[FIR2IR] Recognize postfix inc/dec blocks in sequence of statements

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrVisitor.kt

@@ -542,8 +542,56 @@ class Fir2IrVisitor(
         }
     }
 
-    private fun List<FirStatement>.mapToIrStatements(): List<IrStatement?> {
+    private fun List<FirStatement>.mapToIrStatements(recognizePostfixIncDec: Boolean = true): List<IrStatement?> {
-        return map { it.toIrStatement() }
+        var index = 0
+        val result = ArrayList<IrStatement?>(size)
+        while (index < size) {
+            var irStatement: IrStatement? = null
+            if (recognizePostfixIncDec) {
+                val statementsOrigin = getStatementsOrigin(index)
+                if (statementsOrigin != null) {
+                    val subStatements = this.subList(index, index + 3).mapNotNull { it.toIrStatement() }
+                    irStatement = IrBlockImpl(
+                        subStatements[0].startOffset,
+                        subStatements[2].endOffset,
+                        (subStatements[0] as IrVariable).type,
+                        statementsOrigin,
+                        subStatements
+                    )
+                    index += 3
+                }
+            }
+
+            if (irStatement == null) {
+                irStatement = this[index].toIrStatement()
+                index++
+            }
+            result.add(irStatement)
+        }
+
+        return result
+    }
+
+    private fun List<FirStatement>.getStatementsOrigin(index: Int): IrStatementOrigin? {
+        if (index + 3 > size) return null
+
+        val statement0 = this[index]
+        if (statement0 !is FirProperty || !statement0.isLocal) return null
+        val unarySymbol = statement0.symbol
+        if (unarySymbol.callableId.callableName != SpecialNames.UNARY) return null
+        val variable = statement0.initializer?.toResolvedCallableSymbol() ?: return null
+
+        val statement2 = this[index + 2]
+        if (statement2 !is FirPropertyAccessExpression) return null
+        if (statement2.calleeReference.toResolvedCallableSymbol() != unarySymbol) return null
+
+        val incrementStatement = this[index + 1]
+        if (incrementStatement !is FirVariableAssignment) return null
+
+        if (incrementStatement.lValue.toResolvedCallableSymbol() != variable) return null
+
+        val origin = incrementStatement.getIrAssignmentOrigin()
+        return if (origin == IrStatementOrigin.EQ) null else origin
     }
 
     internal fun convertToIrBlockBody(block: FirBlock): IrBlockBody {
@@ -591,37 +639,25 @@ class Fir2IrVisitor(
         else
             (lastOrNull() as? FirExpression)?.typeRef?.toIrType() ?: irBuiltIns.unitType
         return source.convertWithOffsets { startOffset, endOffset ->
-            val itStatements = mapToIrStatements().filterNotNull()
             if (origin == IrStatementOrigin.DO_WHILE_LOOP) {
-                IrCompositeImpl(startOffset, endOffset, type, origin, itStatements)
+                IrCompositeImpl(
+                    startOffset, endOffset, type, origin,
+                    mapToIrStatements(recognizePostfixIncDec = false).filterNotNull()
+                )
             } else {
-                IrBlockImpl(startOffset, endOffset, type, getStatementsOrigin() ?: origin, itStatements)
+                val irStatements = mapToIrStatements()
+                val singleStatement = irStatements.singleOrNull()
+                if (singleStatement is IrBlock &&
+                    (singleStatement.origin == IrStatementOrigin.POSTFIX_INCR || singleStatement.origin == IrStatementOrigin.POSTFIX_DECR)
+                ) {
+                    singleStatement
+                } else {
+                    IrBlockImpl(startOffset, endOffset, type, origin, irStatements.filterNotNull())
+                }
             }
         }
     }
 
-    private fun List<FirStatement>.getStatementsOrigin(): IrStatementOrigin? {
-        if (size != 3) return null
-
-        val statement0 = this[0]
-        if (statement0 !is FirProperty || !statement0.isLocal) return null
-        val unarySymbol = statement0.symbol
-        if (unarySymbol.callableId.callableName != SpecialNames.UNARY) return null
-
-        val statement2 = this[2]
-        if (statement2 !is FirPropertyAccessExpression) return null
-        if (statement2.calleeReference.toResolvedCallableSymbol() != unarySymbol) return null
-
-        val incrementStatement = this[1]
-        if (incrementStatement !is FirVariableAssignment) return null
-
-        val variable = statement0.initializer?.toResolvedCallableSymbol() ?: return null
-        if (incrementStatement.lValue.toResolvedCallableSymbol() != variable) return null
-
-        val origin = incrementStatement.getIrAssignmentOrigin()
-        return if (origin == IrStatementOrigin.EQ) null else origin
-    }
-
     override fun visitErrorExpression(errorExpression: FirErrorExpression, data: Any?): IrElement {
         return errorExpression.convertWithOffsets { startOffset, endOffset ->
             IrErrorExpressionImpl(

