Is there a documentation of the various magic letters that you can apply to an operand in inline assembly? What I mean is this:
asm volatile ( " some_insn %X[operand] \n" : [operand] "=r" (expr) ); What I look for is documentation of 'X'. In particular, when (expr) is a multi-register object, such as long long or double (or even a short, on a 8-bit chip) and you want to select a particular part of it. The only place I found some information was going through the gcc/config/<chip>/<chip>.c file and trying to find the meaning of such letters in the xxx_print_operand() function. If that is the correct approach, then I think there's a problem with the arm-elf (I know it is dead, but still). According to the comments in that function, for DI and DF arguments the Q and R qualifiers supposed to select the least significant and most significant 32 bits, respectively, of the 64-bit datum. Indeed that's what they do, for a long long. However, for a double they don't seem to take into account that on arm-elf the word order of a double is always big-endian, regardless of the endianness of the rest. Therefore, they select the wrong half of the datum. On arm-eabi, where the endianness of doubles matches the rest, they work fine. Am I completely off-track? Zoltan
