[v2,1/2] RISC-V: Support _Float16 type.

diff --git a/gcc/config/riscv/riscv-builtins.cc b/gcc/config/riscv/riscv-builtins.cc
index 1218fdfc67d..3009311604d 100644
--- a/gcc/config/riscv/riscv-builtins.cc
+++ b/gcc/config/riscv/riscv-builtins.cc
@@ -34,6 +34,7 @@  along with GCC; see the file COPYING3.  If not see
 #include "recog.h"
 #include "diagnostic-core.h"
 #include "stor-layout.h"
+#include "stringpool.h"
 #include "expr.h"
 #include "langhooks.h"
 
@@ -160,6 +161,8 @@  static GTY(()) int riscv_builtin_decl_index[NUM_INSN_CODES];
 #define GET_BUILTIN_DECL(CODE) \
   riscv_builtin_decls[riscv_builtin_decl_index[(CODE)]]
 
+tree riscv_float16_type_node = NULL_TREE;
+
 /* Return the function type associated with function prototype TYPE.  */
 
 static tree
@@ -185,11 +188,32 @@  riscv_build_function_type (enum riscv_function_type type)
   return types[(int) type];
 }
 
+static void
+riscv_init_builtin_types (void)
+{
+  /* Provide the _Float16 type and float16_type_node if needed.  */
+  if (!float16_type_node)
+    {
+      riscv_float16_type_node = make_node (REAL_TYPE);
+      TYPE_PRECISION (riscv_float16_type_node) = 16;
+      SET_TYPE_MODE (riscv_float16_type_node, HFmode);
+      layout_type (riscv_float16_type_node);
+    }
+  else
+    riscv_float16_type_node = float16_type_node;
+
+  if (!maybe_get_identifier ("_Float16"))
+    lang_hooks.types.register_builtin_type (riscv_float16_type_node,
+					    "_Float16");
+}
+
 /* Implement TARGET_INIT_BUILTINS.  */
 
 void
 riscv_init_builtins (void)
 {
+  riscv_init_builtin_types ();
+
   for (size_t i = 0; i < ARRAY_SIZE (riscv_builtins); i++)
     {
       const struct riscv_builtin_description *d = &riscv_builtins[i];
diff --git a/gcc/config/riscv/riscv-modes.def b/gcc/config/riscv/riscv-modes.def
index 653228409a4..5cf2fc8e9e6 100644
--- a/gcc/config/riscv/riscv-modes.def
+++ b/gcc/config/riscv/riscv-modes.def
@@ -19,4 +19,5 @@  You should have received a copy of the GNU General Public License
 along with GCC; see the file COPYING3.  If not see
 <http://www.gnu.org/licenses/>.  */
 
+FLOAT_MODE (HF, 2, ieee_half_format);
 FLOAT_MODE (TF, 16, ieee_quad_format);
diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
index 5a0adffb5ce..47e6110767c 100644
--- a/gcc/config/riscv/riscv.cc
+++ b/gcc/config/riscv/riscv.cc
@@ -2296,11 +2296,13 @@  riscv_output_move (rtx dest, rtx src)
   enum rtx_code dest_code, src_code;
   machine_mode mode;
   bool dbl_p;
+  unsigned width;
 
   dest_code = GET_CODE (dest);
   src_code = GET_CODE (src);
   mode = GET_MODE (dest);
   dbl_p = (GET_MODE_SIZE (mode) == 8);
+  width = GET_MODE_SIZE (mode);
 
   if (dbl_p && riscv_split_64bit_move_p (dest, src))
     return "#";
@@ -2308,10 +2310,19 @@  riscv_output_move (rtx dest, rtx src)
   if (dest_code == REG && GP_REG_P (REGNO (dest)))
     {
       if (src_code == REG && FP_REG_P (REGNO (src)))
-	return dbl_p ? "fmv.x.d\t%0,%1" : "fmv.x.w\t%0,%1";
+	switch (width)
+	  {
+	  case 2:
+	    /* Using fmv.x.s + sign-extend to emulate fmv.x.h.  */
+	    return "fmv.x.s\t%0,%1;slli\t%0,%0,16;srai\t%0,%0,16";
+	  case 4:
+	    return "fmv.x.s\t%0,%1";
+	  case 8:
+	    return "fmv.x.d\t%0,%1";
+	  }
 
