ValueTracking: Ignore -0 for nsz sqrt with UseInstrInfo in computeKnownFPClass

This avoids a regression when SignBitMustBeZero is moved to computeKnownFPClass.

3 files changed, 82 insertions, 1 deletions

diff --git a/llvm/include/llvm/Analysis/InstructionSimplify.h b/llvm/include/llvm/Analysis/InstructionSimplify.h
index c3a9c20..df07846 100644
--- a/llvm/include/llvm/Analysis/InstructionSimplify.h
+++ b/llvm/include/llvm/Analysis/InstructionSimplify.h
@@ -83,6 +83,12 @@ struct InstrInfoQuery {
       return cast<PossiblyExactOperator>(Op)->isExact();
     return false;
   }
+
+  template <class InstT> bool hasNoSignedZeros(const InstT *Op) const {
+    if (UseInstrInfo)
+      return Op->hasNoSignedZeros();
+    return false;
+  }
 };
 
 struct SimplifyQuery {
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 88ed92e..66e810c 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -4469,7 +4469,8 @@ void computeKnownFPClass(const Value *V, const APInt &DemandedElts,
         // If the input denormal mode could be PreserveSign, a negative
         // subnormal input could produce a negative zero output.
         const Function *F = II->getFunction();
-        if (F && KnownSrc.isKnownNeverLogicalNegZero(*F, II->getType())) {
+        if (Q.IIQ.hasNoSignedZeros(II) ||
+            (F && KnownSrc.isKnownNeverLogicalNegZero(*F, II->getType()))) {
           Known.knownNot(fcNegZero);
           if (KnownSrc.isKnownNeverNaN())
             Known.SignBit = false;
diff --git a/llvm/unittests/Analysis/ValueTrackingTest.cpp b/llvm/unittests/Analysis/ValueTrackingTest.cpp
index f8910ea..5cc76e2 100644
--- a/llvm/unittests/Analysis/ValueTrackingTest.cpp
+++ b/llvm/unittests/Analysis/ValueTrackingTest.cpp
@@ -1890,6 +1890,80 @@ TEST_F(ComputeKnownFPClassTest, FCmpToClassTest_PInf) {
   EXPECT_EQ(fcNone, UgtClass);
 }
 
+TEST_F(ComputeKnownFPClassTest, SqrtNszSignBit) {
+  parseAssembly(
+      "declare float @llvm.sqrt.f32(float)\n"
+      "define float @test(float %arg, float nofpclass(nan) %arg.nnan) {\n"
+      "  %A = call float @llvm.sqrt.f32(float %arg)\n"
+      "  %A2 = call nsz float @llvm.sqrt.f32(float %arg)\n"
+      "  %A3 = call float @llvm.sqrt.f32(float %arg.nnan)\n"
+      "  %A4 = call nsz float @llvm.sqrt.f32(float %arg.nnan)\n"
+      "  ret float %A\n"
+      "}\n");
+
+  const FPClassTest SqrtMask = fcPositive | fcNegZero | fcNan;
+  const FPClassTest NszSqrtMask = fcPositive | fcNan;
+
+  {
+    KnownFPClass UseInstrInfo =
+        computeKnownFPClass(A, M->getDataLayout(), fcAllFlags, 0, nullptr,
+                            nullptr, nullptr, nullptr, /*UseInstrInfo=*/true);
+    EXPECT_EQ(SqrtMask, UseInstrInfo.KnownFPClasses);
+    EXPECT_EQ(std::nullopt, UseInstrInfo.SignBit);
+
+    KnownFPClass NoUseInstrInfo =
+        computeKnownFPClass(A, M->getDataLayout(), fcAllFlags, 0, nullptr,
+                            nullptr, nullptr, nullptr, /*UseInstrInfo=*/false);
+    EXPECT_EQ(SqrtMask, NoUseInstrInfo.KnownFPClasses);
+    EXPECT_EQ(std::nullopt, NoUseInstrInfo.SignBit);
+  }
+
+  {
+    KnownFPClass UseInstrInfoNSZ =
+        computeKnownFPClass(A2, M->getDataLayout(), fcAllFlags, 0, nullptr,
+                            nullptr, nullptr, nullptr, /*UseInstrInfo=*/true);
+    EXPECT_EQ(NszSqrtMask, UseInstrInfoNSZ.KnownFPClasses);
+    EXPECT_EQ(std::nullopt, UseInstrInfoNSZ.SignBit);
+
+    KnownFPClass NoUseInstrInfoNSZ =
+        computeKnownFPClass(A2, M->getDataLayout(), fcAllFlags, 0, nullptr,
+                            nullptr, nullptr, nullptr, /*UseInstrInfo=*/false);
+    EXPECT_EQ(SqrtMask, NoUseInstrInfoNSZ.KnownFPClasses);
+    EXPECT_EQ(std::nullopt, NoUseInstrInfoNSZ.SignBit);
+  }
+
+  {
+    KnownFPClass UseInstrInfoNoNan =
+        computeKnownFPClass(A3, M->getDataLayout(), fcAllFlags, 0, nullptr,
+                            nullptr, nullptr, nullptr, /*UseInstrInfo=*/true);
+    EXPECT_EQ(fcPositive | fcNegZero | fcQNan,
+              UseInstrInfoNoNan.KnownFPClasses);
+    EXPECT_EQ(std::nullopt, UseInstrInfoNoNan.SignBit);
+
+    KnownFPClass NoUseInstrInfoNoNan =
+        computeKnownFPClass(A3, M->getDataLayout(), fcAllFlags, 0, nullptr,
+                            nullptr, nullptr, nullptr, /*UseInstrInfo=*/false);
+    EXPECT_EQ(fcPositive | fcNegZero | fcQNan,
+              NoUseInstrInfoNoNan.KnownFPClasses);
+    EXPECT_EQ(std::nullopt, NoUseInstrInfoNoNan.SignBit);
+  }
+
+  {
+    KnownFPClass UseInstrInfoNSZNoNan =
+        computeKnownFPClass(A4, M->getDataLayout(), fcAllFlags, 0, nullptr,
+                            nullptr, nullptr, nullptr, /*UseInstrInfo=*/true);
+    EXPECT_EQ(fcPositive | fcQNan, UseInstrInfoNSZNoNan.KnownFPClasses);
+    EXPECT_EQ(false, UseInstrInfoNSZNoNan.SignBit);
+
+    KnownFPClass NoUseInstrInfoNSZNoNan =
+        computeKnownFPClass(A4, M->getDataLayout(), fcAllFlags, 0, nullptr,
+                            nullptr, nullptr, nullptr, /*UseInstrInfo=*/false);
+    EXPECT_EQ(fcPositive | fcNegZero | fcQNan,
+              NoUseInstrInfoNSZNoNan.KnownFPClasses);
+    EXPECT_EQ(std::nullopt, NoUseInstrInfoNSZNoNan.SignBit);
+  }
+}
+
 TEST_F(ValueTrackingTest, isNonZeroRecurrence) {
   parseAssembly(R"(
     define i1 @test(i8 %n, i8 %r) {