[PATCH][GAS] aarch64: Add atomic 64-byte load/store instructions for Armv8.7

Armv8.7 architecture introduces the "accelerator extension", aka
load/store of 64 bytes. New atomic load/store instructions are: LD64B,
ST64B, ST64BV and ST64BV0.

This patch adds:
+ New feature +ls64 to -march command line.
+ New atomic load/store instructions associated with above feature.

For more details regarding atomic 64-byte load/store instruction for
Armv8.7 please refer to Arm A64 Instruction set documentation for
Armv8-A architecture profile, see document page 157 for load
instruction, and pages 414-418 for store instructions of [0].

    [0]: https://developer.arm.com/docs/ddi0596/i

4 files changed, 62 insertions, 0 deletions

diff --git a/gas/testsuite/gas/aarch64/ls64-invalid.d b/gas/testsuite/gas/aarch64/ls64-invalid.d
new file mode 100644
index 0000000..69e739d
--- /dev/null
+++ b/gas/testsuite/gas/aarch64/ls64-invalid.d
@@ -0,0 +1,3 @@
+#name: Atomic 64-byte load/store instruction
+#source: ls64-invalid.s
+#error_output: ls64-invalid.l
diff --git a/gas/testsuite/gas/aarch64/ls64-invalid.l b/gas/testsuite/gas/aarch64/ls64-invalid.l
new file mode 100644
index 0000000..64b6e58
--- /dev/null
+++ b/gas/testsuite/gas/aarch64/ls64-invalid.l
@@ -0,0 +1,5 @@
+.*: Assembler messages:
+.*: Error: selected processor does not support `ld64b x0,\[x1\]'
+.*: Error: selected processor does not support `st64b x0,\[x1\]'
+.*: Error: selected processor does not support `st64bv x0,x1,\[x2\]'
+.*: Error: selected processor does not support `st64bv0 x0,x1,\[x2\]'
diff --git a/gas/testsuite/gas/aarch64/ls64-invalid.s b/gas/testsuite/gas/aarch64/ls64-invalid.s
new file mode 100644
index 0000000..8c89aaf
--- /dev/null
+++ b/gas/testsuite/gas/aarch64/ls64-invalid.s
@@ -0,0 +1,14 @@
+/* Atomic 64-byte load/store instructions require Armv8.7-a extension.  */
+.arch armv8.6-a
+
+/* Single-copy Atomic 64-byte Load.  */
+	ld64b x0, [x1]
+
+/* Single-copy Atomic 64-byte Store without Return.  */
+	st64b x0, [x1]
+
+/* Single-copy Atomic 64-byte Store with Return.  */
+	st64bv x0, x1, [x2]
+
+/* Single-copy Atomic 64-byte EL0 Store with Return.  */
+	st64bv0 x0, x1, [x2]
diff --git a/gas/testsuite/gas/aarch64/ls64.s b/gas/testsuite/gas/aarch64/ls64.s
new file mode 100644
index 0000000..efbd0bf
--- /dev/null
+++ b/gas/testsuite/gas/aarch64/ls64.s
@@ -0,0 +1,40 @@
+/* Atomic 64-byte load/store instructions.  */
+.arch armv8.7-a+ls64
+
+/* Single-copy Atomic 64-byte Load.  */
+	ld64b x0, [x1]
+	ld64b x1, [x2]
+	ld64b x2, [x4]
+	ld64b x4, [x8]
+	ld64b x8, [x16]
+	ld64b x16, [x1]
+	ld64b x16, [sp]
+
+/* Single-copy Atomic 64-byte Store without Return.  */
+	st64b x0, [x1]
+	st64b x1, [x2]
+	st64b x2, [x4]
+	st64b x4, [x8]
+	st64b x8, [x16]
+	st64b x16, [x1]
+	st64b x16, [sp]
+
+/* Single-copy Atomic 64-byte Store with Return.  */
+	st64bv x0, x1, [x2]
+	st64bv x1, x2, [x4]
+	st64bv x2, x4, [x8]
+	st64bv x4, x8, [x16]
+	st64bv x8, x16, [x30]
+	st64bv x16, x30, [x0]
+	st64bv x30, x1, [x2]
+	st64bv x30, x1, [sp]
+
+/* Single-copy Atomic 64-byte EL0 Store with Return.  */
+	st64bv0 x0, x1, [x2]
+	st64bv0 x1, x2, [x4]
+	st64bv0 x2, x4, [x8]
+	st64bv0 x4, x8, [x16]
+	st64bv0 x8, x16, [x30]
+	st64bv0 x16, x30, [x0]
+	st64bv0 x30, x1, [x2]
+	st64bv0 x30, x1, [sp]