Revert "Avoid creating a result temp for is-expressions (dotnet#68694)…

…" (dotnet#69582)

This reverts commit e1031a7.

src/Compilers/CSharp/Portable/BoundTree/BoundNodes.xml

@@ -2323,7 +2323,6 @@
          'is not Type t') will need to compensate for negated patterns. IsNegated is set if Pattern is the negated
          form of the inner pattern represented by DecisionDag. -->
   <Node Name="BoundIsPatternExpression" Base="BoundExpression">
-    <Field Name="Type" Type="TypeSymbol" Override="true" Null="disallow"/>
     <Field Name="Expression" Type="BoundExpression" Null="disallow"/>
     <Field Name="Pattern" Type="BoundPattern" Null="disallow"/>
     <Field Name="IsNegated" Type="bool"/>
@@ -2332,13 +2331,6 @@
     <Field Name="WhenFalseLabel" Type="LabelSymbol" Null="disallow"/>
   </Node>
 
-  <Node Name="BoundLoweredIsPatternExpression" Base="BoundExpression" HasValidate="true">
-    <Field Name="Type" Type="TypeSymbol" Override="true" Null="disallow"/>
-    <Field Name="Statements" Type="ImmutableArray&lt;BoundStatement&gt;"/>
-    <Field Name="WhenTrueLabel" Type="LabelSymbol" Null="disallow"/>
-    <Field Name="WhenFalseLabel" Type="LabelSymbol" Null="disallow"/>
-  </Node>
-
   <AbstractNode Name="BoundPattern" Base="BoundNode">
     <Field Name="InputType" Type="TypeSymbol" Null="disallow"/>
     <Field Name="NarrowedType" Type="TypeSymbol" Null="disallow"/>

src/Compilers/CSharp/Portable/CodeGen/EmitExpression.cs

@@ -315,10 +315,6 @@ private void EmitExpressionCore(BoundExpression expression, bool used)
                     EmitRefValueOperator((BoundRefValueOperator)expression, used);
                     break;
 
-                case BoundKind.LoweredIsPatternExpression:
-                    EmitLoweredIsPatternExpression((BoundLoweredIsPatternExpression)expression, used);
-                    break;
-
                 case BoundKind.LoweredConditionalAccess:
                     EmitLoweredConditionalAccessExpression((BoundLoweredConditionalAccess)expression, used);
                     break;
@@ -356,42 +352,6 @@ private void EmitExpressionCore(BoundExpression expression, bool used)
             }
         }
 
-        private void EmitLoweredIsPatternExpression(BoundLoweredIsPatternExpression node, bool used, bool sense = true)
-        {
-            EmitSideEffects(node.Statements);
-
-            if (!used)
-            {
-                _builder.MarkLabel(node.WhenTrueLabel);
-                _builder.MarkLabel(node.WhenFalseLabel);
-            }
-            else
-            {
-                var doneLabel = new object();
-                _builder.MarkLabel(node.WhenTrueLabel);
-                _builder.EmitBoolConstant(sense);
-                _builder.EmitBranch(ILOpCode.Br, doneLabel);
-                _builder.AdjustStack(-1);
-                _builder.MarkLabel(node.WhenFalseLabel);
-                _builder.EmitBoolConstant(!sense);
-                _builder.MarkLabel(doneLabel);
-            }
-        }
-
-        private void EmitSideEffects(ImmutableArray<BoundStatement> statements)
-        {
-#if DEBUG
-            int prevStack = _expectedStackDepth;
-            int origStack = _builder.GetStackDepth();
-            _expectedStackDepth = origStack;
-#endif
-            EmitStatements(statements);
-#if DEBUG
-            Debug.Assert(_expectedStackDepth == origStack);
-            _expectedStackDepth = prevStack;
-#endif
-        }
-
         private void EmitThrowExpression(BoundThrowExpression node, bool used)
         {
             this.EmitThrow(node.Expression);
@@ -870,7 +830,7 @@ private void EmitSequencePoint(BoundSequencePointExpression node)
             }
         }
 
-        private void EmitSequenceExpression(BoundSequence sequence, bool used, bool sense = true)
+        private void EmitSequenceExpression(BoundSequence sequence, bool used)
         {
             DefineLocals(sequence);
             EmitSideEffects(sequence);
@@ -884,14 +844,7 @@ private void EmitSequenceExpression(BoundSequence sequence, bool used, bool sens
             Debug.Assert(sequence.Value.Kind != BoundKind.TypeExpression || !used);
             if (sequence.Value.Kind != BoundKind.TypeExpression)
             {
-                if (used && sequence.Type.SpecialType == SpecialType.System_Boolean)
-                {
-                    EmitCondExpr(sequence.Value, sense: sense);
-                }
-                else
-                {
-                    EmitExpression(sequence.Value, used: used);
-                }
+                EmitExpression(sequence.Value, used);
             }
 
             // sequence is used as a value, can release all locals

src/Compilers/CSharp/Portable/CodeGen/EmitOperators.cs

@@ -484,25 +484,14 @@ private void EmitCondExpr(BoundExpression condition, bool sense)
                 return;
             }
 
-            switch (condition.Kind)
+            if (condition.Kind == BoundKind.BinaryOperator)
             {
-                case BoundKind.BinaryOperator:
-                    var binOp = (BoundBinaryOperator)condition;
-                    if (!IsConditional(binOp.OperatorKind))
-                    {
-                        break;
-                    }
-
+                var binOp = (BoundBinaryOperator)condition;
+                if (IsConditional(binOp.OperatorKind))
+                {
                     EmitBinaryCondOperator(binOp, sense);
                     return;
-
-                case BoundKind.Sequence:
-                    EmitSequenceExpression((BoundSequence)condition, used: true, sense);
-                    return;
-
-                case BoundKind.LoweredIsPatternExpression:
-                    EmitLoweredIsPatternExpression((BoundLoweredIsPatternExpression)condition, used: true, sense);
-                    return;
+                }
             }
 
