diff mbox

2015-07-29 Benedikt Huber <benedikt.huber@theobroma-systems.com> Philipp Tomsich <philipp.tomsich@theobroma-systems.com>

Message ID 1438192065-29602-2-git-send-email-benedikt.huber@theobroma-systems.com
State New
Headers show

Commit Message

Benedikt Huber July 29, 2015, 5:47 p.m. UTC
* config/aarch64/aarch64-builtins.c: Builtins for rsqrt and
	rsqrtf.
	* config/aarch64/aarch64-opts.h: -mrecip has a default value
	depending on the core.
	* config/aarch64/aarch64-protos.h: Declare.
	* config/aarch64/aarch64-simd.md: Matching expressions for
	frsqrte and frsqrts.
	* config/aarch64/aarch64.c: New functions. Emit rsqrt
	estimation code in fast math mode.
	* config/aarch64/aarch64.md: Added enum entries.
	* config/aarch64/aarch64.opt: Added options -mrecip and
	-mlow-precision-recip-sqrt.
	* testsuite/gcc.target/aarch64/rsqrt-asm-check.c: Assembly scans
	for frsqrte and frsqrts
	* testsuite/gcc.target/aarch64/rsqrt.c: Functional tests for rsqrt.

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
---
 gcc/ChangeLog                                      |  19 ++++
 gcc/config/aarch64/aarch64-builtins.c              | 103 ++++++++++++++++++++
 gcc/config/aarch64/aarch64-opts.h                  |   7 ++
 gcc/config/aarch64/aarch64-protos.h                |   3 +
 gcc/config/aarch64/aarch64-simd.md                 |  27 ++++++
 gcc/config/aarch64/aarch64.c                       |  81 ++++++++++++++--
 gcc/config/aarch64/aarch64.md                      |   3 +
 gcc/config/aarch64/aarch64.opt                     |   8 ++
 gcc/doc/invoke.texi                                |  19 ++++
 gcc/testsuite/gcc.target/aarch64/rsqrt-asm-check.c |  63 ++++++++++++
 gcc/testsuite/gcc.target/aarch64/rsqrt.c           | 107 +++++++++++++++++++++
 11 files changed, 434 insertions(+), 6 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/aarch64/rsqrt-asm-check.c
 create mode 100644 gcc/testsuite/gcc.target/aarch64/rsqrt.c

Comments

Kyrylo Tkachov July 30, 2015, 12:31 p.m. UTC | #1
Hi Benedikt,

On 29/07/15 18:47, Benedikt Huber wrote:
>          * config/aarch64/aarch64-builtins.c: Builtins for rsqrt and
>          rsqrtf.
>          * config/aarch64/aarch64-opts.h: -mrecip has a default value
>          depending on the core.
>          * config/aarch64/aarch64-protos.h: Declare.
>          * config/aarch64/aarch64-simd.md: Matching expressions for
>          frsqrte and frsqrts.
>          * config/aarch64/aarch64.c: New functions. Emit rsqrt
>          estimation code in fast math mode.
>          * config/aarch64/aarch64.md: Added enum entries.
>          * config/aarch64/aarch64.opt: Added options -mrecip and
>          -mlow-precision-recip-sqrt.
>          * testsuite/gcc.target/aarch64/rsqrt-asm-check.c: Assembly scans
>          for frsqrte and frsqrts
>          * testsuite/gcc.target/aarch64/rsqrt.c: Functional tests for rsqrt.
>
<snip>

> +
>   /* Expand an expression EXP that calls a built-in function,
>      with result going to TARGET if that's convenient.  */
>   rtx
> @@ -1139,6 +1213,13 @@ aarch64_expand_builtin (tree exp,
>     else if (fcode >= AARCH64_CRC32_BUILTIN_BASE && fcode <= AARCH64_CRC32_BUILTIN_MAX)
>       return aarch64_crc32_expand_builtin (fcode, exp, target);
>
> +  if (fcode == AARCH64_BUILTIN_RSQRT_DF   ||
> +      fcode == AARCH64_BUILTIN_RSQRT_SF   ||
> +      fcode == AARCH64_BUILTIN_RSQRT_V2DF ||
> +      fcode == AARCH64_BUILTIN_RSQRT_V2SF ||
> +      fcode == AARCH64_BUILTIN_RSQRT_V4SF)
> +    return aarch64_expand_builtin_rsqrt (fcode, exp, target);
> +

The style guidelines are to put the '||' on a new line like so:

  (fcode == AARCH64_BUILTIN_RSQRT_DF
   || fcode == AARCH64_BUILTIN_RSQRT_SF
   || ...


