Make generated code loading constants relocatable

On 32-bit architectures we were encoding the absolute address of generated
constants in memory into the load instruction. In order to make the code
reloctable, this patch changes the JIT over to use the constant table in the
compilation unit. This means two additional loads per constant. On
architectures that support instruction pointer relative addressing, we can try
to fix this in the future (arm32 for example).

Change-Id: I8ed7aa7c67711696d6c46c72b3b642d610ff2cbc
Reviewed-by: Erik Verbruggen <erik.verbruggen@qt.io>

5 files changed, 16 insertions, 3 deletions

diff --git a/src/qml/jsruntime/qv4context.cpp b/src/qml/jsruntime/qv4context.cpp
index 97b3e26a26..60717c9491 100644
--- a/src/qml/jsruntime/qv4context.cpp
+++ b/src/qml/jsruntime/qv4context.cpp
@@ -73,6 +73,7 @@ Heap::CallContext *ExecutionContext::newCallContext(const FunctionObject *functi
 
     c->compilationUnit = function->function()->compilationUnit;
     c->lookups = c->compilationUnit->runtimeLookups;
+    c->constantTable = c->compilationUnit->data->constants();
     c->locals = (Value *)((quintptr(c + 1) + 7) & ~7);
 
     const CompiledData::Function *compiledFunction = function->function()->compiledFunction;
@@ -172,6 +173,7 @@ Heap::WithContext::WithContext(ExecutionContext *outerContext, Object *with)
     outer = outerContext;
     callData = outer->callData;
     lookups = outer->lookups;
+    constantTable = outer->constantTable;
     compilationUnit = outer->compilationUnit;
 
     withObject = with;
@@ -184,6 +186,7 @@ Heap::CatchContext::CatchContext(ExecutionContext *outerContext, String *excepti
     strictMode = outer->strictMode;
     callData = outer->callData;
     lookups = outer->lookups;
+    constantTable = outer->constantTable;
     compilationUnit = outer->compilationUnit;
 
     this->exceptionVarName = exceptionVarName;
@@ -197,6 +200,7 @@ Heap::QmlContext::QmlContext(QV4::ExecutionContext *outerContext, QV4::QmlContex
     strictMode = false;
     callData = outer->callData;
     lookups = outer->lookups;
+    constantTable = outer->constantTable;
     compilationUnit = outer->compilationUnit;
 
     this->qml = qml->d();
diff --git a/src/qml/jsruntime/qv4context_p.h b/src/qml/jsruntime/qv4context_p.h
index 2e6773a927..368605ca4a 100644
--- a/src/qml/jsruntime/qv4context_p.h
+++ b/src/qml/jsruntime/qv4context_p.h
@@ -108,6 +108,7 @@ struct ExecutionContext : Base {
     ExecutionEngine *engine;
     Pointer<ExecutionContext> outer;
     Lookup *lookups;
+    const QV4::Value *constantTable;
     CompiledData::CompilationUnit *compilationUnit;
 
     ContextType type : 8;
@@ -118,9 +119,10 @@ struct ExecutionContext : Base {
 inline
 ExecutionContext::ExecutionContext(ExecutionEngine *engine, ContextType t)
     : engine(engine)
-    , outer(0)
-    , lookups(0)
-    , compilationUnit(0)
+    , outer(nullptr)
+    , lookups(nullptr)
+    , constantTable(nullptr)
+    , compilationUnit(nullptr)
     , type(t)
     , strictMode(false)
     , lineNumber(-1)
diff --git a/src/qml/jsruntime/qv4functionobject.cpp b/src/qml/jsruntime/qv4functionobject.cpp
index 6b9c552350..805087e389 100644
--- a/src/qml/jsruntime/qv4functionobject.cpp
+++ b/src/qml/jsruntime/qv4functionobject.cpp
@@ -535,6 +535,7 @@ void SimpleScriptFunction::construct(const Managed *that, Scope &scope, CallData
     ctx.function = f->d();
     ctx.compilationUnit = f->function()->compilationUnit;
     ctx.lookups = ctx.compilationUnit->runtimeLookups;
+    ctx.constantTable = ctx.compilationUnit->data->constants();
     ctx.outer = f->scope();
     ctx.locals = scope.alloc(f->varCount());
     for (int i = callData->argc; i < (int)f->formalParameterCount(); ++i)
@@ -572,6 +573,7 @@ void SimpleScriptFunction::call(const Managed *that, Scope &scope, CallData *cal
     ctx.function = f->d();
     ctx.compilationUnit = f->function()->compilationUnit;
     ctx.lookups = ctx.compilationUnit->runtimeLookups;
+    ctx.constantTable = ctx.compilationUnit->data->constants();
     ctx.outer = f->scope();
     ctx.locals = scope.alloc(f->varCount());
     for (int i = callData->argc; i < (int)f->formalParameterCount(); ++i)
diff --git a/src/qml/jsruntime/qv4script.cpp b/src/qml/jsruntime/qv4script.cpp
index a2e379ec1a..46adaf7e79 100644
--- a/src/qml/jsruntime/qv4script.cpp
+++ b/src/qml/jsruntime/qv4script.cpp
@@ -222,6 +222,7 @@ ReturnedValue Script::run()
         ContextStateSaver stateSaver(valueScope, scope);
         scope->d()->strictMode = vmFunction->isStrict();
         scope->d()->lookups = vmFunction->compilationUnit->runtimeLookups;
+        scope->d()->constantTable = vmFunction->compilationUnit->data->constants();
         scope->d()->compilationUnit = vmFunction->compilationUnit;
 
         return Q_V4_PROFILE(engine, vmFunction);
diff --git a/src/qml/jsruntime/qv4script_p.h b/src/qml/jsruntime/qv4script_p.h
index e81bc3049c..2e87a7692b 100644
--- a/src/qml/jsruntime/qv4script_p.h
+++ b/src/qml/jsruntime/qv4script_p.h
@@ -71,6 +71,7 @@ struct ContextStateSaver {
     Value *savedContext;
     bool strictMode;
     Lookup *lookups;
+    const QV4::Value *constantTable;
     CompiledData::CompilationUnit *compilationUnit;
     int lineNumber;
 
@@ -78,6 +79,7 @@ struct ContextStateSaver {
         : savedContext(scope.alloc(1))
         , strictMode(context->d()->strictMode)
         , lookups(context->d()->lookups)
+        , constantTable(context->d()->constantTable)
         , compilationUnit(context->d()->compilationUnit)
         , lineNumber(context->d()->lineNumber)
     {
@@ -87,6 +89,7 @@ struct ContextStateSaver {
         : savedContext(scope.alloc(1))
         , strictMode(context->strictMode)
         , lookups(context->lookups)
+        , constantTable(context->constantTable)
         , compilationUnit(context->compilationUnit)
         , lineNumber(context->lineNumber)
     {
@@ -98,6 +101,7 @@ struct ContextStateSaver {
         Heap::ExecutionContext *ctx = static_cast<Heap::ExecutionContext *>(savedContext->m());
         ctx->strictMode = strictMode;
         ctx->lookups = lookups;
+        ctx->constantTable = constantTable;
         ctx->compilationUnit = compilationUnit;
         ctx->lineNumber = lineNumber;
     }