Implement GcInfo v2 for X86

This commit includes the following changes:
1) Thread GcInfo version through X86 specific APIs
2) Add ReturnKind and ReversePinvokeOffset fields to InfoHdr structure
   GcInfo v1 and v2 use the same InfoHdr structures, because:
   InfoHdrSmall: ReturnKind is encoded within previously unused bits.
   InfoHdr: revPInvokeOffset will never be written to the image,
            since ReversePinvokeOffset==INVALID_REV_PINVOKE_OFFSET for V1.
3) Update the Pre-computed header table to include bits for the above
   [The default setting of ReturnKind=RT_Scalar is used for all entries in the table.
    Optimizing this table based in most frequent usage scenarios is to be done separately]
4) Change the GC encoder/decoder to handle the above two fields
5) Use the ReturnKind in the GCInfo from thread-suspension code.

GcInfo version is changed for CoreCLR X86 only, not for Desktop JIT
Fixes #4379

10 files changed, 151 insertions, 119 deletions

diff --git a/src/vm/codeman.h b/src/vm/codeman.h
index f143dd642c..3b383cf3f4 100644
--- a/src/vm/codeman.h
+++ b/src/vm/codeman.h
@@ -1801,7 +1801,7 @@ public:
     ULONG       GetFixedStackSize()
     {
         WRAPPER_NO_CONTRACT;
-        return GetCodeManager()->GetFrameSize(GetGCInfo());
+        return GetCodeManager()->GetFrameSize(GetGCInfoToken());
     }
 #endif // WIN64EXCEPTIONS
 
diff --git a/src/vm/debughelp.cpp b/src/vm/debughelp.cpp
index df769455aa..9db0ce5197 100644
--- a/src/vm/debughelp.cpp
+++ b/src/vm/debughelp.cpp
@@ -1198,12 +1198,12 @@ void DumpGCInfo(MethodDesc* method)
     _ASSERTE(codeInfo.GetRelOffset() == 0);
 
     ICodeManager* codeMan = codeInfo.GetCodeManager();
-    GCInfoToken table = codeInfo.GetGCInfoToken();
+    GCInfoToken gcInfoToken = codeInfo.GetGCInfoToken();
 
-    unsigned methodSize = (unsigned)codeMan->GetFunctionSize(table);
+    unsigned methodSize = (unsigned)codeMan->GetFunctionSize(gcInfoToken);
 
-    GCDump gcDump(table.Version);
-    PTR_CBYTE gcInfo = PTR_CBYTE(table.Info);
+    GCDump gcDump(gcInfoToken.Version);
+    PTR_CBYTE gcInfo = PTR_CBYTE(gcInfoToken.Info);
 
     gcDump.gcPrintf = printfToDbgOut;
 
diff --git a/src/vm/eedbginterfaceimpl.cpp b/src/vm/eedbginterfaceimpl.cpp
index 93decc9b0d..ff63d846e7 100644
--- a/src/vm/eedbginterfaceimpl.cpp
+++ b/src/vm/eedbginterfaceimpl.cpp
@@ -501,9 +501,9 @@ BOOL EEDbgInterfaceImpl::IsInPrologOrEpilog(const BYTE *address,
 
     if (codeInfo.IsValid())
     {
-        LPVOID methodInfo = codeInfo.GetGCInfo();
+        GCInfoToken gcInfoToken = codeInfo.GetGCInfoToken();
 
-        if (codeInfo.GetCodeManager()->IsInPrologOrEpilog(codeInfo.GetRelOffset(), methodInfo, prologSize))
+        if (codeInfo.GetCodeManager()->IsInPrologOrEpilog(codeInfo.GetRelOffset(), gcInfoToken, prologSize))
         {
             return TRUE;
         }
diff --git a/src/vm/eetwain.cpp b/src/vm/eetwain.cpp
index 032bda7c96..2ce7b59578 100644
--- a/src/vm/eetwain.cpp
+++ b/src/vm/eetwain.cpp
@@ -142,13 +142,15 @@ __forceinline int decodeSigned(PTR_CBYTE& src)
 
 /*****************************************************************************
  *
- *  Decodes the methodInfoPtr and returns the decoded information
- *  in the hdrInfo struct.  The EIP parameter is the PC location
- *  within the active method.
+ *  Decodes the X86 GcInfo header and returns the decoded information
+ *  in the hdrInfo struct. 
+ *  curOffset is the code offset within the active method used in the 
+ *  computation of PrologOffs/EpilogOffs.
+ *  Returns the size of the header (number of bytes decoded).
  */
-static size_t   crackMethodInfoHdr(PTR_VOID    methodInfoPtr,
-                                   unsigned    curOffset,
-                                   hdrInfo   * infoPtr)
+static size_t   DecodeGCHdrInfo(GCInfoToken gcInfoToken,
+                                unsigned    curOffset,
+                                hdrInfo   * infoPtr)
 {
     CONTRACTL {
         NOTHROW;
@@ -157,7 +159,7 @@ static size_t   crackMethodInfoHdr(PTR_VOID    methodInfoPtr,
         SUPPORTS_DAC;
     } CONTRACTL_END;
 
