Zihintpause

README.md

@@ -7,6 +7,10 @@ A small RISC-V emulator written in Rust.
 - [x] Base RV32I instruction set
 - [x] M standard extension
 - [ ] A standard extension
+    - [ ] Zalrsc standard extension
+    - [ ] Zaamo standard extension
 - [ ] F standard extension
 - [ ] D standard extension
 - [ ] C standard extension
+
+- [x] Zihintpause standard extension

src/emu.rs

@@ -105,10 +105,12 @@ impl IndexMut<Reg> for Emulator {
     }
 }
 
-#[derive(Clone, Copy)]
+#[derive(Clone, Copy, PartialEq, Eq)]
 pub struct Reg(pub u32);
 
 impl Reg {
+    pub const ZERO: Reg = Reg(0);
+
     pub const RA: Reg = Reg(1);
     pub const SP: Reg = Reg(2);
     // arguments, return values:

src/inst.rs

@@ -81,6 +81,27 @@ pub struct FenceSet {
     pub memory_write: bool,
 }
 
+impl Fence {
+    pub fn is_pause(&self) -> bool {
+        self.pred
+            == FenceSet {
+                device_input: false,
+                device_output: false,
+                memory_read: false,
+                memory_write: true,
+            }
+            && self.succ
+                == FenceSet {
+                    device_input: false,
+                    device_output: false,
+                    memory_read: false,
+                    memory_write: false,
+                }
+            && self.dest == Reg::ZERO
+            && self.src == Reg::ZERO
+    }
+}
+
 impl Debug for Inst {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         Display::fmt(&self, f)
@@ -184,22 +205,7 @@ impl Display for Inst {
             Inst::And { dest, src1, src2 } => write!(f, "and {dest}, {src1}, {src2}"),
             Inst::Fence { fence } => match fence.fm {
                 0b1000 => write!(f, "fence.TSO"),
-                0b0000
+                0b0000 if fence.is_pause() => {
-                    if fence.pred
-                        == FenceSet {
-                            device_input: false,
-                            device_output: false,
-                            memory_read: false,
-                            memory_write: true,
-                        }
-                        && fence.succ
-                            == FenceSet {
-                                device_input: false,
-                                device_output: false,
-                                memory_read: false,
-                                memory_write: false,
-                            } =>
-                {
                     write!(f, "pause")
                 }
                 _ => write!(f, "fence {},{}", fence.pred, fence.succ),