[MLIR]Crashed on `-convert-scf-to-openmp` with message '<unknown>:0: error: invalid pointer element type: 'index''

[BealZephyr]

Test on LLVM 16

steps to reproduce:

mlir-opt -convert-scf-to-openmp test.mlir

test case:

func.func @single_iteration_reduce(%A: index, %B: index) -> (index, index) {
  %c0 = arith.constant 0 : index
  %c1 = arith.constant 1 : index
  %c2 = arith.constant 2 : index
  %c3 = arith.constant 3 : index
  %c6 = arith.constant 6 : index
  %0:2 = scf.parallel (%i0, %i1) = (%c1, %c3) to (%c2, %c6) step (%c1, %c3) init(%A, %B) -> (index, index) {
    scf.reduce(%i0) : index {
    ^bb0(%lhs: index, %rhs: index):
      %1 = arith.addi %lhs, %rhs : index
      scf.reduce.return %1 : index
    }
    scf.reduce(%i1) : index {
    ^bb0(%lhs: index, %rhs: index):
      %2 = arith.muli %lhs, %rhs : index
      scf.reduce.return %2 : index
    }
    scf.yield
  }
  return %0#0, %0#1 : index, index
}

crash trace:

<unknown>:0: error: invalid pointer element type: 'index'
mlir-opt: /home/ty/llvm16/mlir/include/mlir/IR/StorageUniquerSupport.h:153: static ConcreteT mlir::detail::StorageUserBase<mlir::LLVM::LLVMPointerType, mlir::Type, mlir::LLVM::detail::LLVMPointerTypeStorage, mlir::detail::TypeUniquer, Trait, Trait>::get(mlir::MLIRContext *, Args...) [ConcreteT = mlir::LLVM::LLVMPointerType, BaseT = mlir::Type, StorageT = mlir::LLVM::detail::LLVMPointerTypeStorage, UniquerT = mlir::detail::TypeUniquer, Traits = <Trait, Trait>, Args = <mlir::Type, unsigned int>]: Assertion `succeeded(ConcreteT::verify(getDefaultDiagnosticEmitFn(ctx), args...))' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	Program arguments: /home/ty/llvm16/llvm/mlir/build/bin/mlir-opt -convert-scf-to-openmp test.mlir
 #0 0x0000000000481d7d llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) /home/ty/llvm16/llvm/lib/Support/Unix/Signals.inc:567:11
 #1 0x000000000048220b PrintStackTraceSignalHandler(void*) /home/ty/llvm16/llvm/lib/Support/Unix/Signals.inc:641:1
 #2 0x00000000004805a6 llvm::sys::RunSignalHandlers() /home/ty/llvm16/llvm/lib/Support/Signals.cpp:104:5
 #3 0x0000000000482935 SignalHandler(int) /home/ty/llvm16/llvm/lib/Support/Unix/Signals.inc:412:1
 #4 0x00007f94fd2a0980 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x12980)
 #5 0x00007f94fc190e87 raise /build/glibc-CVJwZb/glibc-2.27/signal/../sysdeps/unix/sysv/linux/raise.c:51:0
 #6 0x00007f94fc1927f1 abort /build/glibc-CVJwZb/glibc-2.27/stdlib/abort.c:81:0
 #7 0x00007f94fc1823fa __assert_fail_base /build/glibc-CVJwZb/glibc-2.27/assert/assert.c:89:0
 #8 0x00007f94fc182472 (/lib/x86_64-linux-gnu/libc.so.6+0x30472)
 #9 0x00000000017c6c7d mlir::LLVM::LLVMPointerType mlir::detail::StorageUserBase<mlir::LLVM::LLVMPointerType, mlir::Type, mlir::LLVM::detail::LLVMPointerTypeStorage, mlir::detail::TypeUniquer, mlir::DataLayoutTypeInterface::Trait, mlir::SubElementTypeInterface::Trait>::get<mlir::Type, unsigned int>(mlir::MLIRContext*, mlir::Type, unsigned int) /home/ty/llvm16/mlir/include/mlir/IR/StorageUniquerSupport.h:152:5
#10 0x00000000017bf35b mlir::LLVM::LLVMPointerType::get(mlir::Type, unsigned int) /home/ty/llvm16/mlir/lib/Dialect/LLVMIR/IR/LLVMTypes.cpp:250:10
#11 0x000000000307ca35 addAtomicRMW(mlir::OpBuilder&, mlir::LLVM::AtomicBinOp, mlir::omp::ReductionDeclareOp, mlir::scf::ReduceOp) /home/ty/llvm16/mlir/lib/Conversion/SCFToOpenMP/SCFToOpenMP.cpp:223:18