>     gcc_unreachable ();
>   }
>
> @@ -1296,6 +1377,28 @@ aarch64_builtin_vectorized_function (tree fndecl, tree type_out, tree type_in)
>     return NULL_TREE;
>   }
>
> +tree
> +aarch64_builtin_rsqrt (unsigned int fn, bool md_fn)
> +{
> +  if (md_fn)
> +    {
> +      if (fn == AARCH64_SIMD_BUILTIN_UNOP_sqrtv2df)
> +        return aarch64_builtin_decls[AARCH64_BUILTIN_RSQRT_V2DF];
> +      if (fn == AARCH64_SIMD_BUILTIN_UNOP_sqrtv2sf)
> +        return aarch64_builtin_decls[AARCH64_BUILTIN_RSQRT_V2SF];
> +      if (fn == AARCH64_SIMD_BUILTIN_UNOP_sqrtv4sf)
> +        return aarch64_builtin_decls[AARCH64_BUILTIN_RSQRT_V4SF];
> +    }
> +  else
> +    {
> +      if (fn == BUILT_IN_SQRT)
> +        return aarch64_builtin_decls[AARCH64_BUILTIN_RSQRT_DF];
> +      if (fn == BUILT_IN_SQRTF)
> +        return aarch64_builtin_decls[AARCH64_BUILTIN_RSQRT_SF];
> +    }
> +  return NULL_TREE;
> +}
> +
>   #undef VAR1
>   #define VAR1(T, N, MAP, A) \
>     case AARCH64_SIMD_BUILTIN_##T##_##N##A:
> diff --git a/gcc/config/aarch64/aarch64-opts.h b/gcc/config/aarch64/aarch64-opts.h
> index 24bfd9f..75e9c67 100644
> --- a/gcc/config/aarch64/aarch64-opts.h
> +++ b/gcc/config/aarch64/aarch64-opts.h
> @@ -64,4 +64,11 @@ enum aarch64_code_model {
>     AARCH64_CMODEL_LARGE
>   };
>
> +/* Each core can have -mrecip enabled or disabled by default. */
> +enum aarch64_mrecip {
> +  AARCH64_MRECIP_OFF = 0,
> +  AARCH64_MRECIP_ON,
> +  AARCH64_MRECIP_DEFAULT,
> +};
> +
>   #endif
> diff --git a/gcc/config/aarch64/aarch64-protos.h b/gcc/config/aarch64/aarch64-protos.h
> index 4062c27..dabe345 100644
> --- a/gcc/config/aarch64/aarch64-protos.h
> +++ b/gcc/config/aarch64/aarch64-protos.h
> @@ -197,6 +197,7 @@ struct tune_params
>     int min_div_recip_mul_sf;
>     int min_div_recip_mul_df;
>     unsigned int extra_tuning_flags;
> +  bool mrecip_default_enabled;
>   };

Please create a new field to put into the extra_tuning_flags.
This involves adding an entry aarch64-tuning-flags.def.
This way we avoid overpopulating the tuning structure with a multitude of
on/off boolean options.

>
>   #define AARCH64_FUSION_PAIR(x, name, index) \
> @@ -321,6 +322,8 @@ void aarch64_print_operand (FILE *, rtx, char);
>   void aarch64_print_operand_address (FILE *, rtx);
>   void aarch64_emit_call_insn (rtx);
>
> +void aarch64_emit_swrsqrt (rtx, rtx);
> +
>   /* Initialize builtins for SIMD intrinsics.  */
>   void init_aarch64_simd_builtins (void);
>
> diff --git a/gcc/config/aarch64/aarch64-simd.md b/gcc/config/aarch64/aarch64-simd.md
> index b90f938..ac8e12d 100644
> --- a/gcc/config/aarch64/aarch64-simd.md
> +++ b/gcc/config/aarch64/aarch64-simd.md
> @@ -353,6 +353,33 @@
>     [(set_attr "type" "neon_fp_mul_d_scalar_q")]
>   )
>
> +(define_insn "*rsqrte_<mode>"
> +  [(set (match_operand:VALLF 0 "register_operand" "=w")
> +       (unspec:VALLF [(match_operand:VALLF 1 "register_operand" "w")]
> +                    UNSPEC_RSQRTE))]
> +  "TARGET_SIMD"
> +  "frsqrte\\t%<v>0<Vmtype>, %<v>1<Vmtype>"
> +  [(set_attr "type" "neon_fp_rsqrte_<Vetype><q>")])
> +
> +(define_insn "*rsqrts_<mode>"
> +  [(set (match_operand:VALLF 0 "register_operand" "=w")
> +       (unspec:VALLF [(match_operand:VALLF 1 "register_operand" "w")
> +               (match_operand:VALLF 2 "register_operand" "w")]
> +                    UNSPEC_RSQRTS))]
> +  "TARGET_SIMD"
> +  "frsqrts\\t%<v>0<Vmtype>, %<v>1<Vmtype>, %<v>2<Vmtype>"
> +  [(set_attr "type" "neon_fp_rsqrts_<Vetype><q>")])
> +
> +(define_expand "rsqrt_<mode>"
> +  [(set (match_operand:VALLF 0 "register_operand" "=w")
> +       (unspec:VALLF [(match_operand:VALLF 1 "register_operand" "w")]
> +                    UNSPEC_RSQRT))]
> +  "TARGET_SIMD"
> +{
> +  aarch64_emit_swrsqrt (operands[0], operands[1]);
> +  DONE;
> +})

Please add the number of operands to the pattern names, for example:
"rsqrte_<mode>2"


> +
>   (define_insn "*aarch64_mul3_elt_to_64v2df"
>     [(set (match_operand:DF 0 "register_operand" "=w")
>        (mult:DF
<snip>

>
>   /* Support for fine-grained override of the tuning structures.  */
> @@ -6961,6 +6967,66 @@ aarch64_memory_move_cost (machine_mode mode ATTRIBUTE_UNUSED,
>     return aarch64_tune_params.memmov_cost;
>   }
>
> +extern tree aarch64_builtin_rsqrt (unsigned int fn, bool md_fn);
> +
> +static tree
> +aarch64_builtin_reciprocal (unsigned int fn,
> +                            bool md_fn,
> +                            bool)
> +{
> +  if (!flag_finite_math_only ||
> +      flag_trapping_math ||
> +      !flag_unsafe_math_optimizations ||
> +      optimize_size ||
> +      flag_mrecip == AARCH64_MRECIP_OFF ||
> +      (flag_mrecip == AARCH64_MRECIP_DEFAULT &&
> +       !aarch64_tune_params.mrecip_default_enabled))

Similar comment on the placement of the '||'.

