On Wed, Nov 26, 2014 at 02:25:54PM -0500, Jason Merrill wrote:
> How about converting the rhs to unsigned int if it is already unsigned?
That is fine. I'm just worried about the casts to wider types.
So perhaps just promote and cast to int if the promoted type is
signed or unsigned if it is unsigned?
E.g. if you have
long long foo (long long x, long long y, long long z)
{
return x << (y * z);
}
and long long multiplication requires say a libcall, while
int * int can be expanded inline, using long long for shift
count penalizes the code unnecessarily. Ditto for
long long foo (void) __attribute__((const));
int
bar (int x)
{
return x << (foo () & ~0xffffffffLL);
}
and similar. I know, we are running here back into the sadly :(
still missing type demotion and promotion passes, but changing this
now when those passes are missing can only hurt code.
Jakub
