On Mon, 17 Aug 2026 at 2:16 PM, Richard Biener <[email protected]> wrote:
> 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. > No, I have not had a bootstrap build. I can have it in few hours and will ping the thread. Thanks for reviewing and pointing that out. Regards, Shivam > > 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 > > >
