[Bug middle-end/112653] We should optimize memmove to memcpy using alias oracle
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112653 --- Comment #6 from Richard Biener --- (In reply to Jan Hubicka from comment #5) > > but the issue is that test2 escapes which makes this conflict: > > It is passed to memmove which is noescape and returned. Why local PTA > considers returned values to escape? The pointed to memory escapes which means that stores to it are not dead. Mind we do not have a separate points-to set for escaped via return (some functions can also "return" like via EH or longjmp, and we can't really know the latter w/o IPA analysis). Pointers can also escape to global memory. Special-casing the regular return path is sth that's possible (also IPA points-to doesn't compute a "local" escaped at all but preserves the non-IPA solution for that), but in the end it didn't seem important enough for me to try doing that ... We have the function entry state which is NONLOAL, ESCAPED is what determines "global memory" for all sorts of optimizations. If we split out RETURN_ESCAPED then that would be ESCAPED | RETURN_ESCAPED and alias disambiguation could avoid RETURN_ESCAPED. But ESCAPED handling is complicated already ...
[Bug middle-end/112653] We should optimize memmove to memcpy using alias oracle
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112653 --- Comment #5 from Jan Hubicka --- > but the issue is that test2 escapes which makes this conflict: It is passed to memmove which is noescape and returned. Why local PTA considers returned values to escape?
[Bug middle-end/112653] We should optimize memmove to memcpy using alias oracle
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112653
--- Comment #4 from Richard Biener ---
We do use the alias oracle in folding memmove:
/* If the destination and source do not alias optimize into
memcpy as well. */
if ((is_gimple_min_invariant (dest)
|| TREE_CODE (dest) == SSA_NAME)
&& (is_gimple_min_invariant (src)
|| TREE_CODE (src) == SSA_NAME))
{
ao_ref destr, srcr;
ao_ref_init_from_ptr_and_size (, dest, len);
ao_ref_init_from_ptr_and_size (, src, len);
if (!refs_may_alias_p_1 (, , false))
{
tree fn;
fn = builtin_decl_implicit (BUILT_IN_MEMCPY);
if (!fn)
return false;
but the issue is that test2 escapes which makes this conflict:
# PT = null { D.2775 } (escaped, escaped heap)
# ALIGN = 8, MISALIGN = 0
# USE = nonlocal escaped
# CLB = nonlocal escaped
test2_4 = __builtin_malloc (1000);
# PT = nonlocal escaped null
test.0_1 = test;
__builtin_memmove (test2_4, test.0_1, 1000);
it works for
char *test, *test3;
void
copy_test ()
{
char *test2 = __builtin_malloc (1000);
__builtin_memmove (test2, test, 1000);
__builtin_memmove (test3, test2, 1000);
__builtin_free (test2);
}
where both memmove calls become memcpy. So this isn't asking for better
folding but for better pointer analysis I guess.
[Bug middle-end/112653] We should optimize memmove to memcpy using alias oracle
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112653 --- Comment #3 from Jan Hubicka --- PR82898 testcases seems to be about type based alias analysis. However PTA should be useable here.
[Bug middle-end/112653] We should optimize memmove to memcpy using alias oracle
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112653 --- Comment #2 from Sam James --- See PR82898 especially...
[Bug middle-end/112653] We should optimize memmove to memcpy using alias oracle
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112653 Andrew Pinski changed: What|Removed |Added CC||pinskia at gcc dot gnu.org Last reconfirmed||2023-11-21 Severity|normal |enhancement Ever confirmed|0 |1 Keywords||alias, missed-optimization Status|UNCONFIRMED |NEW --- Comment #1 from Andrew Pinski --- Confirmed, I had thought that this was recorded before too ...
