ValueTracking: Treat poison more aggressively in computeKnownFPClass (#87990)

Assume no valid values, and the sign bit is 0.

1 files changed, 55 insertions, 0 deletions

diff --git a/llvm/unittests/Analysis/ValueTrackingTest.cpp b/llvm/unittests/Analysis/ValueTrackingTest.cpp
index 6b10448..8ebd9b5 100644
--- a/llvm/unittests/Analysis/ValueTrackingTest.cpp
+++ b/llvm/unittests/Analysis/ValueTrackingTest.cpp
@@ -2035,6 +2035,61 @@ TEST_F(ComputeKnownFPClassTest, Constants) {
     ASSERT_TRUE(ConstAggZero.SignBit);
     EXPECT_FALSE(*ConstAggZero.SignBit);
   }
+
+  {
+    KnownFPClass Undef =
+        computeKnownFPClass(UndefValue::get(F32), M->getDataLayout(),
+                            fcAllFlags, 0, nullptr, nullptr, nullptr, nullptr);
+    EXPECT_EQ(fcAllFlags, Undef.KnownFPClasses);
+    EXPECT_FALSE(Undef.SignBit);
+  }
+
+  {
+    KnownFPClass Poison =
+        computeKnownFPClass(PoisonValue::get(F32), M->getDataLayout(),
+                            fcAllFlags, 0, nullptr, nullptr, nullptr, nullptr);
+    EXPECT_EQ(fcNone, Poison.KnownFPClasses);
+    ASSERT_TRUE(Poison.SignBit);
+    EXPECT_FALSE(*Poison.SignBit);
+  }
+
+  {
+    // Assume the poison element should be 0.
+    Constant *ZeroF32 = ConstantFP::getZero(F32);
+    Constant *PoisonF32 = PoisonValue::get(F32);
+
+    KnownFPClass PartiallyPoison = computeKnownFPClass(
+        ConstantVector::get({ZeroF32, PoisonF32}), M->getDataLayout(),
+        fcAllFlags, 0, nullptr, nullptr, nullptr, nullptr);
+    EXPECT_EQ(fcPosZero, PartiallyPoison.KnownFPClasses);
+    ASSERT_TRUE(PartiallyPoison.SignBit);
+    EXPECT_FALSE(*PartiallyPoison.SignBit);
+  }
+
+  {
+    // Assume the poison element should be 1.
+    Constant *NegZeroF32 = ConstantFP::getZero(F32, true);
+    Constant *PoisonF32 = PoisonValue::get(F32);
+
+    KnownFPClass PartiallyPoison = computeKnownFPClass(
+        ConstantVector::get({NegZeroF32, PoisonF32}), M->getDataLayout(),
+        fcAllFlags, 0, nullptr, nullptr, nullptr, nullptr);
+    EXPECT_EQ(fcNegZero, PartiallyPoison.KnownFPClasses);
+    ASSERT_TRUE(PartiallyPoison.SignBit);
+    EXPECT_TRUE(*PartiallyPoison.SignBit);
+  }
+
+  {
+    // Assume the poison element should be 1.
+    Constant *NegZeroF32 = ConstantFP::getZero(F32, true);
+    Constant *PoisonF32 = PoisonValue::get(F32);
+
+    KnownFPClass PartiallyPoison = computeKnownFPClass(
+        ConstantVector::get({PoisonF32, NegZeroF32}), M->getDataLayout(),
+        fcAllFlags, 0, nullptr, nullptr, nullptr, nullptr);
+    EXPECT_EQ(fcNegZero, PartiallyPoison.KnownFPClasses);
+    EXPECT_TRUE(PartiallyPoison.SignBit);
+  }
 }
 
 TEST_F(ValueTrackingTest, isNonZeroRecurrence) {