On Mon, Aug 23, 2021 at 1:09 PM Jakub Jelinek via Gcc-patches <gcc-patches@gcc.gnu.org> wrote: > > On Mon, Aug 23, 2021 at 01:25:13AM +0100, Roger Sayle wrote: > > This patch has been tested on x86_64-pc-linux-gnu with "make bootstrap" > > and "make -k check" with no new failures. Ok for mainline? > > > > > > 2021-08-23 Roger Sayle <ro...@nextmovesoftware.com> > > > > gcc/ChangeLog > > * match.pd (shift transformations): Change the sign of an > > LSHIFT_EXPR if it reduces the number of explicit conversions. > > This broke bootstrap on i686-linux, where it incorrectly simplifies > a cast from LSHIFT_EXPR with integral type to pointer type of the > same precision into LSHIFT_EXPR performed on the pointer type, > which is invalid IL.
And a reduced testcase for that failure can be found in PR 102029 too. Thanks, Andrew > > > diff --git a/gcc/match.pd b/gcc/match.pd > > index 0fcfd0e..978a1b0 100644 > > --- a/gcc/match.pd > > +++ b/gcc/match.pd > > @@ -3385,6 +3385,15 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) > > (if (integer_zerop (@2) || integer_all_onesp (@2)) > > (cmp @0 @2))))) > > > > +/* Both signed and unsigned lshift produce the same result, so use > > + the form that minimizes the number of conversions. */ > > +(simplify > > + (convert (lshift:s@0 (convert:s@1 @2) INTEGER_CST@3)) > > + (if (tree_nop_conversion_p (type, TREE_TYPE (@0)) > > I think you want > && INTEGRAL_TYPE_P (TREE_TYPE (@1)) > here as well. > > > + && INTEGRAL_TYPE_P (TREE_TYPE (@2)) > > + && TYPE_PRECISION (TREE_TYPE (@2)) <= TYPE_PRECISION (type)) > > + (lshift (convert @2) @3))) > > + > > Jakub >
