Changeset 3e5db5b4 for src/ControlStruct

Timestamp:

Feb 1, 2022, 12:03:50 PM (3 years ago)

Author:

caparsons <caparson@…>

Branches:

ADT, ast-experimental, enum, forall-pointer-decay, master, pthread-emulation, qualifiedEnum

Children:

34c32f0

Parents:

cef7430

Message:

added comments to loop portion of pass

File:

• src/ControlStruct/MultiLevelExit.cpp (modified) (8 diffs)

src/ControlStruct/MultiLevelExit.cpp ¶

@@ -72 +72 @@
         bool isFallDefaultTarget() const { return SwitchStmt == kind; }
 
+        // These routines set a target as being "used" by a BranchStmt
         ast::Label useContExit() { assert( kind <= WhileStmt ); return useTarget(secondTarget); }
         ast::Label useBreakExit() { assert( CaseStmt != kind ); return useTarget(firstTarget); }
@@ -77 +78 @@
         ast::Label useFallDefaultExit() { assert( SwitchStmt == kind ); return useTarget(secondTarget); }
 
+        // These routines check if a specific label for a statement is used by a BranchStmt
         bool isContUsed() const { assert( kind <= WhileStmt ); return secondTarget.used; }
         bool isBreakUsed() const { assert( CaseStmt != kind ); return firstTarget.used; }
@@ -165 +167 @@
                 const ast::CompoundStmt * stmt ) {
         visit_children = false;
+
+        // if the stmt is labelled then generate a label to check in postvisit if the label is used
         bool isLabeled = !stmt->labels.empty();
         if ( isLabeled ) {
@@ -218 +222 @@
 }
 
+// This routine updates targets on enclosing control structures to indicate which
+//     label is used by the BranchStmt that is passed
 const ast::BranchStmt * MultiLevelExitCore::postvisit( const ast::BranchStmt * stmt ) {
         std::vector<Entry>::reverse_iterator targetEntry =
                 enclosing_control_structures.rend();
+
+        // Labels on different stmts require different approaches to access
         switch ( stmt->kind ) {
         case ast::BranchStmt::Goto:
@@ -257 +265 @@
                 break;
         }
+        // handle fallthrough in case/switch stmts
         case ast::BranchStmt::FallThrough: {
                 targetEntry = findEnclosingControlStructure( isFallthroughTarget );
@@ -534 +543 @@
         }
 
+        // if continue is used insert a continue label into the back of the body of the loop
         if ( entry.isContUsed() ) {
                 ast::CompoundStmt * new_body = new ast::CompoundStmt( body->location );
+                // {}
                 new_body->kids.push_back( body );
+                // {
+                //  body
+                // }
                 new_body->kids.push_back(
                         labelledNullStmt( body->location, entry.useContExit() ) );
+                // {
+                //  body
+                //  ContinueLabel: {}
+                // }
                 return new_body;
         }
@@ -552 +570 @@
         ast::Label contLabel = LabelGenerator::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(); } );
 }
@@ -564 +586 @@
         return ast::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
 }