> +  {
> +    return NULL_TREE;
> +  }
> +
> +  return aarch64_builtin_rsqrt (fn, md_fn);
> +}
> +
> +void
> +aarch64_emit_swrsqrt (rtx dst, rtx src)
> +{
> +  enum machine_mode mode = GET_MODE (src);
> +  gcc_assert (
> +    mode == SFmode || mode == V2SFmode || mode == V4SFmode ||
> +    mode == DFmode || mode == V2DFmode);
> +
> +  rtx xsrc = gen_reg_rtx (mode);
> +  emit_move_insn (xsrc, src);
> +  rtx x0 = gen_reg_rtx (mode);
> +  emit_set_insn (x0,
> +    gen_rtx_UNSPEC (mode, gen_rtvec (1, xsrc), UNSPEC_RSQRTE));
> +
> +  bool double_mode = (mode == DFmode || mode == V2DFmode);
> +
> +  int iterations = 2;
> +  if (double_mode)
> +    iterations = 3;
> +
> +  if (flag_mrecip_low_precision_sqrt)
> +    iterations--;
> +
> +  for (int i = 0; i < iterations; ++i)
> +    {
> +      rtx x1 = gen_reg_rtx (mode);
> +      rtx x2 = gen_reg_rtx (mode);
> +      rtx x3 = gen_reg_rtx (mode);
> +      emit_set_insn (x2, gen_rtx_MULT (mode, x0, x0));
> +      emit_set_insn (x3, gen_rtx_UNSPEC (
> +        mode, gen_rtvec (2, xsrc, x2), UNSPEC_RSQRTS));
> +      emit_set_insn (x1, gen_rtx_MULT (mode, x0, x3));
> +      x0 = x1;

You can probably avoid manually creating these RTXes and risking
mis-constructing them (or someone modifying them by mistake in the future)
by just calling the gen_* functions for the patterns you want to generate.
For example, instead of doing:

+      emit_set_insn (x3, gen_rtx_UNSPEC (
+        mode, gen_rtvec (2, xsrc, x2), UNSPEC_RSQRTS));


You can probably just do:
emit_insn (gen_rsqrts_{sf,df}2 (x3, x2));
This will require you to rename the patterns in aarch64.md to not have a '*'
in their name.



> +
> +  emit_move_insn (dst, x0);
> +  return;
> +}
> +
>   /* Return the number of instructions that can be issued per cycle.  */
>   static int
>   aarch64_sched_issue_rate (void)
> @@ -12099,6 +12165,9 @@ aarch64_unspec_may_trap_p (const_rtx x, unsigned flags)
>   #undef TARGET_USE_BLOCKS_FOR_CONSTANT_P
>   #define TARGET_USE_BLOCKS_FOR_CONSTANT_P aarch64_use_blocks_for_constant_p
>
> +#undef TARGET_BUILTIN_RECIPROCAL
> +#define TARGET_BUILTIN_RECIPROCAL aarch64_builtin_reciprocal
> +
>   #undef TARGET_VECTOR_MODE_SUPPORTED_P
>   #define TARGET_VECTOR_MODE_SUPPORTED_P aarch64_vector_mode_supported_p
>
> diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md
> index 1e343fa..d7944b2 100644
> --- a/gcc/config/aarch64/aarch64.md
> +++ b/gcc/config/aarch64/aarch64.md
> @@ -122,6 +122,9 @@
>       UNSPEC_VSTRUCTDUMMY
>       UNSPEC_SP_SET
>       UNSPEC_SP_TEST
> +    UNSPEC_RSQRT
> +    UNSPEC_RSQRTE
> +    UNSPEC_RSQRTS
>   ])
>
>   (define_c_enum "unspecv" [
> diff --git a/gcc/config/aarch64/aarch64.opt b/gcc/config/aarch64/aarch64.opt
> index 98ef9f6..581dc21 100644
> --- a/gcc/config/aarch64/aarch64.opt
> +++ b/gcc/config/aarch64/aarch64.opt
> @@ -124,3 +124,11 @@ Enum(aarch64_abi) String(ilp32) Value(AARCH64_ABI_ILP32)
>
>   EnumValue
>   Enum(aarch64_abi) String(lp64) Value(AARCH64_ABI_LP64)
> +
> +mrecip
> +Common Report Var(flag_mrecip) Optimization Init(AARCH64_MRECIP_DEFAULT)
> +Generate software reciprocal square root for better throughput. Default with fast-math.

s/fast-math/-ffast-math/.
Also, this is not the default with -ffast-math. The default now
depends on the tuning core, right?

Thanks,
Kyrill
diff mbox

Patch

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 3432adb..ac63f70 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,22 @@ 
+2015-07-29  Benedikt Huber  <benedikt.huber@theobroma-systems.com>
+	    Philipp Tomsich  <philipp.tomsich@theobroma-systems.com>
+
+	* config/aarch64/aarch64-builtins.c: Builtins for rsqrt and
+	rsqrtf.
+	* config/aarch64/aarch64-opts.h: -mrecip has a default value
+	depending on the core.
+	* config/aarch64/aarch64-protos.h: Declare.
+	* config/aarch64/aarch64-simd.md: Matching expressions for
+	frsqrte and frsqrts.
+	* config/aarch64/aarch64.c: New functions. Emit rsqrt
+	estimation code in fast math mode.
+	* config/aarch64/aarch64.md: Added enum entries.
+	* config/aarch64/aarch64.opt: Added options -mrecip and
+	-mlow-precision-recip-sqrt.
+	* testsuite/gcc.target/aarch64/rsqrt-asm-check.c: Assembly scans
+	for frsqrte and frsqrts
+	* testsuite/gcc.target/aarch64/rsqrt.c: Functional tests for rsqrt.
+
 2015-07-08  Jiong Wang  <jiong.wang@arm.com>
 
 	* config/aarch64/aarch64.c (aarch64_unspec_may_trap_p): New function.
diff --git a/gcc/config/aarch64/aarch64-builtins.c b/gcc/config/aarch64/aarch64-builtins.c
index b6c89b9..adcea07 100644
--- a/gcc/config/aarch64/aarch64-builtins.c
+++ b/gcc/config/aarch64/aarch64-builtins.c
@@ -335,6 +335,11 @@  enum aarch64_builtins
   AARCH64_BUILTIN_GET_FPSR,
   AARCH64_BUILTIN_SET_FPSR,
 
