On Thu, 13 Jul 2017, Alexander Monakov wrote:
On Thu, 13 Jul 2017, Marc Glisse wrote:
I notice that we do not turn (X*10)*10 into X*100 in GIMPLE.
Sorry, could you clarify what you mean here? I think we certainly do that,
just not via match.pd, but in 'associate:' case of fold_binary_loc.
fold_binary_loc is for GENERIC, so mostly for front-end time optimization
of expressions.
int f(int a){
int b=a*10;
return b*10;
}
$ gcc-snapshot -O3 -S -fdump-tree-optimized a.c
$ cat a.c.228t.optimized
[...]
b_2 = a_1(D) * 10;
_3 = b_2 * 10;
return _3;
Relying on inner expressions being folded can be slightly dangerous,
especially for generic IIRC. It seems easy enough to check that @1 is neither
0 nor -1 for safety.
I wanted to add a gcc_checking_assert to that effect, but it's not used in
match.pd anywhere. Is there a nice way to do that?
You can use (with { arbitrary C++ code } ... ) to add an assertion (you
can use @0 in the block of C++ code).
I was more thinking of an "if" than an assertion though.
--
Marc Glisse
