[flang-commits] [flang] [Flang] Add opt-in affine loop optimization pipeline (PR #191854)

[Tom Eccles via flang-commits]

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@@ -278,6 +278,57 @@ static bool ivDoesNotEscape(ArrayRef<Value> ivAliases) {
   return true;
 }
 
+// ---- Check if a bound value can be safely rematerialized after the loop ---
+// Runs during analysis (pre-transformation) to reject nests whose bounds
+// contain ops that cannot be correctly duplicated after the outermost loop.
+//
+// Safe:  values defined outside the outermost loop, loop IVs (block args of
+//        fir.do_loop — resolved via ivFinalMap), fir.convert, arith constants,
+//        and arithmetic over safe values.  Loads of IV allocas are safe because
+//        transformOneLoop will forward them to fir.convert(IV) before
+//        rematerializeOutside runs.
+// Unsafe: fir.load of a non-IV address inside the loop — the memory may have
+//         been modified between the original load and the post-loop insertion
+//         point, so duplicating the load would read a wrong value.
+
+static bool canSafelyRematerialize(Value val, fir::DoLoopOp outermost,
+                                   ArrayRef<LoopIVInfo> infos) {
+  if (auto blockArg = dyn_cast<BlockArgument>(val)) {
+    auto *owner = blockArg.getOwner()->getParentOp();
+    if (!outermost->isAncestor(owner))
+      return true;
----------------
tblah wrote:

Does isAncestor return true when `owner == outermost`?

https://github.com/llvm/llvm-project/pull/191854