inlineRegionBefore breaks -debug

[tpopp]

Currently, calls to RewriterBase::inlineRegionBefore will result in a failure to use -debug functionality by default. It works with the addition of -mlir-print-op-generic, but without will result in failures such as:

affine.for mlir-opt: llvm-project/mlir/include/mlir/IR/OpDefinition.h:838: mlir::Block *mlir::OpTrait::SingleBlock<mlir::AffineForOp>::getBody(unsigned int) [ConcreteType = mlir::AffineForOp]: Assertion `!region.empty() && "unexpected empty region"' failed. 
...
 #9 0x0000000000511d3a mlir::AffineForOp::print(mlir::OpAsmPrinter&) (build/bin/mlir-opt+0x511d3a)
#10 0x000000000052eeef mlir::Op<mlir::AffineForOp, mlir::OpTrait::OneRegion, mlir::OpTrait::VariadicResults, mlir::OpTrait::ZeroSuccessor, mlir::O
pTrait::VariadicOperands, mlir::OpTrait::SingleBlockImplicitTerminator<mlir::AffineYieldOp>::Impl, mlir::OpTrait::HasRecursiveSideEffects, mlir::L
oopLikeOpInterface::Trait>::printAssembly(mlir::Operation*, mlir::OpAsmPrinter&, llvm::StringRef) (build/bin/mlir-opt+0x52eeef)
#11 0x00000000012ed367 (anonymous namespace)::OperationPrinter::print(mlir::Operation*) AsmPrinter.cpp:0:0
#12 0x00000000012ee080 (anonymous namespace)::OperationPrinter::print(mlir::Block*, bool, bool) AsmPrinter.cpp:0:0
#13 0x00000000012f36dd (anonymous namespace)::OperationPrinter::printRegion(mlir::Region&, bool, bool, bool) AsmPrinter.cpp:0:0
#14 0x00000000013546bf mlir::function_interface_impl::printFunctionOp(mlir::OpAsmPrinter&, mlir::Operation*, llvm::ArrayRef<mlir::Type>, bool, llv
m::ArrayRef<mlir::Type>) (build/bin/mlir-opt+0x13546bf)
#15 0x0000000001322668 mlir::Op<mlir::FuncOp, mlir::OpTrait::OneRegion, mlir::OpTrait::ZeroResult, mlir::OpTrait::ZeroSuccessor, mlir::OpTrait::Ze
roOperands, mlir::OpTrait::AffineScope, mlir::OpTrait::AutomaticAllocationScope, mlir::CallableOpInterface::Trait, mlir::FunctionOpInterface::Trai
t, mlir::OpTrait::IsIsolatedFromAbove, mlir::SymbolOpInterface::Trait>::printAssembly(mlir::Operation*, mlir::OpAsmPrinter&, llvm::StringRef) (build/bin/mlir-opt+0x1322668)
#16 0x00000000012ed367 (anonymous namespace)::OperationPrinter::print(mlir::Operation*) AsmPrinter.cpp:0:0
#17 0x00000000012eb06f mlir::Operation::print(llvm::raw_ostream&, mlir::AsmState&) (build/bin/mlir-opt+0x12eb06f)
#18 0x00000000012eaf35 mlir::Operation::print(llvm::raw_ostream&, mlir::OpPrintingFlags const&) (build/bin/mlir-opt+0x12eaf35)
#19 0x00000000012ed4f4 mlir::Operation::dump() (build/bin/mlir-opt+0x12ed4f4)
#20 0x00000000026f427a mlir::PatternApplicator::matchAndRewrite(mlir::Operation*, mlir::PatternRewriter&, llvm::function_ref<bool (mlir::Pattern c
onst&)>, llvm::function_ref<void (mlir::Pattern const&)>, llvm::function_ref<mlir::LogicalResult (mlir::Pattern const&)>) (build/bin/mlir-opt+0x26f427a)

This makes debugging of passes including dialect conversion often painful as either the less clear generic form has to be used, or the pattern has to insert a block into the deleted operation to avoid the assertion failure.

The above stack trace was generated by adding -debug to Conversion/AffineToStandard/lower-affine.mlir

[llvmbot]

@llvm/issue-subscribers-mlir-core

[River707]

This isn't really specific to inlineRegionBefore in any way. A lot of things within the conversion process can break invariants in ways that will crash pretty printers, it kind of just comes with the territory. https://reviews.llvm.org/D117834 is realistically the path forward to removing the crashes during printing for invalid ops, but defaulting to the generic form is not something we will always be able to avoid during conversions.