On Mon, Jan 12, 2026 at 12:33 AM Richard Biener
<[email protected]> wrote:
>
> On Sun, Jan 11, 2026 at 10:05 PM Andrew Pinski
> <[email protected]> wrote:
> >
> > This adds the simpliciation of:
> > ```
> > <unnamed-signed:3> _1;
> >
> > _2 = (signed char) _1;
> > _3 = _2 ^ -47;
> > _4 = (<unnamed-signed:3>) _3;
> > ```
> >
> > to:
> > ```
> > <unnamed-signed:3> _n;
> > _4 = _1 ^ -47;
> > ```
> >
> > This also fixes PR 122843 by optimizing out the xor such that we get:
> > ```
> > _1 = b.a;
> > _21 = (<unnamed-signed:3>) t_23(D);
> > // t_23 in the original testcase was 200 so this is reduced to 0
> > _5 = _1 ^ _21;
> > # .MEM_24 = VDEF <.MEM_13>
> > b.a = _5;
> > ```
> > And then there is no cast catch this pattern:
> > `(bit_xor (convert1? (bit_xor:c @0 @1)) (convert2? (bit_xor:c @0 @2)))`
> > As we get:
> > ```
> > _21 = (<unnamed-signed:3>) t_23(D);
> > _5 = _1 ^ _21;
> > _22 = (<unnamed-signed:3>) t_23(D);
> > _7 = _5 ^ _22;
> > _25 = (<unnamed-signed:3>) t_23(D);
> > _8 = _7 ^ _25;
> > _26 = (<unnamed-signed:3>) t_23(D);
> > _9 = _7 ^ _26;
> > ```
> > After unrolling and then fre will optimize away all of those xor.
> >
> > Bootstrapped and tested on x86_64-linux-gnu.
> >
> > PR tree-optimization/122845
> > PR tree-optimization/122843
> > gcc/ChangeLog:
> >
> > * match.pd (`(T1)(a bit_op (T2)b)`): Also
> > simplify if T1 is the same type as b and T2 is wider
> > type than T1.
> >
> > gcc/testsuite/ChangeLog:
> >
> > * gcc.dg/tree-ssa/bitops-12.c: New test.
> > * gcc.dg/tree-ssa/bitops-13.c: New test.
> > * gcc.dg/store_merging_18.c: xfail store merging.
> >
> > Signed-off-by: Andrew Pinski <[email protected]>
> > ---
> > gcc/match.pd | 10 +++++++++-
> > gcc/testsuite/gcc.dg/store_merging_18.c | 3 ++-
> > gcc/testsuite/gcc.dg/tree-ssa/bitops-12.c | 18 ++++++++++++++++++
> > gcc/testsuite/gcc.dg/tree-ssa/bitops-13.c | 18 ++++++++++++++++++
> > 4 files changed, 47 insertions(+), 2 deletions(-)
> > create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/bitops-12.c
> > create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/bitops-13.c
> >
> > diff --git a/gcc/match.pd b/gcc/match.pd
> > index 492d88514fc..16ce2d1edd2 100644
> > --- a/gcc/match.pd
> > +++ b/gcc/match.pd
> > @@ -2323,7 +2323,15 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> > && !POINTER_TYPE_P (TREE_TYPE (@0))
> > && TREE_CODE (TREE_TYPE (@0)) != OFFSET_TYPE
> > && TYPE_PRECISION (TREE_TYPE (@0)) > TYPE_PRECISION (type))
> > - (bitop:type (convert @0) (convert @1)))))
> > + (bitop:type (convert @0) (convert @1))
> > + /* Similar as above, but the outer and inner most types match
> > + and it was widening cast; replacing 2 casts with only one. */
> > + (if (GIMPLE
> > + && INTEGRAL_TYPE_P (type)
> > + && INTEGRAL_TYPE_P (TREE_TYPE (@0))
> > + && types_match (type, TREE_TYPE (@0))
> > + && TYPE_PRECISION (TREE_TYPE (@2)) > TYPE_PRECISION (type))
>
> I think you need the pointer and offset type checks here as well given
> bitops are not valid on those in general.
The `INTEGRAL_TYPE_P (type)` check will already reject pointer and
offset types. And the type on @2 will already be an integer type
because it is on the bitop.
So there is no need to add the extra checks.
>
> OK with adding those.
I pushed it without the extra checks added.
Thanks,
Andrew Pinski
> Richard.
>
> > + (bitop:type @0 (convert @1))))))
> >
> > (for bitop (bit_and bit_ior)
> > rbitop (bit_ior bit_and)
> > diff --git a/gcc/testsuite/gcc.dg/store_merging_18.c
> > b/gcc/testsuite/gcc.dg/store_merging_18.c
> > index fdff6b4d812..546c17dc7c4 100644
> > --- a/gcc/testsuite/gcc.dg/store_merging_18.c
> > +++ b/gcc/testsuite/gcc.dg/store_merging_18.c
> > @@ -1,7 +1,8 @@
> > /* PR tree-optimization/83843 */
> > /* { dg-do run } */
> > /* { dg-options "-O2 -fno-tree-vectorize -fdump-tree-store-merging" } */
> > -/* { dg-final { scan-tree-dump-times "Merging successful" 3
> > "store-merging" { target { store_merge && { ! arm*-*-* } } } } } */
> > +/* xfailed after PR 122845, see PR 123541 ( */
> > +/* { dg-final { scan-tree-dump-times "Merging successful" 3
> > "store-merging" { target { store_merge && { ! arm*-*-* } } xfail *-*-* } }
> > } */
> >
> > __attribute__((noipa)) void
> > foo (unsigned char *buf, unsigned char *tab)
> > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/bitops-12.c
> > b/gcc/testsuite/gcc.dg/tree-ssa/bitops-12.c
> > new file mode 100644
> > index 00000000000..50d8dc2180f
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/tree-ssa/bitops-12.c
> > @@ -0,0 +1,18 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O1 -fdump-tree-optimized-raw" } */
> > +/* PR tree-optimization/122845 */
> > +
> > +struct s1
> > +{
> > + signed f1:3;
> > +};
> > +struct s1 p;
> > +void f(void)
> > +{
> > + p.f1 ^= -47;
> > + p.f1 ^= -47;
> > +}
> > +
> > +/* There should be no gimple stmts left except for return.
> > + That is the ^ has been optimized away. */
> > +/* { dg-final { scan-tree-dump-not "gimple_assign <" "optimized" } } */
> > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/bitops-13.c
> > b/gcc/testsuite/gcc.dg/tree-ssa/bitops-13.c
> > new file mode 100644
> > index 00000000000..ecf69738267
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/tree-ssa/bitops-13.c
> > @@ -0,0 +1,18 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O1 -fdump-tree-optimized-raw" } */
> > +/* PR tree-optimization/122845 */
> > +
> > +int f(signed char a, int b)
> > +{
> > + int aa = a;
> > + int bb = b;
> > + aa &= bb;
> > + signed char t = aa;
> > + aa = t;
> > + aa &= bb;
> > + t = aa;
> > + return t;
> > +}
> > +
> > +/* There should be only 1 bit_and_expr left as both ands are the same. */
> > +/* { dg-final { scan-tree-dump-times "bit_and_expr, " 1 "optimized" } } */
> > --
> > 2.43.0
> >
