Add decode functions for immediate shifts (funct6 and imm_shamt), make decode functions not use references, add inline hints to decode functions

src/decode.rs

@@ -11,46 +11,57 @@ const MASK_REGISTER: Word = 0x1f;
 #[derive(Debug, Clone, Copy)]
 pub struct Instruction(pub Word);
 
+#[allow(dead_code)]
 impl Instruction {
-    pub fn opcode(&self) -> u8 {
+    #[inline]
+    pub fn opcode(self) -> u8 {
         (self.0 & 0x7f) as u8
     }
 
     /// Returns the opcode of the instruction, with the last 2 bits stripped away, as they are always 0b11 in a non-compressed instruction
-    pub fn opcode_noncompressed(&self) -> u8 {
+    #[inline]
+    pub fn opcode_noncompressed(self) -> u8 {
         debug_assert_eq!(self.0 & 0b11, 0b11, "Compressed (or invalid) opcode");
         (self.0 >> 2 & 0x1f) as u8
     }
 
-    pub fn rd(&self) -> RegId {
+    #[inline]
+    pub fn rd(self) -> RegId {
         (self.0 >> 7 & MASK_REGISTER) as RegId
     }
 
-    pub fn funct3(&self) -> u8 {
+    #[inline]
+    pub fn funct3(self) -> u8 {
         (self.0 >> 12 & 0x7) as u8
     }
 
-    pub fn rs1(&self) -> RegId {
+    #[inline]
+    pub fn rs1(self) -> RegId {
         (self.0 >> 15 & MASK_REGISTER) as RegId
     }
 
-    pub fn rs2(&self) -> RegId {
+    #[inline]
+    pub fn rs2(self) -> RegId {
         (self.0 >> 20 & MASK_REGISTER) as RegId
     }
 
-    pub fn funct7(&self) -> u8 {
+    #[inline]
+    pub fn funct7(self) -> u8 {
         (self.0 >> 25 & 0x7f) as u8
     }
 
-    pub fn imm_i(&self) -> DWord {
+    #[inline]
+    pub fn imm_i(self) -> DWord {
         (self.0 as i64 >> 20) as DWord
     }
 
-    pub fn imm_s(&self) -> DWord {
+    #[inline]
+    pub fn imm_s(self) -> DWord {
         (self.0 as i64 >> (25 - 5) & (0x7f << 5)) as DWord | (self.0 >> 7 & 0b1111) as DWord
     }
 
-    pub fn imm_b(&self) -> DWord {
+    #[inline]
+    pub fn imm_b(self) -> DWord {
         let imm_12 = ((self.0 & 0x8000_0000) as i32 as i64 >> (31 - 12)) as DWord;
         let imm_10_5 = ((self.0 >> 25 & 0x3f) << 5) as DWord;
         let imm_4_1 = ((self.0 >> 8 & 0xf) << 1) as DWord;
@@ -59,11 +70,13 @@ impl Instruction {
         imm_12 | imm_10_5 | imm_4_1 | imm_11
     }
 
-    pub fn imm_u(&self) -> DWord {
+    #[inline]
+    pub fn imm_u(self) -> DWord {
         (self.0 & 0xffff_f000) as i32 as i64 as DWord
     }
 
-    pub fn imm_j(&self) -> DWord {
+    #[inline]
+    pub fn imm_j(self) -> DWord {
         let imm_20 = ((self.0 & 0x8000_0000) as i32 as i64 >> (31 - 20)) as DWord;
         let imm_10_1 = ((self.0 >> 21 & 0x3ff) << 1) as DWord;
         let imm_11 = ((self.0 >> 20 & 1) << 11) as DWord;
@@ -71,4 +84,16 @@ impl Instruction {
 
         imm_20 | imm_10_1 | imm_11 | imm_19_12
     }
+
+    // The following are AFAIK only used for shift by immediate operations
+
+    #[inline]
+    fn funct6(self) -> u8 {
+        (self.0 >> 26 & 0x3f) as u8
+    }
+
+    #[inline]
+    fn imm_shamt(self) -> usize {
+        (self.0 >> 20 & 0x3f) as usize
+    }
 }