From 05ae121c98be750aeca537ded7338c0cbf5f5b4c Mon Sep 17 00:00:00 2001
From: David Li <li.davidm96@gmail.com>
Date: Fri, 25 Dec 2015 15:15:50 -0700
Subject: Convert PC to u32

---
 src/isa/mod.rs   |  3 +--
 src/memory.rs    | 38 ++++++++++++++++++++++++++++++++------
 src/simulator.rs |  9 +++++----
 3 files changed, 38 insertions(+), 12 deletions(-)

diff --git a/src/isa/mod.rs b/src/isa/mod.rs
index 5458255..b7ac405 100644
--- a/src/isa/mod.rs
+++ b/src/isa/mod.rs
@@ -9,8 +9,7 @@ pub type SignedHalfWord = i16;
 pub type Byte = u8;
 pub type SignedByte = i8;
 
-// TODO: directly encode PC as u32, as architecturally specified
-pub type Address = usize;
+pub type Address = u32;
 
 #[derive(Debug, PartialEq)]
 pub enum Register {
diff --git a/src/memory.rs b/src/memory.rs
index 51d8199..ae3b6fc 100644
--- a/src/memory.rs
+++ b/src/memory.rs
@@ -4,7 +4,9 @@ use binary::{Binary};
 #[derive(Debug)]
 pub enum MemoryError {
     InvalidAddress,
-    CacheMiss,
+    CacheMiss {
+        stall_cycles: u32,
+    },
 }
 
 pub type Result<T> = ::std::result::Result<T, MemoryError>;
@@ -51,6 +53,7 @@ pub struct Cache {
 impl Memory {
     pub fn new(size: isa::Address, binary: Binary) -> Memory {
         let mut memory = binary.words.clone();
+        let size = size as usize;
         if size > memory.len() {
             let remainder = size - memory.len();
             memory.reserve(remainder);
@@ -61,7 +64,9 @@ impl Memory {
     }
 
     pub fn read_instruction(&self, pc: isa::Address) -> Option<Instruction> {
-        self.memory.get(pc / 4).map(Clone::clone).map(Instruction::new)
+        self.memory.get((pc / 4) as usize)
+            .map(Clone::clone)
+            .map(Instruction::new)
     }
 }
 
@@ -70,11 +75,14 @@ impl MemoryInterface for Memory {
 
     fn read_word(&self, address: isa::Address) -> Result<isa::Word> {
         // memory is word-addressed but addresses are byte-addressed
-        self.memory.get(address / 4).map(Clone::clone).ok_or(MemoryError::InvalidAddress)
+        self.memory.get((address / 4) as usize)
+            .map(Clone::clone)
+            .ok_or(MemoryError::InvalidAddress)
     }
 
-    fn write_word(&mut self, address: isa::Address, value: isa::Word) -> Result<()> {
-        let address = address / 4;
+    fn write_word(&mut self, address: isa::Address, value: isa::Word)
+                  -> Result<()> {
+        let address = (address / 4) as usize;
         if address >= self.memory.len() || address <= 0 {
             Err(MemoryError::InvalidAddress)
         }
@@ -99,6 +107,23 @@ impl Cache {
         }
     }
 
+    fn parse_address(&self, address: isa::Address) -> (u32, u32, u32) {
+        // TODO: use constant in ISA module for word->byte conversion
+        let offset_mask = (self.block_words * 4 - 1) as u32;
+        let offset = address & offset_mask;
+        let index_mask = (self.num_sets - 1) as u32;
+        let index_shift = 32 - (self.block_words * 4).leading_zeros();
+        let index = (address >> index_shift) & index_mask;
+        let tag_shift = index_shift + (32 - self.num_sets.leading_zeros());
+        let tag = address >> tag_shift;
+
+        (tag, index, offset)
+    }
+
+    fn prefetch(&mut self, address: isa::Address) {
+
+    }
+
     fn invalidate(&mut self, address: isa::Address) {
 
     }
@@ -111,7 +136,8 @@ impl MemoryInterface for Cache {
         Err(MemoryError::InvalidAddress)
     }
 
-    fn write_word(&mut self, address: isa::Address, value: isa::Word) -> Result<()> {
+    fn write_word(&mut self, address: isa::Address, value: isa::Word)
+                  -> Result<()> {
         Err(MemoryError::InvalidAddress)
     }
 
diff --git a/src/simulator.rs b/src/simulator.rs
index 5eb68e2..127ac8a 100644
--- a/src/simulator.rs
+++ b/src/simulator.rs
@@ -277,8 +277,9 @@ impl Simulator {
                         let base = core.registers.read_word(inst.rs1());
                         let address = ((base as isa::SignedWord) + imm) as isa::Address;
                         match self.memory.read_word(address) {
-                            Ok(value) => core.registers.write_word(inst.rd(), value),
-                            Err(MemoryError::CacheMiss) => return,
+                            Ok(value) =>
+                                core.registers.write_word(inst.rd(), value),
+                            Err(MemoryError::CacheMiss {..}) => return,
                             Err(MemoryError::InvalidAddress) => {
                                 self.trap(core, Trap::IllegalRead {
                                     address: pc,
@@ -300,7 +301,7 @@ impl Simulator {
                          let address = ((base as isa::SignedWord) + imm) as isa::Address;
                          match self.memory.write_word(address, val) {
                              Ok(()) => (),
-                             Err(MemoryError::CacheMiss) => return,
+                             Err(MemoryError::CacheMiss {..}) => return,
                              Err(MemoryError::InvalidAddress) => {
                                  self.trap(core, Trap::IllegalWrite {
                                      address: pc,
@@ -319,7 +320,7 @@ impl Simulator {
                     0x0 => {
                         // System call
                         println!("System call {}:", core.registers.read_word(isa::Register::X10));
-                        let address = core.registers.read_word(isa::Register::X11) as usize;
+                        let address = core.registers.read_word(isa::Register::X11);
                         println!("Argument {:X}: {:?}", address, self.memory.read_word(address));
                     }
                     _ => {
-- 
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