-    PTR_CBYTE table = PTR_CBYTE(methodInfoPtr);
+    PTR_CBYTE table = (PTR_CBYTE) gcInfoToken.Info;
 #if VERIFY_GC_TABLES
     _ASSERTE(*castto(table, unsigned short *)++ == 0xFEEF);
 #endif
@@ -170,7 +172,7 @@ static size_t   crackMethodInfoHdr(PTR_VOID    methodInfoPtr,
     /* Decode the InfoHdr */
 
     InfoHdr header;
-    table = decodeHeader(table, &header);
+    table = decodeHeader(table, gcInfoToken.Version, &header);
 
     BOOL hasArgTabOffset = FALSE;
     if (header.untrackedCnt == HAS_UNTRACKED)
@@ -199,6 +201,10 @@ static size_t   crackMethodInfoHdr(PTR_VOID    methodInfoPtr,
         _ASSERTE(header.syncStartOffset < header.syncEndOffset);
     }
 
+    if (header.revPInvokeOffset == HAS_REV_PINVOKE_FRAME_OFFSET)
+    {
+        header.revPInvokeOffset = fastDecodeUnsigned(table);
+    }
 
     /* Some sanity checks on header */
 
@@ -220,6 +226,7 @@ static size_t   crackMethodInfoHdr(PTR_VOID    methodInfoPtr,
     infoPtr->argSize         = header.argCount * 4;
     infoPtr->ebpFrame        = header.ebpFrame;
     infoPtr->interruptible   = header.interruptible;
+    infoPtr->returnKind      = (ReturnKind) header.returnKind;
 
     infoPtr->prologSize      = header.prologSize;
     infoPtr->epilogSize      = header.epilogSize;
@@ -232,6 +239,7 @@ static size_t   crackMethodInfoHdr(PTR_VOID    methodInfoPtr,
 
     infoPtr->syncStartOffset = header.syncStartOffset;
     infoPtr->syncEndOffset   = header.syncEndOffset;
+    infoPtr->revPInvokeOffset = header.revPInvokeOffset;
 
     infoPtr->doubleAlign     = header.doubleAlign;
     infoPtr->securityCheck   = header.security;
@@ -352,7 +360,7 @@ static size_t   crackMethodInfoHdr(PTR_VOID    methodInfoPtr,
              (infoPtr->gsCookieOffset < infoPtr->stackSize) &&
              ((header.gsCookieOffset % sizeof(void*)) == 0));
     
-    return  table - PTR_CBYTE(methodInfoPtr);
+    return  table - PTR_CBYTE(gcInfoToken.Info);
 }
 
 /*****************************************************************************/
@@ -715,7 +723,7 @@ void EECodeManager::FixContext( ContextType     ctxType,
 
     /* Extract the necessary information from the info block header */
 
-    stateBuf->hdrInfoSize = (DWORD)crackMethodInfoHdr(pCodeInfo->GetGCInfo(),
+    stateBuf->hdrInfoSize = (DWORD)DecodeGCHdrInfo(pCodeInfo->GetGCInfoToken(),
                                        dwRelOffset,
                                        &stateBuf->hdrInfoBody);
     pState->dwIsSet = 1;
@@ -836,11 +844,11 @@ HRESULT EECodeManager::FixContextForEnC(PCONTEXT         pCtx,
 
     hdrInfo  oldInfo, newInfo;
 
-    crackMethodInfoHdr(pOldCodeInfo->GetGCInfo(),
+    DecodeGCHdrInfo(pOldCodeInfo->GetGCInfoToken(),
                        pOldCodeInfo->GetRelOffset(),
                        &oldInfo);
 
-    crackMethodInfoHdr(pNewCodeInfo->GetGCInfo(),
+    DecodeGCHdrInfo(pNewCodeInfo->GetGCInfoToken(),
                        pNewCodeInfo->GetRelOffset(),
                        &newInfo);
 
@@ -1545,7 +1553,7 @@ bool EECodeManager::IsGcSafe( EECodeInfo     *pCodeInfo,
 
     /* Extract the necessary information from the info block header */
 
-    table = (BYTE *)crackMethodInfoHdr(pCodeInfo->GetGCInfo(),
+    table = (BYTE *)DecodeGCHdrInfo(pCodeInfo->GetGCInfoToken(),
                                        dwRelOffset,
                                        &info);
 
@@ -3905,8 +3913,9 @@ bool EECodeManager::UnwindStackFrame(PREGDISPLAY     pContext,
 
     PTR_CBYTE methodStart = PTR_CBYTE(pCodeInfo->GetSavedMethodCode());
 