       if (src_code == MEM)
-	switch (GET_MODE_SIZE (mode))
+	switch (width)
 	  {
 	  case 1: return "lbu\t%0,%1";
 	  case 2: return "lhu\t%0,%1";
@@ -2353,18 +2364,24 @@  riscv_output_move (rtx dest, rtx src)
 	    return "mv\t%0,%z1";
 
 	  if (FP_REG_P (REGNO (dest)))
-	    {
-	      if (!dbl_p)
-		return "fmv.w.x\t%0,%z1";
-	      if (TARGET_64BIT)
-		return "fmv.d.x\t%0,%z1";
-	      /* in RV32, we can emulate fmv.d.x %0, x0 using fcvt.d.w */
-	      gcc_assert (src == CONST0_RTX (mode));
-	      return "fcvt.d.w\t%0,x0";
-	    }
+	    switch (width)
+	      {
+	      case 2:
+		/* High 16 bits should be all-1, otherwise HW will treated
+		   as a n-bit canonical NaN, but isn't matter for softfloat.  */
+		return "fmv.s.x\t%0,%1";
+	      case 4:
+		return "fmv.s.x\t%0,%z1";
+	      case 8:
+		if (TARGET_64BIT)
+		  return "fmv.d.x\t%0,%z1";
+		/* in RV32, we can emulate fmv.d.x %0, x0 using fcvt.d.w */
+		gcc_assert (src == CONST0_RTX (mode));
+		return "fcvt.d.w\t%0,x0";
+	      }
 	}
       if (dest_code == MEM)
-	switch (GET_MODE_SIZE (mode))
+	switch (width)
 	  {
 	  case 1: return "sb\t%z1,%0";
 	  case 2: return "sh\t%z1,%0";
@@ -2375,7 +2392,15 @@  riscv_output_move (rtx dest, rtx src)
   if (src_code == REG && FP_REG_P (REGNO (src)))
     {
       if (dest_code == REG && FP_REG_P (REGNO (dest)))
-	return dbl_p ? "fmv.d\t%0,%1" : "fmv.s\t%0,%1";
+	switch (width)
+	  {
+	  case 2:
+	    return "fmv.s\t%0,%1";
+	  case 4:
+	    return "fmv.s\t%0,%1";
+	  case 8:
+	    return "fmv.d\t%0,%1";
+	  }
 
       if (dest_code == MEM)
 	return dbl_p ? "fsd\t%1,%0" : "fsw\t%1,%0";
@@ -5638,6 +5663,107 @@  riscv_asan_shadow_offset (void)
   return TARGET_64BIT ? (HOST_WIDE_INT_1 << 29) : 0;
 }
 
