feat(lint): accept the wired extension mnemonics

Assisted-by: GLM 5.3 Flash

lint/extension_test.go

@@ -0,0 +1,52 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package lint
+
+import (
+	"testing"
+
+	"sourcedock.dev/petrbalvin/gasm-sdk/arch"
+	"sourcedock.dev/petrbalvin/gasm-sdk/asm"
+)
+
+// TestExtensionInstructionsAreKnown pins the lint side of the
+// extended-instruction layer: every mnemonic the arm64 registry carries
+// lints without unknown-instruction, and a kernel the encoder accepts lints
+// clean, because the wired layer is the acceptance rather than a gap of the
+// generated table.
+func TestExtensionInstructionsAreKnown(t *testing.T) {
+	src := `#include "textflag.h"
+TEXT ·f(SB), NOSPLIT, $0
+	ADD Z1.S, Z2.S, Z0.S
+	SUBR Z1.S, P0/M, Z0.S
+	SQADD Z0.D, Z1.D, Z2.D
+	UQADD Z0.D, Z1.D, Z2.D
+	SQSUB Z0.D, Z1.D, Z2.D
+	UQSUB Z0.D, Z1.D, Z2.D
+	SMULH Z3.D, Z4.D, Z5.D
+	ADD $255, Z0.S
+	MUL $-128, Z0.B
+	RET
+`
+	diags := lintArchFile(t, "ext_arm64.s", src, arch.ARM64, asm.AssembleFileARM64)
+	for _, code := range []string{CodeUnknownInstr, CodeUnencodable} {
+		if n := codes(diags)[code]; n != 0 {
+			t.Errorf("%s fired %d times on the wired extension: %+v", code, n, diags)
+		}
+	}
+	if len(diags) != 0 {
+		t.Errorf("a kernel the encoder accepts must lint clean, got %+v", diags)
+	}
+
+	// The registry consult is the layer's own, not a loosening of the rule:
+	// a mnemonic neither table nor registry carries still fires.
+	diags = lintSrcArch(t, "ext_arm64.s", `#include "textflag.h"
+TEXT ·f(SB), NOSPLIT, $0
+	FROBNICATE Z0.S, Z1.S, Z2.S
+	RET
+`)
+	if codes(diags)[CodeUnknownInstr] != 1 {
+		t.Errorf("an unregistered mnemonic must fire unknown-instruction once: %+v", diags)
+	}
+}