#12 0x000000000307b894 declareReduction(mlir::PatternRewriter&, mlir::scf::ReduceOp) /home/ty/llvm16/mlir/lib/Conversion/SCFToOpenMP/SCFToOpenMP.cpp:270:12
#13 0x000000000307a87c (anonymous namespace)::ParallelOpLowering::matchAndRewrite(mlir::scf::ParallelOp, mlir::PatternRewriter&) const /home/ty/llvm16/mlir/lib/Conversion/SCFToOpenMP/SCFToOpenMP.cpp:349:38
#14 0x0000000000a0e11b mlir::detail::OpOrInterfaceRewritePatternBase<mlir::scf::ParallelOp>::matchAndRewrite(mlir::Operation*, mlir::PatternRewriter&) const /home/ty/llvm16/mlir/include/mlir/IR/PatternMatch.h:330:12
#15 0x0000000004a54ee0 mlir::PatternApplicator::matchAndRewrite(mlir::Operation*, mlir::PatternRewriter&, llvm::function_ref<bool (mlir::Pattern const&)>, llvm::function_ref<void (mlir::Pattern const&)>, llvm::function_ref<mlir::LogicalResult (mlir::Pattern const&)>) /home/ty/llvm16/mlir/lib/Rewrite/PatternApplicator.cpp:200:25
#16 0x0000000003b10ec0 (anonymous namespace)::OperationLegalizer::legalizeWithPattern(mlir::Operation*, mlir::ConversionPatternRewriter&) /home/ty/llvm16/mlir/lib/Transforms/Utils/DialectConversion.cpp:1987:21
#17 0x0000000003b105db (anonymous namespace)::OperationLegalizer::legalize(mlir::Operation*, mlir::ConversionPatternRewriter&) /home/ty/llvm16/mlir/lib/Transforms/Utils/DialectConversion.cpp:1895:17
#18 0x0000000003b0fb1f (anonymous namespace)::OperationConverter::convert(mlir::ConversionPatternRewriter&, mlir::Operation*) /home/ty/llvm16/mlir/lib/Transforms/Utils/DialectConversion.cpp:2406:26
#19 0x0000000003b073ab (anonymous namespace)::OperationConverter::convertOperations(llvm::ArrayRef<mlir::Operation*>, llvm::function_ref<void (mlir::Diagnostic&)>) /home/ty/llvm16/mlir/lib/Transforms/Utils/DialectConversion.cpp:2455:16
#20 0x0000000003b07077 mlir::applyPartialConversion(llvm::ArrayRef<mlir::Operation*>, mlir::ConversionTarget&, mlir::FrozenRewritePatternSet const&, llvm::DenseSet<mlir::Operation*, llvm::DenseMapInfo<mlir::Operation*, void>>*) /home/ty/llvm16/mlir/lib/Transforms/Utils/DialectConversion.cpp:3360:22
#21 0x0000000003b075ee mlir::applyPartialConversion(mlir::Operation*, mlir::ConversionTarget&, mlir::FrozenRewritePatternSet const&, llvm::DenseSet<mlir::Operation*, llvm::DenseMapInfo<mlir::Operation*, void>>*) /home/ty/llvm16/mlir/lib/Transforms/Utils/DialectConversion.cpp:3366:10
#22 0x000000000307a157 (anonymous namespace)::applyPatterns(mlir::ModuleOp) /home/ty/llvm16/mlir/lib/Conversion/SCFToOpenMP/SCFToOpenMP.cpp:449:10
#23 0x0000000003079f26 (anonymous namespace)::SCFToOpenMPPass::runOnOperation() /home/ty/llvm16/mlir/lib/Conversion/SCFToOpenMP/SCFToOpenMP.cpp:456:16
#24 0x0000000003a697a7 mlir::detail::OpToOpPassAdaptor::run(mlir::Pass*, mlir::Operation*, mlir::AnalysisManager, bool, unsigned int) /home/ty/llvm16/mlir/lib/Pass/Pass.cpp:471:21
#25 0x0000000003a69dbd mlir::detail::OpToOpPassAdaptor::runPipeline(mlir::OpPassManager&, mlir::Operation*, mlir::AnalysisManager, bool, unsigned int, mlir::PassInstrumentor*, mlir::PassInstrumentation::PipelineParentInfo const*) /home/ty/llvm16/mlir/lib/Pass/Pass.cpp:534:16
#26 0x0000000003a6b6fc mlir::PassManager::runPasses(mlir::Operation*, mlir::AnalysisManager) /home/ty/llvm16/mlir/lib/Pass/Pass.cpp:839:10
#27 0x0000000003a6b621 mlir::PassManager::run(mlir::Operation*) /home/ty/llvm16/mlir/lib/Pass/Pass.cpp:819:60