+  AARCH64_BUILTIN_RSQRT_DF,
+  AARCH64_BUILTIN_RSQRT_SF,
+  AARCH64_BUILTIN_RSQRT_V2DF,
+  AARCH64_BUILTIN_RSQRT_V2SF,
+  AARCH64_BUILTIN_RSQRT_V4SF,
   AARCH64_SIMD_BUILTIN_BASE,
   AARCH64_SIMD_BUILTIN_LANE_CHECK,
 #include "aarch64-simd-builtins.def"
@@ -824,6 +829,42 @@  aarch64_init_crc32_builtins ()
 }
 
 void
+aarch64_add_builtin_rsqrt (void)
+{
+  tree fndecl = NULL;
+  tree ftype = NULL;
+
+  tree V2SF_type_node = build_vector_type (float_type_node, 2);
+  tree V2DF_type_node = build_vector_type (double_type_node, 2);
+  tree V4SF_type_node = build_vector_type (float_type_node, 4);
+
+  ftype = build_function_type_list (double_type_node, double_type_node, NULL_TREE);
+  fndecl = add_builtin_function ("__builtin_aarch64_rsqrt_df",
+    ftype, AARCH64_BUILTIN_RSQRT_DF, BUILT_IN_MD, NULL, NULL_TREE);
+  aarch64_builtin_decls[AARCH64_BUILTIN_RSQRT_DF] = fndecl;
+
+  ftype = build_function_type_list (float_type_node, float_type_node, NULL_TREE);
+  fndecl = add_builtin_function ("__builtin_aarch64_rsqrt_sf",
+    ftype, AARCH64_BUILTIN_RSQRT_SF, BUILT_IN_MD, NULL, NULL_TREE);
+  aarch64_builtin_decls[AARCH64_BUILTIN_RSQRT_SF] = fndecl;
+
+  ftype = build_function_type_list (V2DF_type_node, V2DF_type_node, NULL_TREE);
+  fndecl = add_builtin_function ("__builtin_aarch64_rsqrt_v2df",
+    ftype, AARCH64_BUILTIN_RSQRT_V2DF, BUILT_IN_MD, NULL, NULL_TREE);
+  aarch64_builtin_decls[AARCH64_BUILTIN_RSQRT_V2DF] = fndecl;
+
+  ftype = build_function_type_list (V2SF_type_node, V2SF_type_node, NULL_TREE);
+  fndecl = add_builtin_function ("__builtin_aarch64_rsqrt_v2sf",
+    ftype, AARCH64_BUILTIN_RSQRT_V2SF, BUILT_IN_MD, NULL, NULL_TREE);
+  aarch64_builtin_decls[AARCH64_BUILTIN_RSQRT_V2SF] = fndecl;
+
+  ftype = build_function_type_list (V4SF_type_node, V4SF_type_node, NULL_TREE);
+  fndecl = add_builtin_function ("__builtin_aarch64_rsqrt_v4sf",
+    ftype, AARCH64_BUILTIN_RSQRT_V4SF, BUILT_IN_MD, NULL, NULL_TREE);
+  aarch64_builtin_decls[AARCH64_BUILTIN_RSQRT_V4SF] = fndecl;
+}
+
+void
 aarch64_init_builtins (void)
 {
   tree ftype_set_fpr
@@ -848,6 +889,7 @@  aarch64_init_builtins (void)
     aarch64_init_simd_builtins ();
   if (TARGET_CRC32)
     aarch64_init_crc32_builtins ();
+  aarch64_add_builtin_rsqrt ();
 }
 
 tree
@@ -1092,6 +1134,38 @@  aarch64_crc32_expand_builtin (int fcode, tree exp, rtx target)
   return target;
 }
 
+static rtx
+aarch64_expand_builtin_rsqrt (int fcode, tree exp, rtx target)
+{
+  rtx pat;
+  tree arg0 = CALL_EXPR_ARG (exp, 0);
+  rtx op0 = expand_normal (arg0);
+
+  enum insn_code c = CODE_FOR_rsqrt_df;
+
+  switch (fcode)
+    {
+      case AARCH64_BUILTIN_RSQRT_DF:
+        c = CODE_FOR_rsqrt_df; break;
+      case AARCH64_BUILTIN_RSQRT_SF:
+        c = CODE_FOR_rsqrt_sf; break;
+      case AARCH64_BUILTIN_RSQRT_V2DF:
+        c = CODE_FOR_rsqrt_v2df; break;
+      case AARCH64_BUILTIN_RSQRT_V2SF:
+        c = CODE_FOR_rsqrt_v2sf; break;
+      case AARCH64_BUILTIN_RSQRT_V4SF:
+        c = CODE_FOR_rsqrt_v4sf; break;
+    }
+
+  if (!target)
+    target = gen_reg_rtx (GET_MODE (op0));
+
+  pat = GEN_FCN (c) (target, op0);
+  emit_insn (pat);
+
+  return target;
+}
+
 /* Expand an expression EXP that calls a built-in function,
    with result going to TARGET if that's convenient.  */
 rtx
@@ -1139,6 +1213,13 @@  aarch64_expand_builtin (tree exp,
   else if (fcode >= AARCH64_CRC32_BUILTIN_BASE && fcode <= AARCH64_CRC32_BUILTIN_MAX)
     return aarch64_crc32_expand_builtin (fcode, exp, target);
 
+  if (fcode == AARCH64_BUILTIN_RSQRT_DF   ||
+      fcode == AARCH64_BUILTIN_RSQRT_SF   ||
+      fcode == AARCH64_BUILTIN_RSQRT_V2DF ||
+      fcode == AARCH64_BUILTIN_RSQRT_V2SF ||
+      fcode == AARCH64_BUILTIN_RSQRT_V4SF)
+    return aarch64_expand_builtin_rsqrt (fcode, exp, target);
+
   gcc_unreachable ();
 }
 
