Improve likely class handling for pgo (#51284)

- Move processing of likely class histogram into the JIT
- Fix cases where the devirtualization logic in crossgen2 behaved incorrectly in the presence of likely class histogram data
- Pre-process histogram at crossgen2 time to reduce the size of the pgo data
  - This removes 3/4 of the data from System.Private.CoreLib

4 files changed, 15 insertions, 39 deletions

diff --git a/src/coreclr/inc/corjit.h b/src/coreclr/inc/corjit.h
index 85cb80bc370..2407a407ac5 100644
--- a/src/coreclr/inc/corjit.h
+++ b/src/coreclr/inc/corjit.h
@@ -363,6 +363,7 @@ public:
         Version = (DescriptorMin * 4) | None, // Version is encoded in the Other field of the schema
         NumRuns = (DescriptorMin * 5) | None, // Number of runs is encoded in the Other field of the schema
         EdgeIntCount = (DescriptorMin * 6) | FourByte, // 4 byte edge counter, using unsigned 4 byte int
+        GetLikelyClass = (DescriptorMin * 7) | TypeHandle, // Compressed get likely class data
     };
 
     struct PgoInstrumentationSchema
@@ -374,6 +375,15 @@ public:
         int32_t Other;
     };
 
+#define DEFAULT_UNKNOWN_TYPEHANDLE 1
+#define UNKNOWN_TYPEHANDLE_MIN 1
+#define UNKNOWN_TYPEHANDLE_MAX 33
+
+    static inline bool IsUnknownTypeHandle(intptr_t typeHandle)
+    {
+        return ((typeHandle >= UNKNOWN_TYPEHANDLE_MIN) && (typeHandle <= UNKNOWN_TYPEHANDLE_MAX));
+    }
+
     // get profile information to be used for optimizing a current method.  The format
     // of the buffer is the same as the format the JIT passes to allocPgoInstrumentationBySchema.
     virtual JITINTERFACE_HRESULT getPgoInstrumentationResults(
@@ -404,24 +414,6 @@ public:
             uint8_t **                pInstrumentationData         // OUT: `*pInstrumentationData` is set to the address of the instrumentation data.
             ) = 0;
 
-    // Get the likely implementing class for a virtual call or interface call made by ftnHnd
-    // at the indicated IL offset. baseHnd is the interface class or base class for the method
-    // being called. May returns NULL.
-    // 
-    // pLikelihood is the estimated percent chance that the class at runtime is the class
-    // returned by this method. A well-estimated monomorphic call site will return a likelihood
-    // of 100.
-    // 
-    // pNumberOfClasses is the estimated number of different classes seen at the site.
-    // A well-estimated monomorphic call site will return 1.
-    virtual CORINFO_CLASS_HANDLE getLikelyClass(
-            CORINFO_METHOD_HANDLE ftnHnd,
-            CORINFO_CLASS_HANDLE  baseHnd,
-            uint32_t                ilOffset,
-            uint32_t *              pLikelihood,      // OUT, estimated likelihood of the class (0...100)
-            uint32_t *              pNumberOfClasses  // OUT, estimated number of possible classes
-            ) = 0;
-
     // Associates a native call site, identified by its offset in the native code stream, with
     // the signature information and method handle the JIT used to lay out the call site. If
     // the call site has no signature information (e.g. a helper call) or has no method handle
diff --git a/src/coreclr/inc/icorjitinfoimpl_generated.h b/src/coreclr/inc/icorjitinfoimpl_generated.h
index 922a854795e..8eef23aa44e 100644
--- a/src/coreclr/inc/icorjitinfoimpl_generated.h
+++ b/src/coreclr/inc/icorjitinfoimpl_generated.h
@@ -693,13 +693,6 @@ JITINTERFACE_HRESULT allocPgoInstrumentationBySchema(
           uint32_t countSchemaItems,
           uint8_t** pInstrumentationData) override;
 
-CORINFO_CLASS_HANDLE getLikelyClass(
-          CORINFO_METHOD_HANDLE ftnHnd,
-          CORINFO_CLASS_HANDLE baseHnd,
-          uint32_t ilOffset,
-          uint32_t* pLikelihood,
-          uint32_t* pNumberOfClasses) override;
-
 void recordCallSite(
           uint32_t instrOffset,
           CORINFO_SIG_INFO* callSig,
diff --git a/src/coreclr/inc/jiteeversionguid.h b/src/coreclr/inc/jiteeversionguid.h
index f76ceb70b11..b32d0edef00 100644
--- a/src/coreclr/inc/jiteeversionguid.h
+++ b/src/coreclr/inc/jiteeversionguid.h
@@ -43,11 +43,11 @@ typedef const GUID *LPCGUID;
 #define GUID_DEFINED
 #endif // !GUID_DEFINED
 
-constexpr GUID JITEEVersionIdentifier = { /* a33f2f79-dd8d-49dd-b4c3-ac86f34f6a87 */
-    0xa33f2f79,
-    0xdd8d,
-    0x49dd,
-    {0xb4, 0xc3, 0xac, 0x86, 0xf3, 0x4f, 0x6a, 0x87}
+constexpr GUID JITEEVersionIdentifier = { /* 12234eca-dfc2-48bc-a320-6155cf25ce17 */
+    0x12234eca,
+    0xdfc2,
+    0x48bc,
+    {0xa3, 0x20, 0x61, 0x55, 0xcf, 0x25, 0xce, 0x17}
 };
 
 //////////////////////////////////////////////////////////////////////////////////////////////////////////
diff --git a/src/coreclr/inc/pgo_formatprocessing.h b/src/coreclr/inc/pgo_formatprocessing.h
index 9ef06e577c3..8d111bf2c89 100644
--- a/src/coreclr/inc/pgo_formatprocessing.h
+++ b/src/coreclr/inc/pgo_formatprocessing.h
@@ -8,10 +8,6 @@
 
 #ifdef FEATURE_PGO
 
-#define DEFAULT_UNKNOWN_TYPEHANDLE 1
-#define UNKNOWN_TYPEHANDLE_MIN 1
-#define UNKNOWN_TYPEHANDLE_MAX 32
-
 inline bool AddTypeHandleToUnknownTypeHandleMask(INT_PTR typeHandle, uint32_t *unknownTypeHandleMask)
 {
     uint32_t bitMask = (uint32_t)(1 << (typeHandle - UNKNOWN_TYPEHANDLE_MIN));
@@ -20,11 +16,6 @@ inline bool AddTypeHandleToUnknownTypeHandleMask(INT_PTR typeHandle, uint32_t *u
     return result;
 }
 
-inline bool IsUnknownTypeHandle(INT_PTR typeHandle)
-{
-    return ((typeHandle >= UNKNOWN_TYPEHANDLE_MIN) && (typeHandle <= UNKNOWN_TYPEHANDLE_MAX));
-}
-
 inline INT_PTR HashToPgoUnknownTypeHandle(uint32_t hash)
 {
     // Map from a 32bit hash to the 32 different unknown type handle values