AVX512FP16: Optimize _Float16 reciprocal for div and sqrt

For _Float16 type, add insn and expanders to optimize x / y to
x * rcp (y), and x / sqrt (y) to x * rsqrt (y).
As Half float only have minor precision difference between div and
mul * rcp, there is no need for Newton-Rhapson approximation.

gcc/ChangeLog:

	* config/i386/i386.c (use_rsqrt_p): Add mode parameter, enable
	  HFmode rsqrt without TARGET_SSE_MATH.
	(ix86_optab_supported_p): Refactor rint, adjust floor, ceil,
	btrunc condition to be restricted by -ftrapping-math, adjust
	use_rsqrt_p function call.
	* config/i386/i386.md (rcphf2): New define_insn.
	(rsqrthf2): Likewise.
	* config/i386/sse.md (div<mode>3): Change VF2H to VF2.
	(div<mode>3): New expander for HF mode.
	(rsqrt<mode>2): Likewise.
	(*avx512fp16_vmrcpv8hf2): New define_insn for rpad pass.
	(*avx512fp16_vmrsqrtv8hf2): Likewise.

gcc/testsuite/ChangeLog:

	* gcc.target/i386/avx512fp16-recip-1.c: New test.
	* gcc.target/i386/avx512fp16-recip-2.c: Ditto.
	* gcc.target/i386/pr102464.c: Add -fno-trapping-math.

6 files changed, 258 insertions, 20 deletions

diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 299e1ab..c578936 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -18905,9 +18905,10 @@ ix86_vectorize_builtin_scatter (const_tree vectype,
    1.0/sqrt.  */
 
 static bool
-use_rsqrt_p ()
+use_rsqrt_p (machine_mode mode)
 {
-  return (TARGET_SSE && TARGET_SSE_MATH
+  return ((mode == HFmode
+	   || (TARGET_SSE && TARGET_SSE_MATH))
 	  && flag_finite_math_only
 	  && !flag_trapping_math
 	  && flag_unsafe_math_optimizations);
@@ -23603,29 +23604,27 @@ ix86_optab_supported_p (int op, machine_mode mode1, machine_mode,
       return opt_type == OPTIMIZE_FOR_SPEED;
 
     case rint_optab:
-      if (mode1 == HFmode)
-	return true;
-      else if (SSE_FLOAT_MODE_P (mode1)
-	       && TARGET_SSE_MATH
-	       && !flag_trapping_math
-	       && !TARGET_SSE4_1)
+      if (SSE_FLOAT_MODE_P (mode1)
+	  && TARGET_SSE_MATH
+	  && !flag_trapping_math
+	  && !TARGET_SSE4_1
+	  && mode1 != HFmode)
 	return opt_type == OPTIMIZE_FOR_SPEED;
       return true;
 
     case floor_optab:
     case ceil_optab:
     case btrunc_optab:
-      if (mode1 == HFmode)
-	return true;
-      else if (SSE_FLOAT_MODE_P (mode1)
-	       && TARGET_SSE_MATH
-	       && !flag_trapping_math
-	       && TARGET_SSE4_1)
+      if (((SSE_FLOAT_MODE_P (mode1)
+	    && TARGET_SSE_MATH
+	    && TARGET_SSE4_1)
+	   || mode1 == HFmode)
+	  && !flag_trapping_math)
 	return true;
       return opt_type == OPTIMIZE_FOR_SPEED;
 
     case rsqrt_optab:
-      return opt_type == OPTIMIZE_FOR_SPEED && use_rsqrt_p ();
+      return opt_type == OPTIMIZE_FOR_SPEED && use_rsqrt_p (mode1);
 
     default:
       return true;
diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
index e733a40..11535df 100644
--- a/gcc/config/i386/i386.md
+++ b/gcc/config/i386/i386.md
@@ -8417,11 +8417,27 @@
 		(match_operand:XF 2 "register_operand")))]
   "TARGET_80387")
 
+/* There is no more precision loss than Newton-Rhapson approximation
+  when using HFmode rcp/rsqrt, so do the transformation directly under
+  TARGET_RECIP_DIV and fast-math.  */
 (define_expand "divhf3"
   [(set (match_operand:HF 0 "register_operand")
 	(div:HF (match_operand:HF 1 "register_operand")
 		   (match_operand:HF 2 "nonimmediate_operand")))]
-  "TARGET_AVX512FP16")
+  "TARGET_AVX512FP16"
+{
+  if (TARGET_RECIP_DIV
+      && optimize_insn_for_speed_p ()
+      && flag_finite_math_only && !flag_trapping_math
+      && flag_unsafe_math_optimizations)
+    {
+      rtx op = gen_reg_rtx (HFmode);
+      operands[2] = force_reg (HFmode, operands[2]);
+      emit_insn (gen_rcphf2 (op, operands[2]));
+      emit_insn (gen_mulhf3 (operands[0], operands[1], op));
+      DONE;
+    }
+})
 
