[FIR] Add kind for back edges in CFG

compiler/fir/analysis-tests/testData/resolve/cfg/complex.dot

@@ -260,7 +260,7 @@ digraph complex_kt {
     79 -> {68} [style=dotted];
     80 -> {68};
     81 -> {82};
-    82 -> {58};
+    82 -> {58} [color=green style=dashed];
     83 -> {84};
     84 -> {52};
     84 -> {85} [style=dotted];

compiler/fir/analysis-tests/testData/resolve/cfg/jumps.dot

@@ -191,7 +191,7 @@ digraph jumps_kt {
     63 -> {64} [style=dotted];
     64 -> {65} [style=dotted];
     65 -> {66} [style=dotted];
-    66 -> {56} [style=dotted];
+    66 -> {56} [color=green style=dotted];
     67 -> {68};
     68 -> {53};
 
@@ -241,7 +241,8 @@ digraph jumps_kt {
     80 -> {81} [style=dotted];
     81 -> {82} [style=dotted];
     82 -> {83} [style=dotted];
-    83 -> {73 72} [style=dotted];
+    83 -> {72} [style=dotted];
+    83 -> {73} [color=green style=dotted];
     84 -> {85};
     85 -> {70};
 
@@ -307,14 +308,14 @@ digraph jumps_kt {
     99 -> {100 106};
     100 -> {101};
     101 -> {102};
-    102 -> {88};
     102 -> {103} [style=dotted];
+    102 -> {88} [color=green style=dashed];
     103 -> {104} [style=dotted];
     104 -> {105} [style=dotted];
     105 -> {96} [style=dotted];
     106 -> {96};
     107 -> {108};
-    108 -> {90};
+    108 -> {90} [color=green style=dashed];
 
     subgraph cluster_30 {
         color=red
@@ -346,8 +347,8 @@ digraph jumps_kt {
     115 -> {116};
     116 -> {113};
     117 -> {118 119};
-    118 -> {117};
     118 -> {115} [color=green];
+    118 -> {117} [color=green style=dashed];
     119 -> {118};
     119 -> {120} [style=dotted];
     120 -> {118} [style=dotted];

compiler/fir/analysis-tests/testData/resolve/cfg/lambdas.dot

@@ -64,8 +64,8 @@ digraph lambdas_kt {
     17 -> {6};
     18 -> {6};
     19 -> {20 21};
-    20 -> {19};
     20 -> {14} [color=green];
+    20 -> {19} [color=green style=dashed];
     21 -> {22};
     22 -> {20};
 
@@ -166,8 +166,8 @@ digraph lambdas_kt {
     52 -> {53} [style=dotted];
     53 -> {48} [style=dotted];
     54 -> {55 56};
-    55 -> {54};
     55 -> {50} [color=green];
+    55 -> {54} [color=green style=dashed];
     56 -> {57};
     57 -> {48};
     57 -> {58} [style=dotted];
@@ -203,8 +203,8 @@ digraph lambdas_kt {
     64 -> {65} [style=dotted];
     65 -> {60} [style=dotted];
     66 -> {67 68};
-    67 -> {66};
     67 -> {62} [color=green];
+    67 -> {66} [color=green style=dashed];
     68 -> {69};
     69 -> {60};
     69 -> {70} [style=dotted];