-    PTR_VOID       methodInfoPtr = pCodeInfo->GetGCInfo();
-    DWORD          curOffs = pCodeInfo->GetRelOffset();
+    GCInfoToken gcInfoToken = pCodeInfo->GetGCInfoToken();
+    PTR_VOID    methodInfoPtr = gcInfoToken.Info;
+    DWORD       curOffs = pCodeInfo->GetRelOffset();
 
     _ASSERTE(sizeof(CodeManStateBuf) <= sizeof(pState->stateBuf));
     CodeManStateBuf * stateBuf = (CodeManStateBuf*)pState->stateBuf;
@@ -3915,7 +3924,7 @@ bool EECodeManager::UnwindStackFrame(PREGDISPLAY     pContext,
     {
         /* Extract the necessary information from the info block header */
 
-        stateBuf->hdrInfoSize = (DWORD)crackMethodInfoHdr(methodInfoPtr,
+        stateBuf->hdrInfoSize = (DWORD)DecodeGCHdrInfo(gcInfoToken,
                                                           curOffs,
                                                           &stateBuf->hdrInfoBody);
     }
@@ -4097,7 +4106,7 @@ bool EECodeManager::EnumGcRefs( PREGDISPLAY     pContext,
         GC_NOTRIGGER;
     } CONTRACTL_END;
 
-    PTR_VOID  methodInfoPtr = pCodeInfo->GetGCInfo();
+    GCInfoToken gcInfoToken = pCodeInfo->GetGCInfoToken();
     unsigned  curOffs = pCodeInfo->GetRelOffset();
 
     unsigned  EBP     = *pContext->pEbp;
@@ -4108,7 +4117,7 @@ bool EECodeManager::EnumGcRefs( PREGDISPLAY     pContext,
     unsigned  count;
 
     hdrInfo   info;
-    PTR_CBYTE table = PTR_CBYTE(methodInfoPtr);
+    PTR_CBYTE table = PTR_CBYTE(gcInfoToken.Info);
 #if 0
     printf("EECodeManager::EnumGcRefs - EIP = %08x ESP = %08x  offset = %x  GC Info is at %08x\n", *pContext->pPC, ESP, curOffs, table);
 #endif
@@ -4116,14 +4125,14 @@ bool EECodeManager::EnumGcRefs( PREGDISPLAY     pContext,
 
     /* Extract the necessary information from the info block header */
 
-    table += crackMethodInfoHdr(methodInfoPtr,
-                                curOffs,
-                                &info);
+    table += DecodeGCHdrInfo(gcInfoToken,
+                             curOffs,
+                             &info);
 
     _ASSERTE( curOffs <= info.methodSize);
 
 #ifdef  _DEBUG
-//    if ((methodInfoPtr == (void*)0x37760d0) && (curOffs == 0x264))
+//    if ((gcInfoToken.Info == (void*)0x37760d0) && (curOffs == 0x264))
 //        __asm int 3;
 
     if (trEnumGCRefs) {
@@ -4220,11 +4229,11 @@ bool EECodeManager::EnumGcRefs( PREGDISPLAY     pContext,
 
             /* Extract the necessary information from the info block header */
 
-            table = PTR_CBYTE(methodInfoPtr);
+            table = PTR_CBYTE(gcInfoToken.Info);
 
-            table += crackMethodInfoHdr(methodInfoPtr,
-                                        curOffs,
-                                        &info);
+            table += DecodeGCHdrInfo(gcInfoToken,
+                                     curOffs,
+                                     &info);
         }
     }
 
@@ -5030,9 +5039,9 @@ OBJECTREF* EECodeManager::GetAddrOfSecurityObject(CrawlFrame *pCF)
     CodeManStateBuf * stateBuf = (CodeManStateBuf*)pState->stateBuf;
 
     /* Extract the necessary information from the info block header */
-    stateBuf->hdrInfoSize = (DWORD)crackMethodInfoHdr(gcInfoToken.Info, // <TODO>truncation</TODO>
-                                                      relOffset,
-                                                      &stateBuf->hdrInfoBody);
+    stateBuf->hdrInfoSize = (DWORD)DecodeGCHdrInfo(gcInfoToken, // <TODO>truncation</TODO>
+                                                   relOffset,
+                                                   &stateBuf->hdrInfoBody);
 
     pState->dwIsSet = 1;
     if  (stateBuf->hdrInfoBody.securityCheck)
@@ -5109,10 +5118,10 @@ OBJECTREF EECodeManager::GetInstance( PREGDISPLAY    pContext,
     } CONTRACTL_END;
 
 #ifdef _TARGET_X86_
-    PTR_VOID       methodInfoPtr = pCodeInfo->GetGCInfo();
-    unsigned       relOffset = pCodeInfo->GetRelOffset();
+    GCInfoToken gcInfoToken = pCodeInfo->GetGCInfoToken();
+    unsigned    relOffset = pCodeInfo->GetRelOffset();
 
