Simplify Push and PopContext instructions

There's no need for a temp register to store the old context in,
as PopContext can simply retrieve the old context from
the current one.

Change-Id: Ife9cfdff7fa8e47fc71e844a7798de88dbc79e26
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

4 files changed, 22 insertions, 23 deletions

diff --git a/src/qml/jit/qv4assembler.cpp b/src/qml/jit/qv4assembler.cpp
index 736dfd0908..45dc87db19 100644
--- a/src/qml/jit/qv4assembler.cpp
+++ b/src/qml/jit/qv4assembler.cpp
@@ -2241,9 +2241,8 @@ void Assembler::clearExceptionHandler()
     pasm()->storePtr(TrustedImmPtr(nullptr), pasm()->exceptionHandlerAddress());
 }
 
-void Assembler::pushCatchContext(int reg, int index, int name)
+void Assembler::pushCatchContext(int index, int name)
 {
-    pasm()->copyReg(pasm()->contextAddress(), regAddr(reg));
     prepareCallWithArgCount(3);
     passInt32AsArg(name, 2);
     passInt32AsArg(index, 1);
@@ -2252,9 +2251,13 @@ void Assembler::pushCatchContext(int reg, int index, int name)
     pasm()->storeAccumulator(pasm()->contextAddress());
 }
 
-void Assembler::popContext(int reg)
+void Assembler::popContext()
 {
-    pasm()->copyReg(regAddr(reg), pasm()->contextAddress());
+    Heap::CallContext ctx;
+    Q_UNUSED(ctx)
+    pasm()->loadPointerFromValue(regAddr(CallData::Context), PlatformAssembler::ScratchRegister);
+    pasm()->loadAccumulator(Address(PlatformAssembler::ScratchRegister, ctx.outer.offset));
+    pasm()->storeAccumulator(regAddr(CallData::Context));
 }
 
 void Assembler::ret()
diff --git a/src/qml/jit/qv4assembler_p.h b/src/qml/jit/qv4assembler_p.h
index 99ae48e5ed..a1596e1640 100644
--- a/src/qml/jit/qv4assembler_p.h
+++ b/src/qml/jit/qv4assembler_p.h
@@ -164,8 +164,8 @@ public:
     void setException();
     void setExceptionHandler(int offset);
     void clearExceptionHandler();
-    void pushCatchContext(int reg, int index, int name);
-    void popContext(int reg);
+    void pushCatchContext(int index, int name);
+    void popContext();
 
     // other stuff
     void ret();
diff --git a/src/qml/jit/qv4jit.cpp b/src/qml/jit/qv4jit.cpp
index 15ece7e903..2bc60bff70 100644
--- a/src/qml/jit/qv4jit.cpp
+++ b/src/qml/jit/qv4jit.cpp
@@ -617,44 +617,40 @@ void BaselineJIT::generate_CreateCallContext()
     as->storeHeapObject(CallData::Context);
 }
 
-void BaselineJIT::generate_PushCatchContext(int reg, int index, int name) { as->pushCatchContext(reg, index, name); }
+void BaselineJIT::generate_PushCatchContext(int index, int name) { as->pushCatchContext(index, name); }
 
-static void pushWithContextHelper(ExecutionEngine *engine, QV4::Value *stack, int reg)
+static void pushWithContextHelper(ExecutionEngine *engine, QV4::Value *stack)
 {
     QV4::Value &accumulator = stack[CallData::Accumulator];
     accumulator = accumulator.toObject(engine);
     if (engine->hasException)
         return;
-    stack[reg] = stack[CallData::Context];
     ExecutionContext *c = static_cast<ExecutionContext *>(stack + CallData::Context);
     stack[CallData::Context] = Runtime::method_createWithContext(c, accumulator);
 }
 
-void BaselineJIT::generate_PushWithContext(int reg)
+void BaselineJIT::generate_PushWithContext()
 {
     STORE_IP();
     as->saveAccumulatorInFrame();
-    as->prepareCallWithArgCount(3);
-    as->passInt32AsArg(reg, 2);
+    as->prepareCallWithArgCount(2);
     as->passRegAsArg(0, 1);
     as->passEngineAsArg(0);
     JIT_GENERATE_RUNTIME_CALL(pushWithContextHelper, Assembler::IgnoreResult);
     as->checkException();
 }
 
-static void pushBlockContextHelper(QV4::Value *stack, int reg, int index)
+static void pushBlockContextHelper(QV4::Value *stack, int index)
 {
-    stack[reg] = stack[CallData::Context];
     ExecutionContext *c = static_cast<ExecutionContext *>(stack + CallData::Context);
     stack[CallData::Context] = Runtime::method_createBlockContext(c, index);
 }
 
-void BaselineJIT::generate_PushBlockContext(int reg, int index)
+void BaselineJIT::generate_PushBlockContext(int index)
 {
     as->saveAccumulatorInFrame();
-    as->prepareCallWithArgCount(3);
-    as->passInt32AsArg(index, 2);
-    as->passInt32AsArg(reg, 1);
+    as->prepareCallWithArgCount(2);
+    as->passInt32AsArg(index, 1);
     as->passRegAsArg(0, 0);
     JIT_GENERATE_RUNTIME_CALL(pushBlockContextHelper, Assembler::IgnoreResult);
 }
@@ -701,7 +697,7 @@ void BaselineJIT::generate_PopScriptContext()
     JIT_GENERATE_RUNTIME_CALL(popScriptContextHelper, Assembler::IgnoreResult);
 }
 
-void BaselineJIT::generate_PopContext(int reg) { as->popContext(reg); }
+void BaselineJIT::generate_PopContext() { as->popContext(); }
 
 void BaselineJIT::generate_GetIterator(int iterator)
 {
diff --git a/src/qml/jit/qv4jit_p.h b/src/qml/jit/qv4jit_p.h
index d48041d954..8aa0cb430e 100644
--- a/src/qml/jit/qv4jit_p.h
+++ b/src/qml/jit/qv4jit_p.h
@@ -178,13 +178,13 @@ public:
     void generate_GetException() override;
     void generate_SetException() override;
     void generate_CreateCallContext() override;
-    void generate_PushCatchContext(int reg, int index, int name) override;
-    void generate_PushWithContext(int reg) override;
-    void generate_PushBlockContext(int reg, int index) override;
+    void generate_PushCatchContext(int index, int name) override;
+    void generate_PushWithContext() override;
+    void generate_PushBlockContext(int index) override;
     void generate_CloneBlockContext() override;
     void generate_PushScriptContext(int index) override;
     void generate_PopScriptContext() override;
-    void generate_PopContext(int reg) override;
+    void generate_PopContext() override;
     void generate_GetIterator(int iterator) override;
     void generate_IteratorNext(int value) override;
     void generate_IteratorClose(int done) override;