#28 0x0000000003a61f82 performActions(llvm::raw_ostream&, bool, bool, std::shared_ptr<llvm::SourceMgr> const&, mlir::MLIRContext*, llvm::function_ref<mlir::LogicalResult (mlir::PassManager&)>, bool, bool) /home/ty/llvm16/mlir/lib/Tools/mlir-opt/MlirOptMain.cpp:91:17
#29 0x0000000003a61bdf processBuffer(llvm::raw_ostream&, std::unique_ptr<llvm::MemoryBuffer, std::default_delete<llvm::MemoryBuffer>>, bool, bool, bool, bool, bool, bool, llvm::function_ref<mlir::LogicalResult (mlir::PassManager&)>, mlir::DialectRegistry&, llvm::ThreadPool*) /home/ty/llvm16/mlir/lib/Tools/mlir-opt/MlirOptMain.cpp:139:12
#30 0x0000000003a61998 mlir::MlirOptMain(llvm::raw_ostream&, std::unique_ptr<llvm::MemoryBuffer, std::default_delete<llvm::MemoryBuffer>>, llvm::function_ref<mlir::LogicalResult (mlir::PassManager&)>, mlir::DialectRegistry&, bool, bool, bool, bool, bool, bool, bool)::$_0::operator()(std::unique_ptr<llvm::MemoryBuffer, std::default_delete<llvm::MemoryBuffer>>, llvm::raw_ostream&) const /home/ty/llvm16/mlir/lib/Tools/mlir-opt/MlirOptMain.cpp:181:12
#31 0x0000000003a6188d mlir::LogicalResult llvm::function_ref<mlir::LogicalResult (std::unique_ptr<llvm::MemoryBuffer, std::default_delete<llvm::MemoryBuffer>>, llvm::raw_ostream&)>::callback_fn<mlir::MlirOptMain(llvm::raw_ostream&, std::unique_ptr<llvm::MemoryBuffer, std::default_delete<llvm::MemoryBuffer>>, llvm::function_ref<mlir::LogicalResult (mlir::PassManager&)>, mlir::DialectRegistry&, bool, bool, bool, bool, bool, bool, bool)::$_0>(long, std::unique_ptr<llvm::MemoryBuffer, std::default_delete<llvm::MemoryBuffer>>, llvm::raw_ostream&) /home/ty/llvm16/llvm/include/llvm/ADT/STLFunctionalExtras.h:45:12
#32 0x0000000003b93ae9 llvm::function_ref<mlir::LogicalResult (std::unique_ptr<llvm::MemoryBuffer, std::default_delete<llvm::MemoryBuffer>>, llvm::raw_ostream&)>::operator()(std::unique_ptr<llvm::MemoryBuffer, std::default_delete<llvm::MemoryBuffer>>, llvm::raw_ostream&) const /home/ty/llvm16/llvm/include/llvm/ADT/STLFunctionalExtras.h:68:12
#33 0x0000000003b930c5 mlir::splitAndProcessBuffer(std::unique_ptr<llvm::MemoryBuffer, std::default_delete<llvm::MemoryBuffer>>, llvm::function_ref<mlir::LogicalResult (std::unique_ptr<llvm::MemoryBuffer, std::default_delete<llvm::MemoryBuffer>>, llvm::raw_ostream&)>, llvm::raw_ostream&, bool, bool) /home/ty/llvm16/mlir/lib/Support/ToolUtilities.cpp:28:12
#34 0x0000000003a608c3 mlir::MlirOptMain(llvm::raw_ostream&, std::unique_ptr<llvm::MemoryBuffer, std::default_delete<llvm::MemoryBuffer>>, llvm::function_ref<mlir::LogicalResult (mlir::PassManager&)>, mlir::DialectRegistry&, bool, bool, bool, bool, bool, bool, bool) /home/ty/llvm16/mlir/lib/Tools/mlir-opt/MlirOptMain.cpp:186:10
#35 0x0000000003a60a5f mlir::MlirOptMain(llvm::raw_ostream&, std::unique_ptr<llvm::MemoryBuffer, std::default_delete<llvm::MemoryBuffer>>, mlir::PassPipelineCLParser const&, mlir::DialectRegistry&, bool, bool, bool, bool, bool, bool, bool, bool) /home/ty/llvm16/mlir/lib/Tools/mlir-opt/MlirOptMain.cpp:209:10
#36 0x0000000003a616a1 mlir::MlirOptMain(int, char**, llvm::StringRef, mlir::DialectRegistry&, bool) /home/ty/llvm16/mlir/lib/Tools/mlir-opt/MlirOptMain.cpp:306:14
#37 0x00000000004116d9 main /home/ty/llvm16/mlir/tools/mlir-opt/mlir-opt.cpp:271:7
#38 0x00007f94fc173c87 __libc_start_main /build/glibc-CVJwZb/glibc-2.27/csu/../csu/libc-start.c:344:0
#39 0x00000000004113ba _start (/home/ty/llvm16/llvm/mlir/build/bin/mlir-opt+0x4113ba)
Aborted (core dumped)