-    PTR_CBYTE    table = PTR_CBYTE(methodInfoPtr);
+    PTR_CBYTE   table = PTR_CBYTE(gcInfoToken.Info);
     hdrInfo     info;
     unsigned    stackDepth;
     TADDR       taArgBase;
@@ -5120,9 +5129,9 @@ OBJECTREF EECodeManager::GetInstance( PREGDISPLAY    pContext,
 
     /* Extract the necessary information from the info block header */
 
-    table += crackMethodInfoHdr(methodInfoPtr,
-                                relOffset,
-                                &info);
+    table += DecodeGCHdrInfo(gcInfoToken,
+                             relOffset,
+                             &info);
 
     // We do not have accurate information in the prolog or the epilog
     if (info.prologOffs != hdrInfo::NOT_IN_PROLOG ||
@@ -5236,14 +5245,15 @@ GenericParamContextType EECodeManager::GetParamContextType(PREGDISPLAY     pCont
 
 #ifdef _TARGET_X86_
     /* Extract the necessary information from the info block header */
-    PTR_VOID       methodInfoPtr = pCodeInfo->GetGCInfo();
-    unsigned       relOffset = pCodeInfo->GetRelOffset();
+    GCInfoToken gcInfoToken = pCodeInfo->GetGCInfoToken();
+    PTR_VOID    methodInfoPtr = pCodeInfo->GetGCInfo();
+    unsigned    relOffset = pCodeInfo->GetRelOffset();
 
     hdrInfo     info;
-    PTR_CBYTE    table = PTR_CBYTE(methodInfoPtr);
-    table += crackMethodInfoHdr(methodInfoPtr,
-                                relOffset,
-                                &info);
+    PTR_CBYTE   table = PTR_CBYTE(gcInfoToken.Info);
+    table += DecodeGCHdrInfo(gcInfoToken,
+                             relOffset,
+                             &info);
 
     if (!info.genericsContext || 
         info.prologOffs != hdrInfo::NOT_IN_PROLOG || 
@@ -5300,15 +5310,16 @@ PTR_VOID EECodeManager::GetParamTypeArg(PREGDISPLAY     pContext,
     LIMITED_METHOD_DAC_CONTRACT;
 
 #ifdef _TARGET_X86_
-    PTR_VOID       methodInfoPtr = pCodeInfo->GetGCInfo();
-    unsigned       relOffset = pCodeInfo->GetRelOffset();
+    GCInfoToken gcInfoToken = pCodeInfo->GetGCInfoToken();
+    PTR_VOID    methodInfoPtr = pCodeInfo->GetGCInfo();
+    unsigned    relOffset = pCodeInfo->GetRelOffset();
 
     /* Extract the necessary information from the info block header */
     hdrInfo     info;
-    PTR_CBYTE    table = PTR_CBYTE(methodInfoPtr);
-    table += crackMethodInfoHdr(methodInfoPtr,
-                                relOffset,
-                                &info);
+    PTR_CBYTE   table = PTR_CBYTE(gcInfoToken.Info);
+    table += DecodeGCHdrInfo(gcInfoToken,
+                             relOffset,
+                             &info);
 
     if (!info.genericsContext || 
         info.prologOffs != hdrInfo::NOT_IN_PROLOG || 
@@ -5424,9 +5435,9 @@ void * EECodeManager::GetGSCookieAddr(PREGDISPLAY     pContext,
     
     /* Extract the necessary information from the info block header */
     hdrInfo * info = &stateBuf->hdrInfoBody;
-    stateBuf->hdrInfoSize = (DWORD)crackMethodInfoHdr(gcInfoToken.Info, // <TODO>truncation</TODO>
-                                                      relOffset,
-                                                      info);
+    stateBuf->hdrInfoSize = (DWORD)DecodeGCHdrInfo(gcInfoToken, // <TODO>truncation</TODO>
+                                                   relOffset,
+                                                   info);
 
     pState->dwIsSet = 1;
     
@@ -5482,9 +5493,9 @@ void * EECodeManager::GetGSCookieAddr(PREGDISPLAY     pContext,
  *
  *  Returns true if the given IP is in the given method's prolog or epilog.
  */
-bool EECodeManager::IsInPrologOrEpilog(DWORD        relPCoffset,
-                                       PTR_VOID     methodInfoPtr,
-                                       size_t*      prologSize)
+bool EECodeManager::IsInPrologOrEpilog(DWORD       relPCoffset,
+                                       GCInfoToken gcInfoToken,
+                                       size_t*     prologSize)
 {
     CONTRACTL {
         NOTHROW;
@@ -5494,7 +5505,7 @@ bool EECodeManager::IsInPrologOrEpilog(DWORD        relPCoffset,
 #ifndef USE_GC_INFO_DECODER
     hdrInfo info;
 
