2 files changed, 20 insertions, 0 deletions
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 52ae9f0..6d0e79e 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -1476,6 +1476,12 @@ static void computeKnownBitsFromOperator(const Operator *I,
       if (RV->getType() == I->getType()) {
         computeKnownBits(RV, Known2, Depth + 1, Q);
         Known = Known.unionWith(Known2);
+        // If the function doesn't return properly for all input values
+        // (e.g. unreachable exits) then there might be conflicts between the
+        // argument value and the range metadata. Simply discard the known bits
+        // in case of conflicts.
+        if (Known.hasConflict())
+          Known.resetAll();
       }
     }
     if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
diff --git a/llvm/unittests/Analysis/ValueTrackingTest.cpp b/llvm/unittests/Analysis/ValueTrackingTest.cpp
index 9e0abe7..6c6897d 100644
--- a/llvm/unittests/Analysis/ValueTrackingTest.cpp
+++ b/llvm/unittests/Analysis/ValueTrackingTest.cpp
@@ -2359,6 +2359,20 @@ TEST_F(ComputeKnownBitsTest, ComputeKnownBitsFreeze) {
   EXPECT_EQ(Known.One.getZExtValue(), 0u);
 }
 
+TEST_F(ComputeKnownBitsTest, ComputeKnownBitsReturnedRangeConflict) {
+  parseAssembly(
+      "declare i16 @foo(i16 returned)\n"
+      "\n"
+      "define i16 @test() {\n"
+      "  %A = call i16 @foo(i16 4095), !range !{i16 32, i16 33}\n"
+      "  ret i16 %A\n"
+      "}\n");
+  // The call returns 32 according to range metadata, but 4095 according to the
+  // returned arg operand. Given the conflicting information we expect that the
+  // known bits information simply is cleared.
+  expectKnownBits(/*zero*/ 0u, /*one*/ 0u);
+}
+
 TEST_F(ComputeKnownBitsTest, ComputeKnownBitsAddWithRange) {
   parseAssembly("define void @test(ptr %p) {\n"
                 "  %A = load i64, ptr %p, !range !{i64 64, i64 65536}\n"