On Sat, Aug 15, 2026 at 8:44 PM Shivam Gupta <[email protected]> wrote: > > Recognize XOR patterns involving zero_one_valued operands compared > against zero and simplify them to direct equality or inequality tests. > > Specifically: > > (a == 0) ^ (b != 0) -> a == b > (a != 0) ^ (b == 0) -> a == b > (a == 0) ^ (b == 0) -> a != b > (a != 0) ^ (b != 0) -> a != b > > Also handle a specific case: > (a == 0) ^ b -> a == b > > Extend the simplifications to handle the corresponding boolean > equality forms as well: > (a == 0) == (b != 0) -> a != b > (a != 0) == (b == 0) -> a != b > (a == 0) == (b == 0) -> a == b > (a != 0) == (b != 0) -> a == b > > Regression tested on aarch64-linux-gnu with RUNTESTFLAGS="tree-ssa.exp".
Note you need to bootstrap and run all regression tests. OK if you did and this showed no errors. Thanks, Richard. > Changes since v1: > * v3: Merge the op1 == op2 and op1 != op2 comparison patterns into a > single pattern using out_cmp. > Wrap the pattern inside (if (INTEGRAL_TYPE_P (type))) to explicitly > guard > against vector types instead of relying on zero_one_valued_p internals. > Drop unnecessary ':s' tree flags and remove outer convert. > Update the regression test to check for the expected canonical > XOR form rather than the absence of comparisons against zero. > > * v2: Simplify (a == 0) ^ b to a == b. > Handle outer EQ as well as outer NE forms. > Use convert:type to handle differing operand types. > > gcc/ChangeLog: > * match.pd: Add simplifications for XORs and boolean > comparisons of zero_one_valued comparisons against zero. > > gcc/testsuite/ChangeLog: > * gcc.dg/tree-ssa/bool-eq-bitxor.c: Update expected number > of optimized XOR forms. > * gcc.dg/tree-ssa/bool-xor-zero-one-valued.c: New test. > > Signed-off-by: Shivam Gupta <[email protected]> > --- > gcc/match.pd | 21 +++++++++++ > .../gcc.dg/tree-ssa/bool-eq-bitxor.c | 5 +-- > .../tree-ssa/bool-xor-zero-one-valued.c | 36 +++++++++++++++++++ > 3 files changed, 58 insertions(+), 4 deletions(-) > create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/bool-xor-zero-one-valued.c > > diff --git a/gcc/match.pd b/gcc/match.pd > index 6addf8fee..edd6cd6a3 100644 > --- a/gcc/match.pd > +++ b/gcc/match.pd > @@ -3989,6 +3989,27 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) > (if (types_match (type, TREE_TYPE (@0))) > (bit_xor @0 { build_one_cst (type); } )))))) > > +/* For zero_one_valued operands: > + (a == 0) != b -> a == b. */ > +(simplify > + (ne:c (convert (eq zero_one_valued_p@0 integer_zerop)) > + (convert zero_one_valued_p@1)) > + (if (INTEGRAL_TYPE_P (TREE_TYPE (@0)) > + && types_match (TREE_TYPE (@0), TREE_TYPE (@1))) > + (eq @0 @1))) > + > +/* For zero_one_valued operands: > + (a op1 0) cmp (b op2 0) -> a out_cmp b > + where out_cmp is cmp if op1 == op2, and the inverse of cmp otherwise. */ > +(if (INTEGRAL_TYPE_P (type)) > + (for cmp (ne ne eq eq ne ne eq eq) > + op1 (eq ne eq ne eq ne eq ne) > + op2 (eq ne eq ne ne eq ne eq) > + out_cmp (ne ne eq eq eq eq ne ne) > + (simplify > + (cmp:c (op1 zero_one_valued_p@0 integer_zerop) > + (op2 zero_one_valued_p@1 integer_zerop)) > + (out_cmp (convert:type @0) (convert:type @1))))) > > /* ((a ^ b) & c) cmp d || a != b --> (0 cmp d || a != b). */ > /* ((a ^ b) & c) cmp d && a == b --> (0 cmp d && a == b). */ > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/bool-eq-bitxor.c > b/gcc/testsuite/gcc.dg/tree-ssa/bool-eq-bitxor.c > index bc263e809..bfb3fe06b 100644 > --- a/gcc/testsuite/gcc.dg/tree-ssa/bool-eq-bitxor.c > +++ b/gcc/testsuite/gcc.dg/tree-ssa/bool-eq-bitxor.c > @@ -36,7 +36,4 @@ xor_ne_ne (u32 a, u32 b) > } > > /* 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 *-*-* } } } > */ > +/* { dg-final { scan-tree-dump-times "a_\[0-9\]+\\(D\\) \\^ > b_\[0-9\]+\\(D\\)" 4 "optimized" } } */ > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/bool-xor-zero-one-valued.c > b/gcc/testsuite/gcc.dg/tree-ssa/bool-xor-zero-one-valued.c > new file mode 100644 > index 000000000..95b369299 > --- /dev/null > +++ b/gcc/testsuite/gcc.dg/tree-ssa/bool-xor-zero-one-valued.c > @@ -0,0 +1,36 @@ > +/* { dg-do compile } */ > +/* { dg-options "-O1 -fdump-tree-optimized" } */ > + > +_Bool > +f1 (unsigned a, unsigned b) > +{ > + if (a != 0 && a != 1) __builtin_unreachable(); > + if (b != 0 && b != 1) __builtin_unreachable(); > + return (a == 0) ^ (b != 0); > +} > + > +_Bool > +f2 (unsigned a, unsigned b) > +{ > + if (a != 0 && a != 1) __builtin_unreachable(); > + if (b != 0 && b != 1) __builtin_unreachable(); > + return (a != 0) ^ (b == 0); > +} > + > +_Bool > +f3 (unsigned a, unsigned b) > +{ > + if (a != 0 && a != 1) __builtin_unreachable(); > + if (b != 0 && b != 1) __builtin_unreachable(); > + return (a == 0) ^ (b == 0); > +} > + > +_Bool > +f4 (unsigned a, unsigned b) > +{ > + if (a != 0 && a != 1) __builtin_unreachable(); > + if (b != 0 && b != 1) __builtin_unreachable(); > + return (a != 0) ^ (b != 0); > +} > + > +/* { dg-final { scan-tree-dump-times "a_\[0-9\]+\\(D\\) \\^ > b_\[0-9\]+\\(D\\)" 4 "optimized" } } */ > -- > 2.43.0 >