 (define_expand "div<mode>3"
   [(set (match_operand:MODEF 0 "register_operand")
@@ -16973,6 +16989,19 @@
 	    ]
 	    (symbol_ref "true")))])
 
+(define_insn "rcphf2"
+  [(set (match_operand:HF 0 "register_operand" "=v,v")
+	(unspec:HF [(match_operand:HF 1 "nonimmediate_operand" "v,m")]
+		   UNSPEC_RCP))]
+  "TARGET_AVX512FP16"
+  "@
+   vrcpsh\t{%d1, %0|%0, %d1}
+   vrcpsh\t{%1, %d0|%d0, %1}"
+  [(set_attr "type" "sse")
+   (set_attr "prefix" "evex")
+   (set_attr "mode" "HF")
+   (set_attr "avx_partial_xmm_update" "false,true")])
+
 (define_insn "*fop_xf_1_i387"
   [(set (match_operand:XF 0 "register_operand" "=f,f")
 	(match_operator:XF 3 "binary_fp_operator"
@@ -17230,6 +17259,19 @@
   DONE;
 })
 
+(define_insn "rsqrthf2"
+  [(set (match_operand:HF 0 "register_operand" "=v,v")
+	(unspec:HF [(match_operand:HF 1 "nonimmediate_operand" "v,m")]
+		   UNSPEC_RSQRT))]
+  "TARGET_AVX512FP16"
+  "@
+   vrsqrtsh\t{%d1, %0|%0, %d1}
+   vrsqrtsh\t{%1, %d0|%d0, %1}"
+  [(set_attr "type" "sse")
+   (set_attr "prefix" "evex")
+   (set_attr "avx_partial_xmm_update" "false,true")
+   (set_attr "mode" "HF")])
+
 (define_insn "sqrthf2"
   [(set (match_operand:HF 0 "register_operand" "=v,v")
 	(sqrt:HF
diff --git a/gcc/config/i386/sse.md b/gcc/config/i386/sse.md
index bdc6067..4685ac9 100644
--- a/gcc/config/i386/sse.md
+++ b/gcc/config/i386/sse.md
@@ -2306,12 +2306,34 @@
    (set_attr "mode" "<ssescalarmode>")])
 
 (define_expand "div<mode>3"
-  [(set (match_operand:VF2H 0 "register_operand")
-	(div:VF2H (match_operand:VF2H 1 "register_operand")
-		  (match_operand:VF2H 2 "vector_operand")))]
+  [(set (match_operand:VF2 0 "register_operand")
+	(div:VF2 (match_operand:VF2 1 "register_operand")
+		  (match_operand:VF2 2 "vector_operand")))]
   "TARGET_SSE2")
 
 (define_expand "div<mode>3"
+  [(set (match_operand:VF_AVX512FP16VL 0 "register_operand")
+	(div:VF_AVX512FP16VL
+	  (match_operand:VF_AVX512FP16VL 1 "register_operand")
+	  (match_operand:VF_AVX512FP16VL 2 "vector_operand")))]
+  "TARGET_AVX512FP16"
+{
+  /* Transform HF vector div to vector mul/rcp.  */
+  if (GET_MODE_INNER (<MODE>mode) == HFmode
+      && TARGET_RECIP_VEC_DIV
+      && optimize_insn_for_speed_p ()
+      && flag_finite_math_only && !flag_trapping_math
+      && flag_unsafe_math_optimizations)
+    {
+      rtx op = gen_reg_rtx (<MODE>mode);
+      operands[2] = force_reg (<MODE>mode, operands[2]);
+      emit_insn (gen_avx512fp16_rcp<mode>2 (op, operands[2]));
+      emit_insn (gen_mul<mode>3 (operands[0], operands[1], op));
+      DONE;
+    }
+})
+
+(define_expand "div<mode>3"
   [(set (match_operand:VF1 0 "register_operand")
 	(div:VF1 (match_operand:VF1 1 "register_operand")
 		 (match_operand:VF1 2 "vector_operand")))]
@@ -2433,6 +2455,20 @@
    (set_attr "prefix" "evex")
    (set_attr "mode" "HF")])
 
