Calling conventions, value stack, and runtime stack layout.

lib/dynasm-backend/src/codegen.rs

@@ -7,6 +7,7 @@ pub trait ModuleCodeGenerator<FCG: FunctionCodeGenerator> {
 pub trait FunctionCodeGenerator {
     fn feed_param(&mut self, ty: WpType) -> Result<(), CodegenError>;
     fn feed_local(&mut self, ty: WpType, n: usize) -> Result<(), CodegenError>;
+    fn begin_body(&mut self) -> Result<(), CodegenError>;
     fn feed_opcode(&mut self, op: Operator) -> Result<(), CodegenError>;
     fn finalize(&mut self) -> Result<(), CodegenError>;
 }

lib/dynasm-backend/src/codegen_x64.rs

@@ -1,5 +1,6 @@
 use super::codegen::*;
-use dynasmrt::{x64::Assembler, DynasmApi};
+use super::stack::ValueStack;
+use dynasmrt::{x64::Assembler, DynamicLabel, DynasmApi, DynasmLabelApi};
 use wasmparser::{Operator, Type as WpType};
 
 #[derive(Default)]
@@ -8,11 +9,18 @@ pub struct X64ModuleCodeGenerator {
 }
 
 pub struct X64FunctionCode {
+    id: usize,
+    begin_label: DynamicLabel,
+    cleanup_label: DynamicLabel,
     assembler: Option<Assembler>,
     locals: Vec<Local>,
+    num_params: usize,
     current_stack_offset: usize,
+    callee_managed_stack_offset: usize,
+    value_stack: ValueStack,
 }
 
+#[derive(Copy, Clone, Debug)]
 struct Local {
     ty: WpType,
     stack_offset: usize,
@@ -26,20 +34,32 @@ impl X64ModuleCodeGenerator {
 
 impl ModuleCodeGenerator<X64FunctionCode> for X64ModuleCodeGenerator {
     fn next_function(&mut self) -> Result<&mut X64FunctionCode, CodegenError> {
+        let mut assembler = match self.functions.last_mut() {
+            Some(x) => x.assembler.take().unwrap(),
+            None => match Assembler::new() {
+                Ok(x) => x,
+                Err(_) => {
+                    return Err(CodegenError {
+                        message: "cannot initialize assembler",
+                    })
+                }
+            },
+        };
+        let begin_label = assembler.new_dynamic_label();
+        dynasm!(
+            assembler
+            ; => begin_label
+        );
         let code = X64FunctionCode {
-            assembler: Some(match self.functions.last_mut() {
-                Some(x) => x.assembler.take().unwrap(),
-                None => match Assembler::new() {
-                    Ok(x) => x,
-                    Err(_) => {
-                        return Err(CodegenError {
-                            message: "cannot initialize assembler",
-                        })
-                    }
-                },
-            }),
+            id: self.functions.len(),
+            begin_label: begin_label,
+            cleanup_label: assembler.new_dynamic_label(),
+            assembler: Some(assembler),
             locals: vec![],
+            num_params: 0,
             current_stack_offset: 0,
+            callee_managed_stack_offset: 0,
+            value_stack: ValueStack::new(13),
         };
         self.functions.push(code);
         Ok(self.functions.last_mut().unwrap())
@@ -49,41 +69,98 @@ impl ModuleCodeGenerator<X64FunctionCode> for X64ModuleCodeGenerator {
 impl FunctionCodeGenerator for X64FunctionCode {
     fn feed_param(&mut self, ty: WpType) -> Result<(), CodegenError> {
         let size = get_size_of_type(&ty)?;
-        self.current_stack_offset -= size;
+        self.current_stack_offset += size;
         self.locals.push(Local {
             ty: ty,
             stack_offset: self.current_stack_offset,
         });
-        // TODO: load parameter values onto stack...
+        self.num_params += 1;
         Ok(())
     }
     fn feed_local(&mut self, ty: WpType, n: usize) -> Result<(), CodegenError> {
         let size = get_size_of_type(&ty)?;
-        let assembler = self.assembler.as_mut().unwrap();
-
-        dynasm!(
-            assembler
-            ; xor rax, rax
-        );
-
         for _ in 0..n {
             // FIXME: check range of n
-            self.current_stack_offset -= size;
+            self.current_stack_offset += size;
+            self.callee_managed_stack_offset += size;
             self.locals.push(Local {
                 ty: ty,
                 stack_offset: self.current_stack_offset,
             });
-            dynasm!(
-                assembler
-                ; mov [rsp - (self.current_stack_offset as i32)], rax
-            );
         }
         Ok(())
     }
+    fn begin_body(&mut self) -> Result<(), CodegenError> {
+        let assembler = self.assembler.as_mut().unwrap();
+        dynasm!(
+            assembler
+            ; mov rax, rsp
+            ; sub rsp, self.callee_managed_stack_offset as i32
+            ; xor rcx, rcx
+        );
+
+        for local in &self.locals[self.num_params..] {
+            let size = get_size_of_type(&local.ty)?;
+            dynasm!(
+                assembler
+                ; sub rax, size as i32
+            );
+            if size == 4 {
+                dynasm!(
+                    assembler
+                    ; mov [rax], ecx
+                );
+            } else if size == 8 {
+                dynasm!(
+                    assembler
+                    ; mov [rax], rcx
+                );
+            } else {
+                return Err(CodegenError {
+                    message: "unsupported size for type",
+                });
+            }
+        }
+        dynasm!(
+            assembler
+            ; push rbp
+            ; mov rbp, rsp
+        );
+        Ok(())
+    }
     fn feed_opcode(&mut self, op: Operator) -> Result<(), CodegenError> {
+        let assembler = self.assembler.as_mut().unwrap();
+        match op {
+            Operator::GetLocal { local_index } => {
+                let local_index = local_index as usize;
+                if local_index >= self.locals.len() {
+                    return Err(CodegenError {
+                        message: "local out of bounds",
+                    });
+                }
+                let local = self.locals[local_index];
+                dynasm!(
+                    assembler
+                    ; mov rax, rbp
+                    ; add rax, (self.current_stack_offset - local.stack_offset) as i32
+                    // TODO: How should we dynamically specify a register?
+                );
+            }
+            _ => unimplemented!(),
+        }
         Ok(())
     }
     fn finalize(&mut self) -> Result<(), CodegenError> {
+        let assembler = self.assembler.as_mut().unwrap();
+        dynasm!(
+            assembler
+            ; ud2
+            ; => self.cleanup_label
+            ; mov rsp, rbp
+            ; pop rbp
+            ; add rsp, self.current_stack_offset as i32
+            ; ret
+        );
         Ok(())
     }
 }

