JIT: Add scalar evolution analysis and do IV widening based on it

src/coreclr/jit/CMakeLists.txt

@@ -94,7 +94,6 @@ set( JIT_SOURCES
   bitset.cpp
   block.cpp
   buildstring.cpp
-  layout.cpp
   codegencommon.cpp
   codegenlinear.cpp
   compiler.cpp
@@ -123,21 +122,23 @@ set( JIT_SOURCES
   gentree.cpp
   gschecks.cpp
   hashbv.cpp
-  hwintrinsic.cpp
+  helperexpansion.cpp
   hostallocator.cpp
+  hwintrinsic.cpp
   ifconversion.cpp
-  helperexpansion.cpp
-  indirectcalltransformer.cpp
-  importercalls.cpp
   importer.cpp
+  importercalls.cpp
   importervectorization.cpp
+  indirectcalltransformer.cpp
+  inductionvariableopts.cpp
   inline.cpp
   inlinepolicy.cpp
   instr.cpp
   jitconfig.cpp
   jiteh.cpp
   jithashtable.cpp
   jitmetadata.cpp
+  layout.cpp
   lclmorph.cpp
   lclvars.cpp
   likelyclass.cpp
@@ -152,7 +153,6 @@ set( JIT_SOURCES
   objectalloc.cpp
   optcse.cpp
   optimizebools.cpp
-  switchrecognition.cpp
   optimizer.cpp
   patchpoint.cpp
   phase.cpp
@@ -173,6 +173,7 @@ set( JIT_SOURCES
   ssabuilder.cpp
   ssarenamestate.cpp
   stacklevelsetter.cpp
+  switchrecognition.cpp
   treelifeupdater.cpp
   unwind.cpp
   utils.cpp

src/coreclr/jit/compiler.cpp

@@ -4893,6 +4893,7 @@ void Compiler::compCompile(void** methodCodePtr, uint32_t* methodCodeSize, JitFl
         bool doValueNum                = true;
         bool doLoopHoisting            = true;
         bool doCopyProp                = true;
+        bool doOptimizeIVs             = true;
         bool doBranchOpt               = true;
         bool doCse                     = true;
         bool doAssertionProp           = true;
@@ -4905,6 +4906,7 @@ void Compiler::compCompile(void** methodCodePtr, uint32_t* methodCodeSize, JitFl
         doSsa                     = (JitConfig.JitDoSsa() != 0);
         doEarlyProp               = doSsa && (JitConfig.JitDoEarlyProp() != 0);
         doValueNum                = doSsa && (JitConfig.JitDoValueNumber() != 0);
+        doOptimizeIVs             = doSsa && (JitConfig.JitDoOptimizeIVs() != 0);
         doLoopHoisting            = doValueNum && (JitConfig.JitDoLoopHoisting() != 0);
         doCopyProp                = doValueNum && (JitConfig.JitDoCopyProp() != 0);
         doBranchOpt               = doValueNum && (JitConfig.JitDoRedundantBranchOpts() != 0);
@@ -5005,6 +5007,13 @@ void Compiler::compCompile(void** methodCodePtr, uint32_t* methodCodeSize, JitFl
                 DoPhase(this, PHASE_OPTIMIZE_INDEX_CHECKS, &Compiler::rangeCheckPhase);
             }
 
+            if (doOptimizeIVs)
+            {
+                // Simplify and optimize induction variables used in natural loops
+                //
+                DoPhase(this, PHASE_OPTIMIZE_INDUCTION_VARIABLES, &Compiler::optInductionVariables);
+            }
+
             if (doVNBasedDeadStoreRemoval)
             {
                 // Note: this invalidates SSA and value numbers on tree nodes.

src/coreclr/jit/compiler.h

@@ -4972,7 +4972,7 @@ class Compiler
 #ifdef DEBUG
     jitstd::vector<BasicBlock*>* fgBBOrder;          // ordered vector of BBs
 #endif
-    // Used as a quick check for whether loop alignment should look for natural loops.
+    // Used as a quick check for whether phases downstream of loop finding should look for natural loops.
     // If true: there may or may not be any natural loops in the flow graph, so try to find them
     // If false: there's definitely not any natural loops in the flow graph
     bool         fgMightHaveNaturalLoops;
@@ -7411,6 +7411,18 @@ class Compiler
                              BasicBlock* basicBlock);
 #endif
 
+    PhaseStatus optInductionVariables();
+    bool optCanSinkWidenedIV(unsigned lclNum, FlowGraphNaturalLoop* loop);
+    bool optIsIVWideningProfitable(unsigned                lclNum,
+                                   BasicBlock*             initBlock,
+                                   bool                    initedToConstant,
+                                   FlowGraphNaturalLoop*   loop,
+                                   ArrayStack<Statement*>& ivUses);
+    void optBestEffortReplaceNarrowIVUsesWith(
+        unsigned lclNum, unsigned ssaNum, unsigned newLclNum, BasicBlock* block, Statement* firstStmt);
+    void optReplaceWidenedIV(unsigned lclNum, unsigned ssaNum, unsigned newLclNum, Statement* stmt);
+    void optSinkWidenedIV(unsigned lclNum, unsigned newLclNum, FlowGraphNaturalLoop* loop);
+
     // Redundant branch opts
     //
     PhaseStatus optRedundantBranches();

src/coreclr/jit/compmemkind.h

@@ -50,6 +50,7 @@ CompMemKindMacro(LoopOpt)
 CompMemKindMacro(LoopClone)
 CompMemKindMacro(LoopUnroll)
 CompMemKindMacro(LoopHoist)
+CompMemKindMacro(LoopIVOpts)
 CompMemKindMacro(Unknown)
 CompMemKindMacro(RangeCheck)
 CompMemKindMacro(CopyProp)

src/coreclr/jit/compphases.h

@@ -84,6 +84,7 @@ CompPhaseNameMacro(PHASE_BUILD_SSA_DF,               "SSA: DF",
 CompPhaseNameMacro(PHASE_BUILD_SSA_INSERT_PHIS,      "SSA: insert phis",               false, PHASE_BUILD_SSA, false)
 CompPhaseNameMacro(PHASE_BUILD_SSA_RENAME,           "SSA: rename",                    false, PHASE_BUILD_SSA, false)
 CompPhaseNameMacro(PHASE_EARLY_PROP,                 "Early Value Propagation",        false, -1, false)
+CompPhaseNameMacro(PHASE_OPTIMIZE_INDUCTION_VARIABLES, "Optimize Induction Variables", false, -1, false)
 CompPhaseNameMacro(PHASE_VALUE_NUMBER,               "Do value numbering",             false, -1, false)
 CompPhaseNameMacro(PHASE_OPTIMIZE_INDEX_CHECKS,      "Optimize index checks",          false, -1, false)
 CompPhaseNameMacro(PHASE_OPTIMIZE_VALNUM_CSES,       "Optimize Valnum CSEs",           false, -1, false)