[llvm] [AARCH64] Add assembly/disassmbly for FIRST, LASTP instr. (PR #114049)

[via llvm-commits]

================
@@ -0,0 +1,32 @@
+// RUN: not llvm-mc -triple=aarch64 -show-encoding -mattr=+sve2p2 2>&1 < %s| FileCheck %s
+
+// ------------------------------------------------------------------------- //
+// Invalid predicate operand
+
+firstp  x0, p15, p0
+// CHECK: [[@LINE-1]]:{{[0-9]+}}: error: invalid predicate register.
+// CHECK-NEXT: firstp  x0, p15, p0
+// CHECK-NOT: [[@LINE-1]]:{{[0-9]+}}:
+
+firstp  x0, p15.b, p0.b
+// CHECK: [[@LINE-1]]:{{[0-9]+}}: error: invalid predicate register.
+// CHECK-NEXT: firstp  x0, p15.b, p0.b
+// CHECK-NOT: [[@LINE-1]]:{{[0-9]+}}:
+
+firstp  x0, p15.q, p0.h
+// CHECK: [[@LINE-1]]:{{[0-9]+}}: error: invalid predicate register.
+// CHECK-NEXT: firstp  x0, p15.q, p0.h
+// CHECK-NOT: [[@LINE-1]]:{{[0-9]+}}:
+
+// ------------------------------------------------------------------------- //
+// Invalid register types
+
+firstp  sp, p15.q, p0.h
+// CHECK: [[@LINE-1]]:{{[0-9]+}}: error: invalid operand for instruction
+// CHECK-NEXT: firstp  sp, p15.q, p0.h
+// CHECK-NOT: [[@LINE-1]]:{{[0-9]+}}:
+
+firstp  w0, p15.q, p0.h
----------------
SpencerAbson wrote:

```suggestion
firstp  w0, p15, p0.h
```

https://github.com/llvm/llvm-project/pull/114049