On Tue, May 26, 2026 at 9:10 PM Shivam Gupta <[email protected]> wrote:
>
>
>
> On Wed, May 27, 2026 at 8:48 AM Andrew Pinski
> <[email protected]> wrote:
>>
>> On Tue, May 26, 2026 at 7:48 PM Andrew Pinski
>> <[email protected]> wrote:
>> >
>> > On Mon, May 25, 2026 at 8:45 PM Shivam Gupta <[email protected]>
>> > wrote:
>> > >
>> > > At -O1, GCC lowers (~a & 1) == (~b & 1) into two different GIMPLE
>> > > forms depending on whether the boolean values come from a function
>> > > return boundary or an inline expression:
>> > >
>> > > 1. Via function return (e.g. inlined is_even), GCC preserves the
>> > > eq/ne form because the function boundary hides the internal
>> > > structure from the gimplifier:
>> > > ((a&1)==0) == ((b&1)==0) outer node is eq/ne
>> > >
>> > > 2. Via inline expression (directly written), GCC sees the full
>> > > boolean expression tree at once and folds to bit_xor during
>> > > gimplification:
>> > > ((a&1)!=0) ^ ((b&1)==0) outer node is bit_xor
>> > >
>> > > Add a generalized match.pd rule handling:
>> > > 1. ((x & c) == 0) OP ((y & c) == 0)
>> > > 2. ((x & c) != 0) OP ((y & c) == 0)
>> > > 3. ((x & c) == 0) OP (y & c)
>> >
>> > Can you leave out 3 for now? We will need to deal with it later I think.
>> > It is needed due to:
>> > ```
>> > /* (type)([0,1]@a != 0) -> (type)a
>> > (type)([0,1]@a == 1) -> (type)a
>> > (type)([0,1]@a == 0) -> a ^ 1
>> > (type)([0,1]@a != 1) -> a ^ 1. */
>> > (for eqne (eq ne)
>> > (simplify
>> > (convert (eqne zero_one_valued_p@0 INTEGER_CST@1))
>> > (if ((integer_zerop (@1) || integer_onep (@1)))
>> > (if ((eqne == EQ_EXPR) ^ integer_zerop (@1))
>> > (convert @0)
>> > /* Only do this if the types match as (type)(a == 0) is
>> > canonical form normally, while `a ^ 1` is canonical when
>> > there is no type change. */
>> > (if (types_match (type, TREE_TYPE (@0)))
>> > (bit_xor @0 { build_one_cst (type); } ))))))
>> > ```
>> > Which was added by
>> > https://inbox.sourceware.org/gcc-patches/[email protected]/
>> > .
>> >
>> > And then we don't support (t1_7 is zero_one_valued_p here):
>> > _1 = t1_7 == 0;
>> > _2 = (int) _1;
>> >
>> > Into:
>> > _t = (t1_7^1)
>> > _2 = (int)_t;
>> >
>> > As types_match is not true. That was not done .
>> >
>> > I didn't realize this came into play for the `&1` part until now :).
>> >
>> > You can keep the testcases for the ones which will match 3 but xfail them.
>>
>> That is because we should handle it differently and separately as that
>> only matters with `&1` there.
>>
>> The pattern there will be something like
>> (ne zero_one_valued_p@0 (convert? (eq zero_one_valued_p@1 integer_zerop)))
>> simplified to:
>> (eq (convert:TREE_TYPE(@1) @0) @1)
>>
>> With that pattern, this:
>> t1_5 = a_4(D) & 1;
>> t2_7 = b_6(D) & 1; // t2_7 is zero_one_valued_p
>> _1 = t1_5 == 0;
>> _2 = (int) _1; // _2 is zero_one_valued_p
>> _3 = (int) t2_7; // _3 is zero_one_valued_p
>> _8 = _2 != _3;
>> return _8;
>>
>> Will gets turned into:
>> _8 = t2_7 == t1_5
>>
>
> OK, I can try that in some time as a different patch.
