JIT: Use likelihood-based edge weights (dotnet#99736)

Part of dotnet#93020. Removes FlowEdge::m_edgeWeightMin and FlowEdge::m_edgeWeightMax, and relies on block weights and edge likelihoods to determine edge weights via FlowEdge::getLikelyWeight.

Author: amanasifkhalid

src/coreclr/jit/block.h

@@ -587,10 +587,6 @@ struct FlowEdge
     // The destination of the control flow
     BasicBlock* m_destBlock;
 
-    // Edge weights
-    weight_t m_edgeWeightMin;
-    weight_t m_edgeWeightMax;
-
     // Likelihood that m_sourceBlock transfers control along this edge.
     // Values in range [0..1]
     weight_t m_likelihood;
@@ -606,8 +602,6 @@ struct FlowEdge
         : m_nextPredEdge(rest)
         , m_sourceBlock(sourceBlock)
         , m_destBlock(destBlock)
-        , m_edgeWeightMin(0)
-        , m_edgeWeightMax(0)
         , m_likelihood(0)
         , m_dupCount(0)
 #ifdef DEBUG
@@ -655,24 +649,6 @@ struct FlowEdge
         m_destBlock = newBlock;
     }
 
-    weight_t edgeWeightMin() const
-    {
-        return m_edgeWeightMin;
-    }
-
-    weight_t edgeWeightMax() const
-    {
-        return m_edgeWeightMax;
-    }
-
-    // These two methods are used to set new values for edge weights.
-    // They return false if the newWeight is not between the current [min..max]
-    // when slop is non-zero we allow for the case where our weights might be off by 'slop'
-    //
-    bool setEdgeWeightMinChecked(weight_t newWeight, BasicBlock* bDst, weight_t slop, bool* wbUsedSlop);
-    bool setEdgeWeightMaxChecked(weight_t newWeight, BasicBlock* bDst, weight_t slop, bool* wbUsedSlop);
-    void setEdgeWeights(weight_t newMinWeight, weight_t newMaxWeight, BasicBlock* bDst);
-
     weight_t getLikelihood() const
     {
         assert(m_likelihoodSet);

src/coreclr/jit/codegencommon.cpp

@@ -1831,8 +1831,7 @@ void CodeGen::genGenerateMachineCode()
 
         if (compiler->fgHaveProfileWeights())
         {
-            printf("; with %s: edge weights are %s, and fgCalledCount is " FMT_WT "\n",
-                   compiler->compGetPgoSourceName(), compiler->fgHaveValidEdgeWeights ? "valid" : "invalid",
+            printf("; with %s: fgCalledCount is " FMT_WT "\n", compiler->compGetPgoSourceName(),
                    compiler->fgCalledCount);
         }
 

src/coreclr/jit/compiler.cpp

@@ -4910,9 +4910,9 @@ void Compiler::compCompile(void** methodCodePtr, uint32_t* methodCodeSize, JitFl
     //
     DoPhase(this, PHASE_GS_COOKIE, &Compiler::gsPhase);
 
-    // Compute the block and edge weights
+    // Compute the block weights
     //
-    DoPhase(this, PHASE_COMPUTE_EDGE_WEIGHTS, &Compiler::fgComputeBlockAndEdgeWeights);
+    DoPhase(this, PHASE_COMPUTE_BLOCK_WEIGHTS, &Compiler::fgComputeBlockWeights);
 
     if (UsesFunclets())
     {
@@ -5148,10 +5148,6 @@ void Compiler::compCompile(void** methodCodePtr, uint32_t* methodCodeSize, JitFl
                 // update the flowgraph if we modified it during the optimization phase
                 //
                 DoPhase(this, PHASE_OPT_UPDATE_FLOW_GRAPH, &Compiler::fgUpdateFlowGraphPhase);
-
-                // Recompute the edge weight if we have modified the flow graph
-                //
-                DoPhase(this, PHASE_COMPUTE_EDGE_WEIGHTS2, &Compiler::fgComputeEdgeWeights);
             }
 
