On Tue, Nov 19, 2013 at 1:06 PM, Richard Sandiford <rdsandif...@googlemail.com> wrote: > This is a case where tree_to_shwi can be used instead of TREE_INT_CST_LOW. > I separated it out because it was using a signed "x * y / y == x" to check > whether "x * y" overflows a HWI, which relies on undefined behaviour.
Please CSE tree_to_shwi (size) (yeah, you may use an ugly && (hsz = tree_to_shwi (size)) <= HOST_WIDE_INT_MAX / BITS_PER_UNIT Ok with that change. Thanks, Richard. > Thanks, > Richard > > > gcc/ > * tree-ssa-alias.c (ao_ref_init_from_ptr_and_size): Avoid signed > overflow. Use tree_to_shwi. > > Index: gcc/tree-ssa-alias.c > =================================================================== > --- gcc/tree-ssa-alias.c 2013-11-19 10:53:54.965643984 +0000 > +++ gcc/tree-ssa-alias.c 2013-11-19 11:08:51.882992035 +0000 > @@ -615,9 +615,8 @@ ao_ref_init_from_ptr_and_size (ao_ref *r > ref->offset += extra_offset; > if (size > && tree_fits_shwi_p (size) > - && TREE_INT_CST_LOW (size) * BITS_PER_UNIT / BITS_PER_UNIT > - == TREE_INT_CST_LOW (size)) > - ref->max_size = ref->size = TREE_INT_CST_LOW (size) * BITS_PER_UNIT; > + && tree_to_shwi (size) <= HOST_WIDE_INT_MAX / BITS_PER_UNIT) > + ref->max_size = ref->size = tree_to_shwi (size) * BITS_PER_UNIT; > else > ref->max_size = ref->size = -1; > ref->ref_alias_set = 0;