compiler/fir/analysis-tests/testData/resolve/cfg/localClassesWithImplicit.dot

@@ -184,8 +184,8 @@ digraph localClassesWithImplicit_kt {
     31 -> {32} [style=dotted];
     32 -> {27} [style=dotted];
     33 -> {34 35};
-    34 -> {33};
     34 -> {29} [color=green];
+    34 -> {33} [color=green style=dashed];
     35 -> {36};
     36 -> {37};
     37 -> {39};
@@ -217,8 +217,8 @@ digraph localClassesWithImplicit_kt {
     62 -> {63} [style=dotted];
     63 -> {58} [style=dotted];
     64 -> {65 66};
-    65 -> {64};
     65 -> {60} [color=green];
+    65 -> {64} [color=green style=dashed];
     66 -> {67};
     67 -> {68};
     68 -> {69};
@@ -320,8 +320,8 @@ digraph localClassesWithImplicit_kt {
     86 -> {87} [style=dotted];
     87 -> {82} [style=dotted];
     88 -> {89 90};
-    89 -> {88};
     89 -> {84} [color=green];
+    89 -> {88} [color=green style=dashed];
     90 -> {91};
     91 -> {92};
     92 -> {94};
@@ -379,8 +379,8 @@ digraph localClassesWithImplicit_kt {
     117 -> {118} [style=dotted];
     118 -> {113} [style=dotted];
     119 -> {120 121};
-    120 -> {119};
     120 -> {115} [color=green];
+    120 -> {119} [color=green style=dashed];
     121 -> {122};
     122 -> {123};
     123 -> {124};

compiler/fir/analysis-tests/testData/resolve/cfg/loops.dot

@@ -46,7 +46,7 @@ digraph loops_kt {
     10 -> {11};
     11 -> {12};
     12 -> {13};
-    13 -> {4};
+    13 -> {4} [color=green style=dashed];
     14 -> {15};
     15 -> {1};
 
@@ -93,7 +93,8 @@ digraph loops_kt {
     26 -> {27};
     27 -> {28};
     28 -> {29};
-    29 -> {20 19};
+    29 -> {19};
+    29 -> {20} [color=green style=dashed];
     30 -> {31};
     31 -> {17};
 
@@ -158,7 +159,7 @@ digraph loops_kt {
     51 -> {52};
     52 -> {53};
     53 -> {54};
-    54 -> {41};
+    54 -> {41} [color=green style=dashed];
     55 -> {56};
     56 -> {33};
 
@@ -201,7 +202,7 @@ digraph loops_kt {
     65 -> {66};
     66 -> {67};
     67 -> {68};
-    68 -> {61};
+    68 -> {61} [color=green style=dashed];
     69 -> {58} [style=dotted];
 
     subgraph cluster_20 {
@@ -275,7 +276,7 @@ digraph loops_kt {
     89 -> {80} [style=dotted];
     90 -> {80};
     91 -> {92};
-    92 -> {74};
+    92 -> {74} [color=green style=dashed];
     93 -> {71};
 
     subgraph cluster_28 {
@@ -317,7 +318,7 @@ digraph loops_kt {
     102 -> {103} [style=dotted];
     103 -> {104} [style=dotted];
     104 -> {105} [style=dotted];
-    105 -> {98} [style=dotted];
+    105 -> {98} [color=green style=dotted];
     106 -> {95};
 
     subgraph cluster_33 {
@@ -358,8 +359,8 @@ digraph loops_kt {
     115 -> {116};
     116 -> {117};
     117 -> {118};
-    118 -> {111};
     118 -> {110} [style=dotted];
+    118 -> {111} [color=green style=dashed];
     119 -> {108} [style=dotted];
 
     subgraph cluster_38 {
@@ -432,8 +433,8 @@ digraph loops_kt {
     139 -> {140};
     140 -> {141};
     141 -> {142};
-    142 -> {124};
     142 -> {123} [style=dotted];
+    142 -> {124} [color=green style=dashed];
     143 -> {121};
 
     subgraph cluster_46 {
@@ -475,7 +476,7 @@ digraph loops_kt {
     153 -> {154};
     154 -> {155};
     155 -> {147};
-    155 -> {148} [style=dotted];
+    155 -> {148} [color=green style=dotted];
     156 -> {145};
 
 }

compiler/fir/analysis-tests/testData/resolve/cfg/postponedLambdas.dot

@@ -34,8 +34,8 @@ digraph postponedLambdas_kt {
     7 -> {8};
     8 -> {3};
     9 -> {10 11};
-    10 -> {9};
     10 -> {6} [color=green];
+    10 -> {9} [color=green style=dashed];
     11 -> {10};
 
