| Message ID | 20170320210520.GM11094@tucnak |
|---|---|
| State | New |
| Headers | show |
On Mon, 20 Mar 2017, Jakub Jelinek wrote: > Hi! > > divisor is unsigned int parameter, if it is 0x80000000, we invoke UB. > val is wide_int, so (int) -divisor achieves the same result without UB. > > Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? Ok. Thanks, Richard. > 2017-03-20 Jakub Jelinek <jakub@redhat.com> > > PR c/67338 > * fold-const.c (round_up_loc): Negate divisor in unsigned type to > avoid UB. > > * gcc.dg/pr67338.c: New test. > > --- gcc/fold-const.c.jj 2017-03-16 17:18:25.000000000 +0100 > +++ gcc/fold-const.c 2017-03-20 07:53:53.680953740 +0100 > @@ -14250,7 +14250,7 @@ round_up_loc (location_t loc, tree value > > overflow_p = TREE_OVERFLOW (value); > val += divisor - 1; > - val &= - (int) divisor; > + val &= (int) -divisor; > if (val == 0) > overflow_p = true; > > --- gcc/testsuite/gcc.dg/pr67338.c.jj 2017-03-20 09:09:05.489002468 +0100 > +++ gcc/testsuite/gcc.dg/pr67338.c 2017-03-20 09:08:54.000000000 +0100 > @@ -0,0 +1,4 @@ > +/* PR c/67338 */ > +/* { dg-do compile { target *-*-linux* *-*-gnu* } } */ > + > +struct S { __attribute__((aligned (1 << 28))) double a; }; > > Jakub > >
--- gcc/fold-const.c.jj 2017-03-16 17:18:25.000000000 +0100 +++ gcc/fold-const.c 2017-03-20 07:53:53.680953740 +0100 @@ -14250,7 +14250,7 @@ round_up_loc (location_t loc, tree value overflow_p = TREE_OVERFLOW (value); val += divisor - 1; - val &= - (int) divisor; + val &= (int) -divisor; if (val == 0) overflow_p = true; --- gcc/testsuite/gcc.dg/pr67338.c.jj 2017-03-20 09:09:05.489002468 +0100 +++ gcc/testsuite/gcc.dg/pr67338.c 2017-03-20 09:08:54.000000000 +0100 @@ -0,0 +1,4 @@ +/* PR c/67338 */ +/* { dg-do compile { target *-*-linux* *-*-gnu* } } */ + +struct S { __attribute__((aligned (1 << 28))) double a; };