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>

1 files changed, 4 insertions, 21 deletions

diff --git a/src/qml/jit/qv4assembler_p.h b/src/qml/jit/qv4assembler_p.h
index 669b0b2ff4..d76a21c74c 100644
--- a/src/qml/jit/qv4assembler_p.h
+++ b/src/qml/jit/qv4assembler_p.h
@@ -89,7 +89,6 @@ struct CompilationUnit : public QV4::CompiledData::CompilationUnit
     // Coderef + execution engine
 
     QVector<JSC::MacroAssemblerCodeRef> codeRefs;
-    QList<QVector<QV4::Primitive> > constantValues;
 };
 
 struct LookupCall {
@@ -297,22 +296,6 @@ public:
         int savedRegCount;
     };
 
-    class ConstantTable
-    {
-    public:
-        ConstantTable(Assembler *as): _as(as) {}
-
-        int add(const QV4::Primitive &v);
-        Address loadValueAddress(IR::Const *c, RegisterID baseReg);
-        Address loadValueAddress(const QV4::Primitive &v, RegisterID baseReg);
-        void finalize(JSC::LinkBuffer &linkBuffer, InstructionSelection *isel);
-
-    private:
-        Assembler *_as;
-        QVector<QV4::Primitive> _values;
-        QVector<DataLabelPtr> _toPatch;
-    };
-
     struct VoidType { VoidType() {} };
     static const VoidType Void;
 
@@ -382,6 +365,8 @@ public:
     Pointer loadTempAddress(IR::Temp *t);
     Pointer loadArgLocalAddress(RegisterID baseReg, IR::ArgLocal *al);
     Pointer loadStringAddress(RegisterID reg, const QString &string);
+    Address loadConstant(IR::Const *c, RegisterID baseReg);
+    Address loadConstant(const Primitive &v, RegisterID baseReg);
     void loadStringRef(RegisterID reg, const QString &string);
     Pointer stackSlotPointer(IR::Temp *t) const
     {
@@ -1029,7 +1014,7 @@ public:
             move(TrustedImm64(i), ReturnValueRegister);
             move64ToDouble(ReturnValueRegister, target);
 #else
-            JSC::MacroAssembler::loadDouble(constantTable().loadValueAddress(c, ScratchRegister), target);
+            JSC::MacroAssembler::loadDouble(loadConstant(c, ScratchRegister), target);
 #endif
             return target;
         }
@@ -1093,7 +1078,7 @@ public:
 
         // it's not in signed int range, so load it as a double, and truncate it down
         loadDouble(addr, FPGpr0);
-        Address inversionAddress = constantTable().loadValueAddress(QV4::Primitive::fromDouble(double(INT_MAX) + 1), scratchReg);
+        Address inversionAddress = loadConstant(QV4::Primitive::fromDouble(double(INT_MAX) + 1), scratchReg);
         subDouble(inversionAddress, FPGpr0);
         Jump canNeverHappen = branchTruncateDoubleToUint32(FPGpr0, scratchReg);
         canNeverHappen.link(this);
@@ -1111,14 +1096,12 @@ public:
 
     void setStackLayout(int maxArgCountForBuiltins, int regularRegistersToSave, int fpRegistersToSave);
     const StackLayout &stackLayout() const { return *_stackLayout.data(); }
-    ConstantTable &constantTable() { return _constTable; }
 
     Label exceptionReturnLabel;
     IR::BasicBlock * catchBlock;
     QVector<Jump> exceptionPropagationJumps;
 private:
     QScopedPointer<const StackLayout> _stackLayout;
-    ConstantTable _constTable;
     IR::Function *_function;
     QHash<IR::BasicBlock *, Label> _addrs;
     QHash<IR::BasicBlock *, QVector<Jump> > _patches;