+/* Implement TARGET_MANGLE_TYPE.  */
+
+static const char *
+riscv_mangle_type (const_tree type)
+{
+  /* Half-precision float, _Float16 is "DF16_".  */
+  if (TREE_CODE (type) == REAL_TYPE && TYPE_PRECISION (type) == 16)
+    return "DF16_";
+
+  /* Use the default mangling.  */
+  return NULL;
+}
+
+/* Implement TARGET_SCALAR_MODE_SUPPORTED_P.  */
+
+static bool
+riscv_scalar_mode_supported_p (scalar_mode mode)
+{
+  if (mode == HFmode)
+    return true;
+  else
+    return default_scalar_mode_supported_p (mode);
+}
+
+/* Implement TARGET_LIBGCC_FLOATING_MODE_SUPPORTED_P - return TRUE
+   if MODE is HFmode, and punt to the generic implementation otherwise.  */
+
+static bool
+riscv_libgcc_floating_mode_supported_p (scalar_float_mode mode)
+{
+  if (mode == HFmode)
+    return true;
+  else
+    return default_libgcc_floating_mode_supported_p (mode);
+}
+
+/* Set the value of FLT_EVAL_METHOD.
+   ISO/IEC TS 18661-3 defines two values that we'd like to make use of:
+
+    0: evaluate all operations and constants, whose semantic type has at
+       most the range and precision of type float, to the range and
+       precision of float; evaluate all other operations and constants to
+       the range and precision of the semantic type;
+
+    N, where _FloatN is a supported interchange floating type
+       evaluate all operations and constants, whose semantic type has at
+       most the range and precision of _FloatN type, to the range and
+       precision of the _FloatN type; evaluate all other operations and
+       constants to the range and precision of the semantic type;
+
+   If we have the zfh extensions then we support _Float16 in native
+   precision, so we should set this to 16.  */
+static enum flt_eval_method
+riscv_excess_precision (enum excess_precision_type type)
+{
+  switch (type)
+    {
+    case EXCESS_PRECISION_TYPE_FAST:
+    case EXCESS_PRECISION_TYPE_STANDARD:
+      return FLT_EVAL_METHOD_PROMOTE_TO_FLOAT;
+    case EXCESS_PRECISION_TYPE_IMPLICIT:
+      return FLT_EVAL_METHOD_PROMOTE_TO_FLOAT16;
+    default:
+      gcc_unreachable ();
+    }
+  return FLT_EVAL_METHOD_UNPREDICTABLE;
+}
+
+/* Implement TARGET_FLOATN_MODE.  */
+static opt_scalar_float_mode
+riscv_floatn_mode (int n, bool extended)
+{
+  if (!extended && n == 16)
+    return HFmode;
+
+  return default_floatn_mode (n, extended);
+}
+
+static void
+riscv_init_libfuncs (void)
+{
+  /* Half-precision float operations.  The compiler handles all operations
+     with NULL libfuncs by converting to SFmode.  */
+
+  /* Arithmetic.  */
+  set_optab_libfunc (add_optab, HFmode, NULL);
+  set_optab_libfunc (sdiv_optab, HFmode, NULL);
+  set_optab_libfunc (smul_optab, HFmode, NULL);
+  set_optab_libfunc (neg_optab, HFmode, NULL);
+  set_optab_libfunc (sub_optab, HFmode, NULL);
+
+  /* Comparisons.  */
+  set_optab_libfunc (eq_optab, HFmode, NULL);
+  set_optab_libfunc (ne_optab, HFmode, NULL);
+  set_optab_libfunc (lt_optab, HFmode, NULL);
+  set_optab_libfunc (le_optab, HFmode, NULL);
+  set_optab_libfunc (ge_optab, HFmode, NULL);
+  set_optab_libfunc (gt_optab, HFmode, NULL);
+  set_optab_libfunc (unord_optab, HFmode, NULL);
+}
+
 /* Initialize the GCC target structure.  */
 #undef TARGET_ASM_ALIGNED_HI_OP
 #define TARGET_ASM_ALIGNED_HI_OP "\t.half\t"
@@ -5821,6 +5947,25 @@  riscv_asan_shadow_offset (void)
 #undef TARGET_NEW_ADDRESS_PROFITABLE_P
 #define TARGET_NEW_ADDRESS_PROFITABLE_P riscv_new_address_profitable_p
 
+#undef TARGET_MANGLE_TYPE
+#define TARGET_MANGLE_TYPE riscv_mangle_type
+
+#undef TARGET_SCALAR_MODE_SUPPORTED_P
+#define TARGET_SCALAR_MODE_SUPPORTED_P riscv_scalar_mode_supported_p
+
+#undef TARGET_LIBGCC_FLOATING_MODE_SUPPORTED_P
+#define TARGET_LIBGCC_FLOATING_MODE_SUPPORTED_P                                \
+  riscv_libgcc_floating_mode_supported_p
+
+#undef TARGET_INIT_LIBFUNCS
+#define TARGET_INIT_LIBFUNCS riscv_init_libfuncs
+
+#undef TARGET_C_EXCESS_PRECISION
+#define TARGET_C_EXCESS_PRECISION riscv_excess_precision
+
+#undef TARGET_FLOATN_MODE
+#define TARGET_FLOATN_MODE riscv_floatn_mode
+
 #undef TARGET_ASAN_SHADOW_OFFSET
 #define TARGET_ASAN_SHADOW_OFFSET riscv_asan_shadow_offset
 
