This is a draft patch. I would like to explain it's hard to make the
simplify generic and ask for some help.
There're 2 categories we need to optimize.
- The op in optab such as div / 1.
- The unspec operation such as mulh * 0, (vadc+vmadc) + 0.
Especially for the unspec operation, I found we need to write one by
one to match the special pattern. Seems there's no way to write a
generic pattern that will match mulh, (vadc+vmadc), sll... This way
is too complicated and not so elegant because need to write so much
md patterns.
Do you have any ideas?
> -----Original Message-----
> From: Wang, Yanzhang <yanzhang.w...@intel.com>
> Sent: Friday, July 28, 2023 7:50 PM
> To: gcc-patches@gcc.gnu.org
> Cc: juzhe.zh...@rivai.ai; kito.ch...@sifive.com; rdapp....@gmail.com; Li,
> Pan2 <pan2...@intel.com>; Wang, Yanzhang <yanzhang.w...@intel.com>
> Subject: [PATCH v2] RISC-V: convert the mulh with 0 to mov 0 to the reg.
>
> From: Yanzhang Wang <yanzhang.w...@intel.com>
>
> This patch will optimize the below mulh example,
>
> vint32m1_t shortcut_for_riscv_vmulh_case_0(vint32m1_t v1, size_t vl) {
> return __riscv_vmulh_vx_i32m1(v1, 0, vl); }
>
> from mulh pattern
>
> vsetvli zero, a2, e32, m1, ta, ma
> vmulh.vx v24, v24, zero
> vs1r.v v24, 0(a0)
>
> to below vmv.
>
> vsetvli zero,a2,e32,m1,ta,ma
> vmv.v.i v1,0
> vs1r.v v1,0(a0)
>
> It will elimate the mul with const 0 instruction to the simple mov
> instruction.
>
> Signed-off-by: Yanzhang Wang <yanzhang.w...@intel.com>
>
> gcc/ChangeLog:
>
> * config/riscv/autovec-opt.md: Add a split pattern.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.target/riscv/rvv/base/binop_vx_constraint-121.c: The mul
> with 0 will be simplified to vmv.v.i.
> * gcc.target/riscv/rvv/autovec/vmulh-with-zero.cc: New test.
> ---
> gcc/config/riscv/autovec-opt.md | 58 +++++++++++++++++++
> gcc/config/riscv/riscv-protos.h | 2 +
> gcc/config/riscv/riscv-v.cc | 57 ++++++++++++++++++
> .../riscv/rvv/autovec/vmulh-with-zero.cc | 19 ++++++
> .../riscv/rvv/base/binop_vx_constraint-121.c | 3 +-
> 5 files changed, 138 insertions(+), 1 deletion(-) create mode 100644
> gcc/testsuite/gcc.target/riscv/rvv/autovec/vmulh-with-zero.cc
>
> diff --git a/gcc/config/riscv/autovec-opt.md b/gcc/config/riscv/autovec-
> opt.md index 28040805b23..0d87572d1a4 100644
> --- a/gcc/config/riscv/autovec-opt.md
> +++ b/gcc/config/riscv/autovec-opt.md
> @@ -405,3 +405,61 @@
> "vmv.x.s\t%0,%1"
> [(set_attr "type" "vimovvx")
> (set_attr "mode" "<MODE>")])
> +
> +;;; Simplify the mulh with 0 to move
> +(define_split
> + [(set (match_operand:VI_QHS 0 "register_operand")
> + (if_then_else:VI_QHS
> + (unspec:<VM>
> + [(match_operand:<VM> 1 "vector_all_trues_mask_operand")
> + (match_operand 5 "vector_length_operand")
> + (match_operand 6 "const_int_operand")
> + (match_operand 7 "const_int_operand")
> + (match_operand 8 "const_int_operand")
> + (reg:SI VL_REGNUM)
> + (reg:SI VTYPE_REGNUM)] UNSPEC_VPREDICATE)
> + (unspec:VI_QHS
> + [(vec_duplicate:VI_QHS
> + (match_operand:<VEL> 4 "reg_or_0_operand"))
> + (match_operand:VI_QHS 3 "register_operand")] VMULH)
> + (match_operand:VI_QHS 2 "vector_merge_operand")
> + ))]
> + "TARGET_VECTOR
> + && rtx_equal_p (operands[4], CONST0_RTX (GET_MODE (operands[4])))"
> + [(const_int 0)]
> +{
> + riscv_vector::simplify_unspec_operations (operands, UNSPEC,
> + <VMULH>, <MODE>mode) ;
> + DONE;
> +})
> +
> +;;; Simplify vmadc + vadc with 0 to a simple move.
