why clang use Ltmp lable

[LukeSTM]

example:

#include <stdio.h>

typedef struct {
    volatile int counter;
} Counter;

void foo(Counter *v, int i) {
    int result, val, tmp;

    __asm__ __volatile__(
        ".arch_extension mp\n"                
        "9998:    " "pldw\t%a0" "\n"           
        "    .pushsection \".alt.smp.init\", \"a\"\n" 
        "  .long   9998b - .\n"                
        "  " "pld\t%a0" "\n"                   
        " .popsection\n"                       
        "1: ldrex   %0, [%4]\n"               
        "   add     %1, %0, %5\n"               
        "   strex   %2, %1, [%4]\n"             
        "   teq     %2, #0\n"                  
        "   bne     1b"                        
        : "=&r" (result), "=&r" (val), "=&r" (tmp), "+Qo" (v->counter) 
        : "r" (&v->counter), "Ir" (i)         
        : "cc"                                
    );

    printf("Updated counter: %d\n", v->counter);
}

int main() {
    Counter c = {0};

    printf("Initial counter: %d\n", c.counter);
    foo(&c, 5);

    return 0;
}

https://godbolt.org/z/Px35ejvbn

compile option：-ffunction-sections -fdata-sections -march=armv7-a

Clang will split the foo function in the example into two parts, using Ltmp0 to represent the embedded assembly logic in the source code. Why is this done?

[LukeSTM]

clang readelf dump：
Symbol mbol table '.symtab' contains 23 entries:
Num: Value Size Type Bind Vis Ndx Name
0: 00000000 0 NOTYPE LOCAL DEFAULT UND
1: 00000000 0 FILE LOCAL DEFAULT ABS example.c
2: 00000000 0 SECTION LOCAL DEFAULT 3 .text.foo
3: 00000000 0 NOTYPE LOCAL DEFAULT 3 $a
4: 00000020 0 NOTYPE LOCAL DEFAULT 3 .Ltmp0
......

[asl]

The function is certainly not "split". Maybe you can elaborate why this is the problem? Essentially the label marks the end of prologue.

[LukeSTM]

https://sourceware.org/binutils/docs/as/L.html

[LukeSTM]

This behavior is not be consistent with GNU as, I want to know why.