From aead0cfbc4ff0a9a40bab2836d39bb8645d49351 Mon Sep 17 00:00:00 2001
From: Sanjay Patel <spatel@rotateright.com>
Date: Tue, 13 Apr 2021 14:46:21 -0400
Subject: [PATCH] [ValueTracking] add unit test for isKnownNonZero(); NFC

We call various value tracking APIs from within -instsimplify,
so I don't think this is visible in a larger test.
---
 unittests/Analysis/ValueTrackingTest.cpp | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/unittests/Analysis/ValueTrackingTest.cpp b/unittests/Analysis/ValueTrackingTest.cpp
index 93bb2635b24..85678bb6653 100644
--- a/unittests/Analysis/ValueTrackingTest.cpp
+++ b/unittests/Analysis/ValueTrackingTest.cpp
@@ -1173,6 +1173,27 @@ TEST_F(ComputeKnownBitsTest, ComputeKnownMulBits) {
   expectKnownBits(/*zero*/ 95u, /*one*/ 32u);
 }
 
+TEST_F(ValueTrackingTest, isNonZeroRecurrence) {
+  parseAssembly(R"(
+    define i1 @test(i8 %n, i8 %r) {
+    entry:
+      br label %loop
+    loop:
+      %p = phi i8 [ -1, %entry ], [ %next, %loop ]
+      %next = add nsw i8 %p, -1
+      %cmp1 = icmp eq i8 %p, %n
+      br i1 %cmp1, label %exit, label %loop
+    exit:
+      %A = or i8 %p, %r
+      %CxtI = icmp eq i8 %A, 0
+      ret i1 %CxtI
+    }
+  )");
+  DataLayout DL = M->getDataLayout();
+  AssumptionCache AC(*F);
+  EXPECT_FALSE(isKnownNonZero(A, DL, 0, &AC, CxtI));
+}
+
 TEST_F(ValueTrackingTest, KnownNonZeroFromDomCond) {
   parseAssembly(R"(
     declare i8* @f_i8()