On Thu, Oct 24, 2024 at 6:22 PM Li Xu <xu...@eswincomputing.com> wrote: > > From: xuli <xu...@eswincomputing.com> > > When the imm operand op1=1 in the unsigned scalar sat_sub form2 below, > we can simplify (x != 0 ? x + ~0 : 0) to (x - x != 0), thereby eliminating > a branch instruction.This simplification also applies to signed integer. > > Form2: > T __attribute__((noinline)) \ > sat_u_sub_imm##IMM##_##T##_fmt_2 (T x) \ > { \ > return x >= (T)IMM ? x - (T)IMM : 0; \ > } > > Take below form 2 as example: > DEF_SAT_U_SUB_IMM_FMT_2(uint8_t, 1) > > Before this patch: > __attribute__((noinline)) > uint8_t sat_u_sub_imm1_uint8_t_fmt_2 (uint8_t x) > { > uint8_t _1; > uint8_t _3; > > <bb 2> [local count: 1073741824]: > if (x_2(D) != 0) > goto <bb 3>; [50.00%] > else > goto <bb 4>; [50.00%] > > <bb 3> [local count: 536870912]: > _3 = x_2(D) + 255; > > <bb 4> [local count: 1073741824]: > # _1 = PHI <x_2(D)(2), _3(3)> > return _1; > > } > > Assembly code: > sat_u_sub_imm1_uint8_t_fmt_2: > beq a0,zero,.L2 > addiw a0,a0,-1 > andi a0,a0,0xff > .L2: > ret > > After this patch: > __attribute__((noinline)) > uint8_t sat_u_sub_imm1_uint8_t_fmt_2 (uint8_t x) > { > _Bool _1; > unsigned char _2; > uint8_t _4; > > <bb 2> [local count: 1073741824]: > _1 = x_3(D) != 0; > _2 = (unsigned char) _1; > _4 = x_3(D) - _2; > return _4; > > } > > Assembly code: > sat_u_sub_imm1_uint8_t_fmt_2: > snez a5,a0 > subw a0,a0,a5 > andi a0,a0,0xff > ret > > The below test suites are passed for this patch: > 1. The rv64gcv fully regression tests. > 2. The x86 bootstrap tests. > 3. The x86 fully regression tests. > > Signed-off-by: Li Xu <xu...@eswincomputing.com> > gcc/ChangeLog: > > * match.pd: Simplify (x != 0 ? x + ~0 : 0) to (x - x != 0). > > gcc/testsuite/ChangeLog: > > * gcc.dg/tree-ssa/phi-opt-44.c: New test. > --- > gcc/match.pd | 10 +++++++++ > gcc/testsuite/gcc.dg/tree-ssa/phi-opt-44.c | 26 ++++++++++++++++++++++ > gcc/testsuite/gcc.dg/tree-ssa/phi-opt-45.c | 26 ++++++++++++++++++++++ > 3 files changed, 62 insertions(+) > create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/phi-opt-44.c > create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/phi-opt-45.c > > diff --git a/gcc/match.pd b/gcc/match.pd > index 0455dfa6993..f48fd7d52ba 100644 > --- a/gcc/match.pd > +++ b/gcc/match.pd > @@ -3383,6 +3383,16 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) > } > (if (wi::eq_p (sum, wi::uhwi (0, precision))))))) > > +/* The boundary condition for case 10: IMM = 1: > + SAT_U_SUB = X >= IMM ? (X - IMM) : 0. > + simplify (X != 0 ? X + ~0 : 0) to (X - X != 0). */ > +(simplify > + (cond (ne@1 @0 integer_zerop) > + (nop_convert? (plus (nop_convert? @0) integer_all_onesp)) > + integer_zerop) > + (if (INTEGRAL_TYPE_P (type)) > + (minus @0 (convert @1))))
This looks good to me, though I can't approve it. Thanks, Andrew > + > /* Signed saturation sub, case 1: > T minus = (T)((UT)X - (UT)Y); > SAT_S_SUB = (X ^ Y) & (X ^ minus) < 0 ? (-(T)(X < 0) ^ MAX) : minus; > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-44.c > b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-44.c > new file mode 100644 > index 00000000000..962bf0954f6 > --- /dev/null > +++ b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-44.c > @@ -0,0 +1,26 @@ > +/* { dg-do compile } */ > +/* { dg-options "-O2 -fdump-tree-phiopt1" } */ > + > +#include <stdint.h> > + > +uint8_t f1 (uint8_t x) > +{ > + return x >= (uint8_t)1 ? x - (uint8_t)1 : 0; > +} > + > +uint16_t f2 (uint16_t x) > +{ > + return x >= (uint16_t)1 ? x - (uint16_t)1 : 0; > +} > + > +uint32_t f3 (uint32_t x) > +{ > + return x >= (uint32_t)1 ? x - (uint32_t)1 : 0; > +} > + > +uint64_t f4 (uint64_t x) > +{ > + return x >= (uint64_t)1 ? x - (uint64_t)1 : 0; > +} > + > +/* { dg-final { scan-tree-dump-not "goto" "phiopt1" } } */ > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-45.c > b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-45.c > new file mode 100644 > index 00000000000..62a2ab63184 > --- /dev/null > +++ b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-45.c > @@ -0,0 +1,26 @@ > +/* { dg-do compile } */ > +/* { dg-options "-O2 -fdump-tree-phiopt1" } */ > + > +#include <stdint.h> > + > +int8_t f1 (int8_t x) > +{ > + return x != 0 ? x - (int8_t)1 : 0; > +} > + > +int16_t f2 (int16_t x) > +{ > + return x != 0 ? x - (int16_t)1 : 0; > +} > + > +int32_t f3 (int32_t x) > +{ > + return x != 0 ? x - (int32_t)1 : 0; > +} > + > +int64_t f4 (int64_t x) > +{ > + return x != 0 ? x - (int64_t)1 : 0; > +} > + > +/* { dg-final { scan-tree-dump-not "goto" "phiopt1" } } */ > -- > 2.17.1 >