From cfb0a8e176379ade0302ccf2f5f0ac487dfdbea2 Mon Sep 17 00:00:00 2001
From: Baptiste <baptiste.meauze@etudiant.univ-rennes1.fr>
Date: Wed, 19 Oct 2022 17:23:41 +0200
Subject: [PATCH] decode (recquire tests)

---
 src/decode.rs | 121 ++++++++++++++++++++++++++++++++------------------
 src/main.rs   |   2 +-
 2 files changed, 78 insertions(+), 45 deletions(-)

diff --git a/src/decode.rs b/src/decode.rs
index ed21275..80ac041 100644
--- a/src/decode.rs
+++ b/src/decode.rs
@@ -1,57 +1,90 @@
 pub struct Instruction {
-    value : u64,
+    pub value : u64,
 
-    opcode : u8, 
-    rs1 : u8, 
-    rs2 : u8, 
-    rs3 : u8, 
-    rd : u8, 
-    funct7 : u8, 
-    funct7_smaller : u8, 
-    funct3 : u8, 
-    shamt : u8,
+    pub opcode : u8, 
+    pub rs1 : u8, 
+    pub rs2 : u8, 
+    pub rs3 : u8, 
+    pub rd : u8, 
+    pub funct7 : u8, 
+    pub funct7_smaller : u8, 
+    pub funct3 : u8, 
+    pub shamt : u8,
 
-    imm12_I : u16,
-    imm12_S : u16,
+    pub imm12_I : u16,
+    pub imm12_S : u16,
 
-    imm12_I_signed : i16, 
-    imm12_S_signed : i16, 
-    imm13 : i16, 
-    imm13_signed : i16,
+    pub imm12_I_signed : i16, 
+    pub imm12_S_signed : i16, 
+    pub imm13 : i16, 
+    pub imm13_signed : i16,
 
-    imm31_12 : u32, 
-    imm21_1 : u32,
+    pub imm31_12 : u32, 
+    pub imm21_1 : u32,
 
-    imm31_12_signed : i32, 
-    imm21_1_signed : i32,
+    pub imm31_12_signed : i32, 
+    pub imm21_1_signed : i32,
 }
 
 pub fn decode(val : u64) -> Instruction {
+
+    let value = val;
+
+    let opcode          = (val & 0x7f) as u8;
+    let rs1             = ((val >> 15) & 0x1f) as u8;
+    let rs2             = ((val >> 20) & 0x1f) as u8;
+    let rs3             = ((val >> 27) & 0x1f) as u8;
+    let rd              = ((val >> 7) & 0x1f) as u8;
+    let funct7          = ((val >> 25) & 0x7f) as u8;
+    let funct7_smaller  = (funct7 & 0x3e) as u8;
+    
+    let funct3          = ((val >> 12) & 0x7) as u8;
+    let imm12_I         = ((val >> 20) & 0xfff) as u16;
+    let imm12_S         = (((val >> 20) & 0xfe0) + ((val >> 7) & 0x1f)) as u16;
+    
+    let imm12_I_signed  = if imm12_I >= 2048 { imm12_I - 4096 } else { imm12_I } as i16;
+    let imm12_S_signed  = if imm12_S >= 2048 { imm12_S - 4096 } else { imm12_S } as i16;
+    
+    let imm13           = (((val >> 19) & 0x1000) + ((val >> 20) & 0x7e0) +
+                        ((val >> 7) & 0x1e) + ((val << 4) & 0x800)) as i16;
+    let imm13_signed    = if imm13 >= 4096 { imm13 - 8192 } else { imm13 } as i16;
+    
+    let imm31_12        = (val & 0xfffff000) as u32;
+    let imm31_12_signed = imm31_12 as i32;
+    
+    let imm21_1         = ((val & 0xff000) + ((val >> 9) & 0x800) +
+                        ((val >> 20) & 0x7fe) + ((val >> 11) & 0x100000)) as u32;
+    let imm21_1_signed  = if imm21_1 >= 1048576 { imm21_1 - 2097152 } else { imm21_1 } as i32;
+    
+    let shamt           = ((val >> 20) & 0x3f) as u8;
+    
     Instruction {
-        value : val,
+        value : value,
 
-        opcode : 0, 
-        rs1 : 0, 
-        rs2 : 0, 
-        rs3 : 0, 
-        rd : 0, 
-        funct7 : 0, 
-        funct7_smaller : 0, 
-        funct3 : 0, 
-        shamt : 0,
-
-        imm12_I : 0,
-        imm12_S : 0,
-
-        imm12_I_signed : 0, 
-        imm12_S_signed : 0, 
-        imm13 : 0, 
-        imm13_signed : 0,
-
-        imm31_12 : 0, 
-        imm21_1 : 0,
-
-        imm31_12_signed : 0, 
-        imm21_1_signed : 0,
+        opcode : opcode,
+        rs1 : rs1,
+        rs2 : rs2,
+        rs3 : rs3,
+        rd  : rd,
+        funct7 : funct7,
+        funct7_smaller : funct7_smaller,
+    
+        funct3 : funct3,
+        imm12_I : imm12_I,
+        imm12_S : imm12_S,
+    
+        imm12_I_signed : imm12_I_signed,
+        imm12_S_signed : imm12_S_signed,
+    
+        imm13 : imm13,
+        imm13_signed : imm13_signed,
+    
+        imm31_12 : imm31_12,
+        imm31_12_signed : imm31_12_signed,
+    
+        imm21_1 : imm21_1,
+        imm21_1_signed : imm21_1_signed,
+    
+        shamt : shamt
     }
 }
\ No newline at end of file
diff --git a/src/main.rs b/src/main.rs
index 9c521f7..16cda16 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -2,5 +2,5 @@ mod decode;
 
 fn main() {
     let instr = decode::decode(98);
-    println!("Hello, world!");
+    println!("Hello, world! opcode : {}", instr.opcode);
 }