From 974e8c2f125e57558dd273753d0c3095affcc847 Mon Sep 17 00:00:00 2001
From: m8pple <dt10@imperial.ac.uk>
Date: Mon, 19 Oct 2015 16:11:51 +0100
Subject: Adding example eie2ugs code from live tutorial + recorded tutorial:
 https://panopto.imperial.ac.uk/Panopto/Pages/Viewer.aspx?id=653bf926-6acd-450f-991a-9cdbdf270852
 https://panopto.imperial.ac.uk/Panopto/Pages/Viewer.aspx?id=fefdb6bc-4205-4113-bf3b-76ecefc201f2
 https://panopto.imperial.ac.uk/Panopto/Pages/Viewer.aspx?id=c4966c37-effd-48f7-b5b9-ebdc5a30b2de

---
 src/eie2ugs/mips_cpu.cpp | 128 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 128 insertions(+)
 create mode 100644 src/eie2ugs/mips_cpu.cpp

(limited to 'src/eie2ugs/mips_cpu.cpp')

diff --git a/src/eie2ugs/mips_cpu.cpp b/src/eie2ugs/mips_cpu.cpp
new file mode 100644
index 0000000..475977e
--- /dev/null
+++ b/src/eie2ugs/mips_cpu.cpp
@@ -0,0 +1,128 @@
+#include "mips.h"
+
+struct mips_cpu_impl
+{
+    uint32_t pc;
+    uint32_t pcNext;
+    
+    uint32_t regs[32];
+    
+    mips_mem_h mem;
+    
+    unsigned logLevel;
+    FILE *logDst;
+};
+
+
+mips_error mips_cpu_get_register(
+	mips_cpu_h state,	//!< Valid (non-empty) handle to a CPU
+	unsigned index,		//!< Index from 0 to 31
+	uint32_t *value		//!< Where to write the value to
+)
+{
+    // TODO : error handling
+    *value = state->regs[index];
+    return mips_Success;
+}
+
+/*! Modifies one of the 32 general purpose MIPS registers. */
+mips_error mips_cpu_set_register(
+	mips_cpu_h state,	//!< Valid (non-empty) handle to a CPU
+	unsigned index,		//!< Index from 0 to 31
+	uint32_t value		//!< New value to write into register file
+)
+{
+    // TODO : error handling
+    state->regs[index] = value;
+    return mips_Success;
+}
+
+mips_error mips_cpu_set_debug_level(mips_cpu_h state, unsigned level, FILE *dest)
+{
+    state->logLevel = level;
+    state->logDst = dest;
+    return mips_Success;
+}
+
+mips_cpu_h mips_cpu_create(mips_mem_h mem)
+{
+    mips_cpu_impl *cpu=new mips_cpu_impl;
+    
+    cpu->pc=0;
+    for(int i=0;i<32;i++){
+        cpu->regs[i]=0;
+    }
+    cpu->mem=mem;
+    
+    return cpu;
+}
+
+/*! \param pData Array of 4 bytes
+    \retval The big-endian equivlent
+*/
+uint32_t to_big(const uint8_t *pData)
+{
+    return
+        (((uint32_t)pData[0])<<24)
+        |
+        (((uint32_t)pData[1])<<16)
+        |
+        (((uint32_t)pData[2])<<8)
+        |
+        (((uint32_t)pData[3])<<0);
+}
+
+mips_error mips_cpu_step(
+	mips_cpu_h state	//! Valid (non-empty) handle to a CPU
+)
+{
+    uint8_t buffer[4];
+    
+    mips_error err=mips_mem_read(
+        state->mem,		//!< Handle to target memory
+        state->pc,	//!< Byte address to start transaction at
+        4,	//!< Number of bytes to transfer
+        buffer	//!< Receives the target bytes
+    );
+    
+    if(err!=0){
+        return err;
+    }
+    
+    uint32_t instruction= to_big(buffer);
+    
+    uint32_t opcode =  (instruction>>26) & 0x3F;
+    uint32_t src1 = (instruction>> 21 ) & 0x1F;
+    uint32_t src2 = (instruction>> 16 ) & 0x1F;   
+    uint32_t dst = (instruction>> 11 ) & 0x1F;    
+    uint32_t shift = (instruction>> 6 ) & 0x1F ;
+    uint32_t function = (instruction>> 0 ) & 0x3F ;
+
+    if(opcode == 0){
+        // This is R-type
+        if(state->logLevel >= 2){
+            fprintf(state->logDst, "R-Type : dst=%u, src1=%u, src2=%u, shift=%u, function=%u.\n  instr=%08x\n",
+                dst, src1, src2, shift, function, instruction
+            );
+        }
+        
+        if(function ==  0x21){
+            if(state->logLevel >= 1){
+                fprintf(state->logDst, "addu %u, %u, %u.\n", dst, src1, src2);
+            }
+            uint32_t va=state->regs[src1];
+            uint32_t vb=state->regs[src2];
+            
+            uint32_t res=va+vb;
+            
+            state->regs[dst] = res; // NOTE: what about zero reg?
+            
+            // NOTE : What about updating the program counter
+            return mips_Success;
+        }else{
+            return mips_ErrorNotImplemented;
+        }
+    }else{
+        return mips_ErrorNotImplemented;
+    }
+}
-- 
cgit