+(define_insn "*avx512fp16_vmrcpv8hf2"
+  [(set (match_operand:V8HF 0 "register_operand" "=v")
+	(vec_merge:V8HF
+	  (vec_duplicate:V8HF
+	    (unspec:HF [(match_operand:HF 1 "nonimmediate_operand" "vm")]
+			 UNSPEC_RCP))
+	  (match_operand:V8HF 2 "register_operand" "v")
+	  (const_int 1)))]
+  "TARGET_AVX512FP16"
+  "vrcpsh\t{%1, %2, %0|%0, %2, %w1}"
+  [(set_attr "type" "sse")
+   (set_attr "prefix" "evex")
+   (set_attr "mode" "HF")])
+
 (define_insn "<mask_codefor>rcp14<mode><mask_name>"
   [(set (match_operand:VF_AVX512VL 0 "register_operand" "=v")
 	(unspec:VF_AVX512VL
@@ -2558,6 +2594,13 @@
   DONE;
 })
 
+(define_expand "rsqrt<mode>2"
+  [(set (match_operand:VF_AVX512FP16VL 0 "register_operand")
+	(unspec:VF_AVX512FP16VL
+	  [(match_operand:VF_AVX512FP16VL 1 "vector_operand")]
+	  UNSPEC_RSQRT))]
+  "TARGET_AVX512FP16")
+
 (define_insn "<sse>_rsqrt<mode>2"
   [(set (match_operand:VF1_128_256 0 "register_operand" "=x")
 	(unspec:VF1_128_256
@@ -2666,6 +2709,20 @@
    (set_attr "prefix" "evex")
    (set_attr "mode" "HF")])
 
