compiling this with 'gcc -O3 -S x.c'
-------- x.c -----------
#define PURE __attribute__((pure))
struct res {int u; };
extern struct res calc_1() PURE;
extern int calc_2() PURE;
int fun_1()
{
return calc_1().u+calc_1().u;
}
int fun_2()
{
return calc_2()+calc_2();
}
--------------------
yields code which calls calc_2() *once* in fun_2() but calls calc_1() *twice*
in fun_1(). Obviously, fun_1 misses an optimization.
Tested on gcc 4.4.3 (Ubuntu 10.04), gcc 4.5.0/4.4.4/4.3.5 (MacPorts)
--
Summary: attribute((pure)) does not work when returning structs
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: marco at technoboredom dot net
GCC host triplet: x86_64-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45115
