On Wed, May 27, 2026 at 8:18 AM 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. > > Thank you for context and background, I have removed the third rule and mark the corresponding case as xfail for now. Thanks, Shivam 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 > > >
