Speed up exception propagation

Avoid catch (...) with re-throw as it turns that this is very slow because it
throws a new exception and the unwinder starts from scratch. Instead use stack
allocated objects and cleaning destructors to restore state before continuing
with the propagation of exceptions.

Change-Id: I6d95026bcd60b58cb6258a9dae28623a46739532
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

1 files changed, 25 insertions, 21 deletions

diff --git a/src/qml/jsruntime/qv4globalobject.cpp b/src/qml/jsruntime/qv4globalobject.cpp
index 3b1e0b1bae..4dcdb08415 100644
--- a/src/qml/jsruntime/qv4globalobject.cpp
+++ b/src/qml/jsruntime/qv4globalobject.cpp
@@ -355,6 +355,27 @@ EvalFunction::EvalFunction(ExecutionContext *scope)
 
 ReturnedValue EvalFunction::evalCall(CallData *callData, bool directCall)
 {
+    struct ContextStateSaver {
+        ExecutionContext *savedContext;
+        bool strictMode;
+        ExecutionContext::EvalCode *evalCode;
+        CompiledData::CompilationUnit *compilationUnit;
+
+        ContextStateSaver(ExecutionContext *context)
+            : savedContext(context)
+            , strictMode(context->strictMode)
+            , evalCode(context->currentEvalCode)
+            , compilationUnit(context->compilationUnit)
+        {}
+
+        ~ContextStateSaver()
+        {
+            savedContext->strictMode = strictMode;
+            savedContext->currentEvalCode = evalCode;
+            savedContext->compilationUnit = compilationUnit;
+        }
+    };
+
     if (callData->argc < 1)
         return Encode::undefined();
 
@@ -395,36 +416,19 @@ ReturnedValue EvalFunction::evalCall(CallData *callData, bool directCall)
         return e->call(callData);
     }
 
+    ExecutionContextSaver ctxSaver(parentContext);
+    ContextStateSaver stateSaver(ctx);
+
     ExecutionContext::EvalCode evalCode;
     evalCode.function = function;
     evalCode.next = ctx->currentEvalCode;
     ctx->currentEvalCode = &evalCode;
 
     // set the correct strict mode flag on the context
-    bool cstrict = ctx->strictMode;
     ctx->strictMode = strictMode;
-
-    CompiledData::CompilationUnit * const oldCompilationUnit = ctx->compilationUnit;
     ctx->compilationUnit = function->compilationUnit;
 
-    ScopedValue result(scope);
-    try {
-        result = function->code(ctx, function->codeData);
-    } catch (...) {
-        ctx->strictMode = cstrict;
-        ctx->currentEvalCode = evalCode.next;
-        ctx->compilationUnit = oldCompilationUnit;
-        ctx->rethrowException();
-    }
-
-    ctx->strictMode = cstrict;
-    ctx->currentEvalCode = evalCode.next;
-    ctx->compilationUnit = oldCompilationUnit;
-
-    while (engine->current != parentContext)
-        engine->popContext();
-
-    return result.asReturnedValue();
+    return function->code(ctx, function->codeData);
 }