[PATCH]AArch64 Optimize right shift rounding narrowing

Tamar Christina Tamar.Christina@arm.com
Tue Nov 23 15:21:00 GMT 2021


Adding ML back in. ☹

> -----Original Message-----
> From: Tamar Christina <Tamar.Christina@arm.com>
> Sent: Tuesday, November 23, 2021 3:17 PM
> To: Tamar Christina <Tamar.Christina@arm.com>
> Cc: Richard Earnshaw <Richard.Earnshaw@arm.com>; nd <nd@arm.com>;
> Richard Sandiford <Richard.Sandiford@arm.com>; Marcus Shawcroft
> <Marcus.Shawcroft@arm.com>; Kyrylo Tkachov <Kyrylo.Tkachov@arm.com>
> Subject: RE: [PATCH]AArch64 Optimize right shift rounding narrowing
> 
> Ping.
> 
> > -----Original Message-----
> > From: Gcc-patches <gcc-patches-
> > bounces+tamar.christina=arm.com@gcc.gnu.org> On Behalf Of Tamar
> > Christina via Gcc-patches
> > Sent: Friday, November 12, 2021 12:08 PM
> > To: gcc-patches@gcc.gnu.org
> > Cc: Richard Earnshaw <Richard.Earnshaw@arm.com>; nd <nd@arm.com>;
> > Richard Sandiford <Richard.Sandiford@arm.com>; Marcus Shawcroft
> > <Marcus.Shawcroft@arm.com>
> > Subject: [PATCH]AArch64 Optimize right shift rounding narrowing
> >
> > Hi All,
> >
> > This optimizes right shift rounding narrow instructions to rounding
> > add narrow high where one vector is 0 when the shift amount is half
> > that of the original input type.
> >
> > i.e.
> >
> > uint32x4_t foo (uint64x2_t a, uint64x2_t b) {
> >   return vrshrn_high_n_u64 (vrshrn_n_u64 (a, 32), b, 32); }
> >
> > now generates:
> >
> > foo:
> >         movi    v3.4s, 0
> >         raddhn  v0.2s, v2.2d, v3.2d
> >         raddhn2 v0.4s, v2.2d, v3.2d
> >
> > instead of:
> >
> > foo:
> >         rshrn   v0.2s, v0.2d, 32
> >         rshrn2  v0.4s, v1.2d, 32
> >         ret
> >
> > On Arm cores this is an improvement in both latency and throughput.
> > Because a vector zero is needed I created a new method
> > aarch64_gen_shareable_zero that creates zeros using V4SI and then
> > takes a subreg of the zero to the desired type.  This allows CSE to
> > share all the zero constants.
> >
> > Bootstrapped Regtested on aarch64-none-linux-gnu and no issues.
> >
> > Ok for master?
> >
> > Thanks,
> > Tamar
> >
> > gcc/ChangeLog:
> >
> > 	* config/aarch64/aarch64-protos.h (aarch64_gen_shareable_zero):
> > New.
> > 	* config/aarch64/aarch64-simd.md (aarch64_rshrn<mode>,
> > 	aarch64_rshrn2<mode>):
> > 	* config/aarch64/aarch64.c (aarch64_gen_shareable_zero): New.
> >
> > gcc/testsuite/ChangeLog:
> >
> > 	* gcc.target/aarch64/advsimd-intrinsics/shrn-1.c: New test.
> > 	* gcc.target/aarch64/advsimd-intrinsics/shrn-2.c: New test.
> > 	* gcc.target/aarch64/advsimd-intrinsics/shrn-3.c: New test.
> > 	* gcc.target/aarch64/advsimd-intrinsics/shrn-4.c: New test.
