[Bug tree-optimization/19347] Invariant load not moved out of loop

[Bug tree-optimization/19347] Invariant load not moved out of loop

[phosit at autistici dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=19347

Phosit <phosit at autistici dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |phosit at autistici dot org

--- Comment #9 from Phosit <phosit at autistici dot org> ---
When there are few iterations (likely when it is unroled) there is no
alias-check:

void fill(int* data, int& value)
{
    for(unsigned long i{0}; i != 4; ++i)
        data[i] = value;
}

--- at -O2 results in:
fill(int*, int&):
        movd    xmm1, DWORD PTR [rsi]
        pshufd  xmm0, xmm1, 0xe0
        movq    QWORD PTR [rdi], xmm0
        movd    xmm0, DWORD PTR [rsi]
        pshufd  xmm0, xmm0, 0xe0
        movq    QWORD PTR [rdi+8], xmm0
        ret

---
At -O3 the loop isn't removed and (thus) there is an alias-check.

[Bug tree-optimization/19347] Invariant load not moved out of loop

[phosit at autistici dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=19347

--- Comment #10 from Phosit <phosit at autistici dot org> ---
The analysis in my previous comment is wrong.
I don't know why there is no alias-check at -O2.
Also the loop _is_ removed at -O3.

[Bug tree-optimization/19347] Invariant load not moved out of loop

[rguenth at gcc dot gnu dot org]

------- Comment #4 from rguenth at gcc dot gnu dot org  2009-04-03 12:06 -------
The store to *ptr aliases the load from osmesa->clearpixel - there
is no (easy) way to otherwise prove that it is not (at least with the
testcase).
We do not see where osmesa->buffer points to (it may point to
&osmesa->clearpixel).


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19347

[Bug tree-optimization/19347] Invariant load not moved out of loop

[pinskia at gcc dot gnu dot org]

------- Comment #3 from pinskia at gcc dot gnu dot org  2005-10-24 00:20 -------
This is the normal, we need offset/varaible aliasing.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dberlin at gcc dot gnu dot
                   |                            |org
           Keywords|                            |alias
   Last reconfirmed|2005-05-04 18:15:55         |2005-10-24 00:20:32
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19347

[Bug tree-optimization/19347] Invariant load not moved out of loop

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pinskia at gcc dot gnu dot
                   |                            |org
   Last reconfirmed|2005-01-09 15:55:15         |2005-04-11 06:09:59
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19347

[Bug tree-optimization/19347] Invariant load not moved out of loop

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-01-09 15:55 -------
Confirmed but add a full testcase here, thanks.

Actually I don't think it would require whole program analysis to do this in LIM (or LICM), we just need 
more information (which might be done on the structure-aliasing branch).

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
           Keywords|                            |missed-optimization
   Last reconfirmed|0000-00-00 00:00:00         |2005-01-09 15:55:15
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19347