Change the instruction encoding for the bytecode

Change the encoding, so that even instructions are short ones,
odd instructions long. This implies that the lowest bit encodes
whether an instruction is short or long (1 vs 4 byte encoded).

This prepares for allowing us to extend the totoal number of
instructions beyond 128.

Change-Id: I4732e7241d3593b24ad25cd69555edc25f38d2f6
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

1 files changed, 10 insertions, 11 deletions

diff --git a/src/qml/compiler/qv4bytecodegenerator.cpp b/src/qml/compiler/qv4bytecodegenerator.cpp
index 1d1e98ea58..6efeac2a31 100644
--- a/src/qml/compiler/qv4bytecodegenerator.cpp
+++ b/src/qml/compiler/qv4bytecodegenerator.cpp
@@ -70,10 +70,9 @@ int BytecodeGenerator::newRegisterArray(int n)
 
 void BytecodeGenerator::packInstruction(I &i)
 {
-    uchar type = *reinterpret_cast<uchar *>(i.packed);
-    Q_ASSERT(type >= MOTH_NUM_INSTRUCTIONS());
-    if (type >= MOTH_NUM_INSTRUCTIONS())
-        type -= MOTH_NUM_INSTRUCTIONS();
+    Instr::Type type = Instr::unpack(i.packed);
+    Q_ASSERT(int(type) < MOTH_NUM_INSTRUCTIONS());
+    type = Instr::narrowInstructionType(type);
     int instructionsAsInts[sizeof(Instr)/sizeof(int)] = {};
     int nMembers = Moth::InstrInfo::argumentCount[static_cast<int>(i.type)];
     for (int j = 0; j < nMembers; ++j) {
@@ -89,10 +88,10 @@ void BytecodeGenerator::packInstruction(I &i)
             break;
         }
     }
-    char *code = i.packed;
+    uchar *code = i.packed;
     switch (width) {
     case Normal:
-        *reinterpret_cast<uchar *>(code) = type;
+        Instr::pack(code, type);
         ++code;
         for (int n = 0; n < nMembers; ++n) {
             qint8 v = static_cast<qint8>(instructionsAsInts[n]);
@@ -122,7 +121,7 @@ void BytecodeGenerator::adjustJumpOffsets()
 //        qDebug() << "adjusting jump offset for instruction" << index << i.position << i.size << "offsetForJump" << i.offsetForJump << "target"
 //                 << labels.at(i.linkedLabel) << linkedInstruction.position << "jumpOffset" << jumpOffset;
         uchar type = *reinterpret_cast<const uchar *>(i.packed);
-        if (type >= MOTH_NUM_INSTRUCTIONS()) {
+        if (Instr::isWide(Instr::Type(type))) {
             Q_ASSERT(i.offsetForJump == i.size - 4);
             qToLittleEndian<qint32>(jumpOffset, c);
         } else {
@@ -177,7 +176,7 @@ void BytecodeGenerator::finalize(Compiler::Context *context)
             entry.line = currentLine;
             lineNumbers.append(entry);
         }
-        code.append(i.packed, i.size);
+        code.append(reinterpret_cast<const char *>(i.packed), i.size);
     }
 
     context->code = code;
@@ -228,10 +227,10 @@ QT_WARNING_POP
     if (offsetOfOffset != -1)
         offsetOfOffset += 1;
     I instr{type, static_cast<short>(s + 1), 0, currentLine, offsetOfOffset, -1, "\0\0" };
-    char *code = instr.packed;
-    *reinterpret_cast<uchar *>(code) = static_cast<uchar>(MOTH_NUM_INSTRUCTIONS() + static_cast<int>(type));
+    uchar *code = instr.packed;
+    Instr::pack(code, Instr::wideInstructionType(type));
     ++code;
-    Q_ASSERT(MOTH_NUM_INSTRUCTIONS() + static_cast<int>(type) < 256);
+    Q_ASSERT(static_cast<uint>(Instr::wideInstructionType(type)) < 256);
 
     for (int j = 0; j < argCount; ++j) {
         qToLittleEndian<qint32>(i.argumentsAsInts[j], code);