> >
> > --- inline copy of patch --
> > diff --git a/gcc/config/aarch64/aarch64-protos.h
> > b/gcc/config/aarch64/aarch64-protos.h
> > index
> >
> f7887d06139f01c1591c4e755538d94e5e608a52..f7f5cae82bc9198e54d0298f25f
> > 7c0f5902d5fb1 100644
> > --- a/gcc/config/aarch64/aarch64-protos.h
> > +++ b/gcc/config/aarch64/aarch64-protos.h
> > @@ -846,6 +846,7 @@ const char *aarch64_output_move_struct (rtx
> > *operands);  rtx aarch64_return_addr_rtx (void);  rtx
> > aarch64_return_addr (int, rtx);  rtx aarch64_simd_gen_const_vector_dup
> > (machine_mode, HOST_WIDE_INT);
> > +rtx aarch64_gen_shareable_zero (machine_mode);
> >  bool aarch64_simd_mem_operand_p (rtx);  bool
> > aarch64_sve_ld1r_operand_p (rtx);  bool aarch64_sve_ld1rq_operand_p
> > (rtx); diff --git a/gcc/config/aarch64/aarch64-simd.md
> > b/gcc/config/aarch64/aarch64- simd.md index
> >
> c71658e2bf52b26bf9fc9fa702dd5446447f4d43..d7f8694add540e32628893a7b7
> > 471c08de6f760f 100644
> > --- a/gcc/config/aarch64/aarch64-simd.md
> > +++ b/gcc/config/aarch64/aarch64-simd.md
> > @@ -1956,20 +1956,32 @@ (define_expand "aarch64_rshrn<mode>"
> >     (match_operand:SI 2 "aarch64_simd_shift_imm_offset_<vn_mode>")]
> >    "TARGET_SIMD"
> >    {
> > -    operands[2] = aarch64_simd_gen_const_vector_dup (<MODE>mode,
> > -						 INTVAL (operands[2]));
> > -    rtx tmp = gen_reg_rtx (<VNARROWQ2>mode);
> > -    if (BYTES_BIG_ENDIAN)
> > -      emit_insn (gen_aarch64_rshrn<mode>_insn_be (tmp, operands[1],
> > -				operands[2], CONST0_RTX
> > (<VNARROWQ>mode)));
> > +    if (INTVAL (operands[2]) == GET_MODE_UNIT_BITSIZE
> > (<VNARROWQ>mode))
> > +      {
> > +	rtx tmp0 = aarch64_gen_shareable_zero (<MODE>mode);
> > +	emit_insn (gen_aarch64_raddhn<mode> (operands[0], operands[1],
> > tmp0));
> > +      }
> >      else
> > -      emit_insn (gen_aarch64_rshrn<mode>_insn_le (tmp, operands[1],
> > -				operands[2], CONST0_RTX
> > (<VNARROWQ>mode)));
> > -
> > -    /* The intrinsic expects a narrow result, so emit a subreg that will get
> > -       optimized away as appropriate.  */
> > -    emit_move_insn (operands[0], lowpart_subreg (<VNARROWQ>mode,
> > tmp,
> > -						 <VNARROWQ2>mode));
> > +      {
> > +	rtx tmp = gen_reg_rtx (<VNARROWQ2>mode);
> > +	operands[2] = aarch64_simd_gen_const_vector_dup
> > (<MODE>mode,
> > +						         INTVAL (operands[2]));
> > +	if (BYTES_BIG_ENDIAN)
> > +	  emit_insn (
> > +		gen_aarch64_rshrn<mode>_insn_be (tmp, operands[1],
> > +						 operands[2],
> > +						 CONST0_RTX
> > (<VNARROWQ>mode)));
> > +	else
> > +	  emit_insn (
> > +		gen_aarch64_rshrn<mode>_insn_le (tmp, operands[1],
> > +						 operands[2],
> > +						 CONST0_RTX
> > (<VNARROWQ>mode)));
> > +
> > +	/* The intrinsic expects a narrow result, so emit a subreg that will
> > +	   get optimized away as appropriate.  */