@@ -1296,6 +1377,28 @@  aarch64_builtin_vectorized_function (tree fndecl, tree type_out, tree type_in)
   return NULL_TREE;
 }
 
+tree
+aarch64_builtin_rsqrt (unsigned int fn, bool md_fn)
+{
+  if (md_fn)
+    {
+      if (fn == AARCH64_SIMD_BUILTIN_UNOP_sqrtv2df)
+        return aarch64_builtin_decls[AARCH64_BUILTIN_RSQRT_V2DF];
+      if (fn == AARCH64_SIMD_BUILTIN_UNOP_sqrtv2sf)
+        return aarch64_builtin_decls[AARCH64_BUILTIN_RSQRT_V2SF];
+      if (fn == AARCH64_SIMD_BUILTIN_UNOP_sqrtv4sf)
+        return aarch64_builtin_decls[AARCH64_BUILTIN_RSQRT_V4SF];
+    }
+  else
+    {
+      if (fn == BUILT_IN_SQRT)
+        return aarch64_builtin_decls[AARCH64_BUILTIN_RSQRT_DF];
+      if (fn == BUILT_IN_SQRTF)
+        return aarch64_builtin_decls[AARCH64_BUILTIN_RSQRT_SF];
+    }
+  return NULL_TREE;
+}
+
 #undef VAR1
 #define VAR1(T, N, MAP, A) \
   case AARCH64_SIMD_BUILTIN_##T##_##N##A:
diff --git a/gcc/config/aarch64/aarch64-opts.h b/gcc/config/aarch64/aarch64-opts.h
index 24bfd9f..75e9c67 100644
--- a/gcc/config/aarch64/aarch64-opts.h
+++ b/gcc/config/aarch64/aarch64-opts.h
@@ -64,4 +64,11 @@  enum aarch64_code_model {
   AARCH64_CMODEL_LARGE
 };
 
+/* Each core can have -mrecip enabled or disabled by default. */
+enum aarch64_mrecip {
+  AARCH64_MRECIP_OFF = 0,
+  AARCH64_MRECIP_ON,
+  AARCH64_MRECIP_DEFAULT,
+};
+
 #endif
diff --git a/gcc/config/aarch64/aarch64-protos.h b/gcc/config/aarch64/aarch64-protos.h
index 4062c27..dabe345 100644
--- a/gcc/config/aarch64/aarch64-protos.h
+++ b/gcc/config/aarch64/aarch64-protos.h
@@ -197,6 +197,7 @@  struct tune_params
   int min_div_recip_mul_sf;
   int min_div_recip_mul_df;
   unsigned int extra_tuning_flags;
+  bool mrecip_default_enabled;
 };
 
 #define AARCH64_FUSION_PAIR(x, name, index) \
@@ -321,6 +322,8 @@  void aarch64_print_operand (FILE *, rtx, char);
 void aarch64_print_operand_address (FILE *, rtx);
 void aarch64_emit_call_insn (rtx);
 
+void aarch64_emit_swrsqrt (rtx, rtx);
+
 /* Initialize builtins for SIMD intrinsics.  */
 void init_aarch64_simd_builtins (void);
 
diff --git a/gcc/config/aarch64/aarch64-simd.md b/gcc/config/aarch64/aarch64-simd.md
index b90f938..ac8e12d 100644
--- a/gcc/config/aarch64/aarch64-simd.md
+++ b/gcc/config/aarch64/aarch64-simd.md
@@ -353,6 +353,33 @@ 
   [(set_attr "type" "neon_fp_mul_d_scalar_q")]
 )
 
+(define_insn "*rsqrte_<mode>"
+  [(set (match_operand:VALLF 0 "register_operand" "=w")
+	(unspec:VALLF [(match_operand:VALLF 1 "register_operand" "w")]
+		     UNSPEC_RSQRTE))]
+  "TARGET_SIMD"
+  "frsqrte\\t%<v>0<Vmtype>, %<v>1<Vmtype>"
+  [(set_attr "type" "neon_fp_rsqrte_<Vetype><q>")])
+
+(define_insn "*rsqrts_<mode>"
+  [(set (match_operand:VALLF 0 "register_operand" "=w")
+	(unspec:VALLF [(match_operand:VALLF 1 "register_operand" "w")
+               (match_operand:VALLF 2 "register_operand" "w")]
+		     UNSPEC_RSQRTS))]
+  "TARGET_SIMD"
+  "frsqrts\\t%<v>0<Vmtype>, %<v>1<Vmtype>, %<v>2<Vmtype>"
+  [(set_attr "type" "neon_fp_rsqrts_<Vetype><q>")])
+
+(define_expand "rsqrt_<mode>"
+  [(set (match_operand:VALLF 0 "register_operand" "=w")
+	(unspec:VALLF [(match_operand:VALLF 1 "register_operand" "w")]
+		     UNSPEC_RSQRT))]
+  "TARGET_SIMD"
+{
+  aarch64_emit_swrsqrt (operands[0], operands[1]);
+  DONE;
+})
+
 (define_insn "*aarch64_mul3_elt_to_64v2df"
   [(set (match_operand:DF 0 "register_operand" "=w")
      (mult:DF
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 6c13a078..b8f5574 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -364,7 +364,8 @@  static const struct tune_params generic_tunings =
   1,	/* vec_reassoc_width.  */
   2,	/* min_div_recip_mul_sf.  */
   2,	/* min_div_recip_mul_df.  */
-  (AARCH64_EXTRA_TUNE_NONE)	/* tune_flags.  */
+  (AARCH64_EXTRA_TUNE_NONE),	/* tune_flags.  */
+  true	/* mrecip_default_enabled.  */
 };
 
 static const struct tune_params cortexa53_tunings =
@@ -386,7 +387,8 @@  static const struct tune_params cortexa53_tunings =
   1,	/* vec_reassoc_width.  */
   2,	/* min_div_recip_mul_sf.  */
   2,	/* min_div_recip_mul_df.  */
-  (AARCH64_EXTRA_TUNE_NONE)	/* tune_flags.  */
+  (AARCH64_EXTRA_TUNE_NONE),	/* tune_flags.  */
+  true	/* mrecip_default_enabled.  */
 };
 
