Finally cloning

Documentation/botr/clr-abi.md

@@ -149,7 +149,9 @@ For x86, all handlers are generated within the method body, typically in lexical
 
 JIT64 attempts to speed the normal control flow by 'inlining' a called finally along the 'normal' control flow (i.e., leaving a try body in a non-exceptional manner via C# fall-through). Because the VM semantics for non-rude Thread.Abort dictate that handlers will not be aborted, the JIT must mark these 'inlined' finally bodies. These show up as special entries at the end of the EH tables and are marked with `COR_ILEXCEPTION_CLAUSE_FINALLY | COR_ILEXCEPTION_CLAUSE_DUPLICATED`, and the try_start, try_end, and handler_start are all the same: the start of the cloned finally.
 
-JIT32 and RyuJIT currently do not implement finally cloning.
+RyuJit also implements finally cloning, for all supported architectures. However, the implementation does not yet handle the thread abort case; cloned finally bodies are not guaranteed to remain intact and are not reported to the runtime. Because of this, finally cloning is disabled for VMs that support thread abort (desktop clr).
+
+JIT32 does not implement finally cloning.
 
 ## Invoking Finallys/Non-local exits
 

src/jit/block.cpp

@@ -365,6 +365,14 @@ void BasicBlock::dspFlags()
     {
         printf("KEEP ");
     }
+    if (bbFlags & BBF_CLONED_FINALLY_BEGIN)
+    {
+        printf("cfb ");
+    }
+    if (bbFlags & BBF_CLONED_FINALLY_END)
+    {
+        printf("cfe ");
+    }
 }
 
 /*****************************************************************************
@@ -664,7 +672,7 @@ bool BasicBlock::IsLIR()
 // Return Value:
 //    The first statement in the block's bbTreeList.
 //
-GenTreeStmt* BasicBlock::firstStmt()
+GenTreeStmt* BasicBlock::firstStmt() const
 {
     if (bbTreeList == nullptr)
     {
@@ -683,7 +691,7 @@ GenTreeStmt* BasicBlock::firstStmt()
 // Return Value:
 //    The last statement in the block's bbTreeList.
 //
-GenTreeStmt* BasicBlock::lastStmt()
+GenTreeStmt* BasicBlock::lastStmt() const
 {
     if (bbTreeList == nullptr)
     {

src/jit/block.h

@@ -353,15 +353,18 @@ struct BasicBlock : private LIR::Range
                                        // BBJ_CALLFINALLY block, as well as, on x86, the final step block out of a
                                        // finally.
 
+#define BBF_CLONED_FINALLY_BEGIN 0x100000000 // First block of a cloned finally region
+#define BBF_CLONED_FINALLY_END 0x200000000   // Last block of a cloned finally region
+
 // Flags that relate blocks to loop structure.
 
 #define BBF_LOOP_FLAGS (BBF_LOOP_PREHEADER | BBF_LOOP_HEAD | BBF_LOOP_CALL0 | BBF_LOOP_CALL1)
 
-    bool isRunRarely()
+    bool isRunRarely() const
     {
         return ((bbFlags & BBF_RUN_RARELY) != 0);
     }
-    bool isLoopHead()
+    bool isLoopHead() const
     {
         return ((bbFlags & BBF_LOOP_HEAD) != 0);
     }
@@ -388,7 +391,7 @@ struct BasicBlock : private LIR::Range
 // For example, the top block might or might not have BBF_GC_SAFE_POINT,
 // but we assume it does not have BBF_GC_SAFE_POINT any more.
 
-#define BBF_SPLIT_LOST (BBF_GC_SAFE_POINT | BBF_HAS_JMP | BBF_KEEP_BBJ_ALWAYS)
+#define BBF_SPLIT_LOST (BBF_GC_SAFE_POINT | BBF_HAS_JMP | BBF_KEEP_BBJ_ALWAYS | BBF_CLONED_FINALLY_END)
 
 // Flags gained by the bottom block when a block is split.
 // Note, this is a conservative guess.
@@ -399,7 +402,7 @@ struct BasicBlock : private LIR::Range
 
 #define BBF_SPLIT_GAINED                                                                                               \
     (BBF_DONT_REMOVE | BBF_HAS_LABEL | BBF_HAS_JMP | BBF_BACKWARD_JUMP | BBF_HAS_IDX_LEN | BBF_HAS_NEWARRAY |          \
-     BBF_PROF_WEIGHT | BBF_HAS_NEWOBJ | BBF_KEEP_BBJ_ALWAYS)
+     BBF_PROF_WEIGHT | BBF_HAS_NEWOBJ | BBF_KEEP_BBJ_ALWAYS | BBF_CLONED_FINALLY_END)
 
 #ifndef __GNUC__ // GCC doesn't like C_ASSERT at global scope
     static_assert_no_msg((BBF_SPLIT_NONEXIST & BBF_SPLIT_LOST) == 0);
@@ -980,8 +983,8 @@ struct BasicBlock : private LIR::Range
         return bbNum - 1;
     }
 
-    GenTreeStmt* firstStmt();
-    GenTreeStmt* lastStmt();
+    GenTreeStmt* firstStmt() const;
+    GenTreeStmt* lastStmt() const;
     GenTreeStmt* lastTopLevelStmt();
 
     GenTree* firstNode();

src/jit/compiler.h

@@ -3500,6 +3500,10 @@ class Compiler
 
     void fgInline();
 
+    void fgRemoveEmptyFinally();
+
+    void fgCloneFinally();
+
     GenTreePtr fgGetCritSectOfStaticMethod();
 
 #if !defined(_TARGET_X86_)
@@ -4271,6 +4275,7 @@ class Compiler
     void fgDebugCheckNodeLinks(BasicBlock* block, GenTreePtr stmt);
     void fgDebugCheckFlags(GenTreePtr tree);
     void fgDebugCheckFlagsHelper(GenTreePtr tree, unsigned treeFlags, unsigned chkFlags);
+    void fgDebugCheckTryFinallyExits();
 #endif
 
 #ifdef LEGACY_BACKEND

src/jit/compphases.h

@@ -11,9 +11,10 @@
 // corresponding array of string names of those phases.  This include file undefines CompPhaseNameMacro
 // after the last use.
 // The arguments are:
-//   CompPhaseNameMacro(enumName, stringName, hasChildren, parent)
+//   CompPhaseNameMacro(enumName, stringName, shortName, hasChildren, parent)
 //     "enumName" is an Enumeration-style all-caps name.
 //     "stringName" is a self-explanatory.
+//     "shortName" is an abbreviated form for stringName
 //     "hasChildren" is true if this phase is broken out into subphases.
 //         (We should never do EndPhase on a phase that has children, only on 'leaf phases.')
 //     "parent" is -1 for leaf phases, otherwise it is the "enumName" of the parent phase.
@@ -97,6 +98,9 @@ CompPhaseNameMacro(PHASE_EMIT_GCEH,              "Emit GC+EH tables",
 // for calls through ICorJitInfo across all "real" phases.
 CompPhaseNameMacro(PHASE_CLR_API,                "CLR API calls",                  "CLR-API",  false, -1)
 #endif
+
+CompPhaseNameMacro(PHASE_EMPTY_FINALLY,          "Remove empty finally",           "EMPTYFIN",  false, -1)
+CompPhaseNameMacro(PHASE_CLONE_FINALLY,          "Clone finally",                  "CLONEFIN",  false, -1)
 // clang-format on
 
 #undef CompPhaseNameMacro