Hi,
I am wondering if the following piece of code is supposed to be valid.
void* reg_v13() {
register void* r __asm__ ("r13");
return r;
}
I did test with gcc on powerpc64, and confirmed that the function
really returns r13 (thread pointer) value.
However, LLVM issues a warning complaining that variable r is not
initialized. The argument is that per
http://gcc.gnu.org/onlinedocs/gcc-4.8.1/gcc/Explicit-Reg-Vars.html#Explicit-Reg-Vars:
"Local register variables in specific registers do not reserve the
registers, except at the point where they are used as input or output
operands in an asm statement and the asm statement itself is not
deleted."
It seems to mean that register variable does not have connection with
the register if the variable is not used in asm statement.
If the understanding correct?
I could not find an example on official gcc document to support that
the example code is valid, although gcc indeed treats r as alias of
r13.
Thanks,
Jing
