Devirtualize calls in some simple cases

Devirtualize calls where the this object type at a call site
is a subtype of the type described at the call site. Currently learns
types from local and arg references and a subset of other operators.

Will devirtualize if either the class or method is final (sealed in C#),
or if the type is known exactly (eg from a newobj).

Devirtualization is run twice, once during importation, and again in a
limited way after inlinining. Calls devirtualized during importation are
are subsequently eligible for inlining. Calls devirtualized during inlining
currently cannot be inlined.

1 files changed, 9 insertions, 0 deletions

diff --git a/src/jit/compiler.h b/src/jit/compiler.h
index cc1caecf33..651aac3a25 100644
--- a/src/jit/compiler.h
+++ b/src/jit/compiler.h
@@ -322,6 +322,8 @@ public:
 #endif                                       // FEATURE_SIMD
     unsigned char lvRegStruct : 1;           // This is a reg-sized non-field-addressed struct.
 
+    unsigned char lvClassIsExact : 1; // lvClassHandle is the exact type
+
     union {
         unsigned lvFieldLclStart; // The index of the local var representing the first field in the promoted struct
                                   // local.
@@ -704,6 +706,8 @@ public:
 
     typeInfo lvVerTypeInfo; // type info needed for verification
 
+    CORINFO_CLASS_HANDLE lvClassHnd; // class handle for the local, or null if not known
+
     BYTE* lvGcLayout; // GC layout info for structs
 
 #if ASSERTION_PROP
@@ -2875,6 +2879,11 @@ protected:
                             CORINFO_CALL_INFO* callInfo,
                             IL_OFFSET          rawILOffset);
 
+    void impDevirtualizeCall(GenTreeCall*            call,
+                             GenTreePtr              obj,
+                             CORINFO_CALL_INFO*      callInfo,
+                             CORINFO_CONTEXT_HANDLE* exactContextHnd);
+
     bool impMethodInfo_hasRetBuffArg(CORINFO_METHOD_INFO* methInfo);
 
     GenTreePtr impFixupCallStructReturn(GenTreePtr call, CORINFO_CLASS_HANDLE retClsHnd);