Hi
I am investigating the following;
in the program code I have calls like
uint16_t x = __crt_func ( 10 );
where the argument is guaranteed to be a compile-time uint16_t literal.
So I’ve arranged a series of crts (built with -flto) where one is like
1/
uint16_t
__crt_func (const uint16_t in) { return in; }
and others are like
2/
uint16_t
__crt_func (const uint16_t in) { return 5; }
====
The objective is for an LTO build to eliminate code that becomes dead when the
crt returns the various constants.
So, case (2) works fine - the calls get eliminated and the resulting dead code
too.
However, case (1) is not doing what I expect.
When I look at the ltrans0.ltrans.272.optimized, the __crt_func () body is
there (so it can see it) but still one call to the crt is made and then the
value from that call is used, instead of figuring out that this can all be
const-propagated &c.
I’ve declared the crt
uint16_t __crt_func (uint16_t) __attribute__((__const__));
So…
am I making a mistake
in expectation?
in how the crt is declared?
any other insights?
thanks
Iain