> > +	emit_move_insn (operands[0], lowpart_subreg
> > (<VNARROWQ>mode, tmp,
> > +						     <VNARROWQ2>mode));
> > +      }
> >      DONE;
> >    }
> >  )
> > @@ -2049,14 +2061,27 @@ (define_expand "aarch64_rshrn2<mode>"
> >     (match_operand:SI 3 "aarch64_simd_shift_imm_offset_<vn_mode>")]
> >    "TARGET_SIMD"
> >    {
> > -    operands[3] = aarch64_simd_gen_const_vector_dup (<MODE>mode,
> > -						 INTVAL (operands[3]));
> > -    if (BYTES_BIG_ENDIAN)
> > -      emit_insn (gen_aarch64_rshrn2<mode>_insn_be (operands[0],
> > operands[1],
> > -						  operands[2], operands[3]));
> > +    if (INTVAL (operands[3]) == GET_MODE_UNIT_BITSIZE
> > (<VNARROWQ2>mode))
> > +      {
> > +	rtx tmp = aarch64_gen_shareable_zero (<MODE>mode);
> > +	emit_insn (gen_aarch64_raddhn2<mode> (operands[0],
> > operands[1],
> > +					      operands[2], tmp));
> > +      }
> >      else
> > -      emit_insn (gen_aarch64_rshrn2<mode>_insn_le (operands[0],
> > operands[1],
> > -						  operands[2], operands[3]));
> > +      {
> > +	operands[3] = aarch64_simd_gen_const_vector_dup
> > (<MODE>mode,
> > +							 INTVAL
> > (operands[3]));
> > +	if (BYTES_BIG_ENDIAN)
> > +	  emit_insn (gen_aarch64_rshrn2<mode>_insn_be (operands[0],
> > +						       operands[1],
> > +						       operands[2],
> > +						       operands[3]));
> > +	else
> > +	  emit_insn (gen_aarch64_rshrn2<mode>_insn_le (operands[0],
> > +						       operands[1],
> > +						       operands[2],
> > +						       operands[3]));
> > +      }
> >      DONE;
> >    }
> >  )
> > diff --git a/gcc/config/aarch64/aarch64.c
> > b/gcc/config/aarch64/aarch64.c index
> >
> fdf05505846721b02059df494d6395ae9423a8ef..11201ea3498beb270c0a7f8da5
> > f5009d710535ee 100644
> > --- a/gcc/config/aarch64/aarch64.c
> > +++ b/gcc/config/aarch64/aarch64.c
> > @@ -20397,6 +20397,18 @@ aarch64_mov_operand_p (rtx x,
> machine_mode
> > mode)
> >      == SYMBOL_TINY_ABSOLUTE;
> >  }
> >
> > +/* Create a 0 constant that is based of V4SI to allow CSE to optimally share
> > +   the constant creation.  */
> > +
> > +rtx
> > +aarch64_gen_shareable_zero (machine_mode mode) {
> > +  machine_mode zmode = V4SImode;
> > +  rtx tmp = gen_reg_rtx (zmode);
> > +  emit_move_insn (tmp, CONST0_RTX (zmode));
> > +  return lowpart_subreg (mode, tmp, zmode); }
> > +
> >  /* Return a const_int vector of VAL.  */  rtx
> > aarch64_simd_gen_const_vector_dup (machine_mode mode,
> HOST_WIDE_INT
> > val) diff --git a/gcc/testsuite/gcc.target/aarch64/advsimd-
> > intrinsics/shrn-1.c b/gcc/testsuite/gcc.target/aarch64/advsimd-
> > intrinsics/shrn-1.c
> > new file mode 100644
> > index
> >
> 0000000000000000000000000000000000000000..4bc3aa9563ee7d0dc46557d30
> > d9a29149706229d
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/aarch64/advsimd-intrinsics/shrn-1.c
> > @@ -0,0 +1,15 @@