             // Iterate if requested, resetting annotations first.

src/coreclr/jit/compiler.h

@@ -1593,12 +1593,11 @@ enum API_ICorJitInfo_Names
 enum class ProfileChecks : unsigned int
 {
     CHECK_NONE          = 0,
-    CHECK_CLASSIC       = 1 << 0, // check "classic" jit weights
-    CHECK_HASLIKELIHOOD = 1 << 1, // check all FlowEdges for hasLikelihood
-    CHECK_LIKELIHOODSUM = 1 << 2, // check block successor likelihoods sum to 1                              
-    CHECK_LIKELY        = 1 << 3, // fully check likelihood based weights
-    RAISE_ASSERT        = 1 << 4, // assert on check failure
-    CHECK_ALL_BLOCKS    = 1 << 5, // check blocks even if bbHasProfileWeight is false
+    CHECK_HASLIKELIHOOD = 1 << 0, // check all FlowEdges for hasLikelihood
+    CHECK_LIKELIHOODSUM = 1 << 1, // check block succesor likelihoods sum to 1                              
+    CHECK_LIKELY        = 1 << 2, // fully check likelihood based weights
+    RAISE_ASSERT        = 1 << 3, // assert on check failure
+    CHECK_ALL_BLOCKS    = 1 << 4, // check blocks even if bbHasProfileWeight is false
 };
 
 inline constexpr ProfileChecks operator ~(ProfileChecks a)
@@ -5207,14 +5206,10 @@ class Compiler
     // - Rationalization links all nodes into linear form which is kept until
     //   the end of compilation. The first and last nodes are stored in the block.
     NodeThreading fgNodeThreading;
-    bool          fgCanRelocateEHRegions;   // true if we are allowed to relocate the EH regions
-    bool          fgEdgeWeightsComputed;    // true after we have called fgComputeEdgeWeights
-    bool          fgHaveValidEdgeWeights;   // true if we were successful in computing all of the edge weights
-    bool          fgSlopUsedInEdgeWeights;  // true if their was some slop used when computing the edge weights
-    bool          fgRangeUsedInEdgeWeights; // true if some of the edgeWeight are expressed in Min..Max form
-    weight_t      fgCalledCount;            // count of the number of times this method was called
-                                            // This is derived from the profile data
-                                            // or is BB_UNITY_WEIGHT when we don't have profile data
+    bool          fgCanRelocateEHRegions; // true if we are allowed to relocate the EH regions
+    weight_t      fgCalledCount;          // count of the number of times this method was called
+                                          // This is derived from the profile data
+                                          // or is BB_UNITY_WEIGHT when we don't have profile data
 
     bool fgFuncletsCreated; // true if the funclet creation phase has been run
 
@@ -6047,10 +6042,9 @@ class Compiler
 #ifdef DEBUG
     void fgPrintEdgeWeights();
 #endif
-    PhaseStatus fgComputeBlockAndEdgeWeights();
+    PhaseStatus fgComputeBlockWeights();
     bool fgComputeMissingBlockWeights(weight_t* returnWeight);
     bool fgComputeCalledCount(weight_t returnWeight);
-    PhaseStatus fgComputeEdgeWeights();
 
     bool fgReorderBlocks(bool useProfile);
 
@@ -6868,7 +6862,6 @@ class Compiler
     BasicBlock* optTryAdvanceLoopCompactionInsertionPoint(FlowGraphNaturalLoop* loop, BasicBlock* insertionPoint, BasicBlock* top, BasicBlock* bottom);
     bool optCreatePreheader(FlowGraphNaturalLoop* loop);
     void optSetWeightForPreheaderOrExit(FlowGraphNaturalLoop* loop, BasicBlock* block);
-    weight_t optEstimateEdgeLikelihood(BasicBlock* from, BasicBlock* to, bool* fromProfile);
 
     bool optCanonicalizeExits(FlowGraphNaturalLoop* loop);
     bool optCanonicalizeExit(FlowGraphNaturalLoop* loop, BasicBlock* exit);