diff --git a/gcc/config/riscv/riscv.md b/gcc/config/riscv/riscv.md
index 0796f91dd30..7af5c90e0f3 100644
--- a/gcc/config/riscv/riscv.md
+++ b/gcc/config/riscv/riscv.md
@@ -134,7 +134,7 @@  (define_attr "move_type"
   (const_string "unknown"))
 
 ;; Main data type used by the insn
-(define_attr "mode" "unknown,none,QI,HI,SI,DI,TI,SF,DF,TF"
+(define_attr "mode" "unknown,none,QI,HI,SI,DI,TI,HF,SF,DF,TF"
   (const_string "unknown"))
 
 ;; True if the main data type is twice the size of a word.
@@ -324,20 +324,20 @@  (define_mode_attr load [(QI "lb") (HI "lh") (SI "lw") (DI "ld") (SF "flw") (DF "
 (define_mode_attr default_load [(QI "lbu") (HI "lhu") (SI "lw") (DI "ld")])
 
 ;; Mode attribute for FP loads into integer registers.
-(define_mode_attr softload [(SF "lw") (DF "ld")])
+(define_mode_attr softload [(HF "lh") (SF "lw") (DF "ld")])
 
 ;; Instruction names for stores.
 (define_mode_attr store [(QI "sb") (HI "sh") (SI "sw") (DI "sd") (SF "fsw") (DF "fsd")])
 
 ;; Instruction names for FP stores from integer registers.
-(define_mode_attr softstore [(SF "sw") (DF "sd")])
+(define_mode_attr softstore [(HF "sh") (SF "sw") (DF "sd")])
 
 ;; This attribute gives the best constraint to use for registers of
 ;; a given mode.
 (define_mode_attr reg [(SI "d") (DI "d") (CC "d")])
 
 ;; This attribute gives the format suffix for floating-point operations.
-(define_mode_attr fmt [(SF "s") (DF "d")])
+(define_mode_attr fmt [(HF "h") (SF "s") (DF "d")])
 
 ;; This attribute gives the integer suffix for floating-point conversions.
 (define_mode_attr ifmt [(SI "w") (DI "l")])
@@ -347,7 +347,7 @@  (define_mode_attr amo [(SI "w") (DI "d")])
 
 ;; This attribute gives the upper-case mode name for one unit of a
 ;; floating-point mode.
-(define_mode_attr UNITMODE [(SF "SF") (DF "DF")])
+(define_mode_attr UNITMODE [(HF "HF") (SF "SF") (DF "DF")])
 
 ;; This attribute gives the integer mode that has half the size of
 ;; the controlling mode.
@@ -1450,6 +1450,26 @@  (define_insn "extendsfdf2"
   [(set_attr "type" "fcvt")
    (set_attr "mode" "DF")])
 
