[Bug tree-optimization/32698] [4.3 regression] inefficient pointer expression

[rguenth at gcc dot gnu dot org]

------- Comment #1 from rguenth at gcc dot gnu dot org  2007-07-09 13:39 -------
With 2.95, 3.3.6 and 3.4.6 I get (for 32bit):

foo:
        pushl %ebp
        movl %esp,%ebp
        movl 8(%ebp),%edx
        movl 12(%ebp),%eax
        movl %ebp,%esp
        popl %ebp
        movl 8(%edx,%eax,4),%ecx
        addl 4(%edx,%eax,4),%ecx
        addl 12(%edx,%eax,4),%ecx
        movl %ecx,%eax
        ret

4.0.3 and 4.1.2 generate:

foo:
        pushl   %ebp
        movl    %esp, %ebp
        movl    12(%ebp), %edx
        sall    $2, %edx
        addl    8(%ebp), %edx
        movl    8(%edx), %eax
        addl    4(%edx), %eax
        addl    12(%edx), %eax
        leave
        ret

4.2.0 generates

foo:
        pushl   %ebp
        movl    %esp, %ebp
        movl    12(%ebp), %ecx
        movl    8(%ebp), %edx
        popl    %ebp
        sall    $2, %ecx
        movl    4(%ecx,%edx), %eax
        addl    8(%ecx,%edx), %eax
        addl    12(%ecx,%edx), %eax
        ret

while mainline generates

foo:
        pushl   %ebp
        movl    %esp, %ebp
        movl    12(%ebp), %ecx
        movl    8(%ebp), %edx
        pushl   %ebx
        leal    0(,%ecx,4), %ebx
        movl    8(%ebx,%edx), %eax
        addl    4(%edx,%ecx,4), %eax
        addl    12(%ebx,%edx), %eax
        popl    %ebx
        popl    %ebp
        ret

64bit variants of all of the above create

foo:
.LFB2:
        leal    1(%rsi), %edx
        leal    2(%rsi), %eax
        addl    $3, %esi
        movl    (%rdi,%rax,4), %eax
        addl    (%rdi,%rdx,4), %eax
        addl    (%rdi,%rsi,4), %eax
        ret

Tree dumps (of mainline) 64bit vs. 32bit are:

  return (*(p + (long unsigned int) (i + 2) * 4) + *(p + (long unsigned int) (i
+ 1) * 4)) + *(p + (long unsigned int) (i + 3) * 4);

  unsigned int D.1660;
  D.1660 = i * 4;
  return (*(p + (D.1660 + 8)) + *(p + (i + 1) * 4)) + *(p + (D.1660 + 12));


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   GCC host triplet|i686-pc-linux-gnu           |
 GCC target triplet|                            |i686-*-*
           Keywords|                            |missed-optimization
   Last reconfirmed|0000-00-00 00:00:00         |2007-07-09 13:39:51
               date|                            |
   Target Milestone|---                         |4.3.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32698