 }

compiler/fir/analysis-tests/testData/resolve/cfg/propertiesAndInitBlocks.dot

@@ -177,8 +177,8 @@ digraph propertiesAndInitBlocks_kt {
     67 -> {64};
     20 -> {21 22};
     20 -> {26 35 38} [color=red];
-    21 -> {20};
     21 -> {66} [color=green];
+    21 -> {20} [color=green style=dashed];
     22 -> {23};
     23 -> {24};
     24 -> {64};

compiler/fir/analysis-tests/testData/resolve/cfg/tryCatch.dot

@@ -280,8 +280,8 @@ digraph tryCatch_kt {
     79 -> {80};
     80 -> {47};
     81 -> {82};
-    82 -> {39};
     82 -> {83} [style=dotted];
+    82 -> {39} [color=green style=dashed];
     83 -> {84} [style=dotted];
     84 -> {85} [style=dotted];
     85 -> {47} [style=dotted];
@@ -294,7 +294,7 @@ digraph tryCatch_kt {
     91 -> {92};
     92 -> {93};
     93 -> {94};
-    94 -> {41};
+    94 -> {41} [color=green style=dashed];
     95 -> {96};
     96 -> {38};
 

compiler/fir/analysis-tests/testData/resolve/smartcasts/boundSmartcasts/boundSmartcastsInBranches.dot

@@ -124,8 +124,8 @@ digraph boundSmartcastsInBranches_kt {
     36 -> {37};
     37 -> {38};
     38 -> {39};
-    39 -> {17};
     39 -> {40} [style=dotted];
+    39 -> {17} [color=green style=dashed];
     40 -> {41} [style=dotted];
     41 -> {42} [style=dotted];
     42 -> {29} [style=dotted];
@@ -133,7 +133,7 @@ digraph boundSmartcastsInBranches_kt {
     44 -> {45};
     45 -> {46};
     46 -> {47};
-    47 -> {19};
+    47 -> {19} [color=green style=dashed];
 
     subgraph cluster_12 {
         color=red

compiler/fir/analysis-tests/testData/resolve/smartcasts/loops/dataFlowInfoFromWhileCondition.dot

@@ -91,6 +91,6 @@ digraph dataFlowInfoFromWhileCondition_kt {
     26 -> {27};
     27 -> {28};
     28 -> {29};
-    29 -> {14};
+    29 -> {14} [color=green style=dashed];
 
 }

compiler/fir/analysis-tests/testData/resolve/smartcasts/loops/endlessLoops.dot

@@ -93,7 +93,7 @@ digraph endlessLoops_kt {
     25 -> {16} [style=dotted];
     26 -> {16};
     27 -> {28};
-    28 -> {8};
+    28 -> {8} [color=green style=dashed];
     29 -> {30};
     30 -> {5};
 
@@ -173,7 +173,7 @@ digraph endlessLoops_kt {
     52 -> {41} [style=dotted];
     53 -> {41};
     54 -> {55};
-    55 -> {35};
+    55 -> {35} [color=green style=dashed];
     56 -> {57};
     57 -> {32};
 
@@ -287,7 +287,7 @@ digraph endlessLoops_kt {
     91 -> {82} [style=dotted];
     92 -> {82};
     93 -> {94};
-    94 -> {62};
+    94 -> {62} [color=green style=dashed];
     95 -> {96};
     96 -> {59};
 
@@ -372,7 +372,7 @@ digraph endlessLoops_kt {
     120 -> {121} [style=dotted];
     121 -> {122} [style=dotted];
     122 -> {123} [style=dotted];
-    123 -> {101} [style=dotted];
+    123 -> {101} [color=green style=dotted];
     124 -> {125};
     125 -> {98};
 