lib/dynasm-backend/src/lib.rs

@@ -9,3 +9,4 @@ extern crate dynasm;
 mod codegen;
 mod codegen_x64;
 mod parse;
+mod stack;

lib/dynasm-backend/src/parse.rs

@@ -281,6 +281,7 @@ pub fn read_module<MCG: ModuleCodeGenerator<FCG>, FCG: FunctionCodeGenerator>(
                         let (count, ty) = local?;
                         fcg.feed_local(ty, count as usize)?;
                     }
+                    fcg.begin_body()?;
                     for op in item.get_operators_reader()? {
                         let op = op?;
                         fcg.feed_opcode(op)?;

lib/dynasm-backend/src/stack.rs

@@ -0,0 +1,109 @@
+use dynasmrt::DynamicLabel;
+use wasmparser::Type as WpType;
+
+/*#[repr(u8)]
+#[derive(Copy, Clone, Debug)]
+pub enum RegisterName {
+    RDI,
+    RSI,
+    RDX,
+    RCX,
+    R8,
+    R9,
+    R10,
+    R11,
+    RBX,
+    R12,
+    R13,
+    R14,
+    R15,
+    Invalid,
+}*/
+
+#[derive(Debug)]
+pub struct ControlFrame {
+    pub label: DynamicLabel,
+    pub loop_like: bool,
+    pub returns: Vec<WpType>,
+    pub value_stack_depth_before: usize,
+}
+
+#[derive(Debug)]
+pub struct ControlStack {
+    pub frames: Vec<ControlFrame>,
+}
+
+#[derive(Debug)]
+pub struct ValueStack {
+    pub num_regs: u8,
+    pub values: Vec<ValueInfo>,
+}
+
+#[derive(Copy, Clone, Debug)]
+pub struct ValueInfo {
+    pub ty: WpType,
+    pub location: ValueLocation,
+}
+
+#[derive(Copy, Clone, Debug)]
+pub enum ValueLocation {
+    Register(u8),
+    Stack,
+}
+
+impl ValueStack {
+    pub fn new(num_regs: u8) -> ValueStack {
+        ValueStack {
+            num_regs: num_regs,
+            values: vec![],
+        }
+    }
+
+    fn next_location(&self, loc: &ValueLocation) -> ValueLocation {
+        match *loc {
+            ValueLocation::Register(x) => {
+                if x >= self.num_regs - 1 {
+                    ValueLocation::Stack
+                } else {
+                    ValueLocation::Register(x + 1)
+                }
+            }
+            ValueLocation::Stack => ValueLocation::Stack,
+        }
+    }
+
+    pub fn push(&mut self, ty: WpType) -> ValueLocation {
+        let loc = self
+            .values
+            .last()
+            .map(|x| self.next_location(&x.location))
+            .unwrap_or(ValueLocation::Register(0));
+        self.values.push(ValueInfo {
+            ty: ty,
+            location: loc,
+        });
+        loc
+    }
+
+    pub fn pop(&mut self) -> Option<ValueInfo> {
+        self.values.pop()
+    }
+
+    pub fn pop2(&mut self) -> Option<(ValueInfo, ValueInfo)> {
+        if self.values.len() < 2 {
+            None
+        } else {
+            let v2 = self.values.pop().unwrap();
+            let v1 = self.values.pop().unwrap();
+            Some((v1, v2))
+        }
+    }
+
+    pub fn peek(&self) -> Option<ValueInfo> {
+        self.values.last().cloned()
+    }
+
+    pub fn reset_depth(&mut self, target_depth: usize) {
+        self.values.truncate(target_depth);
+    }
+}