JIT: Remove old loop code (#97232)

All dependencies on old loop finding have been removed, so remove all
old code associated with it.

Author: jakobbotsch

src/coreclr/jit/block.cpp

@@ -491,7 +491,7 @@ void BasicBlock::dspFlags() const
         {BBF_INTERNAL, "internal"},
         {BBF_FAILED_VERIFICATION, "failV"},
         {BBF_HAS_SUPPRESSGC_CALL, "sup-gc"},
-        {BBF_LOOP_HEAD, "Loop"},
+        {BBF_LOOP_HEAD, "loophead"},
         {BBF_HAS_LABEL, "label"},
         {BBF_HAS_JMP, "jmp"},
         {BBF_HAS_CALL, "hascall"},
@@ -513,7 +513,7 @@ void BasicBlock::dspFlags() const
         {BBF_NO_CSE_IN, "no-cse"},
         {BBF_CAN_ADD_PRED, "add-pred"},
         {BBF_RETLESS_CALL, "retless"},
-        {BBF_LOOP_PREHEADER, "LoopPH"},
+        {BBF_LOOP_PREHEADER, "preheader"},
         {BBF_COLD, "cold"},
         {BBF_KEEP_BBJ_ALWAYS, "KEEP"},
         {BBF_CLONED_FINALLY_BEGIN, "cfb"},
@@ -811,7 +811,6 @@ void BasicBlock::CloneBlockState(
     to->bbCodeOffs    = from->bbCodeOffs;
     to->bbCodeOffsEnd = from->bbCodeOffsEnd;
     VarSetOps::AssignAllowUninitRhs(compiler, to->bbScope, from->bbScope);
-    to->bbNatLoopNum = from->bbNatLoopNum;
 #ifdef DEBUG
     to->bbTgtStkDepth = from->bbTgtStkDepth;
 #endif // DEBUG
@@ -1606,11 +1605,6 @@ BasicBlock* BasicBlock::New(Compiler* compiler)
         block->bbMemorySsaNumOut[memoryKind]  = 0;
     }
 
-    // Make sure we reserve a NOT_IN_LOOP value that isn't a legal table index.
-    static_assert_no_msg(BasicBlock::MAX_LOOP_NUM < BasicBlock::NOT_IN_LOOP);
-
-    block->bbNatLoopNum = BasicBlock::NOT_IN_LOOP;
-
     block->bbPreorderNum  = 0;
     block->bbPostorderNum = 0;
 

src/coreclr/jit/block.h

@@ -43,7 +43,7 @@ typedef BitVec_ValRet_T ASSERT_VALRET_TP;
 // This define is used with string concatenation to put this in printf format strings  (Note that %u means unsigned int)
 #define FMT_BB "BB%02u"
 
-// Use this format for loop table indices.
+// Use this format for loop indices
 #define FMT_LP "L%02u"
 
 // And this format for profile weights
@@ -393,7 +393,7 @@ enum BasicBlockFlags : unsigned __int64
     BBF_HAS_NULLCHECK        = MAKE_BBFLAG(11), // BB contains a null check
     BBF_HAS_SUPPRESSGC_CALL  = MAKE_BBFLAG(12), // BB contains a call to a method with SuppressGCTransitionAttribute
     BBF_RUN_RARELY           = MAKE_BBFLAG(13), // BB is rarely run (catch clauses, blocks with throws etc)
-    BBF_LOOP_HEAD            = MAKE_BBFLAG(14), // BB is the head of a loop
+    BBF_LOOP_HEAD            = MAKE_BBFLAG(14), // BB is the head of a loop (can reach a predecessor)
     BBF_HAS_LABEL            = MAKE_BBFLAG(15), // BB needs a label
     BBF_LOOP_ALIGN           = MAKE_BBFLAG(16), // Block is lexically the first block in a loop we intend to align.
     BBF_HAS_ALIGN            = MAKE_BBFLAG(17), // BB ends with 'align' instruction
@@ -1251,14 +1251,6 @@ struct BasicBlock : private LIR::Range
 #define BBCT_FILTER_HANDLER 0xFFFFFFFF
 #define handlerGetsXcptnObj(hndTyp) ((hndTyp) != BBCT_NONE && (hndTyp) != BBCT_FAULT && (hndTyp) != BBCT_FINALLY)
 
