Index: llvm/lib/Analysis/ValueTracking.cpp
===================================================================
--- llvm/lib/Analysis/ValueTracking.cpp
+++ llvm/lib/Analysis/ValueTracking.cpp
@@ -4071,17 +4071,24 @@
                                           KnownFPClass &Known, unsigned Depth,
                                           const Query &Q,
                                           const TargetLibraryInfo *TLI) {
-  if ((InterestedClasses & fcNan) == fcNone)
+  const FPClassTest NegExcept0 = fcNegative & ~fcNegZero;
+  if ((InterestedClasses & (fcNan | NegExcept0)) == fcNone)
     return;
 
   KnownFPClass KnownSrc;
   computeKnownFPClass(Op->getOperand(0), DemandedElts, InterestedClasses,
                       KnownSrc, Depth + 1, Q, TLI);
-  if (KnownSrc.isKnownNeverNaN())
+
+  // Sign should be preserved
+  if (KnownSrc.cannotBeOrderedLessThanZero())
+    Known.knownNot(NegExcept0);
+
+  if (KnownSrc.isKnownNeverNaN()) {
     Known.knownNot(fcNan);
+    Known.SignBit = KnownSrc.SignBit;
+  }
 
   // Infinity needs a range check.
-  // TODO: Sign bit should be preserved
 }
 
 // TODO: Merge implementation of cannotBeOrderedLessThanZero into here.
Index: llvm/test/Transforms/Attributor/nofpclass-fptrunc.ll
===================================================================
--- llvm/test/Transforms/Attributor/nofpclass-fptrunc.ll
+++ llvm/test/Transforms/Attributor/nofpclass-fptrunc.ll
@@ -134,8 +134,8 @@
 }
 
 define float @ret_fptrunc_posonly(double nofpclass(ninf nnorm nsub nzero) %arg0) {
-; CHECK-LABEL: define float @ret_fptrunc_posonly
-; CHECK-SAME: (double nofpclass(ninf nzero nsub nnorm) [[ARG0:%.*]]) #[[ATTR0]] {
+; CHECK-LABEL: define nofpclass(ninf nsub nnorm) float @ret_fptrunc_posonly
+; CHECK-SAME: (double nofpclass(ninf nzero nsub nnorm) [[ARG0:%.*]]) #[[ATTR1]] {
 ; CHECK-NEXT:    [[EXT:%.*]] = fptrunc double [[ARG0]] to float
 ; CHECK-NEXT:    ret float [[EXT]]
 ;
@@ -144,8 +144,8 @@
 }
 
 define float @ret_fptrunc_posonly_zero(double nofpclass(ninf nnorm nsub) %arg0) {
-; CHECK-LABEL: define float @ret_fptrunc_posonly_zero
-; CHECK-SAME: (double nofpclass(ninf nsub nnorm) [[ARG0:%.*]]) #[[ATTR0]] {
+; CHECK-LABEL: define nofpclass(ninf nsub nnorm) float @ret_fptrunc_posonly_zero
+; CHECK-SAME: (double nofpclass(ninf nsub nnorm) [[ARG0:%.*]]) #[[ATTR1]] {
 ; CHECK-NEXT:    [[EXT:%.*]] = fptrunc double [[ARG0]] to float
 ; CHECK-NEXT:    ret float [[EXT]]
 ;
@@ -154,8 +154,8 @@
 }
 
 define float @ret_fptrunc_posonly_zero_nan(double nofpclass(ninf nnorm nsub nan) %arg0) {
-; CHECK-LABEL: define float @ret_fptrunc_posonly_zero_nan
-; CHECK-SAME: (double nofpclass(nan ninf nsub nnorm) [[ARG0:%.*]]) #[[ATTR0]] {
+; CHECK-LABEL: define nofpclass(nan ninf nsub nnorm) float @ret_fptrunc_posonly_zero_nan
+; CHECK-SAME: (double nofpclass(nan ninf nsub nnorm) [[ARG0:%.*]]) #[[ATTR1]] {
 ; CHECK-NEXT:    [[EXT:%.*]] = fptrunc double [[ARG0]] to float
 ; CHECK-NEXT:    ret float [[EXT]]
 ;
@@ -164,8 +164,8 @@
 }
 
 define float @ret_fptrunc_posonly_nan(double nofpclass(ninf nnorm nsub nzero nan) %arg0) {
-; CHECK-LABEL: define float @ret_fptrunc_posonly_nan
-; CHECK-SAME: (double nofpclass(nan ninf nzero nsub nnorm) [[ARG0:%.*]]) #[[ATTR0]] {
+; CHECK-LABEL: define nofpclass(nan ninf nsub nnorm) float @ret_fptrunc_posonly_nan
+; CHECK-SAME: (double nofpclass(nan ninf nzero nsub nnorm) [[ARG0:%.*]]) #[[ATTR1]] {
 ; CHECK-NEXT:    [[EXT:%.*]] = fptrunc double [[ARG0]] to float
 ; CHECK-NEXT:    ret float [[EXT]]
 ;
@@ -175,7 +175,7 @@
 
 define float @ret_fptrunc_negonly(double nofpclass(pinf pnorm psub pzero) %arg0) {
 ; CHECK-LABEL: define float @ret_fptrunc_negonly
-; CHECK-SAME: (double nofpclass(pinf pzero psub pnorm) [[ARG0:%.*]]) #[[ATTR0]] {
+; CHECK-SAME: (double nofpclass(pinf pzero psub pnorm) [[ARG0:%.*]]) #[[ATTR1]] {
 ; CHECK-NEXT:    [[EXT:%.*]] = fptrunc double [[ARG0]] to float
 ; CHECK-NEXT:    ret float [[EXT]]
 ;
@@ -185,7 +185,7 @@
 
 define float @ret_fptrunc_negonly_zero(double nofpclass(pinf pnorm psub) %arg0) {
 ; CHECK-LABEL: define float @ret_fptrunc_negonly_zero
-; CHECK-SAME: (double nofpclass(pinf psub pnorm) [[ARG0:%.*]]) #[[ATTR0]] {
+; CHECK-SAME: (double nofpclass(pinf psub pnorm) [[ARG0:%.*]]) #[[ATTR1]] {
 ; CHECK-NEXT:    [[EXT:%.*]] = fptrunc double [[ARG0]] to float
 ; CHECK-NEXT:    ret float [[EXT]]
 ;
@@ -194,8 +194,8 @@
 }
 
 define float @ret_fptrunc_negonly_zero_nan(double nofpclass(pinf pnorm psub nan) %arg0) {
-; CHECK-LABEL: define float @ret_fptrunc_negonly_zero_nan
-; CHECK-SAME: (double nofpclass(nan pinf psub pnorm) [[ARG0:%.*]]) #[[ATTR0]] {
+; CHECK-LABEL: define nofpclass(nan) float @ret_fptrunc_negonly_zero_nan
+; CHECK-SAME: (double nofpclass(nan pinf psub pnorm) [[ARG0:%.*]]) #[[ATTR1]] {
 ; CHECK-NEXT:    [[EXT:%.*]] = fptrunc double [[ARG0]] to float
 ; CHECK-NEXT:    ret float [[EXT]]
 ;