feat(lint): eleven new rules over directives, data and addressing

Assisted-by: GLM 5.3

lint/addressing.go

@@ -0,0 +1,63 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package lint
+
+import (
+	"fmt"
+	"strings"
+
+	"sourcedock.dev/petrbalvin/gasm-sdk/ast"
+)
+
+// scanAddressing flags the two pseudo-register spellings the language
+// reference (docs/asm/OPERANDS.md) calls its sharpest edge: a numeric offset
+// against FP names no symbol, and a negative numeric offset against SP
+// addresses the hardware stack pointer rather than the virtual frame.
+func scanAddressing(t *ast.Text, cfg Config) []Diagnostic {
+	var out []Diagnostic
+	for _, s := range t.Body {
+		in, ok := s.(*ast.Instr)
+		if !ok {
+			continue
+		}
+		for _, op := range in.Operands {
+			if op.Kind != ast.OpAddr {
+				continue
+			}
+			// FP is a pseudo-register, never a base register of a memory
+			// operand; a Base of FP only arises from the numeric form
+			// 0(FP), which the parser routes through memory parsing.  The
+			// toolchain rejects it with "cannot reference FP without a
+			// symbol" and gasm with "unknown base register FP".
+			if strings.EqualFold(op.Addr.Base, "FP") && !cfg.Disable[CodeUnnamedFPRef] {
+				out = append(out, Diagnostic{
+					Pos:      op.Pos,
+					Severity: Error,
+					Code:     CodeUnnamedFPRef,
+					Message:  "FP is referenced without a symbol; the assembler requires name+offset(FP)",
+				})
+				continue
+			}
+			// A numeric offset against (SP) addresses the hardware stack
+			// pointer.  Positive offsets are the deliberate runtime idiom
+			// for reading caller frames, but a negative offset is exactly
+			// the local-frame spelling with the name missing: x-8(SP) and
+			// -8(SP) are one character apart and mean different registers.
+			// Only the negative form is flagged, which keeps the rule
+			// silent across GOROOT's 140-odd deliberate hardware-SP
+			// references (all positive) while catching the mistyped local.
+			if strings.EqualFold(op.Addr.Base, "SP") && op.Addr.Sym == nil &&
+				op.Addr.HasOff && op.Addr.Offset < 0 && !cfg.Disable[CodeHardwareSP] {
+				out = append(out, Diagnostic{
+					Pos:      op.Pos,
+					Severity: Warning,
+					Code:     CodeHardwareSP,
+					Message: fmt.Sprintf("%d(SP) addresses the hardware stack pointer, not the virtual frame; "+
+						"a frame local is spelled x%d(SP)", op.Addr.Offset, op.Addr.Offset),
+				})
+			}
+		}
+	}
+	return out
+}