[Bug c/85923] invalid code generation when incrementing pointer referenced by pointer

[sami.kantoluoto at embedtronics dot fi]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85923

--- Comment #3 from Sami Kantoluoto <sami.kantoluoto at embedtronics dot fi> ---
When compiled with:

$ gcc-arm-none-eabi-7-2017-q4-major/bin/arm-none-eabi-gcc -v -save-temps -Wall
-Werror -Os -c skipblk.c -o skipblk.o

The following assembly is generated:

skipblk:
        @ Function supports interworking.
        @ args = 0, pretend = 0, frame = 0
        @ frame_needed = 0, uses_anonymous_args = 0
        ldr     r3, .L5
        ldr     r3, [r3]
        ldr     ip, [r3]
        mov     r3, #0
        ldr     r2, [r0]
        str     lr, [sp, #-4]!
        add     lr, r2, #1
.L2:
        ldrb    r1, [r2]        @ zero_extendqisi2
        ldrb    r1, [ip, r1]    @ zero_extendqisi2
        tst     r1, #8
        bne     .L3
        mov     r0, r3
        ldr     lr, [sp], #4
        bx      lr
.L3:
        str     lr, [r0]
        add     r3, r3, #1
        b       .L2
.L6:
        .align  2
.L5:
        .word   _ctype_tab_ptr

r2 is never incremented.