[llvmbot]

@llvm/issue-subscribers-mlir

[kiranchandramohan]

While trying this with the main branch, I ran into a different error.

test1.mlir:7:10: error: failed to legalize operation 'scf.parallel' that was explicitly marked illegal
  %0:2 = scf.parallel (%i0, %i1) = (%c1, %c3) to (%c2, %c6) step (%c1, %c3) init(%A, %B) -> (i64, i64) 

This can be fixed by creating a reduction declaration to the Multiplication with integer operation (arith.muli).

diff --git a/mlir/lib/Conversion/SCFToOpenMP/SCFToOpenMP.cpp b/mlir/lib/Conversion/SCFToOpenMP/SCFToOpenMP.cpp
index f843c3d815ab..e91cd0c24171 100644
--- a/mlir/lib/Conversion/SCFToOpenMP/SCFToOpenMP.cpp
+++ b/mlir/lib/Conversion/SCFToOpenMP/SCFToOpenMP.cpp
@@ -310,6 +310,10 @@ static omp::ReductionDeclareOp declareReduction(PatternRewriter &builder,
     return createDecl(builder, symbolTable, reduce,
                       builder.getFloatAttr(type, 1.0));
   }
+  if (matchSimpleReduction<arith::MulIOp, LLVM::MulOp>(reduction)) {
+    return createDecl(builder, symbolTable, reduce,
+                      builder.getIntegerAttr(type, 1));
+  }
 
   // Match select-based min/max reductions.
   bool isMin;

Subsequently, I ran into the error where index is not supported for the init field of reductions (

llvm-project/mlir/lib/Conversion/SCFToOpenMP/SCFToOpenMP.cpp

Line 387 in 56cc0bb

init.getType().isa<LLVM::PointerElementTypeInterface>()) &&

). I modified the test slightly to work around this. Note the conversion of some types to i64 and the introduction of an index.cast. Not sure whether this will be fine for the author of this issue.

func.func @single_iteration_reduce(%A: i64, %B: i64) -> (i64, i64) {
  %c0 = arith.constant 0 : index
  %c1 = arith.constant 1 : index
  %c2 = arith.constant 2 : index
  %c3 = arith.constant 3 : index
  %c6 = arith.constant 6 : index
  %0:2 = scf.parallel (%i0, %i1) = (%c1, %c3) to (%c2, %c6) step (%c1, %c3) init(%A, %B) -> (i64, i64) {
    %v0 = index.casts %i0 : index to i64
    scf.reduce(%v0) : i64 {
    ^bb0(%lhs: i64, %rhs: i64):
      %1 = arith.addi %lhs, %rhs : i64
      scf.reduce.return %1 : i64
    }
    %v1 = index.casts %i1 : index to i64
    scf.reduce(%v1) : i64 {
    ^bb0(%lhs: i64, %rhs: i64):
      %2 = arith.muli %lhs, %rhs : i64
      scf.reduce.return %2 : i64
    }
    scf.yield
  }
  return %0#0, %0#1 : i64, i64
}

This worked. But to fully generated LLVM dialect that can be translated to LLVM IR, I had to run these passes.

./bin/mlir-opt -convert-scf-to-openmp -convert-arith-to-llvm -convert-openmp-to-llvm -convert-index-to-llvm --canonicalize test1.mlir

Probably we should allow index types in the init field of scf.parallel. Also noted that while scf.for now supports i32, i64 types for the loop index, start, stop, step etc, scf.parallel does not.