[flang-commits] [flang] [flang][fir] Lower `do concurrent` loop nests to `fir.do_concurrent` (PR #132904)

[Tom Eccles via flang-commits]

================
@@ -2277,96 +2283,77 @@ class FirConverter : public Fortran::lower::AbstractConverter {
       llvm::SmallVectorImpl<const Fortran::parser::CompilerDirective *> &dirs) {
     assert(!incrementLoopNestInfo.empty() && "empty loop nest");
     mlir::Location loc = toLocation();
-    mlir::Operation *boundsAndStepIP = nullptr;
     mlir::arith::IntegerOverflowFlags iofBackup{};
 
-    for (IncrementLoopInfo &info : incrementLoopNestInfo) {
-      mlir::Value lowerValue;
-      mlir::Value upperValue;
-      mlir::Value stepValue;
-
-      {
-        mlir::OpBuilder::InsertionGuard guard(*builder);
+    llvm::SmallVector<mlir::Value> nestLBs;
+    llvm::SmallVector<mlir::Value> nestUBs;
+    llvm::SmallVector<mlir::Value> nestSts;
+    llvm::SmallVector<mlir::Value> nestReduceOperands;
+    llvm::SmallVector<mlir::Attribute> nestReduceAttrs;
+    bool genDoConcurrent = false;
 
-        // Set the IP before the first loop in the nest so that all nest bounds
-        // and step values are created outside the nest.
-        if (boundsAndStepIP)
-          builder->setInsertionPointAfter(boundsAndStepIP);
+    for (IncrementLoopInfo &info : incrementLoopNestInfo) {
+      genDoConcurrent = info.isStructured() && info.isUnordered;
 
+      if (!genDoConcurrent)
         info.loopVariable = genLoopVariableAddress(loc, *info.loopVariableSym,
                                                    info.isUnordered);
-        if (!getLoweringOptions().getIntegerWrapAround()) {
-          iofBackup = builder->getIntegerOverflowFlags();
-          builder->setIntegerOverflowFlags(
-              mlir::arith::IntegerOverflowFlags::nsw);
-        }
-        lowerValue = genControlValue(info.lowerExpr, info);
-        upperValue = genControlValue(info.upperExpr, info);
-        bool isConst = true;
-        stepValue = genControlValue(info.stepExpr, info,
-                                    info.isStructured() ? nullptr : &isConst);
-        if (!getLoweringOptions().getIntegerWrapAround())
-          builder->setIntegerOverflowFlags(iofBackup);
-        boundsAndStepIP = stepValue.getDefiningOp();
-
-        // Use a temp variable for unstructured loops with non-const step.
-        if (!isConst) {
-          info.stepVariable =
-              builder->createTemporary(loc, stepValue.getType());
-          boundsAndStepIP =
-              builder->create<fir::StoreOp>(loc, stepValue, info.stepVariable);
+
+      if (!getLoweringOptions().getIntegerWrapAround()) {
+        iofBackup = builder->getIntegerOverflowFlags();
+        builder->setIntegerOverflowFlags(
+            mlir::arith::IntegerOverflowFlags::nsw);
+      }
+
+      nestLBs.push_back(genControlValue(info.lowerExpr, info));
+      nestUBs.push_back(genControlValue(info.upperExpr, info));
+      bool isConst = true;
+      nestSts.push_back(genControlValue(
+          info.stepExpr, info, info.isStructured() ? nullptr : &isConst));
+
+      if (!getLoweringOptions().getIntegerWrapAround())
+        builder->setIntegerOverflowFlags(iofBackup);
+
+      // Use a temp variable for unstructured loops with non-const step.
+      if (!isConst) {
+        mlir::Value stepValue = nestSts.back();
+        info.stepVariable = builder->createTemporary(loc, stepValue.getType());
+        builder->create<fir::StoreOp>(loc, stepValue, info.stepVariable);
+      }
+
+      if (genDoConcurrent && nestReduceOperands.empty()) {
----------------
tblah wrote:

Thanks for explaining. I am not particularly familiar with this bit of code but only adding them to the last `IncrementLoopInfo` sounds okay to me.

https://github.com/llvm/llvm-project/pull/132904