Writing out long long integers

[Suriya Narayanan M S]

On PowerPC, GCC writes out long long constants in the data section as two
.long directives, but as a single .quad in x86.

For this code,

typedef unsigned long long uint64;
const uint64 bigconst = 1ULL << 34;

in PowerPC

bigconst:
        .long   4
        .long   0

and in x86

bigconst:
        .quad   0x400000000

Is there a place which contains the formal specification for this?

Thanks,
Suriya