Re: [PATCH/RFC] Improve inlining heuristics for 4.0

[Richard Guenther <rguenth at tat dot physik dot uni-tuebingen dot de>]

On Thu, 24 Feb 2005, Richard Guenther wrote:

> Hi!
>
> This is a simple attempt to improve inlining heuristics for 4.0
> while keeping in mind that for 4.1 this will be all done very
> differently.
[...]
> 2. For code like
>      inline int foo(void) { return 0; }
>      int foo1(void) { return foo(); }
>    we do not honour the removed cost of initializing a temporary
>    for the result of the function call to foo.
>    The fix is to subtract the cost of the MODIFY_EXPR (..., CALL_EXPR)
>    in the caller if inlining the call.  We have a cost for this
>    initialization in the inlined function anyway.

It seems this breaks code like

typedef struct { int i; } t;

inline
y(t u)
{}

x()
{
        t u;
        y(u);
}

(aka c-torture/compile/920501-13)

where we get negative size for x after inlining.  I'll need to find
a way to detect if we are in fact ignoring the return value of a
function.  Is there an easy way to do so?

Richard.