[flang-commits] [flang] [llvm] [mlir] [flang][OpenMP] Enable tiling (PR #143715)

[Michael Kruse via flang-commits]

================
@@ -1974,44 +1986,124 @@ bool OmpAttributeVisitor::Pre(const parser::DoConstruct &x) {
   return true;
 }
 
+static bool isSizesClause(const parser::OmpClause *clause) {
+  return std::holds_alternative<parser::OmpClause::Sizes>(clause->u);
+}
+
+std::int64_t OmpAttributeVisitor::SetAssociatedMaxClause(
+    llvm::SmallVector<std::int64_t> &levels,
+    llvm::SmallVector<const parser::OmpClause *> &clauses) {
+
+  // Find the tile level to know how much to reduce the level for collapse
+  std::int64_t tileLevel = 0;
+  for (auto [level, clause] : llvm::zip_equal(levels, clauses)) {
+    if (isSizesClause(clause)) {
+      tileLevel = level;
+    }
+  }
+
+  std::int64_t maxLevel = 1;
+  const parser::OmpClause *maxClause = nullptr;
+  for (auto [level, clause] : llvm::zip_equal(levels, clauses)) {
+    if (tileLevel > 0 && tileLevel < level) {
+      context_.Say(clause->source,
+          "The value of the parameter in the COLLAPSE clause must"
+          " not be larger than the number of the number of tiled loops"
+          " because collapse relies on independent loop iterations."_err_en_US);
+      return 1;
+    }
+
+    if (!isSizesClause(clause)) {
+      level = level - tileLevel;
+    }
+
+    if (level > maxLevel) {
+      maxLevel = level;
+      maxClause = clause;
+    }
+  }
+  if (maxClause)
+    SetAssociatedClause(maxClause);
+  return maxLevel;
+}
+
+std::int64_t OmpAttributeVisitor::GetAssociatedLoopLevelFromLoopConstruct(
----------------
Meinersbur wrote:

OpenMP spec terminology: 
1. The number of loops in a nest is the "depth"
2. The Fortran statement in an OpenMP construct is the "associated statement" (which for loop-associated constructs, must be a loop nest)
3. The loops that an OpenMP loop-associated construct takes into account are the "affected loops"

```suggestion
std::int64_t OmpAttributeVisitor::GetNumAffectedLoopsFromLoopConstruct(
```

https://github.com/llvm/llvm-project/pull/143715