JIT: Add runtime async transformation

src/coreclr/System.Private.CoreLib/src/System/Runtime/CompilerServices/AsyncHelpers.CoreCLR.cs

@@ -57,8 +57,9 @@ internal enum CorInfoContinuationFlags
         // should be placed at index 0 or 1 depending on whether the continuation
         // also expects a result.
         CORINFO_CONTINUATION_NEEDS_EXCEPTION = 2,
-        // If this bit is set the continuation has an OSR IL offset saved in the
-        // beginning of 'Data'.
+        // If this bit is set the continuation has the IL offset that inspired the
+        // OSR method saved in the beginning of 'Data', or -1 if the continuation
+        // belongs to a tier 0 method.
         CORINFO_CONTINUATION_OSR_IL_OFFSET_IN_DATA = 4,
     }
 

src/coreclr/inc/corinfo.h

@@ -1708,8 +1708,9 @@ enum CorInfoContinuationFlags
     // should be placed at index 0 or 1 depending on whether the continuation
     // also expects a result.
     CORINFO_CONTINUATION_NEEDS_EXCEPTION = 2,
-    // If this bit is set the continuation has an OSR IL offset saved in the
-    // beginning of 'Data'.
+    // If this bit is set the continuation has the IL offset that inspired the
+    // OSR method saved in the beginning of 'Data', or -1 if the continuation
+    // belongs to a tier 0 method.
     CORINFO_CONTINUATION_OSR_IL_OFFSET_IN_DATA = 4,
 };
 

src/coreclr/inc/corjitflags.h

@@ -63,7 +63,7 @@ class CORJIT_FLAGS
         CORJIT_FLAG_RELATIVE_CODE_RELOCS    = 29, // JIT should generate PC-relative address computations instead of EE relocation records
         CORJIT_FLAG_SOFTFP_ABI              = 30, // Enable armel calling convention
 #endif
-        CORJIT_FLAG_ASYNC                   = 31, // Generate Code for use as an async function
+        CORJIT_FLAG_ASYNC                   = 31, // Generate code for use as an async function
     };
 
     CORJIT_FLAGS()

src/coreclr/jit/CMakeLists.txt

@@ -89,6 +89,7 @@ set( JIT_SOURCES
   abi.cpp
   alloc.cpp
   assertionprop.cpp
+  async.cpp
   bitset.cpp
   block.cpp
   buildstring.cpp
@@ -286,6 +287,7 @@ set( JIT_HEADERS
   abi.h
   alloc.h
   arraystack.h
+  async.h
   bitset.h
   layout.h
   bitsetasshortlong.h