And here is another testcase for the suggested new pattern here:
```
_Bool
f (unsigned a, unsigned b)
{
if (a!= 0 && a!= 1) __builtin_unreachable();
if (b!= 0 && b!= 1) __builtin_unreachable();
return (a == 0) ^ (b != 0);
}
```
Thanks,
Andrea
>
> Thanks,
> Shivam
>
>> Thanks,
>> Drea
>>
>> >
>> > Thanks,
>> > Andrea
>> >
>> >
>> >
>> > >
>> > > for OP in { ==, !=, ^ } and pow2 masks. The third form is required
>> > > because GCC canonicalize: ((x & c) != 0) into (x & c) before this
>> > > rule runs.
>> > >
>> > > Fold these directly into the canonical xor-mask form:
>> > > ((x ^ y) & c) == 0
>> > > ((x ^ y) & c) != 0
>> > >
>> > > Bootstrapped and tested on aarch64-linux-gnu.
>> > >
>> > > Changes since v1:
>> > > * v3: Collapse both previous simplify rules into one generalized
>> > > matcher covering all combinations of outer {eq, ne, bit_xor}
>> > > and inner {eq, ne} comparisons.
>> > > Add missing mixed-polarity test cases.
>> > >
>> > > * v2: Generalize mask from integer_onep to integer_pow2p.
>> > > Combine both patterns into single one.
>> > > Split test into bool-eq-evenness.c, bool-eq-bitxor.c,
>> > > bool-eq-pow2.c.
>> > >
>> > > PR tree-optimization/112533
>> > > gcc/ChangeLog:
>> > > * match.pd: Canonicalize boolean comparisons of masked pow2
>> > > bits into xor-mask tests.
>> > >
>> > > gcc/testsuite/ChangeLog:
>> > > * gcc.dg/tree-ssa/bool-eq-bitxor.c: New test.
>> > > * gcc.dg/tree-ssa/bool-eq-evenness.c: New test.
>> > > * gcc.dg/tree-ssa/bool-eq-pow2.c: New test.
>> > >
>> > > Signed-off-by: Shivam Gupta <[email protected]>
>> > > ---
>> > > gcc/match.pd | 38 ++++++++
>> > > .../gcc.dg/tree-ssa/bool-eq-bitxor.c | 39 ++++++++
>> > > .../gcc.dg/tree-ssa/bool-eq-evenness.c | 43 +++++++++
>> > > gcc/testsuite/gcc.dg/tree-ssa/bool-eq-pow2.c | 89 +++++++++++++++++++
>> > > 4 files changed, 209 insertions(+)
>> > > create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/bool-eq-bitxor.c
>> > > create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/bool-eq-evenness.c
>> > > create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/bool-eq-pow2.c
>> > >
>> > > diff --git a/gcc/match.pd b/gcc/match.pd
>> > > index ff13a07ea94..d41a2b2f329 100644
>> > > --- a/gcc/match.pd
>> > > +++ b/gcc/match.pd
>> > > @@ -1464,6 +1464,44 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
>> > > (if (TYPE_UNSIGNED (type))
>> > > (bit_and @0 (bit_not (lshift { build_all_ones_cst (type); } @1)))))
>> > >
>> > > +/* PR112533: Canonicalize boolean comparisons of masked pow2 bits into
>> > > + xor-mask tests.