 static const struct tune_params cortexa57_tunings =
@@ -408,7 +410,8 @@  static const struct tune_params cortexa57_tunings =
   1,	/* vec_reassoc_width.  */
   2,	/* min_div_recip_mul_sf.  */
   2,	/* min_div_recip_mul_df.  */
-  (AARCH64_EXTRA_TUNE_RENAME_FMA_REGS)	/* tune_flags.  */
+  (AARCH64_EXTRA_TUNE_RENAME_FMA_REGS),	/* tune_flags.  */
+  true	/* mrecip_default_enabled.  */
 };
 
 static const struct tune_params cortexa72_tunings =
@@ -430,7 +433,8 @@  static const struct tune_params cortexa72_tunings =
   1,	/* vec_reassoc_width.  */
   2,	/* min_div_recip_mul_sf.  */
   2,	/* min_div_recip_mul_df.  */
-  (AARCH64_EXTRA_TUNE_NONE)	/* tune_flags.  */
+  (AARCH64_EXTRA_TUNE_NONE),	/* tune_flags.  */
+  true	/* mrecip_default_enabled.  */
 };
 
 static const struct tune_params thunderx_tunings =
@@ -451,7 +455,8 @@  static const struct tune_params thunderx_tunings =
   1,	/* vec_reassoc_width.  */
   2,	/* min_div_recip_mul_sf.  */
   2,	/* min_div_recip_mul_df.  */
-  (AARCH64_EXTRA_TUNE_NONE)	/* tune_flags.  */
+  (AARCH64_EXTRA_TUNE_NONE),	/* tune_flags.  */
+  false	/* mrecip_default_enabled.  */
 };
 
 static const struct tune_params xgene1_tunings =
@@ -472,7 +477,8 @@  static const struct tune_params xgene1_tunings =
   1,	/* vec_reassoc_width.  */
   2,	/* min_div_recip_mul_sf.  */
   2,	/* min_div_recip_mul_df.  */
-  (AARCH64_EXTRA_TUNE_NONE)	/* tune_flags.  */
+  (AARCH64_EXTRA_TUNE_NONE),	/* tune_flags.  */
+  true	/* mrecip_default_enabled.  */
 };
 
 /* Support for fine-grained override of the tuning structures.  */
@@ -6961,6 +6967,66 @@  aarch64_memory_move_cost (machine_mode mode ATTRIBUTE_UNUSED,
   return aarch64_tune_params.memmov_cost;
 }
 
+extern tree aarch64_builtin_rsqrt (unsigned int fn, bool md_fn);
+
+static tree
+aarch64_builtin_reciprocal (unsigned int fn,
+                            bool md_fn,
+                            bool)
+{
+  if (!flag_finite_math_only ||
+      flag_trapping_math ||
+      !flag_unsafe_math_optimizations ||
+      optimize_size ||
+      flag_mrecip == AARCH64_MRECIP_OFF ||
+      (flag_mrecip == AARCH64_MRECIP_DEFAULT &&
+       !aarch64_tune_params.mrecip_default_enabled))
+  {
+    return NULL_TREE;
+  }
+
+  return aarch64_builtin_rsqrt (fn, md_fn);
+}
+
+void
+aarch64_emit_swrsqrt (rtx dst, rtx src)
+{
+  enum machine_mode mode = GET_MODE (src);
+  gcc_assert (
+    mode == SFmode || mode == V2SFmode || mode == V4SFmode ||
+    mode == DFmode || mode == V2DFmode);
+
+  rtx xsrc = gen_reg_rtx (mode);
+  emit_move_insn (xsrc, src);
+  rtx x0 = gen_reg_rtx (mode);
+  emit_set_insn (x0,
+    gen_rtx_UNSPEC (mode, gen_rtvec (1, xsrc), UNSPEC_RSQRTE));
+
+  bool double_mode = (mode == DFmode || mode == V2DFmode);
+
+  int iterations = 2;
+  if (double_mode)
+    iterations = 3;
+
+  if (flag_mrecip_low_precision_sqrt)
+    iterations--;
+
+  for (int i = 0; i < iterations; ++i)
+    {
+      rtx x1 = gen_reg_rtx (mode);
+      rtx x2 = gen_reg_rtx (mode);
+      rtx x3 = gen_reg_rtx (mode);
+      emit_set_insn (x2, gen_rtx_MULT (mode, x0, x0));
+      emit_set_insn (x3, gen_rtx_UNSPEC (
+        mode, gen_rtvec (2, xsrc, x2), UNSPEC_RSQRTS));
+      emit_set_insn (x1, gen_rtx_MULT (mode, x0, x3));
+      x0 = x1;
+    }
+
+  emit_move_insn (dst, x0);
+  return;
+}
+
 /* Return the number of instructions that can be issued per cycle.  */
 static int
 aarch64_sched_issue_rate (void)
@@ -12099,6 +12165,9 @@  aarch64_unspec_may_trap_p (const_rtx x, unsigned flags)
 #undef TARGET_USE_BLOCKS_FOR_CONSTANT_P
 #define TARGET_USE_BLOCKS_FOR_CONSTANT_P aarch64_use_blocks_for_constant_p
 
+#undef TARGET_BUILTIN_RECIPROCAL
+#define TARGET_BUILTIN_RECIPROCAL aarch64_builtin_reciprocal
+
 #undef TARGET_VECTOR_MODE_SUPPORTED_P
 #define TARGET_VECTOR_MODE_SUPPORTED_P aarch64_vector_mode_supported_p
 
diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md
index 1e343fa..d7944b2 100644
--- a/gcc/config/aarch64/aarch64.md
+++ b/gcc/config/aarch64/aarch64.md
@@ -122,6 +122,9 @@ 
     UNSPEC_VSTRUCTDUMMY
     UNSPEC_SP_SET
     UNSPEC_SP_TEST
+    UNSPEC_RSQRT
+    UNSPEC_RSQRTE
+    UNSPEC_RSQRTS
 ])
 