+;; 16-bit floating point moves
+(define_expand "movhf"
+  [(set (match_operand:HF 0 "")
+	(match_operand:HF 1 ""))]
+  ""
+{
+  if (riscv_legitimize_move (HFmode, operands[0], operands[1]))
+    DONE;
+})
+
+
+(define_insn "*movhf_softfloat"
+  [(set (match_operand:HF 0 "nonimmediate_operand" "=f, r,r,m,*f,*r")
+	(match_operand:HF 1 "move_operand"         " f,Gr,m,r,*r,*f"))]
+  "(register_operand (operands[0], HFmode)
+    || reg_or_0_operand (operands[1], HFmode))"
+  { return riscv_output_move (operands[0], operands[1]); }
+  [(set_attr "move_type" "fmove,move,load,store,mtc,mfc")
+   (set_attr "mode" "HF")])
+
 ;;
 ;;  ....................
 ;;
diff --git a/gcc/testsuite/g++.target/riscv/_Float16.C b/gcc/testsuite/g++.target/riscv/_Float16.C
new file mode 100644
index 00000000000..b97d1fbcf1c
--- /dev/null
+++ b/gcc/testsuite/g++.target/riscv/_Float16.C
@@ -0,0 +1,18 @@ 
+/* { dg-do compile } */
+
+_Float16 x;
+
+_Float16 foo1 (_Float16 a, _Float16 b)
+{
+    return a + b;
+}
+
+_Float16 foo2 (_Float16 a, _Float16 b)
+{
+    return a * b;
+}
+
+int foo3 (_Float16 a, _Float16 b)
+{
+    return a > b;
+}
diff --git a/gcc/testsuite/gcc.target/riscv/_Float16-soft-1.c b/gcc/testsuite/gcc.target/riscv/_Float16-soft-1.c
new file mode 100644
index 00000000000..0622588fdb9
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/_Float16-soft-1.c
@@ -0,0 +1,9 @@ 
+/* { dg-do compile } */
+/* { dg-options "-march=rv64if -mabi=lp64f -O" } */
+
+_Float16 test_soft_move (_Float16 a, _Float16 b)
+{
+    return b;
+}
+
+/* { dg-final { scan-assembler-not "fmv.h" } } */
diff --git a/gcc/testsuite/gcc.target/riscv/_Float16-soft-2.c b/gcc/testsuite/gcc.target/riscv/_Float16-soft-2.c
new file mode 100644
index 00000000000..3d37823fa4d
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/_Float16-soft-2.c
@@ -0,0 +1,13 @@ 
+/* { dg-do compile } */
+/* { dg-options "-march=rv64if -mabi=lp64f -O" } */
+
+_Float16 test_soft_add (_Float16 a, _Float16 b)
+{
+    /* Make sure __addhf3 not invoked here. */
+    /* { dg-final { scan-assembler-times "call\t__extendhfsf2" 2 } } */
+    return a + b;
+    /* { dg-final { scan-assembler-not "call\t__addhf3" } } */
+    /* { dg-final { scan-assembler-times "fadd.s" 1 } } */
+    /* { dg-final { scan-assembler-times "call\t__truncsfhf2" 1 } } */
+}
+
diff --git a/gcc/testsuite/gcc.target/riscv/_Float16-soft-3.c b/gcc/testsuite/gcc.target/riscv/_Float16-soft-3.c
new file mode 100644
index 00000000000..ecce364e310
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/_Float16-soft-3.c
@@ -0,0 +1,12 @@ 
+/* { dg-do compile } */
+/* { dg-options "-march=rv64if -mabi=lp64f -O" } */
+
+int test_soft_compare (_Float16 a, _Float16 b)
+{
+    /* Make sure __gthf2 not invoked here. */
+    /* { dg-final { scan-assembler-times "call\t__extendhfsf2" 2 } } */
+    return a > b;
+    /* { dg-final { scan-assembler-not "call\t__gthf2" } } */
+    /* { dg-final { scan-assembler-times "fgt.s" 1 } } */
+}
+
diff --git a/gcc/testsuite/gcc.target/riscv/_Float16-soft-4.c b/gcc/testsuite/gcc.target/riscv/_Float16-soft-4.c
new file mode 100644
index 00000000000..ce4bc7a6a5d
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/_Float16-soft-4.c
@@ -0,0 +1,12 @@ 
+/* { dg-do compile } */
+/* { dg-options "-march=rv64i -mabi=lp64 -O" } */
+
+int test_soft_compare (_Float16 a, _Float16 b)
+{
+    /* Make sure __gthf2 not invoked here. */
+    /* { dg-final { scan-assembler-times "call\t__extendhfsf2" 2 } } */
+    return a > b;
+    /* { dg-final { scan-assembler-not "call\t__gthf2" } } */
+    /* { dg-final { scan-assembler-times "call\t__gtsf2" 1 } } */
+}
+
diff --git a/gcc/testsuite/gcc.target/riscv/_Float16.c b/gcc/testsuite/gcc.target/riscv/_Float16.c
new file mode 100644
index 00000000000..cc131fd3e2c
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/_Float16.c
@@ -0,0 +1,19 @@ 
+/* { dg-do compile } */
+/* { dg-options "-O" } */
+
+_Float16 x;
+
+_Float16 foo1 (_Float16 a, _Float16 b)
+{
+    return a + b;
+}
+
+_Float16 foo2 (_Float16 a, _Float16 b)
+{
+    return a * b;
+}
+
+int foo3 (_Float16 a, _Float16 b)
+{
+    return a > b;
+}
diff --git a/libgcc/config/riscv/sfp-machine.h b/libgcc/config/riscv/sfp-machine.h
index 27fbe6e84d6..b2901f0b1fd 100644
--- a/libgcc/config/riscv/sfp-machine.h
+++ b/libgcc/config/riscv/sfp-machine.h
@@ -41,6 +41,7 @@  see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 #define _FP_DIV_MEAT_D(R,X,Y)	_FP_DIV_MEAT_2_udiv(D,R,X,Y)
 #define _FP_DIV_MEAT_Q(R,X,Y)	_FP_DIV_MEAT_4_udiv(Q,R,X,Y)
 
