Reland of [ignition/turbo] Perform liveness analysis on the bytecodes

src/compiler/bytecode-analysis.h

Index: src/compiler/bytecode-analysis.h
diff --git a/src/compiler/bytecode-analysis.h b/src/compiler/bytecode-analysis.h
index f50b00f2c696ecd0acf07ef2d8c7276267555df4..ded11d402147116b6237cbbb50df4d4618bb57c9 100644
--- a/src/compiler/bytecode-analysis.h
+++ b/src/compiler/bytecode-analysis.h
@@ -5,6 +5,8 @@
 #ifndef V8_COMPILER_BYTECODE_ANALYSIS_H_
 #define V8_COMPILER_BYTECODE_ANALYSIS_H_
 
+#include "src/base/hashmap.h"
+#include "src/bit-vector.h"
 #include "src/handles.h"
 #include "src/zone/zone-containers.h"
 
@@ -32,6 +34,21 @@ class BytecodeAnalysis BASE_EMBEDDED {
   // at {header_offset}, or -1 for outer-most loops.
   int GetParentLoopFor(int header_offset) const;
 
+  const BitVector* GetInLivenessFor(int offset) const;
+
+  const BitVector* GetOutLivenessFor(int offset) const;
+
+  struct Liveness {
+    BitVector* in;
+    BitVector* out;
+
+    Liveness(int size, Zone* zone);
+  };
+
+  typedef base::TemplateHashMapImpl<
+      int, Liveness, base::KeyEqualityMatcher<int>, ZoneAllocationPolicy>
+      LivenessMap;

[Jarin, 2016/11/24 12:47:17]

Does this offer significant advantage over std::unordered_map?

[Leszek Swirski, 2016/11/25 17:31:27]

I haven't measured here, but I've measured advantages over std::unordered_map
elsewhere (in the ConstantArrayBuilder).

Might be worth revisiting, but I want to think harder about the data structure
here anyway (in a subsequent CL) because I think we can take advantage of the
fact that offsets are reasonably dense and often accessed in order.

+
  private:
   void PushLoop(int loop_header, int loop_end);
 
@@ -46,6 +63,8 @@ class BytecodeAnalysis BASE_EMBEDDED {
   ZoneMap<int, int> end_to_header_;
   ZoneMap<int, int> header_to_parent_;
 
+  LivenessMap liveness_;
+
   DISALLOW_COPY_AND_ASSIGN(BytecodeAnalysis);
 };