Inliner: introduce ReplayPolicy

The ReplayPolicy reads an external script to determine which inlines
to perform. The script is the same Xml syntax that's produced by
the inliner when JitInlineDumpXml is enabled. This format can be edited
by hand or tool to force particular inlining patterns to occur. Methods
or calls sites not mentioned in the script are considered as noinline.

There's a bunch of work still left to make this fully robust, but in
testing it works well enough for my immediate use case that I'll hold
off on further polish until it's needed. But, for future reference,
here's a laundry list:

* Need better ways to identify methods. Token and hash are not enough.
* Need better ways to identify call sites. Callee token is not enough.
* Consider preparsing or mapping the script into memory.
* Consider caching node positions in the InlineContexts.
* Make it robust for multithreading.
* Handle the prejit root case somehow.
* Possibly allow overriding of inline attributes.

1 files changed, 29 insertions, 0 deletions

diff --git a/src/jit/inlinepolicy.h b/src/jit/inlinepolicy.h
index 31a686e52f..29e6af40c0 100644
--- a/src/jit/inlinepolicy.h
+++ b/src/jit/inlinepolicy.h
@@ -338,6 +338,35 @@ public:
     const char* GetName() const override { return "SizePolicy"; }
 };
 
+// The ReplayPolicy performs only inlines specified by an external
+// inline replay log.
+
+class ReplayPolicy : public DiscretionaryPolicy
+{
+public:
+
+    // Construct a ReplayPolicy
+    ReplayPolicy(Compiler* compiler, InlineContext* inlineContext, bool isPrejitRoot);
+
+    // Policy determinations
+    void DetermineProfitability(CORINFO_METHOD_INFO* methodInfo) override;
+
+    // Miscellaneous
+    const char* GetName() const override { return "ReplayPolicy"; }
+
+    static void FinalizeXml();
+
+private:
+
+    bool FindMethod();
+    bool FindContext(InlineContext* context);
+    bool FindInline(CORINFO_METHOD_HANDLE callee);
+    bool FindInline(unsigned token);
+
+    static bool    s_WroteReplayBanner;
+    static FILE*   s_ReplayFile;
+    InlineContext* m_InlineContext;
+};
 
 #endif // defined(DEBUG) || defined(INLINE_DATA)