Zoltán Kócsi <zol...@bendor.com.au> writes: > Is there a documentation of the various magic letters that you can > apply to an operand in inline assembly?
Unfortunately, no. > 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. Right, that is the only current documentation there is. > 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. For a value which is always big-endian you don't need any modifier for the low register, and you can use %H for the high register. Ian
