JIT: Port loop unrolling to new loop representation

src/coreclr/jit/block.cpp

@@ -786,7 +786,6 @@ bool BasicBlock::CloneBlockState(
     assert(to->bbStmtList == nullptr);
     to->CopyFlags(from);
     to->bbWeight = from->bbWeight;
-    BlockSetOps::AssignAllowUninitRhs(compiler, to->bbReach, from->bbReach);
     to->copyEHRegion(from);
     to->bbCatchTyp    = from->bbCatchTyp;
     to->bbStkTempsIn  = from->bbStkTempsIn;

src/coreclr/jit/compiler.cpp

@@ -4914,6 +4914,8 @@ void Compiler::compCompile(void** methodCodePtr, uint32_t* methodCodeSize, JitFl
 
         while (iterations > 0)
         {
+            fgModified = false;
+
             if (doSsa)
             {
                 // Build up SSA form for the IR
@@ -5006,8 +5008,6 @@ void Compiler::compCompile(void** methodCodePtr, uint32_t* methodCodeSize, JitFl
             {
                 // update the flowgraph if we modified it during the optimization phase
                 //
-                // Note: this invalidates loops, dominators and reachability
-                //
                 DoPhase(this, PHASE_OPT_UPDATE_FLOW_GRAPH, &Compiler::fgUpdateFlowGraphPhase);
 
                 // Recompute the edge weight if we have modified the flow graph

src/coreclr/jit/compiler.h

@@ -2029,12 +2029,15 @@ struct NaturalLoopIterInfo
     int ConstInitValue = 0;
 
     // Block outside the loop that initializes the induction variable. Only
-    // value if HasConstInit is true.
+    // valid if HasConstInit is true.
     BasicBlock* InitBlock = nullptr;
 
     // Tree that has the loop test for the induction variable.
     GenTree* TestTree = nullptr;
 
+    // Block that has the loop test.
+    BasicBlock* TestBlock = nullptr;
+
     // Tree that mutates the induction variable.
     GenTree* IterTree = nullptr;
 

src/coreclr/jit/compmemkind.h

@@ -48,6 +48,7 @@ CompMemKindMacro(DebugOnly)
 CompMemKindMacro(Codegen)
 CompMemKindMacro(LoopOpt)
 CompMemKindMacro(LoopClone)
+CompMemKindMacro(LoopUnroll)
 CompMemKindMacro(LoopHoist)
 CompMemKindMacro(Unknown)
 CompMemKindMacro(RangeCheck)

src/coreclr/jit/fgdiagnostic.cpp

@@ -2573,6 +2573,10 @@ void Compiler::fgDumpBlockMemorySsaIn(BasicBlock* block)
         {
             printf(" = m:%u\n", block->bbMemorySsaNumIn[memoryKind]);
         }
+        else if (block->bbMemorySsaPhiFunc[memoryKind] == BasicBlock::EmptyMemoryPhiDef)
+        {
+            printf(" = phi([not filled])\n");
+        }
         else
         {
             printf(" = phi(");

src/coreclr/jit/flowgraph.cpp

@@ -5008,7 +5008,8 @@ bool FlowGraphNaturalLoop::AnalyzeIteration(NaturalLoopIterInfo* info)
         return false;
     }
 
-    info->IterVar = comp->optIsLoopIncrTree(info->IterTree);
+    info->TestBlock = cond;
+    info->IterVar   = comp->optIsLoopIncrTree(info->IterTree);
 
     assert(info->IterVar != BAD_VAR_NUM);
     LclVarDsc* const iterVarDsc = comp->lvaGetDesc(info->IterVar);