common: add decoding tests, 52/52 passing :)

src/common/instructions/args.rs

@@ -32,7 +32,7 @@ impl std::fmt::Display for ArgsDecodeError {
 
 impl std::error::Error for ArgsDecodeError {}
 
-#[derive(Debug, Clone, Copy)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
 /// Used by instructions with 2 registers and an immediate argument.
 pub struct ITypeArgs {
     pub immediate: u16,
@@ -69,16 +69,19 @@ impl TryFrom<u32> for ITypeArgs {
     type Error = ArgsDecodeError;
 
     fn try_from(data: u32) -> Result<Self, Self::Error> {
-        let r1 = ((data >> 21) as u8).try_into()?;
-        let r2 = ((data >> 16) as u8).try_into()?;
+        let r1 = ((data >> 21) & 0x1F) as u8;
+        let r2 = ((data >> 16) & 0x1F) as u8;
         let immediate = data as u16;
 
+        let r1 = r1.try_into()?;
+        let r2 = r2.try_into()?;
+
         Ok(Self { immediate, r1, r2 })
     }
 }
 
 /// Used by instructions not using immediates (besides 5 bit shift values).
-#[derive(Debug, Clone, Copy)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub struct RTypeArgs {
     pub sr1: Register,
     pub sr2: Register,
@@ -132,10 +135,10 @@ impl TryFrom<u32> for RTypeArgs {
     type Error = ArgsDecodeError;
 
     fn try_from(data: u32) -> Result<Self, Self::Error> {
-        let sr1 = (data >> 21) as u8;
-        let sr2 = (data >> 16) as u8;
-        let dr = (data >> 11) as u8;
-        let shamt = (data >> 6) as u8;
+        let sr1 = ((data >> 21) & 0x1F) as u8;
+        let sr2 = ((data >> 16) & 0x1F) as u8;
+        let dr = ((data >> 11) & 0x1F) as u8;
+        let shamt = ((data >> 6) & 0x1F) as u8;
 
         let sr1_reg = sr1.try_into()?;
         let sr2_reg = sr2.try_into()?;