On Thu, Jul 21, 2022 at 4:24 AM Richard Biener via Gcc-patches <gcc-patches@gcc.gnu.org> wrote: > > The following makes sure to fold ~(a ^ b) to a == b for truth > values (but not vectors, we'd have to check for vector support of > equality). That turns the PR106379 testcase into a ranger one. > > Note that while we arrive at ~(a ^ b) in a convoluted way from > original !a == !b one can eventually write the expression this > way directly as well. > > Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed. > > PR tree-optimization/106379 > * match.pd (~(a ^ b) -> a == b): New pattern. > > * gcc.dg/pr106379-1.c: New testcase. > --- > gcc/match.pd | 6 ++++++ > gcc/testsuite/gcc.dg/pr106379-1.c | 9 +++++++++ > 2 files changed, 15 insertions(+) > create mode 100644 gcc/testsuite/gcc.dg/pr106379-1.c > > diff --git a/gcc/match.pd b/gcc/match.pd > index 8bbc0dbd5cd..88a1a5aa9cc 100644 > --- a/gcc/match.pd > +++ b/gcc/match.pd > @@ -1938,6 +1938,12 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) > (if (tree_nop_conversion_p (type, TREE_TYPE (@0))) > (bit_not (bit_xor (view_convert @0) @1)))) > > +/* ~(a ^ b) is a == b for truth valued a and b. */ > +(simplify > + (bit_not (bit_xor:s truth_valued_p@0 truth_valued_p@1)) > + (if (!VECTOR_TYPE_P (type)) > + (convert (eq @0 @1))))
For integers, isn't it wrong to convert ~(boolean exp) to boolean exp? > /* (x & ~m) | (y & m) -> ((x ^ y) & m) ^ x */ > (simplify > (bit_ior:c (bit_and:cs @0 (bit_not @2)) (bit_and:cs @1 @2)) > diff --git a/gcc/testsuite/gcc.dg/pr106379-1.c > b/gcc/testsuite/gcc.dg/pr106379-1.c > new file mode 100644 > index 00000000000..7f2575e02dc > --- /dev/null > +++ b/gcc/testsuite/gcc.dg/pr106379-1.c > @@ -0,0 +1,9 @@ > +/* { dg-do compile } */ > +/* { dg-options "-O -fdump-tree-forwprop1" } */ > + > +_Bool foo (_Bool a, _Bool b) > +{ > + return !a == !b; > +} > + > +/* { dg-final { scan-tree-dump "\[ab\]_\[0-9\]+\\(D\\) == > \[ba\]_\[0-9\]+\\(D\\)" "forwprop1" } } */ > -- > 2.35.3 -- H.J.