@@ -451,8 +451,8 @@ digraph endlessLoops_kt {
     147 -> {148};
     148 -> {149};
     149 -> {150};
-    150 -> {130};
     150 -> {129} [style=dotted];
+    150 -> {130} [color=green style=dashed];
     151 -> {152};
     152 -> {127};
 
@@ -531,8 +531,8 @@ digraph endlessLoops_kt {
     174 -> {175};
     175 -> {176};
     176 -> {177};
-    177 -> {157};
     177 -> {156} [style=dotted];
+    177 -> {157} [color=green style=dashed];
     178 -> {179};
     179 -> {154};
 
@@ -577,8 +577,8 @@ digraph endlessLoops_kt {
     189 -> {190};
     190 -> {191};
     191 -> {192};
-    192 -> {184};
     192 -> {183} [style=dotted];
+    192 -> {184} [color=green style=dashed];
     193 -> {194} [style=dotted];
     194 -> {181} [style=dotted];
 

compiler/fir/analysis-tests/testData/resolve/smartcasts/smartcastToNothing.dot

@@ -250,7 +250,7 @@ digraph smartcastToNothing_kt {
     81 -> {70} [style=dotted];
     82 -> {70} [style=dotted];
     83 -> {84} [style=dotted];
-    84 -> {56} [style=dotted];
+    84 -> {56} [color=green style=dotted];
     85 -> {86 87};
     86 -> {88};
     87 -> {48} [style=dotted];

compiler/fir/analysis-tests/testData/resolveWithStdlib/contracts/fromLibrary/callsInPlace.dot

@@ -59,8 +59,8 @@ digraph callsInPlace_kt {
     17 -> {18};
     18 -> {14};
     19 -> {20 21};
-    20 -> {19};
     20 -> {17} [color=green];
+    20 -> {19} [color=green style=dashed];
     21 -> {20};
 
     subgraph cluster_4 {
@@ -85,8 +85,8 @@ digraph callsInPlace_kt {
     26 -> {27};
     27 -> {23};
     28 -> {29 30};
-    29 -> {28};
     29 -> {25} [color=green];
+    29 -> {28} [color=green style=dashed];
     30 -> {29};
 
     subgraph cluster_6 {
@@ -203,12 +203,12 @@ digraph callsInPlace_kt {
     68 -> {69};
     69 -> {64};
     70 -> {71 72};
-    71 -> {70};
     71 -> {66} [color=green];
+    71 -> {70} [color=green style=dashed];
     72 -> {71};
     73 -> {74 75};
-    74 -> {73};
     74 -> {68} [color=green];
+    74 -> {73} [color=green style=dashed];
     75 -> {74};
 
     subgraph cluster_14 {
@@ -242,12 +242,12 @@ digraph callsInPlace_kt {
     81 -> {82};
     82 -> {77};
     83 -> {84 85};
-    84 -> {83};
     84 -> {79} [color=green];
+    84 -> {83} [color=green style=dashed];
     85 -> {84};
     86 -> {87 88};
-    87 -> {86};
     87 -> {81} [color=green];
+    87 -> {86} [color=green style=dashed];
     88 -> {87};
 
     subgraph cluster_17 {

compiler/fir/analysis-tests/testData/resolveWithStdlib/contracts/fromSource/good/callsInPlace/atLeastOnce.dot

@@ -48,8 +48,8 @@ digraph atLeastOnce_kt {
     12 -> {13};
     13 -> {7};
     14 -> {16};
-    15 -> {14};
     15 -> {10} [color=green];
+    15 -> {14} [color=green style=dashed];
     16 -> {17};
     17 -> {15};
 
@@ -80,8 +80,8 @@ digraph atLeastOnce_kt {
     24 -> {25};
     25 -> {19};
     26 -> {28};
-    27 -> {26};
     27 -> {22} [color=green];
+    27 -> {26} [color=green style=dashed];
     28 -> {29};
     29 -> {27};
 

compiler/fir/analysis-tests/testData/resolveWithStdlib/contracts/fromSource/good/callsInPlace/unknown.dot

