add test_rename_execute_retire_save_restore_gprs

currently it fails due to the L2 reg file running out of output registers

crates/cpu/tests/rename_execute_retire.rs

@@ -4486,3 +4486,120 @@ fn test_rename_execute_retire_head_n1() {
         panic!();
     }
 }
+
+struct SaveRestoreGprsInsns;
+
+impl SaveRestoreGprsInsns {
+    const STATE_OFFSET: usize = 16;
+    const MAIN_STACK_FRAME_SIZE: usize = 16 + 32 * 8;
+    const OK: i16 = i16::from_le_bytes(*b"Ok");
+}
+
+impl MakeInsns for SaveRestoreGprsInsns {
+    fn make_insns() -> Insns {
+        let mut b = InsnsBuilder::new();
+
+        let load_all = b.new_label("load_all");
+        let store_all = b.new_label("store_all");
+        let main = b.new_label("main");
+        b.power_isa_addi(1, 0, 0x4000); // setup stack pointer
+        b.power_isa_bl(main);
+        b.power_isa_addi(0, 0, Self::OK);
+        b.power_isa_std(0, 0, MockMemory::IO_ADDR as i16);
+        let done = b.new_defined_label("done");
+        b.power_isa_b(done);
+
+        b.set_pc(0x1000);
+        b.define_label(main);
+        b.power_isa_mflr(0);
+        b.power_isa_stdu(0, 1, -(Self::MAIN_STACK_FRAME_SIZE as i16));
+        b.power_isa_addi(0, 0, 2);
+        b.power_isa_mtctr(0);
+
+        let main_loop = b.new_defined_label("main_loop");
+        b.power_isa_addi(3, 1, Self::STATE_OFFSET as i16);
+        b.power_isa_bl(store_all);
+        b.power_isa_addi(3, 1, Self::STATE_OFFSET as i16);
+        b.power_isa_bl(load_all);
+        b.power_isa_bdnz(main_loop);
+
+        b.power_isa_ld(0, 1, 0);
+        b.power_isa_addi(1, 1, Self::MAIN_STACK_FRAME_SIZE as i16);
+        b.power_isa_mtlr(0);
+        b.power_isa_blr();
+
+        b.set_pc(0x1800);
+        b.define_label(store_all);
+        for i in 0..32 {
+            b.power_isa_std(i, 3, i as i16 * 8);
+        }
+        b.power_isa_blr();
+
+        b.set_pc(0x2000);
+        b.define_label(load_all);
+        // load r3 last to avoid overwriting pointer
+        for i in (0..32).filter(|i| *i != 3).chain([3]) {
+            b.power_isa_ld(i, 3, i as i16 * 8);
+        }
+        b.power_isa_blr();
+
+        b.build()
+    }
+    fn make_load_store_execution_state() -> MockMemory {
+        MockMemory::new(vec![], vec![Self::OK as u64], [])
+    }
+}
+
+#[hdl]
+#[test]
+fn test_rename_execute_retire_save_restore_gprs() {
+    let _n = SourceLocation::normalize_files_for_tests();
+    let mut config = CpuConfig::new(
+        vec![
+            UnitConfig::new(UnitKind::AluBranch),
+            UnitConfig::new(UnitKind::AluBranch),
+            UnitConfig::new(UnitKind::LoadStore),
+            UnitConfig::new(UnitKind::TransformedMove),
+        ],
+        NonZeroUsize::new(20).unwrap(),
+    );
+    config.fetch_width = NonZeroUsize::new(2).unwrap();
+    let m = rename_execute_retire_test_harness::<SaveRestoreGprsInsns>(
+        PhantomConst::new_sized(config),
+        true,
+    );
+    let mut sim = Simulation::new(m);
+    let writer = RcWriter::default();
+    sim.add_trace_writer(VcdWriterDecls::new(writer.clone()));
+    struct DumpVcdOnDrop {
+        writer: Option<RcWriter>,
+    }
+    impl Drop for DumpVcdOnDrop {
+        fn drop(&mut self) {
+            if let Some(mut writer) = self.writer.take() {
+                let vcd = String::from_utf8(writer.take()).unwrap();
+                println!("####### VCD:\n{vcd}\n#######");
+            }
+        }
+    }
+    let mut writer = DumpVcdOnDrop {
+        writer: Some(writer),
+    };
+    sim.write_clock(sim.io().cd.clk, false);
+    sim.write_reset(sim.io().cd.rst, true);
+    for cycle in 0..700 {
+        sim.advance_time(SimDuration::from_nanos(500));
+        println!("clock tick: {cycle}");
+        sim.write_clock(sim.io().cd.clk, true);
+        sim.advance_time(SimDuration::from_nanos(500));
+        sim.write_clock(sim.io().cd.clk, false);
+        sim.write_reset(sim.io().cd.rst, false);
+    }
+    assert!(sim.read_bool(sim.io().all_outputs_written));
+    // FIXME: vcd is just whatever rename_execute_retire does now, which isn't known to be correct
+    let vcd = String::from_utf8(writer.writer.take().unwrap().take()).unwrap();
+    println!("####### VCD:\n{vcd}\n#######");
+    if vcd != include_str!("expected/rename_execute_retire_save_restore_gprs.vcd") {
+        panic!();
+    }
+}