-    // The following fields are used for loop detection
-    typedef unsigned char loopNumber;
-    static const unsigned NOT_IN_LOOP  = UCHAR_MAX;
-    static const unsigned MAX_LOOP_NUM = 64;
-
-    loopNumber bbNatLoopNum; // Index, in optLoopTable, of most-nested loop that contains this block,
-                             // or else NOT_IN_LOOP if this block is not in a loop.
-
     // TODO-Cleanup: Get rid of bbStkDepth and use bbStackDepthOnEntry() instead
     union {
         unsigned short bbStkDepth; // stack depth on entry

src/coreclr/jit/compiler.cpp

@@ -305,7 +305,6 @@ Histogram computeReachabilitySetsIterationTable(computeReachabilitySetsIteration
 
 unsigned totalLoopMethods;        // counts the total number of methods that have natural loops
 unsigned maxLoopsPerMethod;       // counts the maximum number of loops a method has
-unsigned totalLoopOverflows;      // # of methods that identified more loops than we can represent
 unsigned totalLoopCount;          // counts the total number of natural loops
 unsigned totalUnnatLoopCount;     // counts the total number of (not-necessarily natural) loops
 unsigned totalUnnatLoopOverflows; // # of methods that identified more unnatural loops than we can represent
@@ -1576,7 +1575,6 @@ void Compiler::compShutdown()
     jitprintf("Total number of methods with loops is %5u\n", totalLoopMethods);
     jitprintf("Total number of              loops is %5u\n", totalLoopCount);
     jitprintf("Maximum number of loops per method is %5u\n", maxLoopsPerMethod);
-    jitprintf("# of methods overflowing nat loop table is %5u\n", totalLoopOverflows);
     jitprintf("Total number of 'unnatural' loops is %5u\n", totalUnnatLoopCount);
     jitprintf("# of methods overflowing unnat loop limit is %5u\n", totalUnnatLoopOverflows);
     jitprintf("Total number of loops with an         iterator is %5u\n", iterLoopCount);
@@ -5254,10 +5252,9 @@ void Compiler::compCompile(void** methodCodePtr, uint32_t* methodCodeSize, JitFl
 //
 // Remarks:
 //   All innermost loops whose block weight meets a threshold are candidates for alignment.
-//   The top block of the loop is marked with the BBF_LOOP_ALIGN flag to indicate this
-//   (the loop table itself is not changed).
+//   The top block of the loop is marked with the BBF_LOOP_ALIGN flag to indicate this.
 //
-//   Depends on the loop table, and on block weights being set.
+//   Depends on block weights being set.
 //
 bool Compiler::shouldAlignLoop(FlowGraphNaturalLoop* loop, BasicBlock* top)
 {
@@ -5839,25 +5836,17 @@ void Compiler::RecomputeFlowGraphAnnotations()
 
     fgComputeReachability();
     optSetBlockWeights();
-    optFindLoops();
 
     fgInvalidateDfsTree();
     m_dfsTree = fgComputeDfs();
-    optFindNewLoops();
+    optFindLoops();
 
     if (fgHasLoops)
     {
         optFindAndScaleGeneralLoopBlocks();
     }
 
     m_domTree = FlowGraphDominatorTree::Build(m_dfsTree);
-
-    // Dominators and the loop table are computed above for old<->new loop
-    // crossreferencing, but they are not actually used for optimization
-    // anymore.
-    optLoopTableValid = false;
-    optLoopTable      = nullptr;
-    optLoopCount      = 0;
 }
 
