RISC-V: Modify _Bfloat16 to __bf16

According to the description in:
<https://github.com/riscv-non-isa/riscv-elf-psabi-doc/pull/367>,
the type representation symbol of BF16 has been corrected.

Kito Cheng pointed out relevant information in the email:
<https://gcc.gnu.org/pipermail/gcc-patches/2024-May/651850.html>

gcc/ChangeLog:

	* config/riscv/riscv-builtins.cc (riscv_init_builtin_types):
	Modify _Bfloat16 to __bf16.
	* config/riscv/riscv.cc (riscv_mangle_type): Ditto.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/_Bfloat16-nanboxing.c: Move to...
	* gcc.target/riscv/__bf16-nanboxing.c: ...here.
	* gcc.target/riscv/bf16_arithmetic.c: Modify _Bfloat16 to __bf16.
	* gcc.target/riscv/bf16_call.c: Ditto.
	* gcc.target/riscv/bf16_comparison.c: Ditto.
	* gcc.target/riscv/bf16_float_libcall_convert.c: Ditto.
	* gcc.target/riscv/bf16_integer_libcall_convert.c: Ditto.

gcc/config/riscv/riscv-builtins.cc

@@ -275,7 +275,7 @@ riscv_init_builtin_types (void)
     lang_hooks.types.register_builtin_type (riscv_float16_type_node,
 					    "_Float16");
 
-  /* Provide the _Bfloat16 type and bfloat16_type_node if needed.  */
+  /* Provide the __bf16 type and bfloat16_type_node if needed.  */
   if (!bfloat16_type_node)
     {
       riscv_bfloat16_type_node = make_node (REAL_TYPE);
@@ -286,9 +286,9 @@ riscv_init_builtin_types (void)
   else
     riscv_bfloat16_type_node = bfloat16_type_node;
 
-  if (!maybe_get_identifier ("_Bfloat16"))
+  if (!maybe_get_identifier ("__bf16"))
     lang_hooks.types.register_builtin_type (riscv_bfloat16_type_node,
-					    "_Bfloat16");
+					    "__bf16");
 }
 
 /* Implement TARGET_INIT_BUILTINS.  */

gcc/config/riscv/riscv.cc

@@ -10276,7 +10276,7 @@ riscv_asan_shadow_offset (void)
 static const char *
 riscv_mangle_type (const_tree type)
 {
-  /* Half-precision float, _Float16 is "DF16_" and _Bfloat16 is "DF16b".  */
+  /* Half-precision float, _Float16 is "DF16_" and __bf16 is "DF16b".  */
   if (SCALAR_FLOAT_TYPE_P (type) && TYPE_PRECISION (type) == 16)
     {
       if (TYPE_MODE (type) == HFmode)

gcc/testsuite/gcc.target/riscv/__bf16-nanboxing.c

@@ -1,14 +1,14 @@
 /* { dg-do compile } */
 /* { dg-options "-march=rv64ifd -mabi=lp64d -mcmodel=medlow -O" } */
 
-_Bfloat16 gvar = 9.87654;
+__bf16 gvar = 9.87654;
 union U
 {
   unsigned short i16;
-  _Bfloat16 f16;
+  __bf16 f16;
 };
 
-_Bfloat16
+__bf16
 test1 (unsigned short input)
 {
   union U tmp;
@@ -16,19 +16,19 @@ test1 (unsigned short input)
   return tmp.f16;
 }
 
-_Bfloat16
+__bf16
 test2 ()
 {
   return 1.234f;
 }
 
-_Bfloat16
+__bf16
 test3 ()
 {
   return gvar;
 }
 
-_Bfloat16
+__bf16
 test ()
 {
   return 0.0f;

gcc/testsuite/gcc.target/riscv/bf16_arithmetic.c

@@ -5,9 +5,9 @@
 /* 1) bf -> sf          (call      __extendbfsf2)  */
 /* 2) sf1 [+|-|*|/] sf2 (call      __[add|sub|mul|div]sf3)  */
 /* 3) sf -> bf          (call      __truncsfbf2)  */
-extern _Bfloat16 bf;
-extern _Bfloat16 bf1;
-extern _Bfloat16 bf2;
+extern __bf16 bf;
+extern __bf16 bf1;
+extern __bf16 bf2;
 
 void bf_add_bf () { bf = bf1 + bf2; }
 

gcc/testsuite/gcc.target/riscv/bf16_call.c

@@ -4,9 +4,9 @@
 
 /* 1) bf -> sf (call      __extendbfsf2)  */
 /* 2) sf -> bf (call      __truncsfbf2)  */
-__attribute__ ((noinline)) _Bfloat16 add (_Bfloat16 a, _Bfloat16 b) { return a + b; }
+__attribute__ ((noinline)) __bf16 add (__bf16 a, __bf16 b) { return a + b; }
 
-_Bfloat16 test(_Bfloat16 a, _Bfloat16 b) { return add (a, b); }
+__bf16 test(__bf16 a, __bf16 b) { return add (a, b); }
 
 /* { dg-final { scan-assembler-times "call\t__extendbfsf2" 2 } } */
 /* { dg-final { scan-assembler-times "call\t__truncsfbf2" 1 } } */

gcc/testsuite/gcc.target/riscv/bf16_comparison.c

@@ -4,9 +4,9 @@
 
 /* 1) bf -> sf               (call	__extendbfsf2)  */
 /* 2) sf1 [<|<=|>|>=|==] sf2 (call	__[lt|le|gt|ge|eq]sf2)  */
-extern _Bfloat16 bf;
-extern _Bfloat16 bf1;
-extern _Bfloat16 bf2;
+extern __bf16 bf;
+extern __bf16 bf1;
+extern __bf16 bf2;
 
 void bf_lt_bf () { bf = (bf1 < bf2) ? bf1 : bf2; }
 

gcc/testsuite/gcc.target/riscv/bf16_float_libcall_convert.c

@@ -14,7 +14,7 @@
  *    bf          -> tf == bf -> sf -> tf (call   __extendbfsf2 && __extendsftf2)
 */
 
-extern   _Bfloat16 bf;
+extern   __bf16    bf;
 extern   _Float16  hf;
 extern      float  sf;
 extern      double df;

gcc/testsuite/gcc.target/riscv/bf16_integer_libcall_convert.c

@@ -16,7 +16,7 @@
  *    bf          -> udi/uti     (call   __fixunssf[d|t]i)
 */
 
-extern _Bfloat16 bf;
+extern __bf16 bf;
 
 extern   signed char       qi;
 extern unsigned char      uqi;