[Bug target/49857] New: Put constant switch-tables into flash

[Bug target/49857] New: Put constant switch-tables into flash

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49857

           Summary: Put constant switch-tables into flash
           Product: gcc
           Version: 4.6.1
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: gjl@gcc.gnu.org
                CC: eric.weddington@atmel.com
            Target: avr


Created attachment 24837
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=24837
C source with constant switch statement

For constant switches like

int sw_2 (char x)
{
    switch(x) 
    { 
        case '0': return -1;
        case '1': return  2;
        case '2': return  3;
        case '3': return  5;
        case '4': return  7;
        case '5': return 11;
        case '6': return 13;
        case '7': return 17;
        case '8': return 19;
        case '9': return 23;
        case 'a':return 29;
        case 'A':return 29;
    }

    return -1;
}

avr-gcc 4.6.1 generates a lookup table (-Os -mmcu=atmega8 -S -fverbose-asm)

sw_2:
    subi r24,lo8(-(-49))     ;  csui.0,
    cpi r24,lo8(49)     ;  csui.0,
    brsh .L3     ; ,
    mov r30,r24     ;  tmp50, csui.0
    ldi r31,lo8(0)     ; ,
    subi r30,lo8(-(CSWTCH.1))     ;  tmp50,
    sbci r31,hi8(-(CSWTCH.1))     ;  tmp50,
    ld r24,Z     ;  tmp51, CSWTCH.1
    clr r25     ;  D.1929
    sbrc r24,7     ;  D.1929
    com r25     ;  D.1929
    ret
.L3:
    ldi r24,lo8(-1)     ;  D.1929,
    ldi r25,hi8(-1)     ;  D.1929,
    ret
    .size    sw_2, .-sw_2
    .data
    .type    CSWTCH.1, @object
    .size    CSWTCH.1, 49
CSWTCH.1:
    .byte    2
    .byte    3
    .byte    5
    .byte    7
    .byte    11
    .byte    13
    .byte    17
    .byte    19
    .byte    23
    .byte    -1
    .byte    -1
    .byte    -1
...

CSWTCH.1 is put in .data (.rodata would not be better) so that the lookup table
ends up in RAM.  

The table is constant and could go into flash memory, i.e. .progmem.data.

===================================

avr-gcc -v -Os -fverbose-asm -mmcu=atmega8 -W -Wall -S foo.c # dp
-mmcu=atmega128 foo.c -save-temps -Os -c
Using built-in specs.
COLLECT_GCC=e:\WinAVR\4.6.1\bin\avr-gcc.exe
COLLECT_LTO_WRAPPER=e:/winavr/4.6.1/bin/../libexec/gcc/avr/4.6.1/lto-wrapper.exe
Target: avr
Configured with: ../../gcc.gnu.org/gcc-4_6-branch/configure --target=avr
--prefix=/local/gnu/install/gcc-4.6-mingw32 --host=i586-mingw32
--build=i686-linux-gnu --enable-languages=c,c++ --disable-nls --disable-shared
--with-dwarf2
Thread model: single
gcc version 4.6.1 20110620 (prerelease) (GCC) 

GNU C (GCC) version 4.6.1 20110620 (prerelease) (avr)
    compiled by GNU C version 3.3.1 (mingw special 20030804-1), GMP version
4.3.2, MPFR version 2.4.2, MPC version 0.8.2
GGC heuristics: --param ggc-min-expand=47 --param ggc-min-heapsize=32702

[Bug target/49857] Put constant switch-tables into flash

[eric.weddington at atmel dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49857

Eric Weddington <eric.weddington at atmel dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement

[Bug target/49857] Put constant switch-tables into flash

[eric.weddington at atmel dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49857

Eric Weddington <eric.weddington at atmel dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|2011-07-27 00:00:00         |2011-12-01
     Ever Confirmed|0                           |1

[Bug target/49857] Put constant switch-tables into flash

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49857

Georg-Johann Lay <gjl at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |addr-space
   Target Milestone|---                         |4.8.0

[Bug tree-optimization/49857] Put constant switch-tables into flash

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49857

Georg-Johann Lay <gjl at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|target                      |tree-optimization

--- Comment #1 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2012-01-29 14:55:48 UTC ---
Changed component from "target" to "tree-optimization" because:

The code in tree-switch-conversion.c needs to be extended by, say, a target
hook that queries the backend for the right address space for the generated
lookup table, i.e. the CSWTCH.num objects.

This is needed for two reasons:

1) The data (CSWTCH.num) has to be located in the preferred section,
   i.e. in Flash and not in RAM.

2) The accesses have to use the right instructions, i.e. instructions to read
from non-generic address space (Flash) and not instructions to access generic
address space (RAM).

[Bug rtl-optimization/49857] Put constant switch-tables into flash

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49857

Steven Bosscher <steven at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |steven at gcc dot gnu.org
          Component|tree-optimization           |rtl-optimization

--- Comment #2 from Steven Bosscher <steven at gcc dot gnu.org> 2012-01-29 17:24:32 UTC ---
Jump tables are generated in stmt.c, as part of expanding to RTL.

[Bug rtl-optimization/49857] Put constant switch-tables into flash

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49857

Steven Bosscher <steven at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|steven at gcc dot gnu.org   |

--- Comment #3 from Steven Bosscher <steven at gcc dot gnu.org> 2012-01-29 17:51:04 UTC ---
An, no, tree-switch-conversion.c:build_one_array() must build its value_type
for elements with a specified address space.

[Bug rtl-optimization/49857] Put constant switch-tables into flash

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49857

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.8.0                       |4.8.1

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-03-22 14:44:30 UTC ---
GCC 4.8.0 is being released, adjusting target milestone.

[Bug rtl-optimization/49857] Put constant switch-tables into flash

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49857

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.8.1                       |4.8.2

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 4.8.1 has been released.

[Bug rtl-optimization/49857] Put constant switch-tables into flash

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49857

Georg-Johann Lay <gjl at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.8.2                       |4.9.0

--- Comment #6 from Georg-Johann Lay <gjl at gcc dot gnu.org> ---
Bumped the milestone to 4.9

[Bug rtl-optimization/49857] Put constant switch-tables into flash

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49857

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.9.0                       |4.9.1

--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 4.9.0 has been released

[Bug rtl-optimization/49857] Put constant switch-tables into flash

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49857

Georg-Johann Lay <gjl at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P4
   Target Milestone|4.9.1                       |4.10.0

[Bug rtl-optimization/49857] Put constant switch-tables into flash

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=49857

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|5.0                         |5.2

--- Comment #8 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 5.1 has been released.

[Bug rtl-optimization/49857] Put constant switch-tables into flash

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=49857

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|5.2                         |5.3

--- Comment #9 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 5.2 is being released, adjusting target milestone to 5.3.