[mlir][linalg] check if a function has a body during detensorizing

[okkwon]

Summary

A func may not have a body

[okkwon]

Submitted.

[jurahul]

mlir/lib/Dialect/Linalg/Transforms/Detensorize.cpp

479

Might be more readable to check IsExternal.

mlir/lib/Dialect/Linalg/Transforms/Detensorize.cpp

void runOnOperation() override {
     DetensorizeTypeConverter typeConverter;
     RewritePatternSet patterns(context);
     ConversionTarget target(*context);
     DenseSet<Operation *> opsToDetensor;
     DenseMap<Operation *, DenseSet<int>> detensorableBranchOps;
     DenseSet<BlockArgument> blockArgsToDetensor;
     FunctionOpInterface funcOp = getOperation();
 
+    if (funcOp.getFunctionBody().empty())
+      return;
+
     // Make sure the entry block of the function doesn't contain any Linalg ops.
     // Otherwise, it may lead to the signature of the block being changed by the
     // dialect conversion below, which would make the function op invalid
     // because its type shouldn't change.
     IRRewriter rewriter(funcOp->getContext());
     Block *entryBlock = &funcOp.getFunctionBody().front();
     Block *postEntryBlock =
         rewriter.splitBlock(entryBlock, entryBlock->begin());