From 13ac0c234e114241515f0d937060fb8283cf7e31 Mon Sep 17 00:00:00 2001
From: MerryMage <MerryMage@users.noreply.github.com>
Date: Fri, 24 Feb 2017 20:19:50 +0000
Subject: [PATCH] reg_alloc: Differentiate between ReadLock and WriteLock

---
 src/backend_x64/reg_alloc.cpp | 16 ++++++----------
 src/backend_x64/reg_alloc.h   | 10 +++++++++-
 2 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/src/backend_x64/reg_alloc.cpp b/src/backend_x64/reg_alloc.cpp
index efb31e46..6f9a1f6d 100644
--- a/src/backend_x64/reg_alloc.cpp
+++ b/src/backend_x64/reg_alloc.cpp
@@ -124,7 +124,7 @@ HostLoc RegAlloc::UseHostLocReg(IR::Inst* use_inst, HostLocList desired_location
 
     const bool can_use_current_location = std::find(desired_locations.begin(), desired_locations.end(), current_location) != desired_locations.end();
     if (can_use_current_location) {
-        LocInfo(current_location).Lock();
+        LocInfo(current_location).ReadLock();
         return current_location;
     }
 
@@ -139,7 +139,7 @@ HostLoc RegAlloc::UseHostLocReg(IR::Inst* use_inst, HostLocList desired_location
         MoveOutOfTheWay(destination_location);
         Move(destination_location, current_location);
     }
-    LocInfo(destination_location).Lock();
+    LocInfo(destination_location).ReadLock();
     return destination_location;
 }
 
@@ -169,21 +169,21 @@ HostLoc RegAlloc::UseScratchHostLocReg(IR::Inst* use_inst, HostLocList desired_l
     const bool can_use_current_location = std::find(desired_locations.begin(), desired_locations.end(), current_location) != desired_locations.end();
     if (can_use_current_location && !LocInfo(current_location).IsLocked()) {
         MoveOutOfTheWay(current_location);
-        LocInfo(current_location).Lock();
+        LocInfo(current_location).WriteLock();
         return current_location;
     }
 
     const HostLoc destination_location = SelectARegister(desired_locations);
     MoveOutOfTheWay(destination_location);
     CopyToScratch(destination_location, current_location);
-    LocInfo(destination_location).Lock();
+    LocInfo(destination_location).WriteLock();
     return destination_location;
 }
 
 HostLoc RegAlloc::ScratchHostLocReg(HostLocList desired_locations) {
     HostLoc location = SelectARegister(desired_locations);
     MoveOutOfTheWay(location);
-    LocInfo(location).Lock();
+    LocInfo(location).WriteLock();
     return location;
 }
 
@@ -261,11 +261,7 @@ void RegAlloc::SpillRegister(HostLoc loc) {
     ASSERT_MSG(!LocInfo(loc).IsLocked(), "Registers that have been allocated must not be spilt");
 
     HostLoc new_loc = FindFreeSpill();
-
-    EmitMove(code, new_loc, loc);
-
-    LocInfo(new_loc) = LocInfo(loc);
-    LocInfo(loc) = {};
+    Move(new_loc, loc);
 }
 
 HostLoc RegAlloc::FindFreeSpill() const {
diff --git a/src/backend_x64/reg_alloc.h b/src/backend_x64/reg_alloc.h
index 360f8a9f..3bbc5a04 100644
--- a/src/backend_x64/reg_alloc.h
+++ b/src/backend_x64/reg_alloc.h
@@ -38,9 +38,15 @@ public:
         return std::find(values.begin(), values.end(), inst) != values.end();
     }
 
-    void Lock() {
+    void ReadLock() {
+        ASSERT(!is_scratch);
         is_being_used = true;
     }
+    void WriteLock() {
+        ASSERT(!is_being_used);
+        is_being_used = true;
+        is_scratch = true;
+    }
     void AddValue(IR::Inst* inst) {
         values.push_back(inst);
     }
@@ -50,11 +56,13 @@ public:
         values.erase(to_erase, values.end());
 
         is_being_used = false;
+        is_scratch = false;
     }
 
 private:
     std::vector<IR::Inst*> values;
     bool is_being_used = false;
+    bool is_scratch = false;
 };
 
 class RegAlloc final {