+#define _FP_NANFRAC_H		_FP_QNANBIT_H
 #define _FP_NANFRAC_S		_FP_QNANBIT_S
 #define _FP_NANFRAC_D		_FP_QNANBIT_D, 0
 #define _FP_NANFRAC_Q		_FP_QNANBIT_Q, 0, 0, 0
@@ -63,6 +64,7 @@  see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 #define _FP_DIV_MEAT_D(R,X,Y)	_FP_DIV_MEAT_1_udiv_norm(D,R,X,Y)
 #define _FP_DIV_MEAT_Q(R,X,Y)	_FP_DIV_MEAT_2_udiv(Q,R,X,Y)
 
+#define _FP_NANFRAC_H		_FP_QNANBIT_H
 #define _FP_NANFRAC_S		_FP_QNANBIT_S
 #define _FP_NANFRAC_D		_FP_QNANBIT_D
 #define _FP_NANFRAC_Q		_FP_QNANBIT_Q, 0
@@ -80,6 +82,7 @@  typedef unsigned int UTItype __attribute__ ((mode (TI)));
 typedef int __gcc_CMPtype __attribute__ ((mode (__libgcc_cmp_return__)));
 #define CMPtype __gcc_CMPtype
 
+#define _FP_NANSIGN_H		0
 #define _FP_NANSIGN_S		0
 #define _FP_NANSIGN_D		0
 #define _FP_NANSIGN_Q		0
diff --git a/libgcc/config/riscv/t-softfp32 b/libgcc/config/riscv/t-softfp32
index 59be1df827e..55261f98383 100644
--- a/libgcc/config/riscv/t-softfp32
+++ b/libgcc/config/riscv/t-softfp32
@@ -41,3 +41,8 @@  else
 softfp_extras := divsf3 divdf3 divtf3
 
 endif
+
+softfp_extensions += hfsf hfdf hftf
+softfp_truncations += tfhf dfhf sfhf
+softfp_extras += fixhfsi fixhfdi fixunshfsi fixunshfdi \
+                 floatsihf floatdihf floatunsihf floatundihf
diff --git a/libgcc/config/riscv/t-softfp64 b/libgcc/config/riscv/t-softfp64
index 75870951202..c87d242d5c3 100644
--- a/libgcc/config/riscv/t-softfp64
+++ b/libgcc/config/riscv/t-softfp64
@@ -1,3 +1,4 @@ 
 include $(srcdir)/config/riscv/t-softfp32
 
 softfp_int_modes += ti
+softfp_extras += fixhfti fixunshfti floattihf floatuntihf