blne    baz
.L2:
        str     r4, [r5, #0]
        ldmfd   sp!, {r3, r4, r5, lr}
        bx      lr


-- 
           Summary: SRA optimization issue of bit-field
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jiez at gcc dot gnu dot org
GCC target triplet: arm-none-eabi


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45144

[Bug tree-optimization/45144] SRA optimization issue of bit-field

[jakub at gcc dot gnu dot org]

------- Comment #1 from jakub at gcc dot gnu dot org  2010-07-30 17:09 -------
The solution IMNSHO is to detect adjacent bitfield operations that can be
handled together and lower bitfield ops still at the tree level, though soon
before expansion, rather than disabling SRA for bitfields.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45144

[Bug tree-optimization/45144] SRA optimization issue of bit-field

[rguenth at gcc dot gnu dot org]

------- Comment #2 from rguenth at gcc dot gnu dot org  2010-07-31 09:25 -------
I agree.  SRA might be even the place to do this lowering in.  For ease of
use re-surrecting BIT_FIELD_EXPR from the mem-ref branch might turn out
useful for this.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45144

[Bug tree-optimization/45144] SRA optimization issue of bit-field

[jiez at gcc dot gnu dot org]

------- Comment #3 from jiez at gcc dot gnu dot org  2010-08-02 04:34 -------
Aggregates Copy Propagation should be able to fix this, too.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45144

[Bug tree-optimization/45144] SRA optimization issue of bit-field

[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|0000-00-00 00:00:00         |2010-08-02 07:54:22
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45144

[Bug tree-optimization/45144] SRA optimization issue of bit-field

[jiez at gcc dot gnu dot org]

------- Comment #4 from jiez at gcc dot gnu dot org  2010-08-05 03:06 -------
Subject: Bug 45144

Author: jiez
Date: Thu Aug  5 03:05:35 2010
New Revision: 162897

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=162897
Log:
        PR tree-optimization/45144
        * tree-sra.c (type_consists_of_records_p): Return false
        if the record contains bit-field.

        testsuite/
        PR tree-optimization/45144
        * gcc.dg/tree-ssa/pr45144.c: New test.

Added:
    trunk/gcc/testsuite/gcc.dg/tree-ssa/pr45144.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-sra.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45144

[Bug tree-optimization/45144] SRA optimization issue of bit-field

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45144

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
         AssignedTo|unassigned at gcc dot       |rguenth at gcc dot gnu.org
                   |gnu.org                     |

--- Comment #5 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-05-06 13:33:58 UTC ---
Fixed with my current lowering patch which gets rid of the struct A and
union TMP vars completely.