v4.6.x

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Tricore/AURIX

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The compiler might generate jump tables for switch statements, where the destination code is missing. This cause that the jumps target will be undefined symbols causing linker error at link time.

Compiled with optimizations (e.g. with -O2) then linking the object will abort. The error messages is:

• error: undefined reference to '.L123'

Not needed. As the linker process is interrupted, the output file is not written.

Write the following C-program

extern int gvar_a;
extern int gvar_b;
void foo(void)
{
    int loc_var_a;
    int loc_var_b;
    if (gvar_b)
    {
        loc_var_a = 2;
        switch (gvar_a)
        {
        case 3:
            switch (gvar_b)
            {
            case 0:
                if (gvar_b == 0)
                {
                    loc_var_a = 0;
                }
                break;
            case 1:
                loc_var_a = 7;
                break;
            default:
                loc_var_a = 6;
                break;
            }
            break;
        }
        switch (loc_var_a)
        {
        case 2:
            loc_var_b = 3;
            break;
        case 3:
            loc_var_b = 4;
            break;
        case 4:
            loc_var_b = 5;
            break;
        case 6:
            loc_var_b = 6;
            break;
        default:
            loc_var_b = 7;
            break;
        }
    }
    gvar_a = loc_var_a;
    gvar_b = loc_var_b;
}

Compile it then create the dump with the following commands

tricore-gcc -O2 -c test.c -o test.o

tricore-objdump -d -t -r -w test.o

Objdump output:

SYMBOL TABLE:
00000000 l df *ABS* 00000000 reproducer.c
00000000 l d .text 00000000 .text
00000000 l d .data 00000000 .data
00000000 l d .bss 00000000 .bss
00000000 l d .comment 00000000 .comment
00000000 g F .text 0000003e foo
00000000 O *UND* 00000004 gvar_b
00000000 O *UND* 00000004 gvar_a
00000000 *UND* 00000000 .L14
00000000 *UND* 00000000 .L6
00000000 *UND* 00000000 .L7
00000000 *UND* 00000000 .L5
00000000 *UND* 00000000 .L8

Disassembly of section .text:

00000000 :
foo():
0: 91 00 00 20 movh.a %a2,0 0: R_TRICORE_HIADJ gvar_b
4: 19 2f 00 00 ld.w %d15,[%a2]0 <0 > 4: R_TRICORE_LO2 gvar_b
8: 91 00 00 f0 movh.a %a15,0 8: R_TRICORE_HIADJ gvar_a
c: 6e 14 jz %d15,34 
e: 19 f2 00 00 ld.w %d2,[%a15]0 <0 > e: R_TRICORE_LO2 gvar_a
12: df 32 0d 00 jeq %d2,3,2c 
16: 3c 01 j 18 
18: 1d 00 00 00 j 18  18: R_TRICORE_24REL .L14
1c: 1d 00 00 00 j 1c  1c: R_TRICORE_24REL .L6
20: 1d 00 00 00 j 20  20: R_TRICORE_24REL .L7
24: 1d 00 00 00 j 24  24: R_TRICORE_24REL .L5
28: 1d 00 00 00 j 28  28: R_TRICORE_24REL .L8
2c: ba 1f eq %d15,%d15,1
2e: 82 72 mov %d2,7
30: ea 62 cmovn %d2,%d15,6
32: 02 23 mov %d3,%d2
34: 59 f3 00 00 st.w [%a15]0 <0 >,%d3 34: R_TRICORE_LO2 gvar_a
38: 59 22 00 00 st.w [%a2]0 <0 >,%d2 38: R_TRICORE_LO2 gvar_b
3c: 00 90 ret
...

The jumps (j) leading to nowhere, therefore the target labels are undefined symbols.

• As workaround the option '-fno-jump-tables' can be used. This option disables the generation of jump tables which is the root cause here. Jump tables are not that effective on TriCore, therefore this can even lead to performance increase and better code size.

Confirmed