Changeset 88bc876 for src/ControlStruct/MultiLevelExit.cpp

Timestamp:

Jul 16, 2024, 5:28:10 PM (2 days ago)

Author:

Andrew Beach <ajbeach@…>

Branches:

master

Children:

97f9619

Parents:

2363147

Message:

Breaks (and some other control flow) in a loop else clause now work. I also implemented else clauses in printing and code generation.

File:

• src/ControlStruct/MultiLevelExit.cpp (modified) (7 diffs)

src/ControlStruct/MultiLevelExit.cpp

@@ -78 +78 @@
                 stmt( stmt ), firstTarget( breakExit ), secondTarget(), kind( TryStmtK ) {}
 
+        // Check if this entry can be the target of the given type of control flow.
         bool isContTarget() const { return kind <= WhileDoStmtK; }
         bool isBreakTarget() const { return kind != CaseClauseK; }
@@ -207 +208 @@
 
         // If the label is empty, do not add unused attribute.
-  if ( originalTarget.empty() ) return size;
+        if ( originalTarget.empty() ) return size;
 
         // Search for a label that matches the originalTarget.
@@ -343 +344 @@
                 assert(0);
         }
+        assert( !exitLabel.empty() );
 
         // Add unused attribute to silence warnings.
@@ -486 +488 @@
                 }
 
-                auto caseStmt = mutStmt->cases.back().get();
-                auto mutCase = mutate( caseStmt );
-                mutStmt->cases.back() = mutCase;
+                auto mutCase = mutStmt->cases.back().get_and_mutate();
 
                 Label label( mutCase->location, "breakLabel" );
@@ -597 +597 @@
 template<typename LoopNode>
 void MultiLevelExitCore::prehandleLoopStmt( const LoopNode * loopStmt ) {
-        // Remember is loop before going onto mutate the body.
+        // Create temporary labels and mark the enclosing loop before traversal.
         // The labels will be folded in if they are used.
         Label breakLabel = newLabel( "loopBreak", loopStmt );
         Label contLabel = newLabel( "loopContinue", loopStmt );
         enclosing_control_structures.emplace_back( loopStmt, breakLabel, contLabel );
-        // labels are added temporarily to see if they are used and then added permanently in postvisit if ther are used
-        // children will tag labels as being used during their traversal which occurs before postvisit
-
-        // GuardAction calls the lambda after the node is done being visited
+
         GuardAction( [this](){ enclosing_control_structures.pop_back(); } );
+
+        // Because of fixBlock, this should be empty now (and must be).
+        assert( nullptr == loopStmt->else_ );
 }
 
@@ -617 +617 @@
         // Now check if the labels are used and add them if so.
         return mutate_field( loopStmt, &LoopNode::body, mutateLoop( loopStmt->body, entry ) );
-        // this call to mutate_field compares loopStmt->body and the result of mutateLoop
-        //              if they are the same the node isn't mutated, if they differ then the new mutated node is returned
-        //              the stmts will only differ if a label is used
 }
 
@@ -639 +636 @@
 
                 ptr<Stmt> else_stmt = nullptr;
-                const Stmt * loop_kid = nullptr;
+                const Stmt * to_visit;
                 // check if loop node and if so add else clause if it exists
-                const WhileDoStmt * whilePtr = kid.as<WhileDoStmt>();
-                if ( whilePtr && whilePtr->else_ ) {
-                        else_stmt = whilePtr->else_;
-                        loop_kid = mutate_field( whilePtr, &WhileDoStmt::else_, nullptr );
-                }
-                const ForStmt * forPtr = kid.as<ForStmt>();
-                if ( forPtr && forPtr->else_ ) {
-                        else_stmt = forPtr->else_;
-                        loop_kid = mutate_field( forPtr, &ForStmt::else_, nullptr );
-                }
-
+                if ( auto ptr = kid.as<WhileDoStmt>() ; ptr && ptr->else_ ) {
+                        else_stmt = ptr->else_;
+                        to_visit = mutate_field( ptr, &WhileDoStmt::else_, nullptr );
+                } else if ( auto ptr = kid.as<ForStmt>() ; ptr && ptr->else_ ) {
+                        else_stmt = ptr->else_;
+                        to_visit = mutate_field( ptr, &ForStmt::else_, nullptr );
+                } else {
+                        to_visit = kid.get();
+                }
+
+                // This is the main (safe) visit of the child node.
                 try {
-                        if (else_stmt) ret.push_back( loop_kid->accept( *visitor ) );
-                        else ret.push_back( kid->accept( *visitor ) );
+                        ret.push_back( to_visit->accept( *visitor ) );
                 } catch ( SemanticErrorException & e ) {
                         errors.append( e );
                 }
 
-                if (else_stmt) ret.push_back(else_stmt);
-
-                if ( ! break_label.empty() ) {
+                // The following sections handle visiting loop else clause and makes
+                // sure breaking from a loop body does not execute that clause.
+                Label local_break_label = std::move( break_label );
+                break_label = Label( CodeLocation(), "" );
+
+                if ( else_stmt ) try {
+                        ret.push_back( else_stmt->accept( *visitor ) );
+                } catch ( SemanticErrorException & e ) {
+                        errors.append( e );
+                }
+
+                if ( !break_label.empty() ) {
                         ret.push_back( labelledNullStmt( ret.back()->location, break_label ) );
                         break_label = Label( CodeLocation(), "" );
                 }
-        }
-
-        if ( ! errors.isEmpty() ) {
+
+                // This handles a break from the body or non-loop statement.
+                if ( !local_break_label.empty() ) {
+                        ret.push_back( labelledNullStmt( ret.back()->location, local_break_label ) );
+                }
+        }
+
+        if ( !errors.isEmpty() ) {
                 throw errors;
         }