remove all refops if a basic block is a raising block

ffi/custom_passes.cpp

@@ -283,7 +283,22 @@ struct RefPrunePass : public FunctionPass {
                 stats_per_bb += 1;
             }
 
-            // Second: Find matching pairs of incref decref
+            // Second: if it's a Raising block, then remove all refs
+            if (isRaising(&bb)) {
+                for (CallInst *ci : incref_list) {
+                    ci->eraseFromParent();
+                    mutated = true;
+                    stats_per_bb += 1;
+                }
+                for (CallInst *ci : decref_list) {
+                    ci->eraseFromParent();
+                    mutated = true;
+                    stats_per_bb += 1;
+                }
+                continue;
+            }
+
+            // Third: Find matching pairs of incref decref
             while (incref_list.size() > 0) {
                 // get an incref
                 CallInst *incref = incref_list.pop_back_val();

llvmlite/tests/test_refprune.py

@@ -246,6 +246,32 @@ def test_per_bb_4(self):
         # not pruned
         self.assertIn("call void @NRT_decref(i8* %other)", str(mod))
 
+    # test case is for removing all refs if the BB is raising
+    per_bb_ir_5 = r"""
+define i32 @main(i8* %ptr, i1 %cond1, i1 %cond2, i8** %excinfo) {
+bb_A:
+  br i1 %cond1, label %bb_C, label %bb_B
+bb_B:
+  br i1 %cond2, label %bb_D, label %bb_C
+bb_C:
+  %sroa = phi i8* [ %ptr, %bb_A ], [ null, %bb_B ]
+  tail call void @NRT_decref(i8* %ptr)
+  tail call void @NRT_decref(i8* %sroa)
+  store i8* null, i8** %excinfo, !numba_exception_output !0
+  br label %common.ret
+bb_D:
+  br label %common.ret
+common.ret:
+  %common.ret.op = phi i32 [ 0, %bb_D ], [ 1, %bb_C ]
+  ret i32 %common.ret.op
+}
+!0 = !{i1 1}
+"""
+
+    def test_per_bb_5(self):
+        mod, stats = self.check(self.per_bb_ir_5)
+        self.assertEqual(stats.basicblock, 2)
+
 
 class TestDiamond(BaseTestByIR):
     refprune_bitmask = llvm.RefPruneSubpasses.DIAMOND