[flang-commits] [flang] [flang] Inline hlfir.copy_in for trivial types (PR #138718)

[Tom Eccles via flang-commits]

================
@@ -127,6 +128,121 @@ class InlineHLFIRAssignConversion
   }
 };
 
+class InlineCopyInConversion : public mlir::OpRewritePattern<hlfir::CopyInOp> {
+public:
+  using mlir::OpRewritePattern<hlfir::CopyInOp>::OpRewritePattern;
+
+  llvm::LogicalResult
+  matchAndRewrite(hlfir::CopyInOp copyIn,
+                  mlir::PatternRewriter &rewriter) const override;
+};
+
+llvm::LogicalResult
+InlineCopyInConversion::matchAndRewrite(hlfir::CopyInOp copyIn,
+                                        mlir::PatternRewriter &rewriter) const {
+  fir::FirOpBuilder builder(rewriter, copyIn.getOperation());
+  mlir::Location loc = copyIn.getLoc();
+  hlfir::Entity inputVariable{copyIn.getVar()};
+  if (!fir::isa_trivial(inputVariable.getFortranElementType()))
+    return rewriter.notifyMatchFailure(copyIn,
+                                       "CopyInOp's data type is not trivial");
+
+  if (fir::isPointerType(inputVariable.getType()))
+    return rewriter.notifyMatchFailure(
+        copyIn, "CopyInOp's input variable is a pointer");
+
+  // There should be exactly one user of WasCopied - the corresponding
+  // CopyOutOp.
+  if (copyIn.getWasCopied().getUses().empty())
+    return rewriter.notifyMatchFailure(copyIn,
+                                       "CopyInOp's WasCopied has no uses");
+  // The copy out should always be present, either to actually copy or just
+  // deallocate memory.
+  auto *copyOut =
+      copyIn.getWasCopied().getUsers().begin().getCurrent().getUser();
+
+  if (!mlir::isa<hlfir::CopyOutOp>(copyOut))
+    return rewriter.notifyMatchFailure(copyIn,
+                                       "CopyInOp has no direct CopyOut");
+
+  // Only inline the copy_in when copy_out does not need to be done, i.e. in
+  // case of intent(in).
+  if (::llvm::cast<hlfir::CopyOutOp>(copyOut).getVar())
+    return rewriter.notifyMatchFailure(copyIn, "CopyIn needs a copy-out");
----------------
tblah wrote:

Instead of doing `isa` and then a `cast`, you can do it all in one with `dyn_cast` and then check if the result is `nullptr`.

https://github.com/llvm/llvm-project/pull/138718