> > +/* { dg-do compile { target { aarch64*-*-* } } } */
> > +/* { dg-skip-if "" { *-*-* } { "-O0" } { "" } } */
> > +
> > +#include <arm_neon.h>
> > +
> > +uint8x16_t foo (uint32x4_t a, uint32x4_t b) {
> > +  uint16x4_t a1 = vrshrn_n_u32 (a, 16);
> > +  uint16x8_t b1 = vrshrn_high_n_u32 (a1, b, 16);
> > +  return vrshrn_high_n_u16 (vrshrn_n_u16 (b1, 8), b1, 8); }
> > +
> > +/* { dg-final { scan-assembler-times {\tmovi\t} 1 } } */
> > +/* { dg-final { scan-assembler-times {\traddhn\t} 2 } } */
> > +/* { dg-final { scan-assembler-times {\traddhn2\t} 2 } } */
> > diff --git
> > a/gcc/testsuite/gcc.target/aarch64/advsimd-intrinsics/shrn-2.c
> > b/gcc/testsuite/gcc.target/aarch64/advsimd-intrinsics/shrn-2.c
> > new file mode 100644
> > index
> >
> 0000000000000000000000000000000000000000..09d913e85524f06367c1c2cf51
> > dda0f57578e9ae
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/aarch64/advsimd-intrinsics/shrn-2.c
> > @@ -0,0 +1,11 @@
> > +/* { dg-do compile { target { aarch64*-*-* } } } */
> > +
> > +#include <arm_neon.h>
> > +
> > +uint32x4_t foo (uint64x2_t a, uint64x2_t b) {
> > +  return vrshrn_high_n_u64 (vrshrn_n_u64 (a, 32), b, 32); }
> > +
> > +/* { dg-final { scan-assembler-times {\traddhn\t} 1 } } */
> > +/* { dg-final { scan-assembler-times {\traddhn2\t} 1 } } */
> > diff --git
> > a/gcc/testsuite/gcc.target/aarch64/advsimd-intrinsics/shrn-3.c
> > b/gcc/testsuite/gcc.target/aarch64/advsimd-intrinsics/shrn-3.c
> > new file mode 100644
> > index
> >
> 0000000000000000000000000000000000000000..bdccbb3410f049d7e45aabdcc
> > 3d2964fbabca807
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/aarch64/advsimd-intrinsics/shrn-3.c
> > @@ -0,0 +1,11 @@
> > +/* { dg-do compile { target { aarch64*-*-* } } } */
> > +
> > +#include <arm_neon.h>
> > +
> > +uint16x8_t foo (uint32x4_t a, uint32x4_t b) {
> > +  return vrshrn_high_n_u32 (vrshrn_n_u32 (a, 16), b, 16); }
> > +
> > +/* { dg-final { scan-assembler-times {\traddhn\t} 1 } } */
> > +/* { dg-final { scan-assembler-times {\traddhn2\t} 1 } } */
> > diff --git
> > a/gcc/testsuite/gcc.target/aarch64/advsimd-intrinsics/shrn-4.c
> > b/gcc/testsuite/gcc.target/aarch64/advsimd-intrinsics/shrn-4.c
> > new file mode 100644
> > index
> >
> 0000000000000000000000000000000000000000..4b23eddb85891975b8e122060
> > e2a9ebfe56d842c
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/aarch64/advsimd-intrinsics/shrn-4.c
> > @@ -0,0 +1,11 @@
> > +/* { dg-do compile { target { aarch64*-*-* } } } */
> > +
> > +#include <arm_neon.h>
> > +
> > +uint8x16_t foo (uint16x8_t a, uint16x8_t b) {
> > +  return vrshrn_high_n_u16 (vrshrn_n_u16 (a, 8), b, 8); }
> > +
> > +/* { dg-final { scan-assembler-times {\traddhn\t} 1 } } */
> > +/* { dg-final { scan-assembler-times {\traddhn2\t} 1 } } */
> >
> >
> > --


More information about the Gcc-patches mailing list