[Bug target/69617] New: PowerPC/e6500: Atomic byte/halfword operations not properly supported

[sebastian.huber@embedded-brains.de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69617

            Bug ID: 69617
           Summary: PowerPC/e6500: Atomic byte/halfword operations not
                    properly supported
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: sebastian.huber@embedded-brains.de
  Target Milestone: ---

The PowerPC/e6500 support lacks support for the load/store byte/halfword with
decoration indexed instructions:

#include <stdatomic.h>

unsigned char inc_uchar(atomic_uchar *a)
{
        return atomic_fetch_add(a, 1);
}

unsigned short inc_ushort(atomic_ushort *a)
{
        return atomic_fetch_add(a, 1);
}

powerpc-rtems4.12-gcc -O2 -Wall -Wextra -pedantic -mcpu=e6500 -m32 -S atomic.c
cat atomic.s
        .file   "atomic.c"
        .machine power4
        .section        ".text"
        .align 2
        .p2align 4,,15
        .globl inc_uchar
        .type   inc_uchar, @function
inc_uchar:
        rlwinm 8,3,3,27,28
        li 7,255
        xori 8,8,0x18
        li 6,1
        sync
        slw 7,7,8
        slw 6,6,8
        rlwinm 9,3,0,0,29
.L2:
        lwarx 3,0,9
        add 5,3,6
        andc 10,3,7
        and 5,5,7
        or 10,10,5
        stwcx. 10,0,9
        bne- 0,.L2
        isync
        srw 3,3,8
        rlwinm 3,3,0,0xff
        blr
        .size   inc_uchar, .-inc_uchar
        .align 2
        .p2align 4,,15
        .globl inc_ushort
        .type   inc_ushort, @function
inc_ushort:
        rlwinm 8,3,3,27,27
        li 7,0
        xori 8,8,0x10
        ori 7,7,0xffff
        li 6,1
        sync
        slw 7,7,8
        slw 6,6,8
        rlwinm 9,3,0,0,29
.L6:
        lwarx 3,0,9
        add 5,3,6
        andc 10,3,7
        and 5,5,7
        or 10,10,5
        stwcx. 10,0,9
        bne- 0,.L6
        isync
        srw 3,3,8
        rlwinm 3,3,0,0xffff
        blr
        .size   inc_ushort, .-inc_ushort
        .ident  "GCC: (GNU) 6.0.0 20160202 (experimental)