From d916938c7cd8954fa7f6d21815dc11f8aca211f9 Mon Sep 17 00:00:00 2001
From: David Li <li.davidm96@gmail.com>
Date: Fri, 1 Jan 2016 11:01:38 -0700
Subject: Test use of cache in simulation

---
 src/lib.rs       |  5 +++--
 src/memory.rs    | 16 ++++++++--------
 src/simulator.rs | 25 +++++++++++++++++++++++--
 3 files changed, 34 insertions(+), 12 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index 4c3db9e..f5bf110 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -30,7 +30,8 @@ fn it_works() {
         Ok(b) => {
             let memory = memory::Memory::new_from_binary(0x2000, b);
             let memory_ref = Rc::new(RefCell::new(Box::new(memory) as Box<memory::MemoryInterface>));
-            let core = simulator::Core::new(memory_ref.clone());
+            let cache = Rc::new( RefCell::new( Box::new( memory::DirectMappedCache::new(4, 4, memory_ref.clone())) as Box<memory::MemoryInterface>) );
+            let core = simulator::Core::new(cache.clone());
             let mut simulator = simulator::Simulator::new(vec![core], memory_ref.clone());
             simulator.run();
         },
@@ -47,7 +48,7 @@ mod tests {
         use std::cell::RefCell;
 
         let memory = Memory::new(16);
-        let memory_ref = Rc::new(RefCell::new(memory));
+        let memory_ref = Rc::new(RefCell::new(Box::new(memory) as Box<MemoryInterface>));
         let dm_cache_word = DirectMappedCache::new(4, 1, memory_ref.clone());
         let dm_cache_doubleword = DirectMappedCache::new(4, 2, memory_ref.clone());
 
diff --git a/src/memory.rs b/src/memory.rs
index 5a30e17..8fdf43d 100644
--- a/src/memory.rs
+++ b/src/memory.rs
@@ -52,7 +52,7 @@ pub trait MemoryInterface {
     // fn write_byte(&self, address: isa::Address) -> Result<()>;
 }
 
-pub type SharedMemory = Rc<RefCell<MemoryInterface>>;
+pub type SharedMemory<'a> = Rc<RefCell<Box<MemoryInterface + 'a>>>;
 
 // TODO: should be a trait
 pub struct Mmu<T: MemoryInterface> {
@@ -86,11 +86,11 @@ struct CacheBlock {
 // investigate how LRU is implemented
 // TODO: use hashtable for a way?
 // TODO: hashtable-based FA cache?
-pub struct DirectMappedCache {
+pub struct DirectMappedCache<'a> {
     num_sets: u32,
     block_words: u32,
     cache: Vec<CacheBlock>,
-    next_level: SharedMemory,
+    next_level: SharedMemory<'a>,
 }
 
 impl Memory {
@@ -146,9 +146,9 @@ impl MemoryInterface for Memory {
     }
 }
 
-impl DirectMappedCache {
-    pub fn new(sets: u32, block_words: u32, next_level: SharedMemory)
-               -> DirectMappedCache {
+impl<'a> DirectMappedCache<'a> {
+    pub fn new(sets: u32, block_words: u32, next_level: SharedMemory<'a>)
+               -> DirectMappedCache<'a> {
         let set = CacheBlock {
             valid: false,
             tag: 0,
@@ -190,7 +190,7 @@ impl DirectMappedCache {
     }
 }
 
-impl MemoryInterface for DirectMappedCache {
+impl<'a> MemoryInterface for DirectMappedCache<'a> {
     fn latency(&self) -> u32 {
         100
     }
@@ -254,7 +254,7 @@ impl MemoryInterface for DirectMappedCache {
                 prefetch: false,
                 cycles_left: stall,
                 tag: new_tag,
-                data: vec![0, self.block_words],
+                data: vec![0; self.block_words as usize],
                 error: None,
                 waiting_on: 0,
             });
diff --git a/src/simulator.rs b/src/simulator.rs
index 2238421..e882c9a 100644
--- a/src/simulator.rs
+++ b/src/simulator.rs
@@ -27,6 +27,7 @@ struct RegisterFile {
 pub struct Core<'a> {
     pc: isa::Address,
     registers: RegisterFile,
+    stall: u32,
     running: bool,
     // TODO: change to memory::SharedMemory
     cache: Rc<RefCell<Box<MemoryInterface + 'a>>>,
@@ -81,6 +82,7 @@ impl<'a> Core<'a> {
         Core {
             pc: 0x1002c, // TODO: hardcoded: fix later
             registers: RegisterFile::new(),
+            stall: 0,
             running: true,
             cache: cache,
         }
@@ -88,6 +90,12 @@ impl<'a> Core<'a> {
 
     fn step(&mut self, inst: isa::Instruction) {
         let pc = self.pc;
+
+        if self.stall > 0 {
+            self.stall -= 1;
+            return;
+        }
+
         match inst.opcode() {
             isa::opcodes::JALR => {
                 // TODO: assert funct3 is 0
@@ -273,7 +281,10 @@ impl<'a> Core<'a> {
                     match result {
                         Ok(value) =>
                             self.registers.write_word(inst.rd(), value),
-                        Err(MemoryError::CacheMiss {..}) => return,
+                        Err(MemoryError::CacheMiss { stall_cycles }) => {
+                            self.stall = stall_cycles;
+                            return;
+                        },
                         Err(MemoryError::InvalidAddress) => {
                             self.trap(Trap::IllegalRead {
                                 address: pc,
@@ -296,7 +307,10 @@ impl<'a> Core<'a> {
                     let result = self.cache.borrow_mut().write_word(address, val);
                     match result {
                         Ok(()) => (),
-                        Err(MemoryError::CacheMiss {..}) => return,
+                        Err(MemoryError::CacheMiss { stall_cycles }) => {
+                            self.stall = stall_cycles;
+                            return;
+                        },
                         Err(MemoryError::InvalidAddress) => {
                             self.trap(Trap::IllegalWrite {
                                 address: pc,
@@ -350,12 +364,16 @@ impl<'a> Simulator<'a> {
         self.cores[0].registers.write_word(isa::Register::X3, 0x108D0);
         // hardcode SP
         self.cores[0].registers.write_word(isa::Register::X2, 0x7FFC);
+        let mut total_cycles = 0;
+        let mut stall_cycles = 0;
         loop {
             let mut ran = false;
+            total_cycles += 1;
             for core in self.cores.iter_mut() {
                 if !core.running {
                     continue;
                 }
+                if core.stall > 0 { stall_cycles += 1; }
                 let inst = self.memory.borrow_mut().read_instruction(core.pc);
                 if let Some(inst) = inst {
                     core.step(inst);
@@ -363,10 +381,13 @@ impl<'a> Simulator<'a> {
                 else {
                     // TODO: trap
                 }
+
+                core.cache.borrow_mut().step();
                 ran = true;
             }
             if !ran {
                 println!("All cores are not running, stopping...");
+                println!("Stalled cycles: {} of {}", stall_cycles, total_cycles);
                 break;
             }
         }
-- 
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