src/coreclr/jit/compphases.h

@@ -55,7 +55,7 @@ CompPhaseNameMacro(PHASE_MORPH_GLOBAL,               "Morph - Global",
 CompPhaseNameMacro(PHASE_POST_MORPH,                 "Post-Morph",                     false, -1, false)
 CompPhaseNameMacro(PHASE_MORPH_END,                  "Morph - Finish",                 false, -1, true)
 CompPhaseNameMacro(PHASE_GS_COOKIE,                  "GS Cookie",                      false, -1, false)
-CompPhaseNameMacro(PHASE_COMPUTE_EDGE_WEIGHTS,       "Compute edge weights (1, false)",false, -1, false)
+CompPhaseNameMacro(PHASE_COMPUTE_BLOCK_WEIGHTS,      "Compute block weights",          false, -1, false)
 CompPhaseNameMacro(PHASE_CREATE_FUNCLETS,            "Create EH funclets",             false, -1, false)
 CompPhaseNameMacro(PHASE_HEAD_TAIL_MERGE,            "Head and tail merge",            false, -1, false)
 CompPhaseNameMacro(PHASE_MERGE_THROWS,               "Merge throw blocks",             false, -1, false)
@@ -95,7 +95,6 @@ CompPhaseNameMacro(PHASE_ASSERTION_PROP_MAIN,        "Assertion prop",
 CompPhaseNameMacro(PHASE_IF_CONVERSION,              "If conversion",                  false, -1, false)
 CompPhaseNameMacro(PHASE_VN_BASED_DEAD_STORE_REMOVAL,"VN-based dead store removal",    false, -1, false)
 CompPhaseNameMacro(PHASE_OPT_UPDATE_FLOW_GRAPH,      "Update flow graph opt pass",     false, -1, false)
-CompPhaseNameMacro(PHASE_COMPUTE_EDGE_WEIGHTS2,      "Compute edge weights (2, false)",false, -1, false)
 CompPhaseNameMacro(PHASE_STRESS_SPLIT_TREE,          "Stress gtSplitTree",             false, -1, false)
 CompPhaseNameMacro(PHASE_EXPAND_RTLOOKUPS,           "Expand runtime lookups",         false, -1, true)
 CompPhaseNameMacro(PHASE_EXPAND_STATIC_INIT,         "Expand static init",             false, -1, true)

src/coreclr/jit/fgbasic.cpp

@@ -23,12 +23,8 @@ void Compiler::fgInit()
     /* We haven't yet computed the bbPreds lists */
     fgPredsComputed = false;
 
-    /* We haven't yet computed the edge weight */
-    fgEdgeWeightsComputed    = false;
-    fgHaveValidEdgeWeights   = false;
-    fgSlopUsedInEdgeWeights  = false;
-    fgRangeUsedInEdgeWeights = true;
-    fgCalledCount            = BB_ZERO_WEIGHT;
+    /* We haven't yet computed block weights */
+    fgCalledCount = BB_ZERO_WEIGHT;
 
     /* Initialize the basic block list */
 
@@ -5446,6 +5442,7 @@ BasicBlock* Compiler::fgConnectFallThrough(BasicBlock* bSrc, BasicBlock* bDst)
         // Add a new block after bSrc which jumps to 'bDst'
         jmpBlk                  = fgNewBBafter(BBJ_ALWAYS, bSrc, true);
         FlowEdge* const oldEdge = bSrc->GetFalseEdge();
+
         // Access the likelihood of oldEdge before
         // it gets reset by SetTargetEdge below.
         //
@@ -5457,29 +5454,9 @@ BasicBlock* Compiler::fgConnectFallThrough(BasicBlock* bSrc, BasicBlock* bDst)
 