@@ -48,8 +48,8 @@ digraph unknown_kt {
     12 -> {13};
     13 -> {7};
     14 -> {15 16};
-    15 -> {14};
     15 -> {10} [color=green];
+    15 -> {14} [color=green style=dashed];
     16 -> {17};
     17 -> {15};
 
@@ -80,8 +80,8 @@ digraph unknown_kt {
     24 -> {25};
     25 -> {19};
     26 -> {27 28};
-    27 -> {26};
     27 -> {22} [color=green];
+    27 -> {26} [color=green style=dashed];
     28 -> {29};
     29 -> {27};
 

compiler/fir/analysis-tests/testData/resolveWithStdlib/smartcasts/tryWithLambdaInside.dot

@@ -94,8 +94,8 @@ finally {
     23 -> {24} [style=dotted];
     24 -> {8} [style=dotted];
     25 -> {26 27};
-    26 -> {25};
     26 -> {16} [color=green];
+    26 -> {25} [color=green style=dashed];
     27 -> {26};
 
     subgraph cluster_9 {

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/dfa/cfg/ControlFlowGraph.kt

@@ -69,9 +69,11 @@ class ControlFlowGraph(val declaration: FirDeclaration?, val name: String, val k
     }
 }
 
-enum class EdgeKind(val usedInDfa: Boolean) {
-    Simple(usedInDfa = true),
-    Dead(usedInDfa = false),
-    Cfg(usedInDfa = false),
-    Dfg(usedInDfa = true)
+enum class EdgeKind(val usedInDfa: Boolean, val isBack: Boolean) {
+    Simple(usedInDfa = true, isBack = false),
+    Dead(usedInDfa = false, isBack = false),
+    Cfg(usedInDfa = false, isBack = false),
+    Dfg(usedInDfa = true, isBack = false),
+    Back(usedInDfa = false, isBack = true),
+    DeadBack(usedInDfa = false, isBack = true)
 }

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/dfa/cfg/ControlFlowGraphBuilder.kt

@@ -151,7 +151,7 @@ class ControlFlowGraphBuilder {
             val enterNode = functionEnterNodes.pop()
             @Suppress("NON_EXHAUSTIVE_WHEN")
             when (invocationKind) {
-                InvocationKind.AT_LEAST_ONCE, InvocationKind.UNKNOWN -> addEdge(exitNode, enterNode, propagateDeadness = false)
+                InvocationKind.AT_LEAST_ONCE, InvocationKind.UNKNOWN -> addBackEdge(exitNode, enterNode)
             }
             if (postponedExitNode != null) {
                 CFGNode.addEdge(lastNodes.pop(), postponedExitNode, propagateDeadness = true, kind = EdgeKind.Cfg)
@@ -399,7 +399,7 @@ class ControlFlowGraphBuilder {
             is FirBreakExpression -> loopExitNodes[jump.target.labeledElement]
             else -> throw IllegalArgumentException("Unknown jump type: ${jump.render()}")
         }
-        addNodeWithJump(node, nextNode)
+        addNodeWithJump(node, nextNode, isBack = jump is FirContinueExpression)
         return node
     }
 
