On 10/13/09 03:41, Paul Brook wrote:
Nothing you've said changes the fact that there are a class of users
for whom that information is vital and we ought to spend some time
thinking about how to provide the information in a form they can
digest. GCC dumps as they exist today are largely useless for a non-GCC
developer to use to understand why a particular transformation did or
did not occur in their code. This has come up time and time again and
will continue to do so unless we find a way to provide visibility into
the optimizer's decision making.
My guess is anyone inspecting the code and optimizer decisions at this level
is also going to want to strongarm the result they want when the compiler
makes the "wrong" decision. i.e. detailed unroller diagnostics are only of
limited use without (say) #pragma unroll.
Perhaps. Of course in this customer's case they're looking at 20%+
hits, so a "wrong" decision is quite costly. At least with the inliner
they have a fair number of knobs they can turn once they know which
heuristic is preventing inlining the key function(s) -- for other passes
we don't have nearly as many knobs.
jeff
