[MLIR] Stack overflow in dialect conversion with circular SSA dependencies

[sairam2661]

Test commit: 5a86dc996c26299de63effc927075dcbfb924167

Description:
The dialect conversion system crashes with a stack overflow error when processing a malformed MLIR with some circular SSA value dependencies - this ends up causing a segmentation fault.

Steps to reproduce

• Minimal MLIR program (test.mlir)

"builtin.module"() ({
  %0 = "arith.addi"(%1, %0) <{overflowFlags = #arith.overflow<none>}> : (index, index) -> index
  %1 = "arith.constant"() <{value = 0 : index}> : () -> index
  %2 = "arith.constant"() <{value = 1 : index}> : () -> index
}) : () -> ()

Command

mlir-opt -convert-ub-to-llvm test.mlir

Output
output.txt

[llvmbot]

@llvm/issue-subscribers-mlir

Author: None (sairam2661)

Test commit: [5a86dc9](https://github.com//pull/157520/commits/5a86dc996c26299de63effc927075dcbfb924167)

Description:
The dialect conversion system crashes with a stack overflow error when processing a malformed MLIR with some circular SSA value dependencies - this ends up causing a segmentation fault.

Steps to reproduce

• Minimal MLIR program (test.mlir)

"builtin.module"() ({
  %0 = "arith.addi"(%1, %0) <{overflowFlags = #arith.overflow<none>}> : (index, index) -> index
  %1 = "arith.constant"() <{value = 0 : index}> : () -> index
  %2 = "arith.constant"() <{value = 1 : index}> : () -> index
}) : () -> ()

Command

mlir-opt -convert-ub-to-llvm test.mlir

Output
output.txt

[matthias-springer]

I noticed that this also loops infinitely:

// RUN: mlir-opt -canonicalize
module {
  %c0 = arith.constant 0 : index
  %0 = arith.addi %c0, %0 : index
}