[Openmp-commits] [clang] [flang] [llvm] [openmp] [Clang][OpenMP][LoopTransformations] Add support for "#pragma omp fuse" loop transformation directive and "looprange" clause (PR #139293)

[Michael Kruse via Openmp-commits]

================
@@ -14236,28 +14279,282 @@ bool SemaOpenMP::checkTransformableLoopNest(
         return false;
       },
       [&OriginalInits](OMPLoopBasedDirective *Transform) {
-        Stmt *DependentPreInits;
-        if (auto *Dir = dyn_cast<OMPTileDirective>(Transform))
-          DependentPreInits = Dir->getPreInits();
-        else if (auto *Dir = dyn_cast<OMPStripeDirective>(Transform))
-          DependentPreInits = Dir->getPreInits();
-        else if (auto *Dir = dyn_cast<OMPUnrollDirective>(Transform))
-          DependentPreInits = Dir->getPreInits();
-        else if (auto *Dir = dyn_cast<OMPReverseDirective>(Transform))
-          DependentPreInits = Dir->getPreInits();
-        else if (auto *Dir = dyn_cast<OMPInterchangeDirective>(Transform))
-          DependentPreInits = Dir->getPreInits();
-        else
-          llvm_unreachable("Unhandled loop transformation");
-
-        appendFlattenedStmtList(OriginalInits.back(), DependentPreInits);
+        updatePreInits(Transform, OriginalInits.back());
       });
   assert(OriginalInits.back().empty() && "No preinit after innermost loop");
   OriginalInits.pop_back();
   return Result;
 }
 
-/// Add preinit statements that need to be propageted from the selected loop.
+/// Counts the total number of nested loops, including the outermost loop (the
+/// original loop). PRECONDITION of this visitor is that it must be invoked from
+/// the original loop to be analyzed. The traversal stops for Decl's and
+/// Expr's given that they may contain inner loops that must not be counted.
+///
+/// Example AST structure for the code:
+///
+/// int main() {
+///     #pragma omp fuse
+///     {
+///         for (int i = 0; i < 100; i++) {    <-- Outer loop
+///             []() {
+///                 for(int j = 0; j < 100; j++) {}  <-- NOT A LOOP
+///             };
+///             for(int j = 0; j < 5; ++j) {}    <-- Inner loop
+///         }
+///         for (int r = 0; i < 100; i++) {    <-- Outer loop
+///             struct LocalClass {
+///                 void bar() {
+///                     for(int j = 0; j < 100; j++) {}  <-- NOT A LOOP
+///                 }
+///             };
+///             for(int k = 0; k < 10; ++k) {}    <-- Inner loop
+///             {x = 5; for(k = 0; k < 10; ++k) x += k; x}; <-- NOT A LOOP
+///         }
+///     }
+/// }
+/// Result: Loop 'i' contains 2 loops, Loop 'r' also contains 2 loops.
+class NestedLoopCounterVisitor final : public DynamicRecursiveASTVisitor {
+private:
+  unsigned NestedLoopCount = 0;
+
+public:
+  explicit NestedLoopCounterVisitor() = default;
+
+  unsigned getNestedLoopCount() const { return NestedLoopCount; }
+
+  bool VisitForStmt(ForStmt *FS) override {
+    ++NestedLoopCount;
+    return true;
+  }
+
+  bool VisitCXXForRangeStmt(CXXForRangeStmt *FRS) override {
+    ++NestedLoopCount;
+    return true;
+  }
+
+  bool TraverseStmt(Stmt *S) override {
+    if (!S)
+      return true;
+
+    // Skip traversal of all expressions, including special cases like
+    // LambdaExpr, StmtExpr, BlockExpr, and RequiresExpr. These expressions
+    // may contain inner statements (and even loops), but they are not part
+    // of the syntactic body of the surrounding loop structure.
+    //  Therefore must not be counted.
+    if (isa<Expr>(S))
+      return true;
+
+    // Only recurse into CompoundStmt (block {}) and loop bodies.
+    if (isa<CompoundStmt, ForStmt, CXXForRangeStmt>(S)) {
+      return DynamicRecursiveASTVisitor::TraverseStmt(S);
+    }
+
+    // Stop traversal of the rest of statements, that break perfect
+    // loop nesting, such as control flow (IfStmt, SwitchStmt...).
+    return true;
+  }
+
+  bool TraverseDecl(Decl *D) override {
+    // Stop in the case of finding a declaration, it is not important
+    // in order to find nested loops (Possible CXXRecordDecl, RecordDecl,
+    // FunctionDecl...).
+    return true;
+  }
+};
+
+bool SemaOpenMP::analyzeLoopSequence(Stmt *LoopSeqStmt,
+                                     LoopSequenceAnalysis &SeqAnalysis,
+                                     ASTContext &Context,
+                                     OpenMPDirectiveKind Kind) {
+
+  VarsWithInheritedDSAType TmpDSA;
+  /// Helper Lambda to handle storing initialization and body statements for
+  /// both ForStmt and CXXForRangeStmt.
----------------
Meinersbur wrote:

```suggestion
  // Helper Lambda to handle storing initialization and body statements for
  // both ForStmt and CXXForRangeStmt.
```
Inner lambdas don't need doxygen comments. They cannot be called from outside hence obviously not part of the public API that doxygen generates manuals for

https://github.com/llvm/llvm-project/pull/139293