-    crackMethodInfoHdr(methodInfoPtr, relPCoffset, &info);
+    DecodeGCHdrInfo(gcInfoToken, relPCoffset, &info);
 
     if (prologSize)
         *prologSize = info.prologSize;
@@ -5511,10 +5522,9 @@ bool EECodeManager::IsInPrologOrEpilog(DWORD        relPCoffset,
  *
  *  Returns true if the given IP is in the synchronized region of the method (valid for synchronized functions only)
 */
-bool  EECodeManager::IsInSynchronizedRegion(
-                DWORD           relOffset,
-                PTR_VOID        methodInfoPtr,
-                unsigned        flags)
+bool  EECodeManager::IsInSynchronizedRegion(DWORD       relOffset,
+                                            GCInfoToken gcInfoToken,
+                                            unsigned    flags)
 {
     CONTRACTL {
         NOTHROW;
@@ -5524,7 +5534,7 @@ bool  EECodeManager::IsInSynchronizedRegion(
 #ifndef USE_GC_INFO_DECODER
     hdrInfo info;
 
-    crackMethodInfoHdr(methodInfoPtr, relOffset, &info);
+    DecodeGCHdrInfo(gcInfoToken, relOffset, &info);
 
     // We should be called only for synchronized methods
     _ASSERTE(info.syncStartOffset != INVALID_SYNC_OFFSET && info.syncEndOffset != INVALID_SYNC_OFFSET);
@@ -5558,9 +5568,8 @@ size_t EECodeManager::GetFunctionSize(GCInfoToken gcInfoToken)
 
 #if defined(_TARGET_X86_)
     hdrInfo info;
-    PTR_VOID  methodInfoPtr = gcInfoToken.Info;
 
-    crackMethodInfoHdr(methodInfoPtr, 0, &info);
+    DecodeGCHdrInfo(gcInfoToken, 0, &info);
 
     return info.methodSize;
 #elif defined(USE_GC_INFO_DECODER)
@@ -5578,15 +5587,47 @@ size_t EECodeManager::GetFunctionSize(GCInfoToken gcInfoToken)
     PORTABILITY_ASSERT("EECodeManager::GetFunctionSize is not implemented on this platform.");
     return 0;
 #endif
+}
 
+/*****************************************************************************
+*
+*  Returns the size of a given function.
+*/
+ReturnKind EECodeManager::GetReturnKind(GCInfoToken gcInfoToken)
+{
+    CONTRACTL{
+        NOTHROW;
+    GC_NOTRIGGER;
+    SUPPORTS_DAC;
+    } CONTRACTL_END;
 
+    if (!gcInfoToken.IsReturnKindAvailable())
+    {
+        return RT_Illegal;
+    }
+
+#if defined(_TARGET_X86_)
+    hdrInfo info;
+
+    DecodeGCHdrInfo(gcInfoToken, 0, &info);
+
+    return info.returnKind;
+#elif defined(USE_GC_INFO_DECODER)
+
+    GcInfoDecoder gcInfoDecoder(gcInfoToken, DECODE_RETURN_KIND);
+    return gcInfoDecoder.GetReturnKind();
+
+#else // !_TARGET_X86_ && !USE_GC_INFO_DECODER
+    PORTABILITY_ASSERT("EECodeManager::GetReturnKind is not implemented on this platform.");
+    return 0;
+#endif
 }
 
 /*****************************************************************************
  *
  *  Returns the size of the frame of the given function.
  */
-unsigned int EECodeManager::GetFrameSize(PTR_VOID methodInfoPtr)
+unsigned int EECodeManager::GetFrameSize(GCInfoToken gcInfoToken)
 {
     CONTRACTL {
         NOTHROW;
@@ -5596,7 +5637,7 @@ unsigned int EECodeManager::GetFrameSize(PTR_VOID methodInfoPtr)
 #ifndef USE_GC_INFO_DECODER
     hdrInfo info;
 
-    crackMethodInfoHdr(methodInfoPtr, 0, &info);
+    DecodeGCHdrInfo(gcInfoToken, 0, &info);
 
     // currently only used by E&C callers need to know about doubleAlign
     // in all likelyhood
@@ -5624,10 +5665,10 @@ const BYTE* EECodeManager::GetFinallyReturnAddr(PREGDISPLAY pReg)
 #endif
 }
 
-BOOL EECodeManager::IsInFilter(void *methodInfoPtr,
-                              unsigned offset,
-                              PCONTEXT pCtx,
-                              DWORD curNestLevel)
+BOOL EECodeManager::IsInFilter(GCInfoToken gcInfoToken,
+                               unsigned offset,
+                               PCONTEXT pCtx,
+                               DWORD curNestLevel)
 {
     CONTRACTL {
         NOTHROW;
@@ -5640,9 +5681,9 @@ BOOL EECodeManager::IsInFilter(void *methodInfoPtr,
 
     hdrInfo     info;
 
-    crackMethodInfoHdr(methodInfoPtr,
-                       offset,
-                       &info);
+    DecodeGCHdrInfo(gcInfoToken,
+                    offset,
+                    &info);
 
