On Mon, May 18, 2026 at 12:49 PM Andrew Pinski < [email protected]> wrote:
> On Mon, May 18, 2026 at 12:11 AM Shivam Gupta <[email protected]> > wrote: > > > > This is a follow-up to the -O1 patch for PR112533. > > > > At -O2, GCC lowers (~x & 1) == (~y & 1) via inlining into: > > _14 = ~x; > > _12 = (bool) _14; > > _13 = ~y; > > _9 = (bool) _13; > > _8 = _9 == _12; > > > > The NOT cancellation (~x == ~y -> x == y) is handled by existing > > forwprop rules before this rule fires. > > > > Add match.pd rule for eq and ne: > > > > (T)(x) == (T)(y) -> (T)(x ^ y) == 0 > > (T)(x) != (T)(y) -> (T)(x ^ y) != 0 > > > > Bootstrapped and regression tested on aarch64-linux-gnu with > > RUNTESTFLAGS="tree-ssa.exp". > > > > Changes since v1: > > * v2: Generalize the match rule to generic narrowing > > integral equality comparisons from bool equality. > > > > PR tree-optimization/112533 > > > > gcc/ChangeLog: > > * match.pd: Add generic narrowing eq/ne to XOR-against-zero > > rule for (T)(x) == (T)(y) where precision(T) < precision(x). > > > > gcc/testsuite/ChangeLog: > > * gcc.dg/tree-ssa/narrow-eq-simplify.c: New test covering > > bool parity and short truncation cases. > > > > Signed-off-by: Shivam Gupta <[email protected]> > > --- > > gcc/match.pd | 16 +++++++ > > .../gcc.dg/tree-ssa/narrow-eq-simplify.c | 47 +++++++++++++++++++ > > 2 files changed, 63 insertions(+) > > create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/narrow-eq-simplify.c > > > > diff --git a/gcc/match.pd b/gcc/match.pd > > index ff13a07ea94..1fcf28044ee 100644 > > --- a/gcc/match.pd > > +++ b/gcc/match.pd > > @@ -2033,6 +2033,22 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) > > && element_precision (type) <= element_precision (TREE_TYPE (@1))) > > (bit_xor (convert @0) (convert @1)))) > > > > +/* For narrowing conversations: > > + (T)(X) == (T)(Y) -> (T)(X ^ Y) == 0 > > + (T)(X) != (T)(Y) -> (T)(X ^ Y) != 0 */ > > +(for cmp (eq ne) > > + (simplify > > + (cmp (convert@0 @00) (convert@1 @10)) > > + (if (INTEGRAL_TYPE_P (type) > > + && INTEGRAL_TYPE_P (TREE_TYPE (@00)) > > + && types_match (@00, @10) > > + && types_match (@0, @1) > > + && TYPE_PRECISION (TREE_TYPE (@0)) > > + < TYPE_PRECISION (TREE_TYPE (@00))) > > + (with { tree stype = TREE_TYPE (@0); } > > + (cmp (convert:stype (bit_xor @00 @10)) > > + { build_zero_cst (stype); }))))) > > You need to put this with the other ones that are already doing this > pattern; otherwise this and the other ones won't work. Also I don't > think you need to match the types of @0 and @1 here. Also > INTEGRAL_TYPE_P (type) will be true for INTEGRAL_TYPE_P (TREE_TYPE > (@00)). > > Also use itype rather than stype. s here usually stands for signed > while i would stand for inner. > > Thanks, > Andrea > > Hello, I browsed the match.pd file but I am not sure where else to put this. Rest comments are addressed in v3 of patch. Thanks, Shivam > > + > > /* Convert ~X ^ C to X ^ ~C. */ > > (simplify > > (bit_xor (convert? (bit_not @0)) INTEGER_CST@1) > > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/narrow-eq-simplify.c > b/gcc/testsuite/gcc.dg/tree-ssa/narrow-eq-simplify.c > > new file mode 100644 > > index 00000000000..8b03954719a > > --- /dev/null > > +++ b/gcc/testsuite/gcc.dg/tree-ssa/narrow-eq-simplify.c > > @@ -0,0 +1,47 @@ > > +/* { dg-do compile } */ > > +/* { dg-options "-O2 -fdump-tree-optimized" } */ > > + > > +/* Verify the fix for PR112533 at -O2. > > + (~a & 1) == (~a & 1) is lowered via inlining to > > + (bool)(~a) == (bool)(~b), then existing forwprop rules cancel > > + the NOTs giving (bool)(a) == (bool)(b), which this rule > > + simplifies to (bool)(a ^ b) == 0. */ > > + > > +typedef unsigned int u32; > > + > > +static _Bool > > +is_even (u32 a) > > +{ > > + return a % 2 == 0; > > +} > > + > > +_Bool > > +same_evenness (u32 a, u32 b) > > +{ > > + return is_even (a) == is_even (b); > > +} > > + > > +_Bool > > +diff_evenness (u32 a, u32 b) > > +{ > > + return is_even (a) != is_even (b); > > +} > > + > > +short > > +eq_short_not (int a, int b) > > +{ > > + short sa = ~a; > > + short sb = ~b; > > + return sa == sb; > > +} > > + > > +short > > +ne_short_not (int a, int b) > > +{ > > + short sa = ~a; > > + short sb = ~b; > > + return sa != sb; > > +} > > + > > +/* Verify the XOR form is produced. */ > > +/* { dg-final { scan-tree-dump-times "\\\^" 4 "optimized" } } */ > > -- > > 2.34.1 > > >