 /*****************************************************************************/
@@ -9084,7 +9073,7 @@ void JitTimer::PrintCsvMethodStats(Compiler* comp)
     fprintf(s_csvFile, "%u,", comp->info.compILCodeSize);
     fprintf(s_csvFile, "%u,", comp->fgBBcount);
     fprintf(s_csvFile, "%u,", comp->opts.MinOpts());
-    fprintf(s_csvFile, "%u,", comp->optLoopCount);
+    fprintf(s_csvFile, "%u,", comp->optNumNaturalLoopsFound);
     fprintf(s_csvFile, "%u,", comp->optLoopsCloned);
 #if FEATURE_LOOP_ALIGN
 #ifdef DEBUG
@@ -9337,16 +9326,11 @@ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
  *      cCVarSet,    dCVarSet       : Display a "converted" VARSET_TP: the varset is assumed to be tracked variable
  *                                    indices. These are converted to variable numbers and sorted. (Calls
  *                                    dumpConvertedVarSet()).
- *      cLoop,       dLoop          : Display the blocks of a loop, including the trees, given a loop number (call
- *                                    optPrintLoopInfo()).
- *      cLoopPtr,    dLoopPtr       : Display the blocks of a loop, including the trees, given a LoopDsc* (call
- *                                    optPrintLoopInfo()).
- *      cLoops,      dLoops         : Display the loop table (call optPrintLoopTable()).
- *      cNewLoops,   dNewLoops      : Display the loop table (call FlowGraphNaturalLoops::Dump()) with
+ *      cLoops,      dLoops         : Display the loops (call FlowGraphNaturalLoops::Dump()) with
  *                                    Compiler::m_loops.
- *      cNewLoopsA,  dNewLoopsA     : Display the loop table (call FlowGraphNaturalLoops::Dump()) with a given
+ *      cLoopsA,     dLoopsA        : Display the loops (call FlowGraphNaturalLoops::Dump()) with a given
  *                                    loops arg.
- *      cNewLoop,    dNewLoop       : Display a single loop (call FlowGraphNaturalLoop::Dump()) with given
+ *      cLoop,       dLoop          : Display a single loop (call FlowGraphNaturalLoop::Dump()) with given
  *                                    loop arg.
  *      cTreeFlags,  dTreeFlags     : Display tree flags for a specified tree.
  *      cVN,         dVN            : Display a ValueNum (call vnPrint()).
@@ -9361,7 +9345,7 @@ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
  *      dFindTree                   : Find a tree in the IR, specifying a tree id. Sets `dbTree` and `dbTreeBlock`.
  *      dFindStmt                   : Find a Statement in the IR, specifying a statement id. Sets `dbStmt`.
  *      dFindBlock                  : Find a block in the IR, specifying a block number. Sets `dbBlock`.
- *      dFindLoop                   : Find a loop in the loop table, specifying a loop number. Sets `dbLoop`.
+ *      dFindLoop                   : Find a loop specifying a loop index. Sets `dbLoop`.
  */
 
 // Make the debug helpers available (under #ifdef DEBUG) even though they are unreferenced. When the Microsoft
@@ -9401,12 +9385,9 @@ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
 #pragma comment(linker, "/include:cDoms")
 #pragma comment(linker, "/include:cLiveness")
 #pragma comment(linker, "/include:cCVarSet")
-#pragma comment(linker, "/include:cLoop")
-#pragma comment(linker, "/include:cLoopPtr")
 #pragma comment(linker, "/include:cLoops")
-#pragma comment(linker, "/include:cNewLoops")
-#pragma comment(linker, "/include:cNewLoopsA")
-#pragma comment(linker, "/include:cNewLoop")
+#pragma comment(linker, "/include:cLoopsA")
+#pragma comment(linker, "/include:cLoop")
 #pragma comment(linker, "/include:cTreeFlags")
 #pragma comment(linker, "/include:cVN")
 
@@ -9431,11 +9412,7 @@ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
 #pragma comment(linker, "/include:dLiveness")
 #pragma comment(linker, "/include:dCVarSet")
 #pragma comment(linker, "/include:dLoop")
-#pragma comment(linker, "/include:dLoopPtr")
 #pragma comment(linker, "/include:dLoops")
-#pragma comment(linker, "/include:dNewLoops")
-#pragma comment(linker, "/include:dNewLoopsA")
-#pragma comment(linker, "/include:dNewLoop")
 #pragma comment(linker, "/include:dTreeFlags")
 #pragma comment(linker, "/include:dVN")
 
