aarch64: rcpc3: Add +rcpc3 architectural feature support flag

Indicating the presence of the Armv8.2-a feature adding further
support for the Release Consistency Model, the `+rcpc3' architectural
extension flag is added to the list of possible `-march' options in
Binutils, together with the necessary macro for encoding rcpc3
instructions.

gas/config/tc-aarch64.c

@@ -10363,6 +10363,7 @@ static const struct aarch64_option_cpu_value_table aarch64_features[] = {
   {"b16b16",		AARCH64_FEATURE (B16B16), AARCH64_FEATURE (SVE2)},
   {"sme2p1",		AARCH64_FEATURE (SME2p1), AARCH64_FEATURE (SME2)},
   {"sve2p1",		AARCH64_FEATURE (SVE2p1), AARCH64_FEATURE (SVE2)},
+  {"rcpc3",		AARCH64_FEATURE (RCPC3), AARCH64_FEATURE (RCPC2)},
   {NULL,		AARCH64_NO_FEATURES, AARCH64_NO_FEATURES},
 };
 

gas/doc/c-aarch64.texi

@@ -280,6 +280,9 @@ automatically cause those extensions to be disabled.
  @tab Enable the SME2.1 Extension.
 @item @code{sve2p1} @tab N/A @tab No
  @tab Enable the SVE2.1 Extension.
+@item @code{rcpc3} @tab Armv9.4-A @tab No
+ @tab Enable the rcpc3 additional Support for Release Consistency Model
+ Extension.  This implies @code{rcpc2}.
 @end multitable
 
 @node AArch64 Syntax

include/opcode/aarch64.h

@@ -226,6 +226,8 @@ enum aarch64_feature_bit {
   AARCH64_FEATURE_SME2p1,
   /* SVE2.1 instructions.  */
   AARCH64_FEATURE_SVE2p1,
+  /* RCPC3 instructions.  */
+  AARCH64_FEATURE_RCPC3,
   AARCH64_NUM_FEATURES
 };
 

opcodes/aarch64-tbl.h

@@ -2647,6 +2647,9 @@ static const aarch64_feature_set aarch64_feature_sme2p1 =
   AARCH64_FEATURE (SME2p1);
 static const aarch64_feature_set aarch64_feature_sve2p1 =
   AARCH64_FEATURE (SVE2p1);
+static const aarch64_feature_set aarch64_feature_rcpc3 =
+  AARCH64_FEATURE (RCPC3);
+
 
 #define CORE		&aarch64_feature_v8
 #define FP		&aarch64_feature_fp
@@ -2712,6 +2715,7 @@ static const aarch64_feature_set aarch64_feature_sve2p1 =
 #define B16B16  &aarch64_feature_b16b16
 #define SME2p1  &aarch64_feature_sme2p1
 #define SVE2p1  &aarch64_feature_sve2p1
+#define RCPC3	  &aarch64_feature_rcpc3
 
 #define CORE_INSN(NAME,OPCODE,MASK,CLASS,OP,OPS,QUALS,FLAGS) \
   { NAME, OPCODE, MASK, CLASS, OP, CORE, OPS, QUALS, FLAGS, 0, 0, NULL }