[1.8>1.9] Allow naming labels and highlighting instructions

This change is designed to make following some code paths easier when
doing JIT work. The first change is that it adds debug-only code that
puts names on labels, which should help users looking at instructions
that expand to a great number of blocks. The second change is to have
developers be able to set a color for a particular Instr such that in
dumps it stands out better, which may be useful in some situations.

lib/Backend/IR.cpp

@@ -4301,7 +4301,20 @@ Instr::Dump(IRDumpFlags flags)
 
     const auto PrintOpCodeName = [&]() {
         Output::SkipToColumn(23);
+#if DBG
+        WORD oldValue = 0;
+        if (this->highlight != 0)
+        {
+            oldValue = Output::SetConsoleForeground(this->highlight);
+        }
+#endif
         Output::Print(_u("%s "), Js::OpCodeUtil::GetOpCodeName(m_opcode));
+#if DBG
+        if (this->highlight != 0)
+        {
+            Output::SetConsoleForeground(oldValue);
+        }
+#endif
         Output::SkipToColumn(38);
     };
 
@@ -4585,7 +4598,16 @@ LabelInstr::Dump(IRDumpFlags flags)
     {
         this->m_block->DumpHeader();
     }
-    Output::Print(_u("$L%d:"), this->m_id);
+#if DBG
+    if (this->m_name != nullptr)
+    {
+        Output::Print(_u("$L%d (%s):"), this->m_id, this->m_name);
+    }
+    else
+#endif
+    {
+        Output::Print(_u("$L%d:"), this->m_id);
+    }
     if (this->isOpHelper)
     {
         Output::Print(_u(" [helper]"));

lib/Backend/IR.h

@@ -169,6 +169,9 @@ class Instr
         isCallInstrProtectedByNoProfileBailout(false),
         hasSideEffects(false),
         isNonFastPathFrameDisplay(false)
+#if DBG
+        , highlight(0)
+#endif
     {
     }
 public:
@@ -530,6 +533,9 @@ class Instr
     Opnd *          m_dst;
     Opnd *          m_src1;
     Opnd *          m_src2;
+#if DBG
+    WORD            highlight;
+#endif
 
 
 
@@ -664,6 +670,7 @@ class LabelInstr : public Instr
         m_hasNonBranchRef(false), m_region(nullptr), m_loweredBasicBlock(nullptr), m_isDataLabel(false), m_isForInExit(false)
 #if DBG
         , m_noHelperAssert(false)
+        , m_name(nullptr)
 #endif
     {
 #if DBG_DUMP
@@ -692,6 +699,9 @@ class LabelInstr : public Instr
 #endif
     unsigned int            m_id;
     LoweredBasicBlock*      m_loweredBasicBlock;
+#if DBG
+    const char16*           m_name;
+#endif
 private:
     union labelLocation
     {
@@ -732,7 +742,15 @@ class LabelInstr : public Instr
 
 protected:
     void                    Init(Js::OpCode opcode, IRKind kind, Func *func, bool isOpHelper);
- };
+};
+
+#if DBG
+#define LABELNAMESET(label, name) do { label->m_name = _u(name); } while(false)
+#define LABELNAME(label) do { label->m_name = _u(#label); } while(false)
+#else
+#define LABELNAMESET(label, name)
+#define LABELNAME(label)
+#endif
 
 class ProfiledLabelInstr: public LabelInstr
 {