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

[Michael Kruse via llvm-commits]

================
@@ -2992,18 +2991,59 @@ convertOmpLoopNest(Operation &opInst, llvm::IRBuilderBase &builder,
     loopInfos.push_back(*loopResult);
   }
 
-  // Collapse loops. Store the insertion point because LoopInfos may get
-  // invalidated.
   llvm::OpenMPIRBuilder::InsertPointTy afterIP =
       loopInfos.front()->getAfterIP();
 
-  // Update the stack frame created for this loop to point to the resulting loop
-  // after applying transformations.
-  moduleTranslation.stackWalk<OpenMPLoopInfoStackFrame>(
-      [&](OpenMPLoopInfoStackFrame &frame) {
-        frame.loopInfo = ompBuilder->collapseLoops(ompLoc.DL, loopInfos, {});
-        return WalkResult::interrupt();
-      });
+  // Initialize the new loop info to the current one, in case there
+  // are no loop transformations done.
+  llvm::CanonicalLoopInfo *NewTopLoopInfo = nullptr;
+
+  // Do tiling
+  if (const auto &tiles = loopOp.getTileSizes()) {
+    llvm::Type *IVType = loopInfos.front()->getIndVarType();
+    SmallVector<llvm::Value *> TileSizes;
+
+    for (auto tile : tiles.value()) {
+      llvm::Value *TileVal = llvm::ConstantInt::get(IVType, tile);
+      TileSizes.push_back(TileVal);
+    }
+
+    std::vector<llvm::CanonicalLoopInfo *> NewLoops =
+        ompBuilder->tileLoops(ompLoc.DL, loopInfos, TileSizes);
+
+    // Update afterIP to get the correct insertion point after
+    // tiling.
+    llvm::BasicBlock *AfterBB = NewLoops.front()->getAfter();
+    llvm::BasicBlock *AfterAfterBB = AfterBB->getSingleSuccessor();
+    afterIP = {AfterAfterBB, AfterAfterBB->begin()};
+    NewTopLoopInfo = NewLoops[0];
+
+    // Update the loop infos
+    loopInfos.clear();
+    for (const auto &newLoop : NewLoops) {
+      loopInfos.push_back(newLoop);
+    }
+  } // Tiling done
+
+  // Do collapse
+  if (const auto &numCollapse = loopOp.getNumCollapse()) {
+    SmallVector<llvm::CanonicalLoopInfo *> collapseLoopInfos(
+        loopInfos.begin(), loopInfos.begin() + (numCollapse));
+
+    auto newLoopInfo =
+        ompBuilder->collapseLoops(ompLoc.DL, collapseLoopInfos, {});
----------------
Meinersbur wrote:

Previously this was called withing the OpenMPLoopInfoStackFrame callback. Does it make a difference?

(Doing it outside of it seems more logical to me, but I assume there was a reason)

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