Gentle ping! Thanks, Shivam
On Wed, May 27, 2026 at 9:37 AM 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) > > for OP in { ==, !=, ^ } and pow2 masks. > > 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: > * v4: Removed the ((x & c) == 0) OP (y & c) simplify rule and > mark the corresponding test case as XFAIL. > > * 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 | 21 +++++ > .../gcc.dg/tree-ssa/bool-eq-bitxor.c | 42 +++++++++ > .../gcc.dg/tree-ssa/bool-eq-evenness.c | 43 +++++++++ > gcc/testsuite/gcc.dg/tree-ssa/bool-eq-pow2.c | 89 +++++++++++++++++++ > 4 files changed, 195 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..228bab78428 100644 > --- a/gcc/match.pd > +++ b/gcc/match.pd > @@ -1464,6 +1464,27 @@ 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 masked_ocmp (eq ne bit_xor) > + (for icmp0 (eq eq ne ne) > + icmp1 (eq ne eq ne) > + (simplify > + (masked_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 == (masked_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..bc263e80977 > --- /dev/null > +++ b/gcc/testsuite/gcc.dg/tree-ssa/bool-eq-bitxor.c > @@ -0,0 +1,42 @@ > +/* { 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 "a_\[0-9\]+\\(D\\) \\^ > b_\[0-9\]+\\(D\\)" 3 "optimized" } } */ > + > +/* xor_eq_ne not optimized yet due to zero_one_valued_p canonicalization. */ > +/* { dg-final { scan-tree-dump-times "& 1" 2 "optimized" { xfail *-*-* } } } > */ > 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 >
