Index: llvm/lib/Analysis/ValueTracking.cpp
===================================================================
--- llvm/lib/Analysis/ValueTracking.cpp
+++ llvm/lib/Analysis/ValueTracking.cpp
@@ -4450,6 +4450,15 @@
   case Instruction::FAdd:
   case Instruction::FSub: {
     KnownFPClass KnownLHS, KnownRHS;
+
+    bool WantNegative =
+        Op->getOpcode() == Instruction::FAdd &&
+        (InterestedClasses & (fcNegative & ~fcNegZero)) != fcNone;
+    bool WantNaN = (InterestedClasses & fcNan) != fcNone;
+
+    if (!WantNaN && !WantNegative)
+      break;
+
     computeKnownFPClass(Op->getOperand(1), DemandedElts, fcNan | fcInf,
                         KnownRHS, Depth + 1, Q, TLI);
 
@@ -4457,7 +4466,8 @@
     if (KnownRHS.KnownFPClasses == fcPosZero)
       Known.knownNot(fcNegZero);
 
-    if (KnownRHS.isKnownNeverNaN()) {
+    if ((WantNaN && KnownRHS.isKnownNeverNaN()) ||
+        (WantNegative && KnownRHS.cannotBeOrderedLessThanZero())) {
       // RHS is canonically cheaper to compute. Skip inspecting the LHS if
       // there's no point.
       computeKnownFPClass(Op->getOperand(0), DemandedElts, fcNan | fcInf,
@@ -4467,6 +4477,20 @@
       if (KnownLHS.isKnownNeverNaN() &&
           (KnownLHS.isKnownNeverInfinity() || KnownRHS.isKnownNeverInfinity()))
         Known.knownNot(fcNan);
+
+      // TODO: Handle fsub
+      if (Op->getOpcode() == Instruction::FAdd) {
+        if (KnownLHS.cannotBeOrderedLessThanZero() &&
+            KnownRHS.cannotBeOrderedLessThanZero())
+          Known.knownNot(fcNegative & ~fcNegZero);
+
+        // Only fadd -0, -0 can return -0
+        //
+        // TODO: With denormals are zero, could be more optimistic and ignore
+        // subnormal inputs.
+        if (KnownLHS.isKnownNeverNegZero() && KnownRHS.isKnownNeverNegZero())
+          Known.knownNot(fcNegZero);
+      }
     }
 
     break;
Index: llvm/test/Transforms/Attributor/nofpclass.ll
===================================================================
--- llvm/test/Transforms/Attributor/nofpclass.ll
+++ llvm/test/Transforms/Attributor/nofpclass.ll
@@ -1276,7 +1276,7 @@
 
 define float @fadd_known_positive(float nofpclass(ninf nsub nnorm) %arg0, float nofpclass(ninf nsub nnorm) %arg1) {
 ; CHECK: Function Attrs: nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define float @fadd_known_positive
+; CHECK-LABEL: define nofpclass(ninf nsub nnorm) float @fadd_known_positive
 ; CHECK-SAME: (float nofpclass(ninf nsub nnorm) [[ARG0:%.*]], float nofpclass(ninf nsub nnorm) [[ARG1:%.*]]) #[[ATTR2]] {
 ; CHECK-NEXT:    [[ADD:%.*]] = fadd float [[ARG0]], [[ARG1]]
 ; CHECK-NEXT:    ret float [[ADD]]
@@ -1287,7 +1287,7 @@
 
 define float @fadd_known_positive_daz(float nofpclass(ninf nsub nnorm) %arg0, float nofpclass(ninf nsub nnorm) %arg1) #0 {
 ; CHECK: Function Attrs: nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define float @fadd_known_positive_daz
+; CHECK-LABEL: define nofpclass(ninf nsub nnorm) float @fadd_known_positive_daz
 ; CHECK-SAME: (float nofpclass(ninf nsub nnorm) [[ARG0:%.*]], float nofpclass(ninf nsub nnorm) [[ARG1:%.*]]) #[[ATTR6:[0-9]+]] {
 ; CHECK-NEXT:    [[ADD:%.*]] = fadd float [[ARG0]], [[ARG1]]
 ; CHECK-NEXT:    ret float [[ADD]]
@@ -1298,7 +1298,7 @@
 
 define float @fadd_known_positive_nzero_lhs(float nofpclass(ninf nsub nnorm nzero) %arg0, float nofpclass(ninf nsub nnorm) %arg1) {
 ; CHECK: Function Attrs: nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define float @fadd_known_positive_nzero_lhs
+; CHECK-LABEL: define nofpclass(ninf nsub nnorm) float @fadd_known_positive_nzero_lhs
 ; CHECK-SAME: (float nofpclass(ninf nzero nsub nnorm) [[ARG0:%.*]], float nofpclass(ninf nsub nnorm) [[ARG1:%.*]]) #[[ATTR2]] {
 ; CHECK-NEXT:    [[ADD:%.*]] = fadd float [[ARG0]], [[ARG1]]
 ; CHECK-NEXT:    ret float [[ADD]]
@@ -1309,7 +1309,7 @@
 