>> > > + ((x & c) == 0) == ((y & c) == 0) -> (((x ^ y) & c) == 0)
>> > > + ((x & c) == 0) != ((y & c) == 0) -> (((x ^ y) & c) != 0)
>> > > + and equivalent xor forms. */
>> > > +(for ocmp (eq ne bit_xor)
>> > > + (for icmp0 (eq eq ne ne)
>> > > + icmp1 (eq ne eq ne)
>> > > + (simplify
>> > > + (ocmp
>> > > + (icmp0 (bit_and @0 integer_pow2p@1) integer_zerop@3)
>> > > + (icmp1 (bit_and @2 @1) @3))
>> > > + (if (types_match (@0, @2))
>> > > + (with {
>> > > + bool innersame
>> > > + = (icmp0 == EQ_EXPR) == (icmp1 == EQ_EXPR);
>> > > + }
>> > > + (if (innersame == (ocmp == EQ_EXPR))
>> > > + (eq (bit_and (bit_xor @0 @2) @1) @3)
>> > > + (ne (bit_and (bit_xor @0 @2) @1) @3)))))
>> > > +
>> > > + /* Canonicalized: ((x & c) == 0) OP (y & c)
>> > > + because ((y & c) != 0) may fold into (y & c). */
>> > > + (simplify
>> > > + (ocmp
>> > > + (convert?@4
>> > > + (icmp0 (bit_and @0 integer_pow2p@1) integer_zerop@3))
>> > > + (convert?@5
>> > > + (bit_and @2 @1)))
>> > > + (if (types_match (@0, @2))
>> > > + (with {
>> > > + bool innersame
>> > > + = (icmp0 == EQ_EXPR) == false;
>> > > + }
>> > > + (if (innersame == (ocmp == EQ_EXPR))
>> > > + (eq (bit_and (bit_xor @0 @2) @1) @3)
>> > > + (ne (bit_and (bit_xor @0 @2) @1) @3)))))))
>> > > +
>> > > (for bitop (bit_and bit_ior)
>> > > cmp (eq ne)
>> > > /* PR35691: Transform
>> > > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/bool-eq-bitxor.c
>> > > b/gcc/testsuite/gcc.dg/tree-ssa/bool-eq-bitxor.c
>> > > new file mode 100644
>> > > index 00000000000..05cee9696cf
>> > > --- /dev/null
>> > > +++ b/gcc/testsuite/gcc.dg/tree-ssa/bool-eq-bitxor.c
>> > > @@ -0,0 +1,39 @@
>> > > +/* { dg-do compile } */
>> > > +/* { dg-options "-O1 -fdump-tree-optimized" } */
>> > > +
>> > > +typedef unsigned int u32;
>> > > +
>> > > +_Bool
>> > > +xor_ne_eq (u32 a, u32 b)
>> > > +{
>> > > + u32 t1 = a & 1;
>> > > + u32 t2 = b & 1;
>> > > + return (t1 != 0) ^ (t2 == 0);
>> > > +}
>> > > +
>> > > +_Bool
>> > > +xor_eq_eq (u32 a, u32 b)
>> > > +{
>> > > + u32 t1 = a & 1;
>> > > + u32 t2 = b & 1;
>> > > + return (t1 == 0) ^ (t2 == 0);
>> > > +}
>> > > +
>> > > +_Bool
>> > > +xor_eq_ne (u32 a, u32 b)
>> > > +{
>> > > + u32 t1 = a & 1;
>> > > + u32 t2 = b & 1;
>> > > + return (t1 == 0) ^ (t2 != 0);
>> > > +}
>> > > +
>> > > +_Bool
>> > > +xor_ne_ne (u32 a, u32 b)
>> > > +{
>> > > + u32 t1 = a & 1;
>> > > + u32 t2 = b & 1;
>> > > + return (t1 != 0) ^ (t2 != 0);
>> > > +}
>> > > +
>> > > +/* Verify all functions canonicalize to xor-mask tests. */
>> > > +/* { dg-final { scan-tree-dump-times "& 1" 4 "optimized" } } */
>> > > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/bool-eq-evenness.c
>> > > b/gcc/testsuite/gcc.dg/tree-ssa/bool-eq-evenness.c
>> > > new file mode 100644
>> > > index 00000000000..75df70dc6a4
>> > > --- /dev/null
>> > > +++ b/gcc/testsuite/gcc.dg/tree-ssa/bool-eq-evenness.c
>> > > @@ -0,0 +1,43 @@
>> > > +/* { dg-do compile } */
>> > > +/* { dg-options "-O1 -fdump-tree-optimized" } */
>> > > +
>> > > +/* Verify the GIMPLE-level fix for PR112533. */
>> > > +
