feat(asm): encode indirect JMP and CALL on all four architectures

Assisted-by: GLM 5.3 Flash

lint/lint_test.go

@@ -8,6 +8,7 @@ import (
 	"testing"
 
 	"sourcedock.dev/petrbalvin/gasm-devkit/arch"
+	"sourcedock.dev/petrbalvin/gasm-devkit/ast"
 	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
 )
 
@@ -495,3 +496,33 @@ TEXT ·f(SB), NOSPLIT, $0
 		t.Fatalf("amd64 must not be flagged: %+v", diags)
 	}
 }
+
+// TestHasIndirectBranchShape checks that a JMP/CALL through a register or
+// memory suppresses reachability analysis, while a same-named label does not.
+func TestHasIndirectBranchShape(t *testing.T) {
+	tab := arch.ForArch(arch.AMD64)
+	indirect := `TEXT ·f(SB), NOSPLIT, $0
+	JMP AX
+	RET
+`
+	f, errs := parser.Parse("t_amd64.s", indirect)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	if !hasIndirectBranch(f.Decls[0].(*ast.Text), tab) {
+		t.Error("JMP AX: indirect branch not detected")
+	}
+
+	label := `TEXT ·f(SB), NOSPLIT, $0
+loop:
+	JMP loop
+	RET
+`
+	f, errs = parser.Parse("t_amd64.s", label)
+	if len(errs) > 0 {
+		t.Fatalf("parse: %v", errs)
+	}
+	if hasIndirectBranch(f.Decls[0].(*ast.Text), tab) {
+		t.Error("JMP loop: label treated as an indirect branch")
+	}
+}