@@ -9473,11 +9450,8 @@ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
 #pragma comment(linker, "/include:_cLiveness")
 #pragma comment(linker, "/include:_cCVarSet")
 #pragma comment(linker, "/include:_cLoop")
-#pragma comment(linker, "/include:_cLoopPtr")
 #pragma comment(linker, "/include:_cLoops")
-#pragma comment(linker, "/include:_cNewLoops")
-#pragma comment(linker, "/include:_cNewLoopsA")
-#pragma comment(linker, "/include:_cNewLoop")
+#pragma comment(linker, "/include:_cLoopsA")
 #pragma comment(linker, "/include:_cTreeFlags")
 #pragma comment(linker, "/include:_cVN")
 
@@ -9501,12 +9475,9 @@ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
 #pragma comment(linker, "/include:_dDoms")
 #pragma comment(linker, "/include:_dLiveness")
 #pragma comment(linker, "/include:_dCVarSet")
-#pragma comment(linker, "/include:_dLoop")
-#pragma comment(linker, "/include:_dLoopPtr")
 #pragma comment(linker, "/include:_dLoops")
-#pragma comment(linker, "/include:_dNewLoops")
-#pragma comment(linker, "/include:_dNewLoopsA")
-#pragma comment(linker, "/include:_dNewLoop")
+#pragma comment(linker, "/include:_dLoopsA")
+#pragma comment(linker, "/include:_dLoop")
 #pragma comment(linker, "/include:_dTreeFlags")
 #pragma comment(linker, "/include:_dVN")
 
@@ -9682,44 +9653,21 @@ JITDBGAPI void __cdecl cCVarSet(Compiler* comp, VARSET_VALARG_TP vars)
     printf("\n"); // dumpConvertedVarSet() doesn't emit a trailing newline
 }
 
-JITDBGAPI void __cdecl cLoop(Compiler* comp, unsigned loopNum)
-{
-    static unsigned sequenceNumber = 0; // separate calls with a number to indicate this function has been called
-    printf("===================================================================== *Loop %u\n", sequenceNumber++);
-    comp->optPrintLoopInfo(loopNum, /* verbose */ true);
-    printf("\n");
-}
-
-JITDBGAPI void __cdecl cLoopPtr(Compiler* comp, const Compiler::LoopDsc* loop)
-{
-    static unsigned sequenceNumber = 0; // separate calls with a number to indicate this function has been called
-    printf("===================================================================== *LoopPtr %u\n", sequenceNumber++);
-    comp->optPrintLoopInfo(loop, /* verbose */ true);
-    printf("\n");
-}
-
 JITDBGAPI void __cdecl cLoops(Compiler* comp)
-{
-    static unsigned sequenceNumber = 0; // separate calls with a number to indicate this function has been called
-    printf("===================================================================== *Loops %u\n", sequenceNumber++);
-    comp->optPrintLoopTable();
-}
-
-JITDBGAPI void __cdecl cNewLoops(Compiler* comp)
 {
     static unsigned sequenceNumber = 0; // separate calls with a number to indicate this function has been called
     printf("===================================================================== *NewLoops %u\n", sequenceNumber++);
     FlowGraphNaturalLoops::Dump(comp->m_loops);
 }
 
-JITDBGAPI void __cdecl cNewLoopsA(Compiler* comp, FlowGraphNaturalLoops* loops)
+JITDBGAPI void __cdecl cLoopsA(Compiler* comp, FlowGraphNaturalLoops* loops)
 {
     static unsigned sequenceNumber = 0; // separate calls with a number to indicate this function has been called
     printf("===================================================================== *NewLoopsA %u\n", sequenceNumber++);
     FlowGraphNaturalLoops::Dump(loops);
 }
 
