[flang-commits] [flang] [flang][OpenMP] Fix wrong results for FORALL in a workshare construct (PR #211371)

[Carlos Seo via flang-commits]

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@@ -328,9 +359,19 @@ static void collectThreadLocalWrites(Operation *op,
 // Reads are matched by their underlying thread-local allocation, mirroring
 // collectThreadLocalWrites, so that a load through a fir.declare/fir.convert
 // still keeps the corresponding write live for broadcasting.
-static void collectThreadLocalReads(Region &scope,
-                                    llvm::SmallDenseSet<Value> &reads) {
+//
+// An opaque call may read any thread-local location inside its callee, and a
+// memory-effecting operation may report a read of unspecified memory (a read
+// effect with no attached value). Neither read can be attributed to a specific
+// location, so reads.unknown is set to force every thread-local write to be
+// broadcasted. Other interface-less operations (e.g. omp.barrier, fir.declare)
+// have known, inspectable behaviour and are safe to ignore here.
+static void collectThreadLocalReads(Region &scope, ThreadLocalReads &reads) {
   scope.walk([&](Operation *op) {
+    if (isa<mlir::CallOpInterface>(op)) {
+      reads.unknown = true;
+      return;
+    }
     auto memEffects = dyn_cast<MemoryEffectOpInterface>(op);
     if (!memEffects)
       return;
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ceseo wrote:

Will do.

You may take it if you wish. I still have a bunch of patches to review and submit in the following weeks. If you do start working on this, please check the Fujitsu testsuite board (https://github.com/orgs/llvm/projects/20/views/1). I think it's likely that there are bugs reported there for other dialects that may be related to this.

https://github.com/llvm/llvm-project/pull/211371