Add instructions to simplify for-of loops

Added an IteratorNext instruction to fetch the next
iteration value (empty if the iterator is done).

This will also help to implement array destructuring without
requiring huge amounts of byte code.

Change-Id: If96c1e81471e5e2b0b7b2af122238d87741aa371
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

1 files changed, 19 insertions, 0 deletions

diff --git a/src/qml/jit/qv4assembler.cpp b/src/qml/jit/qv4assembler.cpp
index c73b3919ae..736dfd0908 100644
--- a/src/qml/jit/qv4assembler.cpp
+++ b/src/qml/jit/qv4assembler.cpp
@@ -707,6 +707,12 @@ struct PlatformAssembler64 : PlatformAssemblerCommon
         patches.push_back({ jump, offset });
     }
 
+    void jumpEmpty(int offset)
+    {
+        auto jump = branch64(Equal, AccumulatorRegister, TrustedImm64(Primitive::emptyValue().asReturnedValue()));
+        patches.push_back({ jump, offset });
+    }
+
     void toBoolean(std::function<void(RegisterID)> continuation)
     {
         urshift64(AccumulatorRegister, TrustedImm32(Value::IsIntegerConvertible_Shift), ScratchRegister);
@@ -1150,6 +1156,14 @@ struct PlatformAssembler32 : PlatformAssemblerCommon
         patches.push_back({ jump, offset });
     }
 
+    void jumpEmpty(int offset)
+    {
+        auto notEqual = branch32(NotEqual, AccumulatorRegisterTag, TrustedImm32(Primitive::emptyValue().asReturnedValue() >> 32));
+        auto jump = branch32(Equal, AccumulatorRegisterValue, TrustedImm32(Primitive::emptyValue().asReturnedValue() & 0xffffffff));
+        notEqual.link(this);
+        patches.push_back({ jump, offset });
+    }
+
     void toBoolean(std::function<void(RegisterID)> continuation)
     {
         urshift32(AccumulatorRegisterTag, TrustedImm32(Value::IsIntegerConvertible_Shift - 32),
@@ -2001,6 +2015,11 @@ void Assembler::jumpNotUndefined(int offset)
     pasm()->jumpNotUndefined(offset);
 }
 
+void JIT::Assembler::jumpEmpty(int offset)
+{
+    pasm()->jumpEmpty(offset);
+}
+
 void Assembler::jumpStrictEqualStackSlotInt(int lhs, int rhs, int offset)
 {
     pasm()->jumpStrictEqualStackSlotInt(lhs, rhs, offset);