On Tue, Nov 8, 2022 at 9:02 PM Michael Collison <colli...@rivosinc.com> wrote: > > This patches transforms (cond (and (x , 0x1) == 0), y, (z op y)) into > (-(and (x , 0x1)) & z ) op y, where op is a '^' or a '|'. It also > transforms (cond (and (x , 0x1) != 0), (z op y), y ) into (-(and (x , > 0x1)) & z ) op y. > > Matching this patterns allows GCC to generate branchless code for one of > the functions in coremark. > > Bootstrapped and tested on x86 and RISC-V. Okay? > > Michael. > > 2022-11-08 Michael Collison <colli...@rivosinc.com> > > * match.pd ((cond (and (x , 0x1) == 0), y, (z op y) ) > -> (-(and (x , 0x1)) & z ) op y) > > 2022-11-08 Michael Collison <colli...@rivosinc.com> > > * gcc.dg/tree-ssa/branchless-cond.c: New test. > > --- > gcc/match.pd | 22 ++++++++++++++++ > .../gcc.dg/tree-ssa/branchless-cond.c | 26 +++++++++++++++++++ > 2 files changed, 48 insertions(+) > create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/branchless-cond.c > > diff --git a/gcc/match.pd b/gcc/match.pd > index 194ba8f5188..722f517ac6d 100644 > --- a/gcc/match.pd > +++ b/gcc/match.pd > @@ -3486,6 +3486,28 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) > (cond (le @0 integer_zerop@1) (negate@2 @0) integer_zerop@1) > (max @2 @1)) > > +/* (cond (and (x , 0x1) == 0), y, (z ^ y) ) -> (-(and (x , 0x1)) & z ) > ^ y */
Please write the match as a C expression in the comment, as present it's a weird mix. So x & 0x1 == 0 ? y : z <op> y -> (-(typeof(y))(x & 0x1) & z) <op> y > +(for op (bit_xor bit_ior) > + (simplify > + (cond (eq (bit_and @0 integer_onep@1) > + integer_zerop) > + @2 > + (op:c @3 @2)) > + (if (INTEGRAL_TYPE_P (type) > + && (INTEGRAL_TYPE_P (TREE_TYPE (@0)))) > + (op (bit_and (negate (convert:type (bit_and @0 @1))) @3) @2)))) Since you are literally keeping (bit_and @0 @1) and not matching @0 with anything I suspect you could instead use (simplify (cond (eq zero_one_valued_p@0 integer_zerop) ... eventually extending that to cover bit_and with one. Do you need to guard this against 'type' being a signed/unsigned 1-bit precision integer? > + > +/* (cond (and (x , 0x1) != 0), (z ^ y), y ) -> (-(and (x , 0x1)) & z ) > ^ y */ > +(for op (bit_xor bit_ior) > + (simplify > + (cond (ne (bit_and @0 integer_onep@1) > + integer_zerop) > + (op:c @3 @2) > + @2) > + (if (INTEGRAL_TYPE_P (type) > + && (INTEGRAL_TYPE_P (TREE_TYPE (@0)))) > + (op (bit_and (negate (convert:type (bit_and @0 @1))) @3) @2)))) > + > /* Simplifications of shift and rotates. */ > > (for rotate (lrotate rrotate) > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/branchless-cond.c > b/gcc/testsuite/gcc.dg/tree-ssa/branchless-cond.c > new file mode 100644 > index 00000000000..68087ae6568 > --- /dev/null > +++ b/gcc/testsuite/gcc.dg/tree-ssa/branchless-cond.c > @@ -0,0 +1,26 @@ > +/* { dg-do compile } */ > +/* { dg-options "-O2 -fdump-tree-optimized" } */ > + > +int f1(unsigned int x, unsigned int y, unsigned int z) > +{ > + return ((x & 1) == 0) ? y : z ^ y; > +} > + > +int f2(unsigned int x, unsigned int y, unsigned int z) > +{ > + return ((x & 1) != 0) ? z ^ y : y; > +} > + > +int f3(unsigned int x, unsigned int y, unsigned int z) > +{ > + return ((x & 1) == 0) ? y : z | y; > +} > + > +int f4(unsigned int x, unsigned int y, unsigned int z) > +{ > + return ((x & 1) != 0) ? z | y : y; > +} > + > +/* { dg-final { scan-tree-dump-times " -" 4 "optimized" } } */ > +/* { dg-final { scan-tree-dump-times " & " 8 "optimized" } } */ > +/* { dg-final { scan-tree-dump-not "if" "optimized" } } */ > -- > 2.34.1 > > > >