> +(define_split
> + [(set (match_operand:VI 0 "register_operand")
> + (if_then_else:VI
> + (unspec:<VM>
> + [(match_operand 4 "vector_length_operand")
> + (match_operand 5 "const_int_operand")
> + (match_operand 6 "const_int_operand")
> + (reg:SI VL_REGNUM)
> + (reg:SI VTYPE_REGNUM)] UNSPEC_VPREDICATE)
> + (unspec:VI
> + [(match_operand:VI 2 "register_operand")
> + (unspec:<VM>
> + [(match_operand:VI 3 "register_operand")
> + (unspec:<VM>
> + [(match_operand 7 "vector_length_operand")
> + (match_operand 8 "const_int_operand")
> + (reg:SI VL_REGNUM)
> + (reg:SI VTYPE_REGNUM)] UNSPEC_VPREDICATE)
> + ] UNSPEC_OVERFLOW)
> + ] UNSPEC_VADC)
> + (match_operand:VI 1 "vector_merge_operand")))]
> + "TARGET_VECTOR"
> + [(const_int 0)]
> +{
> + riscv_vector::simplify_unspec_operations (operands, PLUS, UNSPEC_VADC,
> + <MODE>mode);
> + DONE;
> +})
> +
> diff --git a/gcc/config/riscv/riscv-protos.h b/gcc/config/riscv/riscv-
> protos.h index f052757cede..6a188a3d0ef 100644
> --- a/gcc/config/riscv/riscv-protos.h
> +++ b/gcc/config/riscv/riscv-protos.h
> @@ -228,6 +228,8 @@ bool neg_simm5_p (rtx); bool has_vi_variant_p
> (rtx_code, rtx); void expand_vec_cmp (rtx, rtx_code, rtx, rtx); bool
> expand_vec_cmp_float (rtx, rtx_code, rtx, rtx, bool);
> +void simplify_complement (rtx *, rtx_code, machine_mode); void
> +simplify_unspec_operations (rtx*, rtx_code, int, machine_mode);
> #endif
> bool sew64_scalar_helper (rtx *, rtx *, rtx, machine_mode,
> bool, void (*)(rtx *, rtx));
> diff --git a/gcc/config/riscv/riscv-v.cc b/gcc/config/riscv/riscv-v.cc
> index 839a2c6ba71..9a9428ce18d 100644
> --- a/gcc/config/riscv/riscv-v.cc
> +++ b/gcc/config/riscv/riscv-v.cc
> @@ -2721,4 +2721,61 @@ expand_select_vl (rtx *ops)
> emit_insn (gen_no_side_effects_vsetvl_rtx (rvv_mode, ops[0], ops[1])); }
>
> +void simplify_mulh (rtx *operands,
> + machine_mode mode)
> +{
> + rtx zero_operand = CONST0_RTX(GET_MODE(operands[4]));
> + if (rtx_equal_p(operands[4], zero_operand))
> + {
> + machine_mode mask_mode = riscv_vector::get_mask_mode (mode).require
> ();
> + emit_insn (gen_pred_mov (mode, operands[0], CONST1_RTX (mask_mode),
> + RVV_VUNDEF (mode),
> + CONST0_RTX (GET_MODE (operands[0])),
> + operands[5], operands[6], operands[7],
> + operands[8]));
> + }
> +}
> +
> +void simplify_vadc (rtx *operands,
> + machine_mode mode)
> +{
> + machine_mode mask_mode = riscv_vector::get_mask_mode (mode).require
> +();
> +
> + if (rtx_equal_p(operands[2], operands[3]))