     /* make sure that we have an ebp stack frame */
 
@@ -5668,7 +5709,7 @@ BOOL EECodeManager::IsInFilter(void *methodInfoPtr,
 }
 
 
-BOOL EECodeManager::LeaveFinally(void *methodInfoPtr,
+BOOL EECodeManager::LeaveFinally(GCInfoToken gcInfoToken,
                                 unsigned offset,
                                 PCONTEXT pCtx)
 {
@@ -5681,9 +5722,9 @@ BOOL EECodeManager::LeaveFinally(void *methodInfoPtr,
 
     hdrInfo info;
 
-    crackMethodInfoHdr(methodInfoPtr,
-                       offset,
-                       &info);
+    DecodeGCHdrInfo(gcInfoToken,
+                    offset,
+                    &info);
 
     DWORD       nestingLevel;
     GetHandlerFrameInfo(&info, pCtx->Ebp, pCtx->Esp, (DWORD) IGNORE_VAL, NULL, &nestingLevel);
@@ -5707,7 +5748,7 @@ BOOL EECodeManager::LeaveFinally(void *methodInfoPtr,
 #endif
 }
 
-void EECodeManager::LeaveCatch(void *methodInfoPtr,
+void EECodeManager::LeaveCatch(GCInfoToken gcInfoToken,
                                 unsigned offset,
                                 PCONTEXT pCtx)
 {
@@ -5724,7 +5765,7 @@ void EECodeManager::LeaveCatch(void *methodInfoPtr,
     bool        hasInnerFilter;
     hdrInfo     info;
 
-    crackMethodInfoHdr(methodInfoPtr, offset, &info);
+    DecodeGCHdrInfo(gcInfoToken, offset, &info);
     GetHandlerFrameInfo(&info, pCtx->Ebp, pCtx->Esp, (DWORD) IGNORE_VAL,
                         &baseSP, &nestingLevel, &hasInnerFilter);
 //    _ASSERTE(frameType == FR_HANDLER);
@@ -5774,17 +5815,17 @@ TADDR EECodeManager::GetAmbientSP(PREGDISPLAY     pContext,
     } CONTRACTL_END;
 
 #ifdef _TARGET_X86_
-    PTR_VOID  methodInfoPtr = pCodeInfo->GetGCInfo();
+    GCInfoToken gcInfoToken = pCodeInfo->GetGCInfoToken();
 
     _ASSERTE(sizeof(CodeManStateBuf) <= sizeof(pState->stateBuf));
     CodeManStateBuf * stateBuf = (CodeManStateBuf*)pState->stateBuf;
-    PTR_CBYTE table = PTR_CBYTE(methodInfoPtr);
+    PTR_CBYTE table = PTR_CBYTE(gcInfoToken.Info);
 
     /* Extract the necessary information from the info block header */
 
-    stateBuf->hdrInfoSize = (DWORD)crackMethodInfoHdr(methodInfoPtr,
-                                       dwRelOffset,
-                                       &stateBuf->hdrInfoBody);
+    stateBuf->hdrInfoSize = (DWORD)DecodeGCHdrInfo(gcInfoToken,
+                                                   dwRelOffset,
+                                                   &stateBuf->hdrInfoBody);
     table += stateBuf->hdrInfoSize;
 
     pState->dwIsSet = 1;
@@ -5868,8 +5909,8 @@ ULONG32 EECodeManager::GetStackParameterSize(EECodeInfo * pCodeInfo)
     } CONTRACTL_END;
 
 #if defined(_TARGET_X86_)
-    PTR_VOID       methodInfoPtr = pCodeInfo->GetGCInfo();
-    unsigned       dwOffset = pCodeInfo->GetRelOffset();
+    GCInfoToken gcInfoToken = pCodeInfo->GetGCInfoToken();
+    unsigned    dwOffset = pCodeInfo->GetRelOffset();
 
     CodeManState state;
     state.dwIsSet = 0;
@@ -5878,7 +5919,7 @@ ULONG32 EECodeManager::GetStackParameterSize(EECodeInfo * pCodeInfo)
     CodeManStateBuf * pStateBuf = reinterpret_cast<CodeManStateBuf *>(state.stateBuf);
 
     hdrInfo * pHdrInfo = &(pStateBuf->hdrInfoBody);
-    pStateBuf->hdrInfoSize = (DWORD)crackMethodInfoHdr(methodInfoPtr, dwOffset, pHdrInfo);
+    pStateBuf->hdrInfoSize = (DWORD)DecodeGCHdrInfo(gcInfoToken, dwOffset, pHdrInfo);
 
