JIT: Port VN and loop hoisting to new loop representation

src/coreclr/jit/block.cpp

@@ -1585,8 +1585,9 @@ BasicBlock* BasicBlock::New(Compiler* compiler)
 
     block->bbNatLoopNum = BasicBlock::NOT_IN_LOOP;
 
-    block->bbPreorderNum  = 0;
-    block->bbPostorderNum = 0;
+    block->bbPreorderNum     = 0;
+    block->bbPostorderNum    = 0;
+    block->bbNewPostorderNum = 0;
 
     return block;
 }

src/coreclr/jit/block.h

@@ -1220,8 +1220,9 @@ struct BasicBlock : private LIR::Range
 
     void* bbSparseCountInfo; // Used early on by fgIncorporateEdgeCounts
 
-    unsigned bbPreorderNum;  // the block's  preorder number in the graph (1...fgMaxBBNum]
-    unsigned bbPostorderNum; // the block's postorder number in the graph (1...fgMaxBBNum]
+    unsigned bbPreorderNum;     // the block's  preorder number in the graph (1...fgMaxBBNum]
+    unsigned bbPostorderNum;    // the block's postorder number in the graph (1...fgMaxBBNum]
+    unsigned bbNewPostorderNum; // the block's postorder number in the graph [0...postOrderCount)
 
     IL_OFFSET bbCodeOffs;    // IL offset of the beginning of the block
     IL_OFFSET bbCodeOffsEnd; // IL offset past the end of the block. Thus, the [bbCodeOffs..bbCodeOffsEnd)

src/coreclr/jit/compiler.cpp

@@ -5765,6 +5765,9 @@ void Compiler::RecomputeLoopInfo()
     optSetBlockWeights();
     // Rebuild the loop tree annotations themselves
     optFindLoops();
+
+    m_dfsTree = fgComputeDfs();
+    optFindNewLoops();
 }
 
 /*****************************************************************************/