[llvm-branch-commits] [flang] [flang][OpenMP] Map simple `do concurrent` loops to OpenMP host constructs (PR #127633)

[Sergio Afonso via llvm-branch-commits]

================
@@ -152,26 +199,140 @@ class DoConcurrentConversion : public 
mlir::OpConversionPattern<fir::DoLoopOp> {
 public:
   using mlir::OpConversionPattern<fir::DoLoopOp>::OpConversionPattern;
 
-  DoConcurrentConversion(mlir::MLIRContext *context, bool mapToDevice)
-      : OpConversionPattern(context), mapToDevice(mapToDevice) {}
+  DoConcurrentConversion(mlir::MLIRContext *context, bool mapToDevice,
+                         llvm::DenseSet<fir::DoLoopOp> &concurrentLoopsToSkip)
+      : OpConversionPattern(context), mapToDevice(mapToDevice),
+        concurrentLoopsToSkip(concurrentLoopsToSkip) {}
 
   mlir::LogicalResult
   matchAndRewrite(fir::DoLoopOp doLoop, OpAdaptor adaptor,
                   mlir::ConversionPatternRewriter &rewriter) const override {
-    looputils::LoopNest loopNest;
+    if (mapToDevice)
+      return doLoop.emitError(
+          "not yet implemented: Mapping `do concurrent` loops to device");
+
+    looputils::LoopNestToIndVarMap loopNest;
     bool hasRemainingNestedLoops =
         failed(looputils::collectLoopNest(doLoop, loopNest));
     if (hasRemainingNestedLoops)
       mlir::emitWarning(doLoop.getLoc(),
                         "Some `do concurent` loops are not perfectly-nested. "
                         "These will be serialized.");
 
-    // TODO This will be filled in with the next PRs that upstreams the rest of
-    // the ROCm implementaion.
+    mlir::IRMapping mapper;
+    genParallelOp(doLoop.getLoc(), rewriter, loopNest, mapper);
+    mlir::omp::LoopNestOperands loopNestClauseOps;
+    genLoopNestClauseOps(doLoop.getLoc(), rewriter, loopNest, mapper,
+                         loopNestClauseOps);
+
+    mlir::omp::LoopNestOp ompLoopNest =
+        genWsLoopOp(rewriter, loopNest.back().first, mapper, loopNestClauseOps,
+                    /*isComposite=*/mapToDevice);
+
+    rewriter.eraseOp(doLoop);
+
+    // Mark `unordered` loops that are not perfectly nested to be skipped from
+    // the legality check of the `ConversionTarget` since we are not interested
+    // in mapping them to OpenMP.
+    ompLoopNest->walk([&](fir::DoLoopOp doLoop) {
+      if (doLoop.getUnordered()) {
+        concurrentLoopsToSkip.insert(doLoop);
+      }
+    });
+
     return mlir::success();
   }
 
+private:
+  mlir::omp::ParallelOp genParallelOp(mlir::Location loc,
+                                      mlir::ConversionPatternRewriter 
&rewriter,
+                                      looputils::LoopNestToIndVarMap &loopNest,
+                                      mlir::IRMapping &mapper) const {
+    auto parallelOp = rewriter.create<mlir::omp::ParallelOp>(loc);
+    rewriter.createBlock(&parallelOp.getRegion());
+    rewriter.setInsertionPoint(rewriter.create<mlir::omp::TerminatorOp>(loc));
+
+    genLoopNestIndVarAllocs(rewriter, loopNest, mapper);
+    return parallelOp;
+  }
+
+  void genLoopNestIndVarAllocs(mlir::ConversionPatternRewriter &rewriter,
+                               looputils::LoopNestToIndVarMap &loopNest,
+                               mlir::IRMapping &mapper) const {
+
+    for (auto &[_, indVarInfo] : loopNest)
+      genInductionVariableAlloc(rewriter, indVarInfo.iterVarMemDef, mapper);
+  }
+
+  mlir::Operation *
+  genInductionVariableAlloc(mlir::ConversionPatternRewriter &rewriter,
+                            mlir::Operation *indVarMemDef,
+                            mlir::IRMapping &mapper) const {
+    assert(
+        indVarMemDef != nullptr &&
+        "Induction variable memdef is expected to have a defining operation.");
+
+    llvm::SmallSetVector<mlir::Operation *, 2> indVarDeclareAndAlloc;
+    for (auto operand : indVarMemDef->getOperands())
+      indVarDeclareAndAlloc.insert(operand.getDefiningOp());
+    indVarDeclareAndAlloc.insert(indVarMemDef);
+
+    mlir::Operation *result;
+    for (mlir::Operation *opToClone : indVarDeclareAndAlloc)
+      result = rewriter.clone(*opToClone, mapper);
+
+    return result;
+  }
+
+  void genLoopNestClauseOps(
+      mlir::Location loc, mlir::ConversionPatternRewriter &rewriter,
+      looputils::LoopNestToIndVarMap &loopNest, mlir::IRMapping &mapper,
+      mlir::omp::LoopNestOperands &loopNestClauseOps) const {
+    assert(loopNestClauseOps.loopLowerBounds.empty() &&
+           "Loop nest bounds were already emitted!");
+
+    auto populateBounds = [&](mlir::Value var,
----------------
skatrak wrote:

Nit: No need to capture anything here.
```suggestion
    auto populateBounds = [](mlir::Value var,
```

https://github.com/llvm/llvm-project/pull/127633
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