             EmitExpression(condition, true);

src/Compilers/CSharp/Portable/CodeGen/EmitStatement.cs

@@ -24,10 +24,6 @@ namespace Microsoft.CodeAnalysis.CSharp.CodeGen
 {
     internal partial class CodeGenerator
     {
-#if DEBUG
-        private int _expectedStackDepth = 0;
-#endif
-
         private void EmitStatement(BoundStatement statement)
         {
             switch (statement.Kind)
@@ -112,7 +108,7 @@ private void EmitStatement(BoundStatement statement)
 #if DEBUG
             if (_stackLocals == null || _stackLocals.Count == 0)
             {
-                _builder.AssertStackDepth(_expectedStackDepth);
+                _builder.AssertStackEmpty();
             }
 #endif
 
@@ -576,28 +572,6 @@ top.condition is BoundBinaryOperator binary &&
                     }
                     return;
 
-                case BoundKind.LoweredIsPatternExpression:
-                    {
-                        var loweredIs = (BoundLoweredIsPatternExpression)condition;
-                        dest ??= new object();
-
-                        EmitSideEffects(loweredIs.Statements);
-
-                        if (sense)
-                        {
-                            _builder.MarkLabel(loweredIs.WhenTrueLabel);
-                            _builder.EmitBranch(ILOpCode.Br, dest);
-                            _builder.MarkLabel(loweredIs.WhenFalseLabel);
-                        }
-                        else
-                        {
-                            _builder.MarkLabel(loweredIs.WhenFalseLabel);
-                            _builder.EmitBranch(ILOpCode.Br, dest);
-                            _builder.MarkLabel(loweredIs.WhenTrueLabel);
-                        }
-                    }
-                    return;
-
                 case BoundKind.UnaryOperator:
                     var unOp = (BoundUnaryOperator)condition;
                     if (unOp.OperatorKind == UnaryOperatorKind.BoolLogicalNegation)

src/Compilers/CSharp/Portable/CodeGen/Optimizer.cs

@@ -415,10 +415,6 @@ internal sealed class StackOptimizerPass1 : BoundTreeRewriter
 
         private int _recursionDepth;
 
-#if DEBUG
-        private int _expectedStackDepth = 0;
-#endif
-
         private StackOptimizerPass1(Dictionary<LocalSymbol, LocalDefUseInfo> locals,
             ArrayBuilder<ValueTuple<BoundExpression, ExprContext>> evalStack,
             bool debugFriendly)
@@ -569,27 +565,10 @@ private void PopEvalStack()
 
         public BoundNode VisitStatement(BoundNode node)
         {
-#if DEBUG
-            Debug.Assert(node == null || StackDepth() == _expectedStackDepth);
-#endif
+            Debug.Assert(node == null || EvalStackIsEmpty());
             return VisitSideEffect(node);
         }
 
-        public ImmutableArray<BoundStatement> VisitSideEffects(ImmutableArray<BoundStatement> statements)
-        {
-#if DEBUG
-            int prevStack = _expectedStackDepth;
-            int origStack = StackDepth();
-            _expectedStackDepth = origStack;
-#endif
-            var result = this.VisitList(statements);
-#if DEBUG
-            Debug.Assert(_expectedStackDepth == origStack);
-            _expectedStackDepth = prevStack;
-#endif
-            return result;
-        }
-
         public BoundNode VisitSideEffect(BoundNode node)
         {
             var origStack = StackDepth();
@@ -1437,6 +1416,8 @@ public override BoundNode VisitConditionalGoto(BoundConditionalGoto node)
 
         public override BoundNode VisitSwitchDispatch(BoundSwitchDispatch node)
         {
+            Debug.Assert(EvalStackIsEmpty());
+
             // switch dispatch needs a byval local or a parameter as a key.
             // if this is already a fitting local, let's keep it that way
             BoundExpression boundExpression = node.Expression;
@@ -1466,14 +1447,6 @@ public override BoundNode VisitSwitchDispatch(BoundSwitchDispatch node)
             return node.Update(boundExpression, node.Cases, node.DefaultLabel, node.LengthBasedStringSwitchDataOpt);
         }
 
-        public override BoundNode VisitLoweredIsPatternExpression(BoundLoweredIsPatternExpression node)
-        {
-            var statements = VisitSideEffects(node.Statements);
-            RecordBranch(node.WhenTrueLabel);
-            RecordBranch(node.WhenFalseLabel);
-            return node.Update(statements, node.WhenTrueLabel, node.WhenFalseLabel, VisitType(node.Type));
-        }
-
         public override BoundNode VisitConditionalOperator(BoundConditionalOperator node)
         {
             var origStack = StackDepth();

src/Compilers/CSharp/Portable/FlowAnalysis/AbstractFlowPass.cs

@@ -3031,12 +3031,6 @@ public override BoundNode VisitConditionalReceiver(BoundConditionalReceiver node
             return null;
         }
 
-        public override BoundNode VisitLoweredIsPatternExpression(BoundLoweredIsPatternExpression node)
-        {
-            VisitStatements(node.Statements);
-            return null;
-        }
-
         public override BoundNode VisitComplexConditionalReceiver(BoundComplexConditionalReceiver node)
         {
             var savedState = this.State.Clone();