         // When adding a new jmpBlk we will set the bbWeight and bbFlags
         //
-        if (fgHaveValidEdgeWeights && fgHaveProfileWeights())
+        if (fgHaveProfileWeights())
         {
-            jmpBlk->bbWeight = (newEdge->edgeWeightMin() + newEdge->edgeWeightMax()) / 2;
-            if (bSrc->bbWeight == BB_ZERO_WEIGHT)
-            {
-                jmpBlk->bbWeight = BB_ZERO_WEIGHT;
-            }
-
-            if (jmpBlk->bbWeight == BB_ZERO_WEIGHT)
-            {
-                jmpBlk->SetFlags(BBF_RUN_RARELY);
-            }
-
-            weight_t weightDiff = (newEdge->edgeWeightMax() - newEdge->edgeWeightMin());
-            weight_t slop       = BasicBlock::GetSlopFraction(bSrc, bDst);
-            //
-            // If the [min/max] values for our edge weight is within the slop factor
-            //  then we will set the BBF_PROF_WEIGHT flag for the block
-            //
-            if (weightDiff <= slop)
-            {
-                jmpBlk->SetFlags(BBF_PROF_WEIGHT);
-            }
+            jmpBlk->setBBProfileWeight(newEdge->getLikelyWeight());
         }
         else
         {

src/coreclr/jit/fgdiagnostic.cpp

@@ -28,26 +28,17 @@ void Compiler::fgPrintEdgeWeights()
 
                 printf(FMT_BB " ", bSrc->bbNum);
 
-                if (edge->edgeWeightMin() < BB_MAX_WEIGHT)
+                const weight_t weight = edge->getLikelyWeight();
+
+                if (weight < BB_MAX_WEIGHT)
                 {
-                    printf("(%f", edge->edgeWeightMin());
+                    printf("(%f)", weight);
                 }
                 else
                 {
-                    printf("(MAX");
-                }
-                if (edge->edgeWeightMin() != edge->edgeWeightMax())
-                {
-                    if (edge->edgeWeightMax() < BB_MAX_WEIGHT)
-                    {
-                        printf("..%f", edge->edgeWeightMax());
-                    }
-                    else
-                    {
-                        printf("..MAX");
-                    }
+                    printf("(MAX)");
                 }
-                printf(")");
+
                 if (edge->getNextPredEdge() != nullptr)
                 {
                     printf(", ");
@@ -735,7 +726,6 @@ bool Compiler::fgDumpFlowGraph(Phases phase, PhasePosition pos)
     JITDUMP("Writing out flow graph %s phase %s\n", (pos == PhasePosition::PrePhase) ? "before" : "after",
             PhaseNames[phase]);
 
-    bool        validWeights  = fgHaveValidEdgeWeights;
     double      weightDivisor = (double)BasicBlock::getCalledCount(this);
     const char* escapedString;
     const char* regionString = "NONE";
@@ -791,14 +781,6 @@ bool Compiler::fgDumpFlowGraph(Phases phase, PhasePosition pos)
         {
             fprintf(fgxFile, "\n    hasLoops=\"true\"");
         }
-        if (validWeights)
-        {
-            fprintf(fgxFile, "\n    validEdgeWeights=\"true\"");
-            if (!fgSlopUsedInEdgeWeights && !fgRangeUsedInEdgeWeights)
-            {
-                fprintf(fgxFile, "\n    exactEdgeWeights=\"true\"");
-            }
-        }
         if (fgFirstColdBlock != nullptr)
         {
             fprintf(fgxFile, "\n    firstColdBlock=\"%d\"", fgFirstColdBlock->bbNum);
@@ -1081,11 +1063,8 @@ bool Compiler::fgDumpFlowGraph(Phases phase, PhasePosition pos)
                         fprintf(fgxFile, " [");
                     }
 
