Promote MemRefDescriptor to a pointer to struct when passing function boundaries in LLVMLowering.

The strided MemRef RFC discusses a normalized descriptor and interaction with library calls (https://groups.google.com/a/tensorflow.org/forum/#!topic/mlir/MaL8m2nXuio).
Lowering of nested LLVM structs as value types does not play nicely with externally compiled C/C++ functions due to ABI issues.
Solving the ABI problem generally is a very complex problem and most likely involves taking
a dependence on clang that we do not want atm.

A simple workaround is to pass pointers to memref descriptors at function boundaries, which this CL implement.

PiperOrigin-RevId: 271591708

1 files changed, 10 insertions, 0 deletions

diff --git a/mlir/lib/Transforms/DialectConversion.cpp b/mlir/lib/Transforms/DialectConversion.cpp
index 3fababb3d34..cdd5be84568 100644
--- a/mlir/lib/Transforms/DialectConversion.cpp
+++ b/mlir/lib/Transforms/DialectConversion.cpp
@@ -618,6 +618,16 @@ void ConversionPatternRewriter::applySignatureConversion(
   impl->applySignatureConversion(region, conversion);
 }
 
+void ConversionPatternRewriter::replaceUsesOfBlockArgument(BlockArgument *from,
+                                                           Value *to) {
+  for (auto &u : from->getUses()) {
+    if (u.getOwner() == to->getDefiningOp())
+      continue;
+    u.getOwner()->replaceUsesOfWith(from, to);
+  }
+  impl->mapping.map(impl->mapping.lookupOrDefault(from), to);
+}
+
 /// Clone the given operation without cloning its regions.
 Operation *ConversionPatternRewriter::cloneWithoutRegions(Operation *op) {
   Operation *newOp = OpBuilder::cloneWithoutRegions(*op);