     // We need to subtract 4 here because ESPIncrOnReturn() includes the stack slot containing the return
     // address.
diff --git a/src/vm/excep.cpp b/src/vm/excep.cpp
index d26f2d62d8..4f72702af6 100644
--- a/src/vm/excep.cpp
+++ b/src/vm/excep.cpp
@@ -1679,7 +1679,7 @@ bool FinallyIsUnwinding(EHRangeTreeNode *pNode,
 BOOL LeaveCatch(ICodeManager* pEECM,
                 Thread *pThread,
                 CONTEXT *pCtx,
-                void *methodInfoPtr,
+                GCInfoToken gcInfoToken,
                 unsigned offset)
 {
     CONTRACTL
@@ -1703,7 +1703,7 @@ BOOL LeaveCatch(ICodeManager* pEECM,
     PopNestedExceptionRecords(esp, pCtx, pThread->GetExceptionListPtr());
 
     // Do JIT-specific work
-    pEECM->LeaveCatch(methodInfoPtr, offset, pCtx);
+    pEECM->LeaveCatch(gcInfoToken, offset, pCtx);
 
     SetSP(pCtx, (UINT_PTR)esp);
     return TRUE;
@@ -1762,7 +1762,7 @@ HRESULT IsLegalTransition(Thread *pThread,
                           ICodeManager* pEECM,
                           PREGDISPLAY pReg,
                           SLOT addrStart,
-                          void *methodInfoPtr,
+                          GCInfoToken gcInfoToken,
                           PCONTEXT pCtx)
 {
     CONTRACTL
@@ -1875,7 +1875,7 @@ HRESULT IsLegalTransition(Thread *pThread,
                         if (!LeaveCatch(pEECM,
                                         pThread,
                                         pFilterCtx,
-                                        methodInfoPtr,
+                                        gcInfoToken,
                                         offFrom))
                             return E_FAIL;
                     }
@@ -1930,7 +1930,7 @@ HRESULT IsLegalTransition(Thread *pThread,
 
                         if (!fCanSetIPOnly)
                         {
-                            if (!pEECM->LeaveFinally(methodInfoPtr,
+                            if (!pEECM->LeaveFinally(gcInfoToken,
                                                      offFrom,
                                                      pFilterCtx))
                                 return E_FAIL;
@@ -2041,7 +2041,7 @@ HRESULT SetIPFromSrcToDst(Thread *pThread,
     EECodeInfo codeInfo((TADDR)(addrStart));
 
     ICodeManager * pEECM = codeInfo.GetCodeManager();
-    LPVOID methodInfoPtr = codeInfo.GetGCInfo();
+    GCInfoToken gcInfoToken = codeInfo.GetGCInfoToken();
 
     // Do both checks here so compiler doesn't complain about skipping
     // initialization b/c of goto.
@@ -2097,7 +2097,7 @@ retryForCommit:
                                pEECM,
                                pReg,
                                addrStart,
-                               methodInfoPtr,
+                               gcInfoToken,
                                pCtx);
 
         if (FAILED(hr))
@@ -2120,7 +2120,7 @@ retryForCommit:
                                pEECM,
                                pReg,
                                addrStart,
-                               methodInfoPtr,
+                               gcInfoToken,
                                pCtx);
 
         if (FAILED(hr))
@@ -2143,7 +2143,7 @@ retryForCommit:
                                pEECM,
                                pReg,
                                addrStart,
-                               methodInfoPtr,
+                               gcInfoToken,
                                pCtx);
 
         if (FAILED(hr))
diff --git a/src/vm/gccover.cpp b/src/vm/gccover.cpp
index 89f271cdd0..24f9435641 100644
--- a/src/vm/gccover.cpp
+++ b/src/vm/gccover.cpp
@@ -80,7 +80,7 @@ void SetupAndSprinkleBreakpoints(
 
     gcCover->methodRegion      = methodRegionInfo;
     gcCover->codeMan           = pCodeInfo->GetCodeManager();
-    gcCover->gcInfoToken           = pCodeInfo->GetGCInfoToken();
+    gcCover->gcInfoToken       = pCodeInfo->GetGCInfoToken();
     gcCover->callerThread      = 0;
     gcCover->doingEpilogChecks = true;    
 
@@ -583,7 +583,7 @@ void GCCoverageInfo::SprinkleBreakpoints(
 #ifdef _TARGET_X86_
         // we will whack every instruction in the prolog and epilog to make certain
         // our unwinding logic works there.  
-        if (codeMan->IsInPrologOrEpilog((cur - codeStart) + (DWORD)regionOffsetAdj, gcInfoToken.Info, NULL)) {
+        if (codeMan->IsInPrologOrEpilog((cur - codeStart) + (DWORD)regionOffsetAdj, gcInfoToken, NULL)) {
             *cur = INTERRUPT_INSTR;
         }
 #endif
@@ -1527,7 +1527,7 @@ void DoGcStress (PCONTEXT regs, MethodDesc *pMD)
     /* are we in a prolog or epilog?  If so just test the unwind logic
        but don't actually do a GC since the prolog and epilog are not
        GC safe points */
-    if (gcCover->codeMan->IsInPrologOrEpilog(offset, gcCover->gcInfoToken.Info, NULL))
+    if (gcCover->codeMan->IsInPrologOrEpilog(offset, gcCover->gcInfoToken, NULL))
     {
         // We are not at a GC safe point so we can't Suspend EE (Suspend EE will yield to GC).
         // But we still have to update the GC Stress instruction. We do it directly without suspending
diff --git a/src/vm/gcenv.ee.cpp b/src/vm/gcenv.ee.cpp
index 8dc1692643..b294581009 100644
--- a/src/vm/gcenv.ee.cpp
+++ b/src/vm/gcenv.ee.cpp
@@ -125,7 +125,7 @@ inline bool SafeToReportGenericParamContext(CrawlFrame* pCF)
 #ifndef USE_GC_INFO_DECODER
 
