test(asm): seed the riscv64 and loong64 assemble fuzz targets

Assisted-by: GLM 5.3

asm/testdata/seeds/loong64/vshuf4iv.s

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+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Seed corpus for FuzzAssembleLOONG64: the shuffle/permute immediate family.
+// VSHUF4I.B/H/W take a ui8 packing two position nibbles; VSHUF4I.V is
+// range-gated to 0..15 although its field is ui8, the same gate the
+// toolchain keeps.  VPERMI.W and the VEXTRINS pack an element index and an
+// insert/extract order in one ui8.
+
+#include "textflag.h"
+
+TEXT ·shuf4(SB), NOSPLIT, $0
+	VSHUF4IB $0, V2, V1
+	VSHUF4IB $16, V2, V1
+	VSHUF4IB $255, V2, V1
+	VSHUF4IH $0, V2, V1
+	VSHUF4IH $128, V2, V1
+	VSHUF4IH $255, V2, V1
+	VSHUF4IW $0, V2, V1
+	VSHUF4IW $96, V2, V1
+	VSHUF4IW $255, V2, V1
+	VSHUF4IV $0, V2, V1
+	VSHUF4IV $8, V2, V1
+	VSHUF4IV $15, V2, V1
+	RET
+
+TEXT ·shuf4X(SB), NOSPLIT, $0
+	XVSHUF4IB $0, X2, X1
+	XVSHUF4IB $255, X2, X1
+	XVSHUF4IH $255, X2, X1
+	XVSHUF4IW $255, X2, X1
+	XVSHUF4IV $0, X2, X1
+	XVSHUF4IV $15, X2, X1
+	RET
+
+TEXT ·permi(SB), NOSPLIT, $0
+	VPERMIW  $0, V2, V1
+	VPERMIW  $255, V2, V1
+	XVPERMIW $0, X2, X1
+	XVPERMIW $255, X2, X1
+	XVPERMIV $0, X2, X1
+	XVPERMIV $255, X2, X1
+	XVPERMIQ $0, X2, X1
+	XVPERMIQ $255, X2, X1
+	RET
+
+TEXT ·extrins(SB), NOSPLIT, $0
+	VEXTRINSB  $0, V2, V1
+	VEXTRINSB  $255, V2, V1
+	VEXTRINSH  $0, V2, V1
+	VEXTRINSH  $255, V2, V1
+	VEXTRINSW  $0, V2, V1
+	VEXTRINSW  $255, V2, V1
+	VEXTRINSV  $0, V2, V1
+	VEXTRINSV  $255, V2, V1
+	XVEXTRINSB $0, X2, X1
+	XVEXTRINSB $255, X2, X1
+	XVEXTRINSH $255, X2, X1
+	XVEXTRINSW $255, X2, X1
+	XVEXTRINSV $255, X2, X1
+	RET