fix(cmd/gasm): probe the arm64 operand shapes the encoder accepts

Assisted-by: GLM 5.3 Flash

cmd/gasm/audit.go

@@ -298,6 +298,37 @@ func probeShapes(a arch.Arch) []string {
 			// insert/extract family, as the toolchain's own
 			// testdata spells them.
 			"C", "$1, $0", "$0, R1, $1, R2",
+			// The narrowing and lengthening vector families carry
+			// mixed-lane operands (the widened half names the
+			// operation's wide view), with and without the shift
+			// immediate, as arm64enc.s spells them: the plain
+			// halves, the doubled high halves of the 2-suffix
+			// forms, and the narrowing shift's reversed operand
+			// order.
+			"V1.S2, V2.D2", "V1.S4, V2.D2", "V1.B8, V2.H8",
+			"V1.H8, V2.S4", "V1.D2, V2.S2", "V1.D2, V2.S4",
+			"V9.B8, V12.H8, V14.H8", "V0.B8, V1.B8, V2.H8",
+			"V0.H4, V1.H4, V2.S4", "V0.S4, V1.S4, V2.D2",
+			"V0.H8, V1.S4, V2.S4",
+			"$1, V1.B8, V2.H8", "$0, V1.H8, V2.S4",
+			"$0, V1.B16, V2.H8", "$0, V1.S4, V2.D2",
+			"$7, V1.H8, V0.B8", "$15, V1.S4, V0.H8",
+			// The vector move immediate and the structure
+			// loads/stores: pairs, triples and quads in the
+			// bracketed register lists, loads with the base first
+			// and stores with the list first.
+			"$146, V22.B16",
+			"(R15), [V15.H4, V16.H4]", "(RSP), [V31.S2, V0.S2, V1.S2]",
+			"[V22.H8, V23.H8], (R23)", "[V1.D2, V2.D2, V3.D2], (R11)",
+			"[V22.D2, V23.D2, V24.D2, V25.D2], (R3)",
+			// The paired FP loads and stores, the CASP pair compare
+			// (its two value registers bracketed), the remote
+			// prefetch and the system operations with their bare
+			// operand names.
+			"(R0), (F1, F2)", "(F3, F4), (R5)",
+			"(R2, R3), (R2), (R8, R9)",
+			"(R6), R12, $25",
+			"$285440, R12", "ALLE1",
 		}
 	case arch.RISCV:
 		return []string{