aarch64: Add support for FEAT_MTETC

This patch adds two new DC operations:

   *gbva
   *zgbva

gas/config/tc-aarch64.c

@@ -11011,6 +11011,7 @@ static const struct aarch64_option_cpu_value_table aarch64_features[] = {
   {"f16mm",		AARCH64_FEATURE (F16MM), AARCH64_FEATURES (2, SIMD, F16)},
   {"sve-b16mm",		AARCH64_FEATURE (SVE_B16MM), AARCH64_FEATURE (SVE)},
   {"mpamv2",		AARCH64_FEATURE (MPAMv2), AARCH64_NO_FEATURES},
+  {"mtetc",		AARCH64_FEATURE (MTETC), AARCH64_FEATURE (MEMTAG)},
   {NULL,		AARCH64_NO_FEATURES, AARCH64_NO_FEATURES},
 };
 

gas/doc/c-aarch64.texi

@@ -259,6 +259,8 @@ automatically cause those extensions to be disabled.
  @tab Enable the Lookup Table (LUT) extension.
 @item @code{memtag} @tab
  @tab Enable Armv8.5-A Memory Tagging Extensions.
+@item @code{mtetc} @tab @code{memtag}
+ @tab Enable Data cache tag block operations.
 @item @code{mops} @tab
  @tab Enable Armv8.8-A memcpy and memset acceleration instructions
 @item @code{mpamv2} @tab

gas/testsuite/gas/aarch64/mtetc-invalid.d

@@ -0,0 +1,4 @@
+#name: FEAT_MTETC dc instructions without +mtetc.
+#as: -march=armv8-a
+#source: mtetc.s
+#error_output: mtetc-invalid.l

gas/testsuite/gas/aarch64/mtetc-invalid.l

@@ -0,0 +1,5 @@
+.*: Assembler messages:
+.*: Error: selected processor does not support system register name 'gbva'
+.*: Error: selected processor does not support system register name 'gbva'
+.*: Error: selected processor does not support system register name 'zgbva'
+.*: Error: selected processor does not support system register name 'zgbva'

gas/testsuite/gas/aarch64/mtetc.d

@@ -0,0 +1,12 @@
+#as: -march=armv8-a+mtetc
+#objdump: -dr
+
+[^:]+:     file format .*
+
+Disassembly of section \.text:
+
+[^:]+:
+.*:	d50b74e0 	dc	gbva, x0
+.*:	d50b74ff 	dc	gbva, xzr
+.*:	d50b74a0 	dc	zgbva, x0
+.*:	d50b74bf 	dc	zgbva, xzr

gas/testsuite/gas/aarch64/mtetc.s

@@ -0,0 +1,4 @@
+dc	gbva, x0
+dc	gbva, xzr
+dc	zgbva, x0
+dc	zgbva, xzr