Improve machine state abstraction.

lib/dynasm-backend/src/machine.rs

@@ -2,44 +2,38 @@ use crate::emitter_x64::*;
 use std::collections::HashSet;
 use wasmparser::Type as WpType;
 
-pub struct Machine<E: Emitter> {
+struct MachineStackOffset(usize);
+
+pub struct Machine {
     used_gprs: HashSet<GPR>,
     used_xmms: HashSet<XMM>,
-    control: Vec<ControlFrame<E>>,
-    stack_offset: usize,
+    stack_offset: MachineStackOffset
 }
 
-#[derive(Debug)]
-pub struct ControlFrame<E: Emitter> {
-    pub label: E::Label,
-    pub loop_like: bool,
-    pub returns: Vec<WpType>,
-    pub stack_offset_snapshot: usize,
-}
+impl Machine {
+    pub fn new() -> Self {
+        Machine {
+            used_gprs: HashSet::new(),
+            used_xmms: HashSet::new(),
+            stack_offset: MachineStackOffset(0),
+        }
+    }
 
-impl<E: Emitter> Machine<E> {
-    /// Picks an unused general purpose register.
+    /// Picks an unused general purpose register for local/stack/argument use.
     /// 
     /// This method does not mark the register as used.
     pub fn pick_gpr(&self) -> Option<GPR> {
         use GPR::*;
         static REGS: &'static [GPR] = &[
-            //RAX,
             RCX,
             RDX,
             RBX,
-            RSP,
-            RBP,
             RSI,
             RDI,
             R8,
             R9,
             R10,
             R11,
-            //R12,
-            //R13,
-            //R14,
-            //R15
         ];
         for r in REGS {
             if !self.used_gprs.contains(r) {
@@ -49,15 +43,46 @@ impl<E: Emitter> Machine<E> {
         None
     }
 
+    /// Picks an unused general purpose register for internal temporary use.
+    /// 
+    /// This method does not mark the register as used.
+    pub fn pick_temp_gpr(&self) -> Option<GPR> {
+        use GPR::*;
+        static REGS: &'static [GPR] = &[
+            RAX,
+            R12,
+            R13,
+            R14,
+            R15
+        ];
+        for r in REGS {
+            if !self.used_gprs.contains(r) {
+                return Some(*r)
+            }
+        }
+        None
+    }
+
+    /// Acquires a temporary GPR.
+    pub fn acquire_temp_gpr(&mut self) -> Option<GPR> {
+        let gpr = self.pick_temp_gpr();
+        if let Some(x) = gpr {
+            self.used_gprs.insert(x);
+        }
+        gpr
+    }
+
+    /// Releases a temporary GPR.
+    pub fn release_temp_gpr(&mut self, gpr: GPR) {
+        assert_eq!(self.used_gprs.remove(&gpr), true);
+    }
+
     /// Picks an unused XMM register.
     /// 
     /// This method does not mark the register as used.
     pub fn pick_xmm(&self) -> Option<XMM> {
         use XMM::*;
         static REGS: &'static [XMM] = &[
-            //XMM0,
-            //XMM1,
-            //XMM2,
             XMM3,
             XMM4,
             XMM5,
@@ -72,14 +97,47 @@ impl<E: Emitter> Machine<E> {
         None
     }
 
+    /// Picks an unused XMM register for internal temporary use.
+    /// 
+    /// This method does not mark the register as used.
+    pub fn pick_temp_xmm(&self) -> Option<XMM> {
+        use XMM::*;
+        static REGS: &'static [XMM] = &[
+            XMM0,
+            XMM1,
+            XMM2,
+        ];
+        for r in REGS {
+            if !self.used_xmms.contains(r) {
+                return Some(*r)
+            }
+        }
+        None
+    }
+
+    /// Acquires a temporary XMM register.
+    pub fn acquire_temp_xmm(&mut self) -> Option<XMM> {
+        let xmm = self.pick_temp_xmm();
+        if let Some(x) = xmm {
+            self.used_xmms.insert(x);
+        }
+        xmm
+    }
+
+    /// Releases a temporary XMM register.
+    pub fn release_temp_xmm(&mut self, xmm: XMM) {
+        assert_eq!(self.used_xmms.remove(&xmm), true);
+    }
+
     /// Acquires locations from the machine state.
     /// 
     /// If the returned locations are used for stack value, `release_location` needs to be called on them;
     /// Otherwise, if the returned locations are used for locals, `release_location` does not need to be called on them.
-    pub fn acquire_locations(
+    pub fn acquire_locations<E: Emitter>(
         &mut self,
         assembler: &mut E,
         tys: &[WpType],
+        zeroed: bool,
     ) -> Vec<Location> {
         let mut ret = vec![];
         let mut delta_stack_offset: usize = 0;
@@ -100,9 +158,9 @@ impl<E: Emitter> Machine<E> {
             let loc = if let Some(x) = loc {
                 x
             } else {
-                self.stack_offset += 8;
+                self.stack_offset.0 += 8;
                 delta_stack_offset += 8;
-                Location::Memory(GPR::RBP, -(self.stack_offset as i32))
+                Location::Memory(GPR::RBP, -(self.stack_offset.0 as i32))
             };
             if let Location::GPR(x) = loc {
                 self.used_gprs.insert(x);
@@ -113,11 +171,16 @@ impl<E: Emitter> Machine<E> {
         }
 
         assembler.emit_sub(Size::S64, Location::Imm32(delta_stack_offset as u32), Location::GPR(GPR::RSP));
+        if zeroed {
+            for i in 0..tys.len() {
+                assembler.emit_mov(Size::S64, Location::Imm32(0), Location::Memory(GPR::RSP, (i * 8) as i32));
+            }
+        }
         ret
     }
 
     /// Releases locations used for stack value.
-    pub fn release_locations(
+    pub fn release_locations<E: Emitter>(
         &mut self,
         assembler: &mut E,
         locs: &[Location]
@@ -137,10 +200,10 @@ impl<E: Emitter> Machine<E> {
                         unreachable!();
                     }
                     let offset = (-x) as usize;
-                    if offset != self.stack_offset {
+                    if offset != self.stack_offset.0 {
                         unreachable!();
                     }
-                    self.stack_offset -= 8;
+                    self.stack_offset.0 -= 8;
                     delta_stack_offset += 8;
                 },
                 _ => {}