Index: llvm/lib/Analysis/ValueTracking.cpp
===================================================================
--- llvm/lib/Analysis/ValueTracking.cpp
+++ llvm/lib/Analysis/ValueTracking.cpp
@@ -4339,18 +4339,21 @@
     return;
   }
 
+  const Operator *Op = dyn_cast<Operator>(V);
   FPClassTest KnownNotFromFlags = fcNone;
-  if (const auto *CB = dyn_cast<CallBase>(V))
-    KnownNotFromFlags |= CB->getRetNoFPClass();
-  else if (const auto *Arg = dyn_cast<Argument>(V))
-    KnownNotFromFlags |= Arg->getNoFPClass();
 
-  const Operator *Op = dyn_cast<Operator>(V);
-  if (const FPMathOperator *FPOp = dyn_cast_or_null<FPMathOperator>(Op)) {
-    if (FPOp->hasNoNaNs())
-      KnownNotFromFlags |= fcNan;
-    if (FPOp->hasNoInfs())
-      KnownNotFromFlags |= fcInf;
+  if (Q.IIQ.UseInstrInfo) {
+    if (const auto *CB = dyn_cast<CallBase>(V))
+      KnownNotFromFlags |= CB->getRetNoFPClass();
+    else if (const auto *Arg = dyn_cast<Argument>(V))
+      KnownNotFromFlags |= Arg->getNoFPClass();
+
+    if (const FPMathOperator *FPOp = dyn_cast_or_null<FPMathOperator>(Op)) {
+      if (FPOp->hasNoNaNs())
+        KnownNotFromFlags |= fcNan;
+      if (FPOp->hasNoInfs())
+        KnownNotFromFlags |= fcInf;
+    }
   }
 
   if (Q.AC) {
Index: llvm/unittests/Analysis/ValueTrackingTest.cpp
===================================================================
--- llvm/unittests/Analysis/ValueTrackingTest.cpp
+++ llvm/unittests/Analysis/ValueTrackingTest.cpp
@@ -1943,7 +1943,7 @@
     KnownFPClass NoUseInstrInfoNoNan =
         computeKnownFPClass(A3, M->getDataLayout(), fcAllFlags, 0, nullptr,
                             nullptr, nullptr, nullptr, /*UseInstrInfo=*/false);
-    EXPECT_EQ(fcPositive | fcNegZero | fcQNan,
+    EXPECT_EQ(fcPositive | fcNegZero | fcNan,
               NoUseInstrInfoNoNan.KnownFPClasses);
     EXPECT_EQ(std::nullopt, NoUseInstrInfoNoNan.SignBit);
   }
@@ -1958,12 +1958,73 @@
     KnownFPClass NoUseInstrInfoNSZNoNan =
         computeKnownFPClass(A4, M->getDataLayout(), fcAllFlags, 0, nullptr,
                             nullptr, nullptr, nullptr, /*UseInstrInfo=*/false);
-    EXPECT_EQ(fcPositive | fcNegZero | fcQNan,
+    EXPECT_EQ(fcPositive | fcNegZero | fcNan,
               NoUseInstrInfoNSZNoNan.KnownFPClasses);
     EXPECT_EQ(std::nullopt, NoUseInstrInfoNSZNoNan.SignBit);
   }
 }
 
+/// Test that the UseInstrInfo parameter is respected.
+TEST_F(ComputeKnownFPClassTest, RespectIgnoreFlags) {
+  parseAssembly(
+      "declare float @func()\n"
+      "define float @test(i1 %cond, float %arg0, float %arg1) {\n"
+      "  %A = fadd nnan float %arg0, %arg1\n"
+      "  %A2 = fmul ninf float %arg0, %arg1\n"
+      "  %A3 = call nofpclass(inf nan) float @func()\n"
+      "  ret float %A\n"
+      "}\n");
+
+  {
+    KnownFPClass UseInstrInfoNoNaN =
+        computeKnownFPClass(A, M->getDataLayout(), fcAllFlags, 0, nullptr,
+                            nullptr, nullptr, nullptr, /*UseInstrInfo=*/true);
+    EXPECT_EQ(~fcNan, UseInstrInfoNoNaN.KnownFPClasses);
+    EXPECT_EQ(std::nullopt, UseInstrInfoNoNaN.SignBit);
+  }
+
+  {
+    KnownFPClass UseInstrInfoNoInf =
+        computeKnownFPClass(A2, M->getDataLayout(), fcAllFlags, 0, nullptr,
+                            nullptr, nullptr, nullptr, /*UseInstrInfo=*/true);
+    EXPECT_EQ(~fcInf, UseInstrInfoNoInf.KnownFPClasses);
+    EXPECT_EQ(std::nullopt, UseInstrInfoNoInf.SignBit);
+  }
+
+  {
+    KnownFPClass NoUseInstrInfoNoNaN =
+        computeKnownFPClass(A, M->getDataLayout(), fcAllFlags, 0, nullptr,
+                            nullptr, nullptr, nullptr, /*UseInstrInfo=*/false);
+    EXPECT_EQ(fcAllFlags, NoUseInstrInfoNoNaN.KnownFPClasses);
+    EXPECT_EQ(std::nullopt, NoUseInstrInfoNoNaN.SignBit);
+  }
+
+  {
+    KnownFPClass NoUseInstrInfoNoInf =
+        computeKnownFPClass(A2, M->getDataLayout(), fcAllFlags, 0, nullptr,
+                            nullptr, nullptr, nullptr, /*UseInstrInfo=*/false);
+    EXPECT_EQ(fcAllFlags, NoUseInstrInfoNoInf.KnownFPClasses);
+    EXPECT_EQ(std::nullopt, NoUseInstrInfoNoInf.SignBit);
+  }
+
+  {
+    KnownFPClass UseInstrUsesOther =
+        computeKnownFPClass(A3, M->getDataLayout(), fcAllFlags, 0, nullptr,
+                            nullptr, nullptr, nullptr, /*UseInstrInfo=*/true);
+    EXPECT_EQ(~(fcNan | fcInf), UseInstrUsesOther.KnownFPClasses);
+    EXPECT_EQ(std::nullopt, UseInstrUsesOther.SignBit);
+  }
+
+  // No looking at nofpclass attribute
+  {
+    KnownFPClass NoUseInstrUsesOther =
+        computeKnownFPClass(A3, M->getDataLayout(), fcAllFlags, 0, nullptr,
+                            nullptr, nullptr, nullptr, /*UseInstrInfo=*/false);
+    EXPECT_EQ(fcAllFlags, NoUseInstrUsesOther.KnownFPClasses);
+    EXPECT_EQ(std::nullopt, NoUseInstrUsesOther.SignBit);
+  }
+}
+
 TEST_F(ValueTrackingTest, isNonZeroRecurrence) {
   parseAssembly(R"(
     define i1 @test(i8 %n, i8 %r) {