compiler/testData/ir/irText/lambdas/localFunction.fir.ir.txt

@@ -5,11 +5,12 @@ FILE fqName:<root> fileName:/localFunction.kt
         CONST Int type=kotlin.Int value=0
       FUN LOCAL_FUNCTION name:local visibility:local modality:FINAL <> () returnType:kotlin.Unit
         BLOCK_BODY
-          VAR IR_TEMPORARY_VARIABLE name:tmp_0 type:kotlin.Int [val]
-            GET_VAR 'var x: kotlin.Int [var] declared in <root>.outer' type=kotlin.Int origin=null
-          SET_VAR 'var x: kotlin.Int [var] declared in <root>.outer' type=kotlin.Unit origin=POSTFIX_INCR
-            CALL 'public final fun inc (): kotlin.Int [operator] declared in kotlin.Int' type=kotlin.Int origin=null
-              $this: GET_VAR 'val tmp_0: kotlin.Int [val] declared in <root>.outer.local' type=kotlin.Int origin=null
           TYPE_OP type=kotlin.Unit origin=IMPLICIT_COERCION_TO_UNIT typeOperand=kotlin.Unit
-            GET_VAR 'val tmp_0: kotlin.Int [val] declared in <root>.outer.local' type=kotlin.Int origin=null
+            BLOCK type=kotlin.Int origin=POSTFIX_INCR
+              VAR IR_TEMPORARY_VARIABLE name:tmp_0 type:kotlin.Int [val]
+                GET_VAR 'var x: kotlin.Int [var] declared in <root>.outer' type=kotlin.Int origin=null
+              SET_VAR 'var x: kotlin.Int [var] declared in <root>.outer' type=kotlin.Unit origin=POSTFIX_INCR
+                CALL 'public final fun inc (): kotlin.Int [operator] declared in kotlin.Int' type=kotlin.Int origin=null
+                  $this: GET_VAR 'val tmp_0: kotlin.Int [val] declared in <root>.outer.local' type=kotlin.Int origin=null
+              GET_VAR 'val tmp_0: kotlin.Int [val] declared in <root>.outer.local' type=kotlin.Int origin=null
       CALL 'local final fun local (): kotlin.Unit declared in <root>.outer' type=kotlin.Unit origin=null

compiler/testData/ir/irText/lambdas/localFunction.fir.kt.txt

@@ -1,10 +1,13 @@
 fun outer() {
   var x: Int = 0
   local fun local() {
-    val <unary>: Int = x
+    { // BLOCK
-    x = <unary>.inc()
+      val <unary>: Int = x
-    <unary> /*~> Unit */
+      x = <unary>.inc()
+      <unary>
+    } /*~> Unit */
   }
 
   local()
 }
+

compiler/testData/ir/irText/regressions/coercionInLoop.fir.ir.txt

@@ -26,11 +26,12 @@ FILE fqName:<root> fileName:/coercionInLoop.kt
                 STRING_CONCATENATION type=kotlin.String
                   CONST String type=kotlin.String value="Fail "
                   GET_VAR 'var i: kotlin.Int [var] declared in <root>.box' type=kotlin.Int origin=null
-          VAR IR_TEMPORARY_VARIABLE name:tmp_0 type:kotlin.Int [val]
+          BLOCK type=kotlin.Int origin=POSTFIX_INCR
-            GET_VAR 'var i: kotlin.Int [var] declared in <root>.box' type=kotlin.Int origin=null
+            VAR IR_TEMPORARY_VARIABLE name:tmp_0 type:kotlin.Int [val]
-          SET_VAR 'var i: kotlin.Int [var] declared in <root>.box' type=kotlin.Unit origin=POSTFIX_INCR
+              GET_VAR 'var i: kotlin.Int [var] declared in <root>.box' type=kotlin.Int origin=null
-            CALL 'public final fun inc (): kotlin.Int [operator] declared in kotlin.Int' type=kotlin.Int origin=null
+            SET_VAR 'var i: kotlin.Int [var] declared in <root>.box' type=kotlin.Unit origin=POSTFIX_INCR
-              $this: GET_VAR 'val tmp_0: kotlin.Int [val] declared in <root>.box' type=kotlin.Int origin=null
+              CALL 'public final fun inc (): kotlin.Int [operator] declared in kotlin.Int' type=kotlin.Int origin=null
-          GET_VAR 'val tmp_0: kotlin.Int [val] declared in <root>.box' type=kotlin.Int origin=null
+                $this: GET_VAR 'val tmp_0: kotlin.Int [val] declared in <root>.box' type=kotlin.Int origin=null
+            GET_VAR 'val tmp_0: kotlin.Int [val] declared in <root>.box' type=kotlin.Int origin=null
       RETURN type=kotlin.Nothing from='public final fun box (): kotlin.String declared in <root>'
         CONST String type=kotlin.String value="OK"

compiler/testData/ir/irText/regressions/coercionInLoop.fir.kt.txt

@@ -6,9 +6,12 @@ fun box(): String {
     when {
       ieee754equals(arg0 = a.get(index = i), arg1 = x.next()).not() -> return "Fail " + i
     }
-    val <unary>: Int = i
+    { // BLOCK
-    i = <unary>.inc()
+      val <unary>: Int = i
-    <unary>
+      i = <unary>.inc()
+      <unary>
+    }
   }
   return "OK"
 }
+