Bug 989759 part 2 - Dispatch base on the instruction identifier. r=jandem

js/src/jit/IonFrameIterator.h

@@ -244,6 +244,8 @@ class IonFrameIterator
 class IonJSFrameLayout;
 class IonBailoutIterator;
 
+class RResumePoint;
+
 // Reads frame information in snapshot-encoding order (that is, outermost frame
 // to innermost frame).
 class SnapshotIterator
@@ -291,8 +293,9 @@ class SnapshotIterator
         return UndefinedValue();
     }
 
-    const RResumePoint *resumePoint() const {
-        return recover_.resumePoint();
+    const RResumePoint *resumePoint() const;
+    const RInstruction *instruction() const {
+        return recover_.instruction();
     }
 
     uint32_t numAllocations() const;

js/src/jit/IonFrames.cpp

@@ -1499,6 +1499,12 @@ SnapshotIterator::allocationValue(const RValueAllocation &alloc)
     }
 }
 
+const RResumePoint *
+SnapshotIterator::resumePoint() const
+{
+    return instruction()->toResumePoint();
+}
+
 uint32_t
 SnapshotIterator::numAllocations() const
 {

js/src/jit/Recover.cpp

@@ -13,10 +13,24 @@
 using namespace js;
 using namespace js::jit;
 
+void
+RInstruction::readRecoverData(CompactBufferReader &reader, RInstructionStorage *raw)
+{
+    uint32_t op = reader.readUnsigned();
+    switch (Opcode(op)) {
+      case Recover_ResumePoint:
+        new (raw->addr()) RResumePoint(reader);
+        break;
+      default:
+        MOZ_ASSUME_UNREACHABLE("Bad decoding of the previous instruction?");
+        break;
+    }
+}
+
 bool
 MResumePoint::writeRecoverData(CompactBufferWriter &writer) const
 {
-    writer.writeUnsigned(uint32_t(Recover_ResumePoint));
+    writer.writeUnsigned(uint32_t(RInstruction::Recover_ResumePoint));
 
     MBasicBlock *bb = block();
     JSFunction *fun = bb->info().funMaybeLazy();
@@ -94,11 +108,3 @@ RResumePoint::RResumePoint(CompactBufferReader &reader)
     IonSpew(IonSpew_Snapshots, "Read RResumePoint (pc offset %u, nslots %u)",
             pcOffset_, numOperands_);
 }
-
-void
-RResumePoint::readRecoverData(CompactBufferReader &reader, RInstructionStorage *raw)
-{
-    mozilla::DebugOnly<uint32_t> op = reader.readUnsigned();
-    MOZ_ASSERT(op == uint32_t(Recover_ResumePoint));
-    new (raw->addr()) RResumePoint(reader);
-}

js/src/jit/Recover.h

@@ -7,35 +7,64 @@
 #ifndef jit_Recover_h
 #define jit_Recover_h
 
+#include "mozilla/Attributes.h"
+
 #include "jit/Snapshots.h"
 
 namespace js {
 namespace jit {
 
-enum RecoverOpcode
+class RResumePoint;
+
+class RInstruction
 {
-    Recover_ResumePoint = 0
+  public:
+    enum Opcode
+    {
+        Recover_ResumePoint = 0
+    };
+
+    virtual Opcode opcode() const = 0;
+
+    bool isResumePoint() const {
+        return opcode() == Recover_ResumePoint;
+    }
+    inline const RResumePoint *toResumePoint() const;
+
+    virtual uint32_t numOperands() const = 0;
+
+    static void readRecoverData(CompactBufferReader &reader, RInstructionStorage *raw);
 };
 
-class RResumePoint
+class RResumePoint MOZ_FINAL : public RInstruction
 {
   private:
     uint32_t pcOffset_;           // Offset from script->code.
     uint32_t numOperands_;        // Number of slots.
 
+    friend RInstruction;
     RResumePoint(CompactBufferReader &reader);
 
   public:
-    static void readRecoverData(CompactBufferReader &reader, RInstructionStorage *raw);
+    virtual Opcode opcode() const {
+        return Recover_ResumePoint;
+    }
 
     uint32_t pcOffset() const {
         return pcOffset_;
     }
-    uint32_t numOperands() const {
+    virtual uint32_t numOperands() const {
         return numOperands_;
     }
 };
 
+const RResumePoint *
+RInstruction::toResumePoint() const
+{
+    MOZ_ASSERT(isResumePoint());
+    return static_cast<const RResumePoint *>(this);
+}
+
 }
 }
 

js/src/jit/Snapshots.cpp

@@ -580,7 +580,7 @@ void
 RecoverReader::readFrame()
 {
     JS_ASSERT(moreFrames());
-    RResumePoint::readRecoverData(reader_, &rawData_);
+    RInstruction::readRecoverData(reader_, &rawData_);
     framesRead_++;
 }
 

js/src/jit/Snapshots.h

@@ -441,8 +441,8 @@ class SnapshotReader
     }
 };
 
-typedef mozilla::AlignedStorage<2 * sizeof(uint32_t)> RInstructionStorage;
-class RResumePoint;
+typedef mozilla::AlignedStorage<4 * sizeof(uint32_t)> RInstructionStorage;
+class RInstruction;
 
 class RecoverReader
 {
@@ -473,8 +473,8 @@ class RecoverReader
         return frameCount_;
     }
 
-    const RResumePoint *resumePoint() const {
-        return reinterpret_cast<const RResumePoint *>(rawData_.addr());
+    const RInstruction *instruction() const {
+        return reinterpret_cast<const RInstruction *>(rawData_.addr());
     }
 
     bool resumeAfter() const {