+(define_insn "*avx512fp16_vmrsqrtv8hf2"
+  [(set (match_operand:V8HF 0 "register_operand" "=v")
+	(vec_merge:V8HF
+	  (vec_duplicate:V8HF
+	    (unspec:HF [(match_operand:HF 1 "nonimmediate_operand" "vm")]
+		       UNSPEC_RSQRT))
+	  (match_operand:V8HF 2 "register_operand" "v")
+	  (const_int 1)))]
+  "TARGET_AVX512FP16"
+  "vrsqrtsh\t{%1, %2, %0<mask_scalar_operand3>|%0<mask_scalar_operand3>, %2, %w1}"
+  [(set_attr "type" "sse")
+   (set_attr "prefix" "evex")
+   (set_attr "mode" "HF")])
+
 (define_expand "cond_<code><mode>"
   [(set (match_operand:VFH 0 "register_operand")
 	(vec_merge:VFH
diff --git a/gcc/testsuite/gcc.target/i386/avx512fp16-recip-1.c b/gcc/testsuite/gcc.target/i386/avx512fp16-recip-1.c
new file mode 100644
index 0000000..bc7cbbc
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/avx512fp16-recip-1.c
@@ -0,0 +1,43 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -mavx512fp16 -mavx512vl -ffast-math" } */
+/* { dg-final { scan-assembler "vrcpsh.*\n.*vmulsh" } } */
+/* { dg-final { scan-assembler "vrcpph.*\n.*vmulph" } } */
+/* { dg-final { scan-assembler "vrsqrtsh.*\n.*vmulsh" } } */
+/* { dg-final { scan-assembler "vrsqrtph.*\n.*vmulph" } } */
+/* { dg-final { scan-assembler-not "vsqrtsh" } } */
+/* { dg-final { scan-assembler-not "vsqrtph" } } */
+/* { dg-final { scan-assembler-not "vdivsh" } } */
+/* { dg-final { scan-assembler-not "vdivph" } } */
+
+#define FAST_ATTR \
+  __attribute__((noinline, noclone, optimize("fast-math"), target("recip")))
+
+_Float16 FAST_ATTR
+scalar_hf_rcp_fast (_Float16 a, _Float16 b)
+{
+  return a / b;
+}
+
+_Float16 FAST_ATTR
+scalar_hf_rsqrt_fast (_Float16 a, _Float16 b)
+{
+  return a / __builtin_sqrtf16 (b);
+}
+
+void FAST_ATTR
+vector_hf_rcp_fast (_Float16 * restrict a, _Float16 * restrict b,
+		    _Float16 * restrict c, int n)
+{
+  int i;
+  for (i = 0; i < n; i++)
+    c[i] = a[i] / b[i];
+}
+
+void FAST_ATTR
+vector_hf_rsqrt_fast (_Float16 * restrict a, _Float16 * restrict b,
+		    _Float16 * restrict c, int n)
+{
+  int i;
+  for (i = 0; i < n; i++)
+    c[i] = a[i] / __builtin_sqrtf16(b[i]);
+}
diff --git a/gcc/testsuite/gcc.target/i386/avx512fp16-recip-2.c b/gcc/testsuite/gcc.target/i386/avx512fp16-recip-2.c
new file mode 100644
index 0000000..ed7e0a2
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/avx512fp16-recip-2.c
@@ -0,0 +1,97 @@
+/* { dg-do run { target avx512fp16 } } */
+/* { dg-options "-O3 -mavx512fp16 -mavx512vl -ffast-math" } */
+
+static void recip_op_test (void);
+#define DO_TEST recip_op_test
+#define AVX512FP16
+#define AVX512VL
+#include "avx512f-check.h"
+#include "avx512fp16-recip-1.c"
+
+_Float16 a[32], b[32], vexp[32], vref[32], sa, sb, sexp, sref;
+
+#define NO_FAST_ATTR  \
+  __attribute__((noinline, noclone, \
+		 optimize("fast-math,trapping-math")))
+
+_Float16 NO_FAST_ATTR
+scalar_hf_rcp_no_fast (_Float16 a, _Float16 b)
+{
+  return a / b;
+}
+
+_Float16 NO_FAST_ATTR
+scalar_hf_rsqrt_no_fast (_Float16 a, _Float16 b)
+{
+  return a / __builtin_sqrtf16 (b);
+}
+
+void NO_FAST_ATTR
+vector_hf_rcp_no_fast (_Float16 * restrict a, _Float16 * restrict b,
+		    _Float16 * restrict c, int n)
+{
+  int i;
+  for (i = 0; i < n; i++)
+    c[i] = a[i] / b[i];
+}
+
+void NO_FAST_ATTR
+vector_hf_rsqrt_no_fast (_Float16 * restrict a, _Float16 * restrict b,
+		    _Float16 * restrict c, int n)
+{
+  int i;
+  for (i = 0; i < n; i++)
+    c[i] = a[i] / __builtin_sqrtf16 (b[i]);
+}
+
+void init()
+{
+  int i;
+  sa = 3.75;
+  sb = 6.25;
+  sexp = sref = 2.75;
+  for (i = 0; i < 32; i++)
+    {
+      a[i] = i + 0.5; 
+      b[i] = i * 1.5;
+      vexp[i] = vref[i] = 2.75 * i;
+    }
+}
+
+int check_cond(void *a, void *b, int size)
+{
+  int i;
+  unsigned short *pa = (unsigned short *)a,
+		 *pb = (unsigned short *)b;
+  for (i = 0; i < size; i++)
+    if (pa[i] != pb[i])
+      return 0;
+  return 1;
+}
+
+static void recip_op_test()
+{
+  init ();
+  sexp = scalar_hf_rcp_fast (sa, sb);
+  sref = scalar_hf_rcp_no_fast (sa, sb);
+  if (!check_cond (&sexp, &sref, 1))
+    abort ();
+
+  init ();
+  sexp = scalar_hf_rsqrt_fast (sa, sb);
+  sref = scalar_hf_rsqrt_no_fast (sa, sb);
+  if (!check_cond (&sexp, &sref, 1))
+    abort ();
+
+  init ();
+  vector_hf_rcp_fast (a, b, vexp, 32);
+  vector_hf_rcp_no_fast (a, b, vref, 32);
+  if (!check_cond (vexp, vref, 1))
+    abort ();
+
+  init ();
+  vector_hf_rsqrt_fast (a, b, vexp, 32);
+  vector_hf_rsqrt_no_fast (a, b, vref, 32);
+  if (!check_cond (vexp, vref, 1))
+    abort ();
+}
diff --git a/gcc/testsuite/gcc.target/i386/pr102464.c b/gcc/testsuite/gcc.target/i386/pr102464.c
index e3e060e..7e1fbdc 100644
--- a/gcc/testsuite/gcc.target/i386/pr102464.c
+++ b/gcc/testsuite/gcc.target/i386/pr102464.c
@@ -1,6 +1,6 @@
 /* PR target/102464.  */
 /* { dg-do compile } */
-/* { dg-options "-O2 -mavx512fp16" } */
+/* { dg-options "-O2 -mavx512fp16 -fno-trapping-math" } */
 
 #define FOO(FUNC,SUFFIX)                       \
   _Float16                                     \