     ICodeManager * pEECM = pCF->GetCodeManager();
-    if (pEECM != NULL && pEECM->IsInPrologOrEpilog(pCF->GetRelOffset(), pCF->GetGCInfo(), NULL))
+    if (pEECM != NULL && pEECM->IsInPrologOrEpilog(pCF->GetRelOffset(), pCF->GetGCInfoToken(), NULL))
     {
         return false;
     }
diff --git a/src/vm/proftoeeinterfaceimpl.cpp b/src/vm/proftoeeinterfaceimpl.cpp
index fee883f0ef..20dceed1e4 100644
--- a/src/vm/proftoeeinterfaceimpl.cpp
+++ b/src/vm/proftoeeinterfaceimpl.cpp
@@ -7081,12 +7081,13 @@ Loop:
 
             // GC info will assist us in determining whether this is a non-EBP frame and
             // info about pushed arguments.
-            PTR_VOID gcInfo = codeInfo.GetGCInfo();
+            GCInfoToken gcInfoToken = codeInfo.GetGCInfoToken();
+            PTR_VOID gcInfo = gcInfoToken.Info;
             InfoHdr header;
             unsigned uiMethodSizeDummy;
             PTR_CBYTE table = PTR_CBYTE(gcInfo);
             table += decodeUnsigned(table, &uiMethodSizeDummy);
-            table = decodeHeader(table, &header);
+            table = decodeHeader(table, gcInfoToken.Version, &header);
 
             // Ok, GCInfo, can we do a simple EBP walk or what?
 
diff --git a/src/vm/stackwalk.cpp b/src/vm/stackwalk.cpp
index 3b0b4720f7..29b5617414 100644
--- a/src/vm/stackwalk.cpp
+++ b/src/vm/stackwalk.cpp
@@ -2416,7 +2416,7 @@ StackWalkAction StackFrameIterator::NextRaw(void)
                 OBJECTREF      orUnwind = NULL;
 
                 if (m_crawl.GetCodeManager()->IsInSynchronizedRegion(m_crawl.GetRelOffset(),
-                                                                    m_crawl.GetGCInfo(), 
+                                                                    m_crawl.GetGCInfoToken(), 
                                                                     m_crawl.GetCodeManagerFlags()))
                 {
                     if (pMD->IsStatic())
@@ -3158,7 +3158,7 @@ void StackFrameIterator::PreProcessingForManagedFrames(void)
          m_crawl.pFunc->IsSynchronized() && 
          !m_crawl.pFunc->IsStatic()      &&
          m_crawl.GetCodeManager()->IsInSynchronizedRegion(m_crawl.GetRelOffset(), 
-                                                         m_crawl.GetGCInfo(), 
+                                                         m_crawl.GetGCInfoToken(), 
                                                          m_crawl.GetCodeManagerFlags()))
     {
         BEGIN_GCX_ASSERT_COOP;
diff --git a/src/vm/threadsuspend.cpp b/src/vm/threadsuspend.cpp
index 0458b7dd57..e5c54368ca 100644
--- a/src/vm/threadsuspend.cpp
+++ b/src/vm/threadsuspend.cpp
@@ -7275,18 +7275,8 @@ ReturnKind GetReturnKindFromMethodTable(Thread *pThread, EECodeInfo *codeInfo)
 
 ReturnKind GetReturnKind(Thread *pThread, EECodeInfo *codeInfo)
 {
-    ReturnKind returnKind = RT_Illegal;
-
-#ifdef _TARGET_X86_  
-    // X86 GCInfo updates yet to be implemented.
-#else
     GCInfoToken gcInfoToken = codeInfo->GetGCInfoToken();
-    if (gcInfoToken.IsReturnKindAvailable()) 
-    {
-        GcInfoDecoder gcInfoDecoder(gcInfoToken, DECODE_RETURN_KIND);
-        returnKind = gcInfoDecoder.GetReturnKind();
-    }
-#endif // _TARGET_X86_
+    ReturnKind returnKind = codeInfo->GetCodeManager()->GetReturnKind(gcInfoToken);
 
     if (!IsValidReturnKind(returnKind))
     {