feat(lint): add unused-label and invalid-textflag rules

Assisted-by: MiMo V2.5 Pro

lint/lint.go

@@ -74,8 +74,17 @@ const (
 	CodeNosplitFrame    = "nosplit-frame"
 	CodeRegisterClobber = "register-clobber"
 	CodeFuncdata        = "funcdata-pcdata"
+	CodeUnusedLabel     = "unused-label"
+	CodeInvalidFlag     = "invalid-textflag"
 )
 
+// knownTextFlags are the flags recognised by the Go assembler's textflag.h.
+var knownTextFlags = map[string]bool{
+	"NOSPLIT": true, "DUPOK": true, "RODATA": true, "NOPROF": true,
+	"WRIT": true, "TLSBSS": true, "NOFRAME": true, "REFLECTED": true,
+	"TOPFRAME": true, "ABIWRAPPER": true,
+}
+
 // pseudoOps are assembler pseudo-operations that are valid instruction-position
 // tokens but are not machine instructions and so absent from the arch tables.
 var pseudoOps = map[string]bool{
@@ -141,6 +150,38 @@ func File(f *ast.File, cfg Config) []Diagnostic {
 		})
 	}
 
+	// Invalid TEXT/GLOBL flags.
+	if !cfg.Disable[CodeInvalidFlag] {
+		for _, d := range f.Decls {
+			var flags []string
+			var pos token.Position
+			switch dd := d.(type) {
+			case *ast.Text:
+				flags = dd.Flags
+				pos = dd.Keyword.Pos
+			case *ast.Globl:
+				flags = dd.Flags
+				if dd.Name != nil {
+					pos = dd.Name.Pos
+				}
+			}
+			for _, fl := range flags {
+				// Numeric flags (1, 8, 9) are legacy Go toolchain constants.
+				if fl >= "0" && fl <= "9" {
+					continue
+				}
+				if !knownTextFlags[fl] {
+					out = append(out, Diagnostic{
+						Pos:      pos,
+						Severity: Warning,
+						Code:     CodeInvalidFlag,
+						Message:  fmt.Sprintf("unknown TEXT/GLOBL flag %q", fl),
+					})
+				}
+			}
+		}
+	}
+
 	sortDiagnostics(out)
 	return out
 }
@@ -282,6 +323,22 @@ func lintText(t *ast.Text, tab *arch.Table, archKnown bool, cfg Config, macros m
 		}
 	}
 
+	// Unused labels: defined but never referenced.  Suppressed when macros
+	// or indirect branches are present (the reference may be invisible).
+	if doLabelChecks && !cfg.Disable[CodeUnusedLabel] && !hasIndirect {
+		for name, pos := range defined {
+			if _, ok := referenced[name]; !ok {
+				out = append(out, Diagnostic{
+					Pos:      pos,
+					End:      token.Position{Line: pos.Line, Column: pos.Column + len(name)},
+					Severity: Hint,
+					Code:     CodeUnusedLabel,
+					Message:  fmt.Sprintf("label %q is defined but never referenced", name),
+				})
+			}
+		}
+	}
+
 	// Missing RET heuristic.  Functions that invoke a macro are skipped: the
 	// macro body (opaque to us) may supply the RET.
 	if doLabelChecks && !cfg.Disable[CodeMissingRet] && instrCount > 0 && !hasRet && !lastTerminal && !hasMacro {

lint/lint_test.go

@@ -233,3 +233,52 @@ TEXT ·f(SB), NOSPLIT, $0
 		t.Fatalf("label rules should be suppressed in macro files: %+v", diags)
 	}
 }
+
+func TestUnusedLabel(t *testing.T) {
+	diags := lintSrc(t, `
+#include "textflag.h"
+TEXT ·f(SB), NOSPLIT, $0
+unused:
+	ADDQ $1, AX
+	RET
+`)
+	if codes(diags)[CodeUnusedLabel] != 1 {
+		t.Fatalf("want one unused-label, got %+v", diags)
+	}
+}
+
+func TestUsedLabelNotFlagged(t *testing.T) {
+	diags := lintSrc(t, `
+#include "textflag.h"
+TEXT ·f(SB), NOSPLIT, $0
+loop:
+	ADDQ $1, AX
+	JMP loop
+	RET
+`)
+	if codes(diags)[CodeUnusedLabel] != 0 {
+		t.Fatalf("used label must not be flagged: %+v", diags)
+	}
+}
+
+func TestInvalidTextflag(t *testing.T) {
+	diags := lintSrc(t, `
+#include "textflag.h"
+TEXT ·f(SB), NOSPLIT|BOGUS, $0
+	RET
+`)
+	if codes(diags)[CodeInvalidFlag] != 1 {
+		t.Fatalf("want one invalid-textflag, got %+v", diags)
+	}
+}
+
+func TestValidTextflags(t *testing.T) {
+	diags := lintSrc(t, `
+#include "textflag.h"
+TEXT ·f(SB), NOSPLIT|NOFRAME|DUPOK, $0
+	RET
+`)
+	if codes(diags)[CodeInvalidFlag] != 0 {
+		t.Fatalf("valid flags must not be flagged: %+v", diags)
+	}
+}