From fa61b66516165770b7afae378747e2d7c5a9136c Mon Sep 17 00:00:00 2001
From: losfair <zhy20000919@hotmail.com>
Date: Tue, 5 Mar 2019 00:23:49 +0800
Subject: [PATCH] Strongly type scratch registers and fixed an unwinding issue.

---
 lib/dynasm-backend/src/codegen_x64.rs | 10 ++++++----
 lib/dynasm-backend/src/stack.rs       | 19 ++++++++++++++-----
 2 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/lib/dynasm-backend/src/codegen_x64.rs b/lib/dynasm-backend/src/codegen_x64.rs
index 38833a491..610ac9a2f 100644
--- a/lib/dynasm-backend/src/codegen_x64.rs
+++ b/lib/dynasm-backend/src/codegen_x64.rs
@@ -1,5 +1,7 @@
 use super::codegen::*;
-use super::stack::{ControlFrame, ControlStack, IfElseState, ValueInfo, ValueLocation, ValueStack};
+use super::stack::{
+    ControlFrame, ControlStack, IfElseState, ScratchRegister, ValueInfo, ValueLocation, ValueStack,
+};
 use byteorder::{ByteOrder, LittleEndian};
 use dynasmrt::{
     x64::Assembler, AssemblyOffset, DynamicLabel, DynasmApi, DynasmLabelApi, ExecutableBuffer,
@@ -85,9 +87,9 @@ pub enum Register {
 }
 
 impl Register {
-    pub fn from_scratch_reg(id: u8) -> Register {
+    pub fn from_scratch_reg(sr: ScratchRegister) -> Register {
         use self::Register::*;
-        match id {
+        match sr.raw_id() {
             0 => RDI,
             1 => RSI,
             2 => RDX,
@@ -804,7 +806,7 @@ impl X64FunctionCode {
                     let reg = Register::from_scratch_reg(x);
                     dynasm!(
                         assembler
-                        ; mov Rq(x as u8), rax
+                        ; mov Rq(reg as u8), rax
                     );
                 }
                 ValueLocation::Stack => {
diff --git a/lib/dynasm-backend/src/stack.rs b/lib/dynasm-backend/src/stack.rs
index 8e45c6d38..e78eaa0ed 100644
--- a/lib/dynasm-backend/src/stack.rs
+++ b/lib/dynasm-backend/src/stack.rs
@@ -56,10 +56,19 @@ pub struct ValueInfo {
 
 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
 pub enum ValueLocation {
-    Register(u8),
+    Register(ScratchRegister),
     Stack,
 }
 
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+pub struct ScratchRegister(u8);
+
+impl ScratchRegister {
+    pub fn raw_id(&self) -> u8 {
+        self.0
+    }
+}
+
 impl ValueLocation {
     pub fn is_register(&self) -> bool {
         if let ValueLocation::Register(_) = *self {
@@ -69,7 +78,7 @@ impl ValueLocation {
         }
     }
 
-    pub fn get_register(&self) -> Result<u8, CodegenError> {
+    pub fn get_register(&self) -> Result<ScratchRegister, CodegenError> {
         if let ValueLocation::Register(id) = *self {
             Ok(id)
         } else {
@@ -90,11 +99,11 @@ impl ValueStack {
 
     fn next_location(&self, loc: &ValueLocation) -> ValueLocation {
         match *loc {
-            ValueLocation::Register(x) => {
+            ValueLocation::Register(ScratchRegister(x)) => {
                 if x >= self.num_regs - 1 {
                     ValueLocation::Stack
                 } else {
-                    ValueLocation::Register(x + 1)
+                    ValueLocation::Register(ScratchRegister(x + 1))
                 }
             }
             ValueLocation::Stack => ValueLocation::Stack,
@@ -106,7 +115,7 @@ impl ValueStack {
             .values
             .last()
             .map(|x| self.next_location(&x.location))
-            .unwrap_or(ValueLocation::Register(0));
+            .unwrap_or(ValueLocation::Register(ScratchRegister(0)));
         self.values.push(ValueInfo {
             ty: ty,
             location: loc,