-                    if (validWeights)
-                    {
-                        weight_t edgeWeight = (edge->edgeWeightMin() + edge->edgeWeightMax()) / 2;
-                        fprintf(fgxFile, "%slabel=\"%7.2f\"", sep, (double)edgeWeight / weightDivisor);
-                    }
+                    const weight_t edgeWeight = edge->getLikelyWeight();
+                    fprintf(fgxFile, "%slabel=\"%7.2f\"", sep, (double)edgeWeight / weightDivisor);
 
                     fprintf(fgxFile, "];\n");
                 }
@@ -1106,32 +1085,22 @@ bool Compiler::fgDumpFlowGraph(Phases phase, PhasePosition pos)
                             fprintf(fgxFile, "\n            switchDefault=\"true\"");
                         }
                     }
-                    if (validWeights)
-                    {
-                        weight_t edgeWeight = (edge->edgeWeightMin() + edge->edgeWeightMax()) / 2;
-                        fprintf(fgxFile, "\n            weight=");
-                        fprintfDouble(fgxFile, ((double)edgeWeight) / weightDivisor);
 
-                        if (edge->edgeWeightMin() != edge->edgeWeightMax())
+                    const weight_t edgeWeight = edge->getLikelyWeight();
+                    fprintf(fgxFile, "\n            weight=");
+                    fprintfDouble(fgxFile, ((double)edgeWeight) / weightDivisor);
+
+                    if (edgeWeight > 0)
+                    {
+                        if (edgeWeight < bSource->bbWeight)
                         {
-                            fprintf(fgxFile, "\n            minWeight=");
-                            fprintfDouble(fgxFile, ((double)edge->edgeWeightMin()) / weightDivisor);
-                            fprintf(fgxFile, "\n            maxWeight=");
-                            fprintfDouble(fgxFile, ((double)edge->edgeWeightMax()) / weightDivisor);
+                            fprintf(fgxFile, "\n            out=");
+                            fprintfDouble(fgxFile, ((double)edgeWeight) / sourceWeightDivisor);
                         }
-
-                        if (edgeWeight > 0)
+                        if (edgeWeight < bTarget->bbWeight)
                         {
-                            if (edgeWeight < bSource->bbWeight)
-                            {
-                                fprintf(fgxFile, "\n            out=");
-                                fprintfDouble(fgxFile, ((double)edgeWeight) / sourceWeightDivisor);
-                            }
-                            if (edgeWeight < bTarget->bbWeight)
-                            {
-                                fprintf(fgxFile, "\n            in=");
-                                fprintfDouble(fgxFile, ((double)edgeWeight) / targetWeightDivisor);
-                            }
+                            fprintf(fgxFile, "\n            in=");
+                            fprintfDouble(fgxFile, ((double)edgeWeight) / targetWeightDivisor);
                         }
                     }
                 }

src/coreclr/jit/fgflow.cpp

@@ -191,42 +191,6 @@ FlowEdge* Compiler::fgAddRefPred(BasicBlock* block, BasicBlock* blockPred, FlowE
             //
             flow->setLikelihood(oldEdge->getLikelihood());
         }
-
-        if (fgHaveValidEdgeWeights)
-        {
-            // We are creating an edge from blockPred to block
-            // and we have already computed the edge weights, so
-            // we will try to setup this new edge with valid edge weights.
-            //
-            if (oldEdge != nullptr)
-            {
-                // If our caller has given us the old edge weights
-                // then we will use them.
-                //
-                flow->setEdgeWeights(oldEdge->edgeWeightMin(), oldEdge->edgeWeightMax(), block);
-            }
-            else
-            {
-                // Set the max edge weight to be the minimum of block's or blockPred's weight
-                //
-                weight_t newWeightMax = min(block->bbWeight, blockPred->bbWeight);
-
-                // If we are inserting a conditional block the minimum weight is zero,
-                // otherwise it is the same as the edge's max weight.
-                if (blockPred->NumSucc() > 1)
-                {
-                    flow->setEdgeWeights(BB_ZERO_WEIGHT, newWeightMax, block);
-                }
-                else
-                {
-                    flow->setEdgeWeights(flow->edgeWeightMax(), newWeightMax, block);
-                }
-            }
-        }
-        else
-        {
-            flow->setEdgeWeights(BB_ZERO_WEIGHT, BB_MAX_WEIGHT, block);
-        }
     }
 
     // Pred list should (still) be ordered.