[RISCV] Add test case for pr84200. NFC

Author: topperc

llvm/test/CodeGen/RISCV/pr84200.ll

@@ -0,0 +1,23 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 4
+; RUN: llc < %s -mtriple=riscv64 | FileCheck %s
+
+; The sub nuw produces poison if the input is not 0 or 1. We must insert a
+; freeze before converting the sub to AND so that we don't propagate poison.
+define i64 @foo(i64 %1) {
+; CHECK-LABEL: foo:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    li a1, 1
+; CHECK-NEXT:    sub a1, a1, a0
+; CHECK-NEXT:    sltiu a0, a0, 2
+; CHECK-NEXT:    not a0, a0
+; CHECK-NEXT:    xori a1, a1, 1
+; CHECK-NEXT:    addi a0, a0, -1
+; CHECK-NEXT:    and a0, a0, a1
+; CHECK-NEXT:    ret
+entry:
+  %.urem.i = sub nuw i64 1, %1
+  %.cmp.i = icmp ugt i64 %1, 1
+  %2 = xor i64 %.urem.i, 1
+  %3 = select i1 %.cmp.i, i64 0, i64 %2
+  ret i64 %3
+}