 (define_c_enum "unspecv" [
diff --git a/gcc/config/aarch64/aarch64.opt b/gcc/config/aarch64/aarch64.opt
index 98ef9f6..581dc21 100644
--- a/gcc/config/aarch64/aarch64.opt
+++ b/gcc/config/aarch64/aarch64.opt
@@ -124,3 +124,11 @@  Enum(aarch64_abi) String(ilp32) Value(AARCH64_ABI_ILP32)
 
 EnumValue
 Enum(aarch64_abi) String(lp64) Value(AARCH64_ABI_LP64)
+
+mrecip
+Common Report Var(flag_mrecip) Optimization Init(AARCH64_MRECIP_DEFAULT)
+Generate software reciprocal square root for better throughput. Default with fast-math.
+
+mlow-precision-recip-sqrt
+Common Var(flag_mrecip_low_precision_sqrt) Optimization
+Run fewer approximation steps to reduce latency and precision.
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index b28e5d6..bd922a3 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -515,6 +515,8 @@  Objective-C and Objective-C++ Dialects}.
 -mtls-dialect=desc  -mtls-dialect=traditional @gol
 -mfix-cortex-a53-835769  -mno-fix-cortex-a53-835769 @gol
 -mfix-cortex-a53-843419  -mno-fix-cortex-a53-843419 @gol
+-mrecip -mno-recip @gol
+-mlow-precision-recip-sqrt -mno-low-precision-recip-sqrt@gol
 -march=@var{name}  -mcpu=@var{name}  -mtune=@var{name}}
 
 @emph{Adapteva Epiphany Options}
@@ -12426,6 +12428,23 @@  Enable or disable the workaround for the ARM Cortex-A53 erratum number 843419.
 This erratum workaround is made at link time and this will only pass the
 corresponding flag to the linker.
 
