1 files changed, 38 insertions, 0 deletions
diff --git a/linux/bootstrap/021div.cc b/linux/bootstrap/021div.cc
new file mode 100644
index 00000000..15ed89d8
--- /dev/null
+++ b/linux/bootstrap/021div.cc
@@ -0,0 +1,38 @@
+//: helper for division operations: sign-extend EAX into EDX
+
+:(before "End Initialize Op Names")
+put_new(Name, "99", "sign-extend EAX into EDX (cdq)");
+
+:(code)
+void test_cdq() {
+  Reg[EAX].i = 10;
+  run(
+      "== code 0x1\n"
+      "99\n"
+  );
+  CHECK_TRACE_CONTENTS(
+      "run: sign-extend EAX into EDX\n"
+      "run: EDX is now 0x00000000\n"
+  );
+}
+
+:(before "End Single-Byte Opcodes")
+case 0x99: {  // sign-extend EAX into EDX
+  trace(Callstack_depth+1, "run") << "sign-extend EAX into EDX" << end();
+  Reg[EDX].i = (Reg[EAX].i < 0) ? -1 : 0;
+  trace(Callstack_depth+1, "run") << "EDX is now 0x" << HEXWORD << Reg[EDX].u << end();
+  break;
+}
+
+:(code)
+void test_cdq_negative() {
+  Reg[EAX].i = -10;
+  run(
+      "== code 0x1\n"
+      "99\n"
+  );
+  CHECK_TRACE_CONTENTS(
+      "run: sign-extend EAX into EDX\n"
+      "run: EDX is now 0xffffffff\n"
+  );
+}