Multiple return values causes stack trace in secret-to-bgv

[j2kun]

Even after fixing #1298 (comment), the example from that issue gives a stack trace in a later compiler pass in this pipeline

// RUN: heir-opt --mlir-to-bgv %s

func.func @foo(%x: i16 {secret.secret}, %y: i16 {secret.secret}) -> (i16, i16) {
  %0 = arith.addi %x, %y : i16
  return %0, %0: i16, i16
}

Stack trace (with assertion failure)

Trying to match "mlir::heir::SecretGenericOpCipherConversion<mlir::arith::AddIOp, mlir::heir::bgv::AddOp>"
heir-opt: bazel-out/k8-dbg/bin/lib/Dialect/BGV/IR/BGVOps.cpp.inc:161: static void mlir::heir::bgv::AddOp::build(::mlir::OpBuilder &, ::mlir::OperationState &, ::mlir::TypeRange, ::mlir::ValueRange, ::llvm::ArrayRef< ::mlir::NamedAttribute>): Assertion `resultTypes.size() == 1u && "mismatched number of return types"' 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/j2kun/.cache/bazel/_bazel_j2kun/b07a48cf9da8c73a462d3608e5c508dd/execroot/heir/bazel-out/k8-dbg/bin/tools/heir-opt --mlir-to-bgv --debug --mlir-print-ir-after-failure /home/j2kun/fhe/heir/tests/Transforms/optimize_relinearization/multiple_return_values.mlir
 #0 0x0000564e524143fd llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) /proc/self/cwd/external/llvm-project/llvm/lib/Support/Unix/Signals.inc:796:11
 #1 0x0000564e524148eb PrintStackTraceSignalHandler(void*) /proc/self/cwd/external/llvm-project/llvm/lib/Support/Unix/Signals.inc:872:1
 #2 0x0000564e52411fa6 llvm::sys::RunSignalHandlers() /proc/self/cwd/external/llvm-project/llvm/lib/Support/Signals.cpp:105:5
 #3 0x0000564e52414fe5 SignalHandler(int) /proc/self/cwd/external/llvm-project/llvm/lib/Support/Unix/Signals.inc:413:1
 #4 0x00007f3b4c75a520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #5 0x00007f3b4c7ae9fc __pthread_kill_implementation ./nptl/pthread_kill.c:44:76
 #6 0x00007f3b4c7ae9fc __pthread_kill_internal ./nptl/pthread_kill.c:78:10
 #7 0x00007f3b4c7ae9fc pthread_kill ./nptl/pthread_kill.c:89:10
 #8 0x00007f3b4c75a476 gsignal ./signal/../sysdeps/posix/raise.c:27:6
 #9 0x00007f3b4c7407f3 abort ./stdlib/abort.c:81:7
#10 0x00007f3b4c74071b _nl_load_domain ./intl/loadmsgcat.c:1177:9
#11 0x00007f3b4c751e96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
#12 0x0000564e4d8e46cc mlir::heir::bgv::AddOp::build(mlir::OpBuilder&, mlir::OperationState&, mlir::TypeRange, mlir::ValueRange, llvm::ArrayRef<mlir::NamedAttribute>) /proc/self/cwd/bazel-out/k8-dbg/bin/lib/Dialect/BGV/IR/BGVOps.cpp.inc:162:3
#13 0x0000564e4bdc06a5 mlir::heir::bgv::AddOp mlir::OpBuilder::create<mlir::heir::bgv::AddOp, mlir::TypeRange&, mlir::ValueRange&>(mlir::Location, mlir::TypeRange&, mlir::ValueRange&) /proc/self/cwd/external/llvm-project/mlir/include/mlir/IR/Builders.h:518:5
#14 0x0000564e4bdbfe2a mlir::heir::bgv::AddOp mlir::RewriterBase::replaceOpWithNewOp<mlir::heir::bgv::AddOp, mlir::TypeRange&, mlir::ValueRange&>(mlir::Operation*, mlir::TypeRange&, mlir::ValueRange&) /proc/self/cwd/external/llvm-project/mlir/include/mlir/IR/PatternMatch.h:543:18
#15 0x0000564e4bdbee59 mlir::heir::SecretGenericOpCipherConversion<mlir::arith::AddIOp, mlir::heir::bgv::AddOp>::matchAndRewriteInner(mlir::heir::secret::GenericOp, mlir::TypeRange, mlir::ValueRange, llvm::ArrayRef<mlir::NamedAttribute>, mlir::ConversionPatternRewriter&) const /proc/self/cwd/./lib/Utils/ConversionUtils.h:277:14
#16 0x0000564e4bdbed2b mlir::heir::SecretGenericOpConversion<mlir::arith::AddIOp, mlir::heir::bgv::AddOp>::matchAndRewrite(mlir::heir::secret::GenericOp, mlir::heir::secret::GenericOpAdaptor, mlir::ConversionPatternRewriter&) const /proc/self/cwd/./lib/Utils/ConversionUtils.h:247:12
#17 0x0000564e4bbf6c8a mlir::OpConversionPattern<mlir::heir::secret::GenericOp>::matchAndRewrite(mlir::heir::secret::GenericOp, mlir::heir::secret::GenericOpGenericAdaptor<llvm::ArrayRef<mlir::ValueRange>>, mlir::ConversionPatternRewriter&) const /proc/self/cwd/external/llvm-project/mlir/include/mlir/Transforms/DialectConversion.h:688:12
#18 0x0000564e4bbf68ca mlir::OpConversionPattern<mlir::heir::secret::GenericOp>::matchAndRewrite(mlir::Operation*, llvm::ArrayRef<mlir::ValueRange>, mlir::ConversionPatternRewriter&) const /proc/self/cwd/external/llvm-project/mlir/include/mlir/Transforms/DialectConversion.h:656:12
#19 0x0000564e51928b56 mlir::ConversionPattern::matchAndRewrite(mlir::Operation*, mlir::PatternRewriter&) const /proc/self/cwd/external/llvm-project/mlir/lib/Transforms/Utils/DialectConversion.cpp:1868:10