>> > > +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);
>> > > +}
>> > > +
>> > > +_Bool
>> > > +same_evenness_cmp_zero (u32 a, u32 b)
>> > > +{
>> > > + u32 t1 = a & 1;
>> > > + u32 t2 = b & 1;
>> > > + return (t1 == 0) == (t2 == 0);
>> > > +}
>> > > +
>> > > +_Bool
>> > > +diff_evenness_cmp_zero (u32 a, u32 b)
>> > > +{
>> > > + u32 t1 = a & 1;
>> > > + u32 t2 = b & 1;
>> > > + return (t1 == 0) != (t2 == 0);
>> > > +}
>> > > +
>> > > +/* Verify all functions canonicalize to xor forms. */
>> > > +/* { dg-final { scan-tree-dump-times "\\^" 4 "optimized" } } */
>> > > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/bool-eq-pow2.c
>> > > b/gcc/testsuite/gcc.dg/tree-ssa/bool-eq-pow2.c
>> > > new file mode 100644
>> > > index 00000000000..109c5f03610
>> > > --- /dev/null
>> > > +++ b/gcc/testsuite/gcc.dg/tree-ssa/bool-eq-pow2.c
>> > > @@ -0,0 +1,89 @@
>> > > +/* { dg-do compile } */
>> > > +/* { dg-options "-O1 -fdump-tree-optimized" } */
>> > > +
>> > > +typedef unsigned int u32;
>> > > +
>> > > +_Bool
>> > > +eq_eq_outer_eq_mask2 (u32 a, u32 b)
>> > > +{
>> > > + u32 t1 = a & 2;
>> > > + u32 t2 = b & 2;
>> > > + return (t1 == 0) == (t2 == 0);
>> > > +}
>> > > +
>> > > +_Bool
>> > > +eq_eq_outer_eq_mask4 (u32 a, u32 b)
>> > > +{
>> > > + u32 t1 = a & 4;
>> > > + u32 t2 = b & 4;
>> > > + return (t1 == 0) == (t2 == 0);
>> > > +}
>> > > +
>> > > +_Bool
>> > > +eq_eq_outer_ne (u32 a, u32 b)
>> > > +{
>> > > + u32 t1 = a & 1;
>> > > + u32 t2 = b & 1;
>> > > + return (t1 == 0) != (t2 == 0);
>> > > +}
>> > > +
>> > > +_Bool
>> > > +ne_eq_outer_eq (u32 a, u32 b)
>> > > +{
>> > > + u32 t1 = a & 1;
>> > > + u32 t2 = b & 1;
>> > > + return (t1 != 0) == (t2 == 0);
>> > > +}
>> > > +
>> > > +_Bool
>> > > +ne_eq_outer_ne (u32 a, u32 b)
>> > > +{
>> > > + u32 t1 = a & 1;
>> > > + u32 t2 = b & 1;
>> > > + return (t1 != 0) != (t2 == 0);
>> > > +}
>> > > +
>> > > +_Bool
>> > > +eq_ne_outer_eq (u32 a, u32 b)
>> > > +{
>> > > + u32 t1 = a & 1;
>> > > + u32 t2 = b & 1;
>> > > + return (t1 == 0) == (t2 != 0);
>> > > +}
>> > > +
>> > > +_Bool
>> > > +eq_ne_outer_ne (u32 a, u32 b)
>> > > +{
>> > > + u32 t1 = a & 1;
>> > > + u32 t2 = b & 1;
>> > > + return (t1 == 0) != (t2 != 0);
>> > > +}
>> > > +
>> > > +_Bool
>> > > +ne_ne_outer_eq (u32 a, u32 b)
>> > > +{
>> > > + u32 t1 = a & 1;
>> > > + u32 t2 = b & 1;
>> > > + return (t1 != 0) == (t2 != 0);
>> > > +}
>> > > +
>> > > +_Bool
>> > > +ne_ne_outer_ne (u32 a, u32 b)
>> > > +{
>> > > + u32 t1 = a & 1;
>> > > + u32 t2 = b & 1;
>> > > + return (t1 != 0) != (t2 != 0);
>> > > +}
>> > > +
>> > > +/* Non-power-of-2: should not be simplified. */
>> > > +_Bool
>> > > +eq_eq_outer_eq_nonpow2 (u32 a, u32 b)
>> > > +{
>> > > + u32 t1 = a & 3;
>> > > + u32 t2 = b & 3;
>> > > + return (t1 == 0) == (t2 == 0);
>> > > +}
>> > > +
>> > > +/* Verify power-of-2 masks are simplified, non-power-of-2 masks are
>> > > not. */
>> > > +/* { dg-final { scan-tree-dump-times "a_\[0-9\]+\\(D\\) \\^
>> > > b_\[0-9\]+\\(D\\)" 9 "optimized" } } */
>> > > +/* { dg-final { scan-tree-dump-times "& 3" 2 "optimized" } } */
>> > > --
>> > > 2.34.1
>> > >
