[ValueTracking] Add test for issue 124275

Author: goldsteinn

llvm/test/Analysis/ValueTracking/phi-known-bits.ll

@@ -1112,3 +1112,36 @@ cleanup:
   %retval.0 = phi i1 [ %cmp, %if.then ], [ %tobool, %if.end4 ]
   ret i1 %retval.0
 }
+
+
+define i32 @issue_124275_wrong_br_direction(i32 noundef %inp) {
+; CHECK-LABEL: @issue_124275_wrong_br_direction(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP_NE_NOT:%.*]] = icmp eq i32 [[INP:%.*]], 1
+; CHECK-NEXT:    br i1 [[CMP_NE_NOT]], label [[B1:%.*]], label [[B0:%.*]]
+; CHECK:       B0:
+; CHECK-NEXT:    br label [[B1]]
+; CHECK:       B1:
+; CHECK-NEXT:    br i1 true, label [[B0]], label [[END:%.*]]
+; CHECK:       end:
+; CHECK-NEXT:    ret i32 0
+;
+entry:
+  %xor_inp = xor i32 %inp, 1
+  %sub = sub i32 0, %xor_inp
+  %cmp_ne = icmp ne i32 %sub, 0
+  br i1 %cmp_ne, label %B0, label %B1
+
+B0:
+  %phi_B0 = phi i32 [ %phi_B1, %B1 ], [ %sub, %entry ]
+  br label %B1
+
+B1:
+  %phi_B1 = phi i32 [ %phi_B0, %B0 ], [ 0, %entry ]
+  %cmp_ne_B1 = icmp ne i32 %phi_B1, 0
+  %cmp_eq_B1 = xor i1 %cmp_ne_B1, true
+  br i1 %cmp_eq_B1, label %B0, label %end
+
+end:
+  ret i32 0
+}