[Clang][ICE][x86_64] Inline assembly symbols

[xavetar]

Code:

#include <stdio.h>
#include <inttypes.h>

unsigned long SYMBOL = 0x000000000000002A;

__attribute__((noinline, used))
unsigned long read_symbol(void) {
    unsigned long result = 0;
    __asm__ __volatile__ (
        "movq %[symbol]@GOTPCREL(%%rip), %%rax\n\t"
        "movq (%%rax), %[result]"
        : [result] "=r" (result)
        : [symbol] "m" (SYMBOL)
        : "rax"
    );
    return result;
}

int main(void) {
    unsigned long result = read_symbol();
    printf("Value of symbol: 0x%08" PRIx64 "\n", result);
    return 0;
}

Compiler automatically adds (%rip), error:

<FILE>:10:9: error: unexpected token in argument list
   10 |         "movq %[symbol]@GOTPCREL(%%rip), %%rax\n\t"
      |         ^
<inline asm>:1:19: note: instantiated into assembly here
    1 |         movq SYMBOL(%rip)@GOTPCREL(%rip), %rax
      |                          ^
1 error generated.

It is also not entirely clear how to specify the symbol; in some cases, "m" is sufficient, while in other cases, ":" is documented, but it does not work. This is a temporary solution:

__attribute__((noinline, used))
unsigned long read_symbol(void) {
    unsigned long result = 0;
    __asm__ __volatile__ (
        "movq SYMBOL@GOTPCREL(%%rip), %%rax\n\t"
        "movq (%%rax), %[result]"
        : [result] "=r" (result)
        :
        : "rax"
    );
    return result;
}

But this version is difficult to manage; when you change the slot name, you also need to change ASM. This problem exists only for x86 (64) for i686, i386 - everything is fine! The compiler automatically expands %[symbol] to %[symbol](%rip) on the x86 (64) platform, which is true for all cases:

"movq %[symbol](%%rip), %[result]\n\t"
"leaq %[symbol](%%rip), %%rax\n\t"
"movq %[symbol]@GOTPCREL(%%rip), %%rax\n\t"