Re: [avr-llvm-devel] Inline assembly.

[Borja F. <bor...@gm...>]

Hello Stepan,

1) It seems clang mangles assembly functions names by prefixing a \01
character. I haven't found yet the code that does this depending on the
target used.

2) About the code above, I'm assuming you got that inline asm code from the
__LPM_dword_classic__ macro. This is what I'm getting for the following C
code:
typedef unsigned int uint16_t;
typedef unsigned long uint32_t;

#define __LPM_dword_classic__(addr)         \
(__extension__({                            \
    uint16_t __addr16 = (uint16_t)(addr);   \
    uint32_t __result;                      \
    __asm__ __volatile__                    \
    (                                       \
        "lpm"           "\n\t"              \
        "mov %A0, r0"   "\n\t"              \
        "adiw r30, 1"   "\n\t"              \
        "lpm"           "\n\t"              \
        "mov %B0, r0"   "\n\t"              \
        "adiw r30, 1"   "\n\t"              \
        "lpm"           "\n\t"              \
        "mov %C0, r0"   "\n\t"              \
        "adiw r30, 1"   "\n\t"              \
        "lpm"           "\n\t"              \
        "mov %D0, r0"   "\n\t"              \
        : "=r" (__result), "=z" (__addr16)  \
        : "1" (__addr16)                    \
        : "r0"                              \
    );                                      \
    __result;                               \
}))
unsigned long inlineasm(unsigned int addr)
{
    return __LPM_dword_classic__(addr);
}

clang produces:

define i32 @inlineasm(i16 %addr) #0 {
entry:
  %0 = tail call { i32, i16 } asm sideeffect "lpm\0A\09mov ${0:A},
r0\0A\09adiw r30, 1\0A\09lpm\0A\09mov ${0:B}, r0\0A\09adiw r30,
1\0A\09lpm\0A\09mov ${0:C}, r0\0A\09adiw r30, 1\0A\09lpm\0A\09mov ${0:D},
r0\0A\09", "=r,=z,1,~{r0}"(i16 %addr) #2, !srcloc !4
  %asmresult = extractvalue { i32, i16 } %0, 0
  ret i32 %asmresult
}

No truncations here as far i can tell. Try this code and see what you get.