arm-eabi-gcc with -O2 is wrong code output.

[Ry deen]

Hi all,

The code that contains the code shown below is compiled
with arm-eabi-gcc -O2.

#include <stdio.h>

typedef struct {
        int member1;
} aaa_struct;

int bbb;

void test(aaa_struct *aaa)
{
        if((aaa_struct *)NULL == aaa) {
                printf("1\n");
        }
        else {
                printf("2\n");
        }

        bbb = aaa->member1;

        if((aaa_struct *)NULL == aaa) {
                printf("3\n");
        }
        else {
                printf("4\n");
        }
}

When the argument is NULL, this function outputs the
following result.

1
4

However, when optional -O1 is  specified, it is  correctly
executed.

When the assembler code is confirmed, the character string
"3" does lost by optimization. 

/* Output wrong code  : arm-eabi-gcc -O2 -S -o test.s
test.c */

        .cpu arm7tdmi
        .fpu softvfp
        .eabi_attribute 20, 1
        .eabi_attribute 21, 1
        .eabi_attribute 23, 3
        .eabi_attribute 24, 1
        .eabi_attribute 25, 1
        .eabi_attribute 26, 1
        .eabi_attribute 30, 2
        .eabi_attribute 18, 4
        .file   "test.c"
        .text
        .align  2
        .global test
        .type   test, %function
test:
        @ Function supports interworking.
        @ args = 0, pretend = 0, frame = 0
        @ frame_needed = 0, uses_anonymous_args = 0
        stmfd   sp!, {r4, lr}
        subs    r4, r0, #0
        beq     .L5
        ldr     r0, .L6
        bl      puts
.L3:
        ldr     r2, [r4, #0]
        ldr     r3, .L6+4
        ldr     r0, .L6+8
        str     r2, [r3, #0]
        bl      puts
        ldmfd   sp!, {r4, lr}
        bx      lr
.L5:
        ldr     r0, .L6+12
        bl      puts
        b       .L3
.L7:
        .align  2
.L6:
        .word   .LC1
        .word   bbb
        .word   .LC2
        .word   .LC0
        .size   test, .-test
        .comm   bbb,4,4
        .section        .rodata.str1.4,"aMS",%progbits,1
        .align  2
.LC0:
        .ascii  "1\000"
        .space  2
.LC1:
        .ascii  "2\000"
        .space  2
.LC2:
        .ascii  "4\000"
        .ident  "GCC: (GNU) 4.5.2"

arm-eabi-gcc that I used is as follows.

$ arm-eabi-gcc -v
Using built-in specs.
COLLECT_GCC=arm-eabi-gcc
COLLECT_LTO_WRAPPER=/home/user/opt/arm-eabi-4.5.2/bin/../libexec/gcc/arm-eabi/4.5.2/lto-wrapper
Target: arm-eabi
Configured with: ../configure --target=arm-eabi
--prefix=/home/user/opt/arm-eabi --enable-interwork
--enable-multilib --with-float=soft --with-fpu=vfp
--enable-languages=c,c++ --with-gnu-as --with-gnu-ld
--with-newlib
--with-headers=/home/user/work01/tmp/gcc-4.5.2/build/../newlib/libc/include/
--disable-newlib-supplied-syscalls
Thread model: single
gcc version 4.5.2 (GCC)
$ 

Regards,
Yuki HOSAKA.