[flang] use set_union instead of merge in added DerivedTypeCache

[jeanPerier]

When merging the list of recursive reference under two components, duplicates should be removed.
If the recursive reference to parents nodes (referred by depth of the parents node) are [1, 2, 5] and [4, 5], the new list should be [1,2,4,5].

With std::merge, the order was correct but 5 was duplicated use std::set_union instead that removes duplicates.

With this patch Fujitsu tests 0394_0030.f90 and 0390_0230.f90 finally compile with -g in about 10s. Their compilation was hanging before #146543, and they were now hitting an error "LLVM ERROR: SmallVector unable to grow" which is fixed by this patch.

[llvmbot]

@llvm/pr-subscribers-flang-fir-hlfir

Author: None (jeanPerier)

Changes

When merging the list of recursive reference under two components, duplicates should be removed.
If the recursive reference to parents nodes (referred by depth of the parents node) are [1, 2, 5] and [4, 5], the new list should be [1,2,4,5].

With std::merge, the order was correct but 5 was duplicated use std::set_union instead that removes duplicates.

With this patch Fujitsu tests 0394_0030.f90 and 0390_0230.f90 finally compile with -g in about 10s. Their compilation was hanging before #146543, and they were now hitting an error "LLVM ERROR: SmallVector unable to grow" which is fixed by this patch.

---

Full diff: https://github.com/llvm/llvm-project/pull/147024.diff

1 Files Affected:

• (modified) flang/lib/Optimizer/Transforms/DebugTypeGenerator.cpp (+3-3)

diff --git a/flang/lib/Optimizer/Transforms/DebugTypeGenerator.cpp b/flang/lib/Optimizer/Transforms/DebugTypeGenerator.cpp
index a848058486e2c..abad500d3f657 100644
--- a/flang/lib/Optimizer/Transforms/DebugTypeGenerator.cpp
+++ b/flang/lib/Optimizer/Transforms/DebugTypeGenerator.cpp
@@ -303,9 +303,9 @@ void DerivedTypeCache::postComponentVisitUpdate(
     return;
   ActiveLevels oldLevels;
   oldLevels.swap(activeRecursionLevels);
-  std::merge(componentActiveRecursionLevels.begin(),
-             componentActiveRecursionLevels.end(), oldLevels.begin(),
-             oldLevels.end(), std::back_inserter(activeRecursionLevels));
+  std::set_union(componentActiveRecursionLevels.begin(),
+                 componentActiveRecursionLevels.end(), oldLevels.begin(),
+                 oldLevels.end(), std::back_inserter(activeRecursionLevels));
 }
 
 void DerivedTypeCache::finalize(mlir::Type ty, mlir::LLVM::DITypeAttr attr,

[abidh]

Thanks. This looks good to me.