> + {
> + emit_insn (gen_pred_mov (mode, operands[0], CONST1_RTX (mask_mode),
> + operands[1], operands[2], operands[4],
> + operands[5], operands[6],
> + get_avl_type_rtx (riscv_vector::VLMAX)));
> + }
> +}
> +
> +void simplify_unspec_operations (rtx *operands,
> + rtx_code code,
> + int unspec,
> + machine_mode mode)
> +{
> + switch (unspec)
> + {
> + case UNSPEC_VMULHS:
> + case UNSPEC_VMULHU:
> + case UNSPEC_VMULHSU:
> + simplify_mulh (operands, mode);
> + break;
> +
> + case UNSPEC_VADC:
> + case UNSPEC_VSBC:
> + simplify_vadc(operands, mode);
> + break;
> +
> + default:
> + break;
> + }
> +}
> +
> +void simplify_complement (rtx *operands,
> + rtx_code code,
> + machine_mode mode)
> +{
> +}
> } // namespace riscv_vector
> diff --git a/gcc/testsuite/gcc.target/riscv/rvv/autovec/vmulh-with-zero.cc
> b/gcc/testsuite/gcc.target/riscv/rvv/autovec/vmulh-with-zero.cc
> new file mode 100644
> index 00000000000..6e4a3d62bc0
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/riscv/rvv/autovec/vmulh-with-zero.cc
> @@ -0,0 +1,19 @@
> +/* { dg-do compile } */
> +/* { dg-options "-march=rv64gcv -mabi=lp64 -O3 -Wno-psabi" } */
> +
> +#include "riscv_vector.h"
> +
> +#define VMULH_WITH_LMUL(X) \
> + vint32m##X##_t shortcut_for_riscv_vmulh_case_##X (vint32m##X##_t v1,\
> + size_t vl) { \
> + return __riscv_vmulh_vx_i32m ##X (v1, 0, vl); \
> + }
> +
> +
> +VMULH_WITH_LMUL (1)
> +VMULH_WITH_LMUL (2)
> +VMULH_WITH_LMUL (4)
> +VMULH_WITH_LMUL (8)
> +VMULH_WITH_LMUL (f2)
> +
> +/* { dg-final { scan-assembler-times {vmv\.v\.i\sv[0-9]+,0} 5} */
> diff --git a/gcc/testsuite/gcc.target/riscv/rvv/base/binop_vx_constraint-
> 121.c b/gcc/testsuite/gcc.target/riscv/rvv/base/binop_vx_constraint-121.c
> index 4d2de91bc14..d1473274137 100644
> --- a/gcc/testsuite/gcc.target/riscv/rvv/base/binop_vx_constraint-121.c
> +++ b/gcc/testsuite/gcc.target/riscv/rvv/base/binop_vx_constraint-121.c
> @@ -50,6 +50,7 @@ void f6 (void * in, void *out, int32_t x)
> __riscv_vse64_v_i64m1 (out, v3, 4); }
>
> -/* { dg-final { scan-assembler-times {vmulh\.vx\s+v[0-9]+,\s*v[0-9]+,zero}
> 2 } } */
> +/* { dg-final { scan-assembler-times {vmv\.v\.i\sv[0-9]+,0} 1 } } */
> +/* { dg-final { scan-assembler-times
> +{vmulh\.vx\s+v[0-9]+,\s*v[0-9]+,zero} 1 } } */
> /* { dg-final { scan-assembler-times {vdiv\.vx\s+v[0-9]+,\s*v[0-9]+,zero}
> 2 } } */
> /* { dg-final { scan-assembler-times {vrem\.vx\s+v[0-9]+,\s*v[0-9]+,zero}
> 2 } } */
> --
> 2.41.0
