[Bug target/99530] [i386] 'P' inline assembly operand modifier should obey -fno-plt

["thiago at kde dot org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99530

--- Comment #13 from Thiago Macieira <thiago at kde dot org> ---
> Since my patch uses output_asm_insn to finish the instruction, %P must be
> the last operand.

Okay.

If I wanted to abuse, I could just swap it around:

$ ~/dev/gcc/bin/gcc -fPIC -fno-plt -S -o - -O2 -xc - <<<'extern void f(void);
void g() { asm("cmp%z0 $0, %P0" : : "X" (f)); }' | grep GOTPC
        cmpq $0,        *f@GOTPCREL(%rip)

I can't see the need to do that.

The reason I needed to "call %P0" was to call an assembly function that did not
respect the ABI (intel-ipsec-mb's sha512_x8_avx512). The code looks like this:

#ifdef _WIN32
#  define EXTRA_CLOBBER "rsi", "rdi",
#  define OUT0          "+c" /* rcx */
#  define OUT1          "+d" /* rdx */
#else
#  define EXTRA_CLOBBER "rcx", "rdx",
#  define OUT0          "+D" /* rdi */
#  define OUT1          "+S" /* rsi */
#endif
    extern void sha512_x8_avx512(void *data, size_t size_in_blocks);
    __asm__ volatile ("call %P[func]"
            : OUT0 (data),
              OUT1 (size_in_blocks),
              "+m" (*(char (*)[])data)
            : [func] "X" (sha512_x8_avx512)
            :
    // caller-save registers
              "rax", "r8", "r9", "r10", "r11",
              EXTRA_CLOBBER
    // the current implementation does not use RBX and RBP
              // "rbx", "rbp",
    // the current implementation does clobber these callee-save registers
              "r12", "r13", "r14", "r15"
    );

https://github.com/intel/intel-ipsec-mb/blob/master/lib/avx512/sha512_x8_avx512.asm#L417