 define float @fadd_known_positive_nzero_rhs(float nofpclass(ninf nsub nnorm) %arg0, float nofpclass(ninf nsub nnorm nzero) %arg1) {
 ; CHECK: Function Attrs: nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define float @fadd_known_positive_nzero_rhs
+; CHECK-LABEL: define nofpclass(ninf nsub nnorm) float @fadd_known_positive_nzero_rhs
 ; CHECK-SAME: (float nofpclass(ninf nsub nnorm) [[ARG0:%.*]], float nofpclass(ninf nzero nsub nnorm) [[ARG1:%.*]]) #[[ATTR2]] {
 ; CHECK-NEXT:    [[ADD:%.*]] = fadd float [[ARG0]], [[ARG1]]
 ; CHECK-NEXT:    ret float [[ADD]]
@@ -1320,7 +1320,7 @@
 
 define float @fadd_known_positive_nzero(float nofpclass(ninf nsub nnorm nzero) %arg0, float nofpclass(ninf nsub nnorm nzero) %arg1) {
 ; CHECK: Function Attrs: nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define float @fadd_known_positive_nzero
+; CHECK-LABEL: define nofpclass(ninf nzero nsub nnorm) float @fadd_known_positive_nzero
 ; CHECK-SAME: (float nofpclass(ninf nzero nsub nnorm) [[ARG0:%.*]], float nofpclass(ninf nzero nsub nnorm) [[ARG1:%.*]]) #[[ATTR2]] {
 ; CHECK-NEXT:    [[ADD:%.*]] = fadd float [[ARG0]], [[ARG1]]
 ; CHECK-NEXT:    ret float [[ADD]]
@@ -1331,7 +1331,7 @@
 
 define float @fadd_known_positive_nzero_ftz_daz(float nofpclass(ninf nsub nnorm nzero) %arg0, float nofpclass(ninf nsub nnorm nzero) %arg1) #0 {
 ; CHECK: Function Attrs: nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define float @fadd_known_positive_nzero_ftz_daz
+; CHECK-LABEL: define nofpclass(ninf nzero nsub nnorm) float @fadd_known_positive_nzero_ftz_daz
 ; CHECK-SAME: (float nofpclass(ninf nzero nsub nnorm) [[ARG0:%.*]], float nofpclass(ninf nzero nsub nnorm) [[ARG1:%.*]]) #[[ATTR6]] {
 ; CHECK-NEXT:    [[ADD:%.*]] = fadd float [[ARG0]], [[ARG1]]
 ; CHECK-NEXT:    ret float [[ADD]]
@@ -1342,7 +1342,7 @@
 
 define float @fadd_known_positive_nzero_ftz(float nofpclass(ninf nsub nnorm nzero) %arg0, float nofpclass(ninf nsub nnorm nzero) %arg1) #1 {
 ; CHECK: Function Attrs: nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define float @fadd_known_positive_nzero_ftz
+; CHECK-LABEL: define nofpclass(ninf nzero nsub nnorm) float @fadd_known_positive_nzero_ftz
 ; CHECK-SAME: (float nofpclass(ninf nzero nsub nnorm) [[ARG0:%.*]], float nofpclass(ninf nzero nsub nnorm) [[ARG1:%.*]]) #[[ATTR7:[0-9]+]] {
 ; CHECK-NEXT:    [[ADD:%.*]] = fadd float [[ARG0]], [[ARG1]]
 ; CHECK-NEXT:    ret float [[ADD]]
@@ -1353,7 +1353,7 @@
 
 define float @fadd_known_positive_nzero_daz(float nofpclass(ninf nsub nnorm nzero) %arg0, float nofpclass(ninf nsub nnorm nzero) %arg1) #2 {
 ; CHECK: Function Attrs: nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define float @fadd_known_positive_nzero_daz
+; CHECK-LABEL: define nofpclass(ninf nzero nsub nnorm) float @fadd_known_positive_nzero_daz
 ; CHECK-SAME: (float nofpclass(ninf nzero nsub nnorm) [[ARG0:%.*]], float nofpclass(ninf nzero nsub nnorm) [[ARG1:%.*]]) #[[ATTR8:[0-9]+]] {
 ; CHECK-NEXT:    [[ADD:%.*]] = fadd float [[ARG0]], [[ARG1]]
 ; CHECK-NEXT:    ret float [[ADD]]