+@item -mrecip
+@item -mno-recip
+@opindex mrecip
+@opindex mno-recip
+This option enables use of the
+reciprocal square root estimate instructions with additional
+Newton-Raphson steps to increase precision instead of doing a square root and
+divide for floating-point arguments.
+It can only be used together with @option{-ffast-math}.
+
+@item -mlow-precision-recip-sqrt
+@item -mno-low-precision-recip-sqrt
+@opindex -mlow-precision-recip-sqrt
+@opindex -mno-low-precision-recip-sqrt
+The square root estimate uses two steps instead of three for double-precision,
+and one step instead of two for single-precision. Thus reducing latency and precision.
+
 @item -march=@var{name}
 @opindex march
 Specify the name of the target architecture, optionally suffixed by one or
diff --git a/gcc/testsuite/gcc.target/aarch64/rsqrt-asm-check.c b/gcc/testsuite/gcc.target/aarch64/rsqrt-asm-check.c
new file mode 100644
index 0000000..d6cfe11
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/rsqrt-asm-check.c
@@ -0,0 +1,63 @@ 
+/* { dg-do compile } */
+/* { dg-options "-O3 --save-temps -fverbose-asm -ffast-math -mrecip" } */
+
+#include <math.h>
+
+#define sqrt_float   __builtin_sqrtf
+#define sqrt_double  __builtin_sqrt
+
+#define TESTTYPE(TYPE)                                          \
+typedef struct {                                                \
+  TYPE a;                                                       \
+  TYPE b;                                                       \
+  TYPE c;                                                       \
+  TYPE d;                                                       \
+} s4_##TYPE;                                                    \
+                                                                \
+typedef struct {                                                \
+  TYPE a;                                                       \
+  TYPE b;                                                       \
+} s2_##TYPE;                                                    \
+                                                                \
+s4_##TYPE rsqrtv4_##TYPE (s4_##TYPE i)                          \
+{                                                               \
+  s4_##TYPE o;                                                  \
+  o.a = 1.0 / sqrt_##TYPE (i.a);                                \
+  o.b = 1.0 / sqrt_##TYPE (i.b);                                \
+  o.c = 1.0 / sqrt_##TYPE (i.c);                                \
+  o.d = 1.0 / sqrt_##TYPE (i.d);                                \
+  return o;                                                     \
+}                                                               \
+                                                                \
+s2_##TYPE rsqrtv2_##TYPE (s2_##TYPE i)                          \
+{                                                               \
+  s2_##TYPE o;                                                  \
+  o.a = 1.0 / sqrt_##TYPE (i.a);                                \
+  o.b = 1.0 / sqrt_##TYPE (i.b);                                \
+  return o;                                                     \
+}                                                               \
+                                                                \
+TYPE rsqrt_##TYPE (TYPE i)                                      \
+{                                                               \
+  return 1.0 / sqrt_##TYPE (i);                                 \
+}                                                               \
+                                                                \
+
+TESTTYPE(double)
+TESTTYPE(float)
+
+/* { dg-final { scan-assembler-times "frsqrte\\td\[0-9\]+, d\[0-9\]+" 1 } } */
+/* { dg-final { scan-assembler-times "frsqrts\\td\[0-9\]+, d\[0-9\]+, d\[0-9\]+" 3 } } */
+
+/* { dg-final { scan-assembler-times "frsqrte\\tv\[0-9\]+.2d, v\[0-9\]+.2d" 3 } } */
+/* { dg-final { scan-assembler-times "frsqrts\\tv\[0-9\]+.2d, v\[0-9\]+.2d, v\[0-9\]+.2d" 9 } } */
+
+
+/* { dg-final { scan-assembler-times "frsqrte\\ts\[0-9\]+, s\[0-9\]+" 1 } } */
+/* { dg-final { scan-assembler-times "frsqrts\\ts\[0-9\]+, s\[0-9\]+, s\[0-9\]+" 2 } } */
+
+/* { dg-final { scan-assembler-times "frsqrte\\tv\[0-9\]+.4s, v\[0-9\]+.4s" 1 } } */
+/* { dg-final { scan-assembler-times "frsqrts\\tv\[0-9\]+.4s, v\[0-9\]+.4s, v\[0-9\]+.4s" 2 } } */
+
+/* { dg-final { scan-assembler-times "frsqrte\\tv\[0-9\]+.2s, v\[0-9\]+.2s" 1 } } */
+/* { dg-final { scan-assembler-times "frsqrts\\tv\[0-9\]+.2s, v\[0-9\]+.2s, v\[0-9\]+.2s" 2 } } */
diff --git a/gcc/testsuite/gcc.target/aarch64/rsqrt.c b/gcc/testsuite/gcc.target/aarch64/rsqrt.c
new file mode 100644
index 0000000..4a5c008
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/rsqrt.c
@@ -0,0 +1,107 @@ 
+/* { dg-do run } */
+/* { dg-options "-O3 --save-temps -fverbose-asm -ffast-math -mrecip" } */
+
+#include <math.h>
+#include <stdio.h>
+
+#include <float.h>
+
+#define PI    3.141592653589793
+#define SQRT2 1.4142135623730951
+
+#define PI_4 0.7853981633974483
+#define SQRT1_2 0.7071067811865475
+
+/* 2^25+1, float has 24 significand bits
+ *       according to Single-precision floating-point format.  */
+#define TESTA8_FLT 33554433
+/* 2^54+1, double has 53 significand bits
+ *       according to Double-precision floating-point format.  */
+#define TESTA8_DBL 18014398509481985
+
+#define SD(a, b) t_double ((#a), (a), (b));
+#define SF(a, b) t_float ((#a), (a), (b));
+
+#define EPSILON_double __DBL_EPSILON__
+#define EPSILON_float __FLT_EPSILON__
+#define ABS_double __builtin_fabs
+#define ABS_float __builtin_fabsf
+#define SQRT_double __builtin_sqrt
+#define SQRT_float __builtin_sqrtf
+
+extern void abort (void);
+
+#define TESTTYPE(TYPE)                                                     \
+TYPE rsqrt_##TYPE (TYPE a)                                                 \
+{                                                                          \
+  return 1.0/SQRT_##TYPE(a);                                               \
+}                                                                          \
+                                                                           \
+int equals_##TYPE (TYPE a, TYPE b)                                         \
+{                                                                          \
+  return (a == b ||                                                        \
+          (isnan (a) && isnan (b)) ||                                      \
+          (ABS_##TYPE (a - b) < EPSILON_##TYPE));                          \
+}                                                                          \
+                                                                           \
+void t_##TYPE (const char *s, TYPE a, TYPE result)                         \
+{                                                                          \
+  TYPE r = rsqrt_##TYPE (a);                                               \
+  if (!equals_##TYPE (r, result))                                          \
+  {                                                                        \
+    abort ();                                                              \
+  }                                                                        \
+}                                                                          \
+
+//  printf ("Problem in %20s: %30.18A should be %30.18A\n", s, r, result); \
+
+TESTTYPE(double)
+TESTTYPE(float)
+
+int main ()
+{
+  SD(    1.0/256, 0X1.00000000000000P+4  );
+  SD(        1.0, 0X1.00000000000000P+0  );
+  SD(       -1.0,                     NAN);
+  SD(       11.0, 0X1.34BF63D1568260P-2  );
+  SD(        0.0,                INFINITY);
+  SD(   INFINITY, 0X0.00000000000000P+0  );
+  SD(        NAN,                     NAN);
+  SD(       -NAN,                    -NAN);
+  SD(    DBL_MAX, 0X1.00000000000010P-512);
+  SD(    DBL_MIN, 0X1.00000000000000P+511);
+  SD(         PI, 0X1.20DD750429B6D0P-1  );
+  SD(       PI_4, 0X1.20DD750429B6D0P+0  );
+  SD(      SQRT2, 0X1.AE89F995AD3AE0P-1  );
+  SD(    SQRT1_2, 0X1.306FE0A31B7150P+0  );
+  SD(        -PI,                     NAN);
+  SD(     -SQRT2,                     NAN);
+  SD( TESTA8_DBL, 0X1.00000000000000P-27 );
+
+  SF(    1.0/256, 0X1.00000000000000P+4  );
+  SF(        1.0, 0X1.00000000000000P+0  );
+  SF(       -1.0,                     NAN);
+  SF(       11.0, 0X1.34BF6400000000P-2  );
+  SF(        0.0,                INFINITY);
+  SF(   INFINITY, 0X0.00000000000000P+0  );
+  SF(        NAN,                     NAN);
+  SF(       -NAN,                    -NAN);
+  SF(    FLT_MAX, 0X1.00000200000000P-64 );
+  SF(    FLT_MIN, 0X1.00000000000000P+63 );
+  SF(         PI, 0X1.20DD7400000000P-1  );
+  SF(       PI_4, 0X1.20DD7400000000P+0  );
+  SF(      SQRT2, 0X1.AE89FA00000000P-1  );
+  SF(    SQRT1_2, 0X1.306FE000000000P+0  );
+  SF(        -PI,                     NAN);
+  SF(     -SQRT2,                     NAN);
+  SF( TESTA8_FLT, 0X1.6A09E600000000P-13 );
+
+//   With -ffast-math these return positive INF.
+//   SD(       -0.0,               -INFINITY);
+//   SF(       -0.0,               -INFINITY);
+//   The reason here is that -ffast-math flushes to zero.
+//   SD(DBL_MIN/256, 0X1.00000000000000P+515);
+//   SF(FLT_MIN/256, 0X1.00000000000000P+67 );
+
+  return 0;
+}