JIT: refactor CSE heuristics (#95705)

Split the heuristics into a common base class and (currently) two
derived classes, one for normal CSEs and another for random CSEs.

Author: AndyAyersMS

src/coreclr/jit/CMakeLists.txt

@@ -346,6 +346,7 @@ set( JIT_HEADERS
   namedintrinsiclist.h
   objectalloc.h
   opcode.h
+  optcse.h
   phase.h
   promotion.h
   rangecheck.h

src/coreclr/jit/compiler.h

@@ -77,7 +77,8 @@ struct InitVarDscInfo;       // defined in registerargconvention.h
 class FgStack;               // defined in fgbasic.cpp
 class Instrumentor;          // defined in fgprofile.cpp
 class SpanningTreeVisitor;   // defined in fgprofile.cpp
-class CSE_DataFlow;          // defined in OptCSE.cpp
+class CSE_DataFlow;          // defined in optcse.cpp
+struct CSEdsc;               // defined in optcse.h
 class OptBoolsDsc;           // defined in optimizer.cpp
 struct RelopImplicationInfo; // defined in redundantbranchopts.cpp
 struct JumpThreadInfo;       // defined in redundantbranchopts.cpp
@@ -2482,6 +2483,8 @@ class Compiler
     friend class Phase;
     friend class Lowering;
     friend class CSE_DataFlow;
+    friend class CSE_HeuristicCommon;
+    friend class CSE_HeuristicRandom;
     friend class CSE_Heuristic;
     friend class CodeGenInterface;
     friend class CodeGen;
@@ -7308,58 +7311,6 @@ class Compiler
 
     EXPSET_TP cseCallKillsMask; // Computed once - A mask that is used to kill available CSEs at callsites
 
-    /* Generic list of nodes - used by the CSE logic */
-
-    struct treeLst
-    {
-        treeLst* tlNext;
-        GenTree* tlTree;
-    };
-
-    struct treeStmtLst
-    {
-        treeStmtLst* tslNext;
-        GenTree*     tslTree;  // tree node
-        Statement*   tslStmt;  // statement containing the tree
-        BasicBlock*  tslBlock; // block containing the statement
-    };
-
-    // The following logic keeps track of expressions via a simple hash table.
-
-    struct CSEdsc
-    {
-        CSEdsc*  csdNextInBucket;  // used by the hash table
-        size_t   csdHashKey;       // the original hashkey
-        ssize_t  csdConstDefValue; // When we CSE similar constants, this is the value that we use as the def
-        ValueNum csdConstDefVN;    // When we CSE similar constants, this is the ValueNumber that we use for the LclVar
-                                   // assignment
-        unsigned csdIndex;         // 1..optCSECandidateCount
-        bool     csdIsSharedConst; // true if this CSE is a shared const
-        bool     csdLiveAcrossCall;
-
-        unsigned short csdDefCount; // definition   count
-        unsigned short csdUseCount; // use          count  (excluding the implicit uses at defs)
-
-        weight_t csdDefWtCnt; // weighted def count
-        weight_t csdUseWtCnt; // weighted use count  (excluding the implicit uses at defs)
-
-        GenTree*    csdTree;  // treenode containing the 1st occurrence
-        Statement*  csdStmt;  // stmt containing the 1st occurrence
-        BasicBlock* csdBlock; // block containing the 1st occurrence
-
-        treeStmtLst* csdTreeList; // list of matching tree nodes: head
-        treeStmtLst* csdTreeLast; // list of matching tree nodes: tail
-
-        ValueNum defExcSetPromise; // The exception set that is now required for all defs of this CSE.
-                                   // This will be set to NoVN if we decide to abandon this CSE
-
-        ValueNum defExcSetCurrent; // The set of exceptions we currently can use for CSE uses.
-
-        ValueNum defConservNormVN; // if all def occurrences share the same conservative normal value
-                                   // number, this will reflect it; otherwise, NoVN.
-                                   // not used for shared const CSE's
-    };
-
     static const size_t s_optCSEhashSizeInitial;
     static const size_t s_optCSEhashGrowthFactor;
     static const size_t s_optCSEhashBucketSize;

src/coreclr/jit/jitconfigvalues.h

@@ -160,10 +160,6 @@ CONFIG_INTEGER(JitStackChecks, W("JitStackChecks"), 0)
 CONFIG_INTEGER(JitStress, W("JitStress"), 0) // Internal Jit stress mode: 0 = no stress, 2 = all stress, other = vary
                                              // stress based on a hash of the method and this value
 CONFIG_INTEGER(JitStressBBProf, W("JitStressBBProf"), 0)               // Internal Jit stress mode
-CONFIG_INTEGER(JitStressBiasedCSE, W("JitStressBiasedCSE"), 0x101)     // Internal Jit stress mode: decimal bias value
-                                                                       // between (0,100) to perform CSE on a candidate.
-                                                                       // 100% = All CSEs. 0% = 0 CSE. (> 100) means no
-                                                                       // stress.
 CONFIG_INTEGER(JitStressModeNamesOnly, W("JitStressModeNamesOnly"), 0) // Internal Jit stress: if nonzero, only enable
                                                                        // stress modes listed in JitStressModeNames
 CONFIG_INTEGER(JitStressProcedureSplitting, W("JitStressProcedureSplitting"), 0) // Always split after the first basic
@@ -402,6 +398,11 @@ CONFIG_INTEGER(JitCSEMask, W("JitCSEMask"), 0)
 
 // Enable metric output in jit disasm & elsewhere
 CONFIG_INTEGER(JitMetrics, W("JitMetrics"), 0)
+
+// When nonzero, choose CSE candidates randomly, with probability
+// specified by the (decimal) value of the config
+CONFIG_INTEGER(JitRandomCSE, W("JitRandomCSE"), 0)
+
 #endif
 
 ///