[Mlir-commits] [mlir] [mlir][UB] Erase ops that precede `ub.unreachable` (PR #179104)

[Jakub Kuderski]

================
@@ -9,3 +9,28 @@ func.func @merge_poison() -> (i32, i32) {
   %1 = ub.poison : i32
   return %0, %1 : i32, i32
 }
+
+// -----
+
+// CHECK-LABEL: func @drop_ops_before_unreachable( 
+//  CHECK-NEXT:   arith.constant
+//  CHECK-NEXT:   arith.constant
+//  CHECK-NEXT:   arith.constant
+//  CHECK-NEXT:   vector.print
+//  CHECK-NEXT:   scf.for {{.*}} {
+//  CHECK-NEXT:     vector.print
+//  CHECK-NEXT:   }
+//  CHECK-NEXT:   ub.unreachable
+func.func @drop_ops_before_unreachable(%arg0: i32) {
+  %lb = arith.constant 3 : index
+  %ub = arith.constant 4 : index
+  %step = arith.constant 0 : index
+  vector.print %arg0 : i32
+  // Infinite loop that may not progress. Such ops (and everything before)
+  // is not erased.
+  scf.for %iv = %lb to %ub step %step {
+    vector.print %arg0 : i32
+  } {mustProgress = false}
+  vector.print %arg0 : i32
+  ub.unreachable
----------------
kuhar wrote:

Maybe add a couple of more ops to be erased before unreachable to it obvious that the backwards iteration is fully exercised?

https://github.com/llvm/llvm-project/pull/179104