-JITDBGAPI void __cdecl cNewLoop(Compiler* comp, FlowGraphNaturalLoop* loop)
+JITDBGAPI void __cdecl cLoop(Compiler* comp, FlowGraphNaturalLoop* loop)
 {
     static unsigned sequenceNumber = 0; // separate calls with a number to indicate this function has been called
     printf("===================================================================== *NewLoop %u\n", sequenceNumber++);
@@ -9778,10 +9726,6 @@ JITDBGAPI void __cdecl cTreeFlags(Compiler* comp, GenTree* tree)
                 {
                     chars += printf("[VAR_USEASG]");
                 }
-                if (tree->gtFlags & GTF_VAR_ITERATOR)
-                {
-                    chars += printf("[VAR_ITERATOR]");
-                }
                 if (tree->gtFlags & GTF_VAR_MOREUSES)
                 {
                     chars += printf("[VAR_MOREUSES]");
@@ -10318,34 +10262,19 @@ JITDBGAPI void __cdecl dCVarSet(VARSET_VALARG_TP vars)
     cCVarSet(JitTls::GetCompiler(), vars);
 }
 
-JITDBGAPI void __cdecl dLoop(unsigned loopNum)
-{
-    cLoop(JitTls::GetCompiler(), loopNum);
-}
-
-JITDBGAPI void __cdecl dLoopPtr(const Compiler::LoopDsc* loop)
-{
-    cLoopPtr(JitTls::GetCompiler(), loop);
-}
-
 JITDBGAPI void __cdecl dLoops()
 {
     cLoops(JitTls::GetCompiler());
 }
 
-JITDBGAPI void __cdecl dNewLoops()
-{
-    cNewLoops(JitTls::GetCompiler());
-}
-
-JITDBGAPI void __cdecl dNewLoopsA(FlowGraphNaturalLoops* loops)
+JITDBGAPI void __cdecl dLoopsA(FlowGraphNaturalLoops* loops)
 {
-    cNewLoopsA(JitTls::GetCompiler(), loops);
+    cLoopsA(JitTls::GetCompiler(), loops);
 }
 
-JITDBGAPI void __cdecl dNewLoop(FlowGraphNaturalLoop* loop)
+JITDBGAPI void __cdecl dLoop(FlowGraphNaturalLoop* loop)
 {
-    cNewLoop(JitTls::GetCompiler(), loop);
+    cLoop(JitTls::GetCompiler(), loop);
 }
 
 JITDBGAPI void __cdecl dTreeFlags(GenTree* tree)
@@ -10382,11 +10311,11 @@ JITDBGAPI void __cdecl dBlockList(BasicBlockList* list)
 // Trees, Stmts, and/or Blocks using id or bbNum.
 // That can be used in watch window or as a way to get address of fields for data breakpoints.
 
-GenTree*           dbTree;
-Statement*         dbStmt;
-BasicBlock*        dbTreeBlock;
-BasicBlock*        dbBlock;
-Compiler::LoopDsc* dbLoop;
+GenTree*              dbTree;
+Statement*            dbStmt;
+BasicBlock*           dbTreeBlock;
+BasicBlock*           dbBlock;
+FlowGraphNaturalLoop* dbLoop;
 
 // Debug APIs for finding Trees, Stmts, and/or Blocks.
 // As a side effect, they set the debug variables above.
@@ -10478,18 +10407,18 @@ JITDBGAPI BasicBlock* __cdecl dFindBlock(unsigned bbNum)
     return nullptr;
 }
 
-JITDBGAPI Compiler::LoopDsc* __cdecl dFindLoop(unsigned loopNum)
+JITDBGAPI FlowGraphNaturalLoop* __cdecl dFindLoop(unsigned index)
 {
     Compiler* comp = JitTls::GetCompiler();
     dbLoop         = nullptr;
 
-    if (loopNum >= comp->optLoopCount)
+    if ((comp->m_loops == nullptr) || (index >= comp->m_loops->NumLoops()))
     {
-        printf("loopNum %u out of range\n", loopNum);
+        printf("Index %u out of range\n", index);
         return nullptr;
     }
 
-    dbLoop = &comp->optLoopTable[loopNum];
+    dbLoop = comp->m_loops->GetLoopByIndex(index);
     return dbLoop;
 }