@@ -502,7 +502,7 @@ class ControlFlowGraphBuilder {
         if (lastNodes.isNotEmpty) {
             val conditionEnterNode = lastNodes.pop()
             require(conditionEnterNode is LoopConditionEnterNode) { loop.render() }
-            addEdge(loopBlockExitNode, conditionEnterNode, propagateDeadness = false)
+            addBackEdge(loopBlockExitNode, conditionEnterNode)
         }
         val loopExitNode = loopExitNodes.pop()
         loopExitNode.updateDeadStatus()
@@ -543,7 +543,7 @@ class ControlFlowGraphBuilder {
         addEdge(lastNodes.pop(), conditionExitNode)
         val blockEnterNode = lastNodes.pop()
         require(blockEnterNode is LoopBlockEnterNode)
-        addEdge(conditionExitNode, blockEnterNode, propagateDeadness = false, isDead = conditionBooleanValue == false)
+        addBackEdge(conditionExitNode, blockEnterNode, isDead = conditionBooleanValue == false)
         val loopExit = loopExitNodes.pop()
         addEdge(conditionExitNode, loopExit, propagateDeadness = false, isDead = conditionBooleanValue == true)
         loopExit.updateDeadStatus()
@@ -903,13 +903,17 @@ class ControlFlowGraphBuilder {
          * it will be replaced after correct implementation of CFG for class initialization
          */
         val exitNode: CFGNode<*> = exitNodes.top()
-        addNodeWithJump(node, exitNode, preferredKind)
+        addNodeWithJump(node, exitNode)
     }
 
-    private fun addNodeWithJump(node: CFGNode<*>, targetNode: CFGNode<*>?, preferredKind: EdgeKind = EdgeKind.Simple) {
+    private fun addNodeWithJump(node: CFGNode<*>, targetNode: CFGNode<*>?, isBack: Boolean = false) {
         addEdge(lastNodes.pop(), node)
         if (targetNode != null) {
-            addEdge(node, targetNode)
+            if (isBack) {
+                addBackEdge(node, targetNode)
+            } else {
+                addEdge(node, targetNode)
+            }
         }
         val stub = createStubNode()
         addEdge(node, stub)
@@ -933,12 +937,23 @@ class ControlFlowGraphBuilder {
         to: CFGNode<*>,
         propagateDeadness: Boolean = true,
         isDead: Boolean = false,
-        preferredKind: EdgeKind = EdgeKind.Simple
+        isBack: Boolean = false,
+        preferredKind: EdgeKind = EdgeKind.Simple,
     ) {
-        val kind = if (isDead || from.isDead || to.isDead) EdgeKind.Dead else preferredKind
+        val kind = if (isDead || from.isDead || to.isDead) {
+            if (isBack) EdgeKind.DeadBack else EdgeKind.Dead
+        } else preferredKind
         CFGNode.addEdge(from, to, kind, propagateDeadness)
     }
 
+    private fun addBackEdge(
+        from: CFGNode<*>,
+        to: CFGNode<*>,
+        isDead: Boolean = false
+    ) {
+        addEdge(from, to, propagateDeadness = false, isDead = isDead, isBack = true, preferredKind = EdgeKind.Back)
+    }
+
     private val FirFunction<*>.invocationKind: InvocationKind?
         get() = (this as? FirAnonymousFunction)?.invocationKind
 

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/dfa/cfg/ControlFlowGraphRenderer.kt

@@ -30,6 +30,8 @@ class FirControlFlowGraphRenderVisitor(
                 EdgeKind.Dead to "[style=dotted]",
                 EdgeKind.Cfg to "[color=green]",
                 EdgeKind.Dfg to "[color=red]",
+                EdgeKind.Back to "[color=green style=dashed]",
+                EdgeKind.DeadBack to "[color=green style=dotted]"
             )
         )
     }

compiler/tests-common/tests/org/jetbrains/kotlin/fir/AbstractFirDiagnosticTest.kt

@@ -308,7 +308,7 @@ abstract class AbstractFirDiagnosticsTest : AbstractFirBaseDiagnosticsTest() {
             val toKind = to.incomingEdges.getValue(from)
             TestCase.assertEquals(fromKind, toKind)
             if (from.isDead || to.isDead) {
-                KtUsefulTestCase.assertContainsElements(listOf(EdgeKind.Dead, EdgeKind.Cfg), toKind)
+                KtUsefulTestCase.assertContainsElements(listOf(EdgeKind.Dead, EdgeKind.Cfg, EdgeKind.DeadBack, EdgeKind.Back), toKind)
             }
         }
     }