ValueTracking: Fix computeKnownFPClass for fabs

[arsenm]

Summary

The fabs utility functions have the opposite purpose and
probably should not be a general utility.

[foad]

Code LGTM.

The situation with the fabs helpers is not great. We have two, they do opposite things, one isn't documented and the other is documented in a way that I can't understand.

[arsenm]

b0aa6d76eb3aa7c1ea4abf509d5177a92bfd72a5

llvm/include/llvm/Analysis/ValueTracking.h

struct KnownFPClass {
 
   void fneg() {
     KnownFPClasses = llvm::fneg(KnownFPClasses);
     if (SignBit)
       SignBit = !*SignBit;
   }
 
   void fabs() {
-    KnownFPClasses = llvm::fabs(KnownFPClasses);
+    KnownFPClasses &= (fcPositive | fcNan);
     SignBit = false;
   }
 
   /// Assume the sign bit is zero.
   void signBitIsZero() {
     KnownFPClasses = (KnownFPClasses & fcPositive) |
                      (KnownFPClasses & fcNan);
     SignBit = false;

llvm/lib/Analysis/ValueTracking.cpp

computeKnownFPClass(Op->getOperand(2), DemandedElts, InterestedClasses,
                         Known2, Depth + 1, Q, TLI);
     Known |= Known2;
     break;
   }
   case Instruction::Call: {
     if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Op)) {
       const Intrinsic::ID IID = II->getIntrinsicID();
       switch (IID) {
-      case Intrinsic::fabs:
+      case Intrinsic::fabs: {
+        if ((InterestedClasses & (fcNan | fcPositive)) != fcNone) {
+          // If we only care about the sign bit we don't need to inspect the
+          // operand.
           computeKnownFPClass(II->getArgOperand(0), DemandedElts,
                               InterestedClasses, Known, Depth + 1, Q, TLI);
+        }
+
         Known.fabs();
         break;
+      }
       case Intrinsic::copysign: {
         KnownFPClass KnownSign;
 
         computeKnownFPClass(II->getArgOperand(0), DemandedElts,
                             InterestedClasses, Known, Depth + 1, Q, TLI);
         computeKnownFPClass(II->getArgOperand(1), DemandedElts,
                             InterestedClasses, KnownSign, Depth + 1, Q, TLI);
         Known.copysign(KnownSign);

llvm/test/Transforms/Attributor/nofpclass.ll

entry:
   call void @extern.use(float %arg)
   ret float %arg
 }
 
 define half @fcmp_assume_issubnormal_callsite_arg_return(half %arg) {
 ; CHECK-LABEL: define nofpclass(nan inf norm) half @fcmp_assume_issubnormal_callsite_arg_return
 ; CHECK-SAME: (half returned nofpclass(nan inf norm) [[ARG:%.*]]) {
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[FABS:%.*]] = call half @llvm.fabs.f16(half nofpclass(nan inf norm) [[ARG]]) #[[ATTR7]]
+; CHECK-NEXT:    [[FABS:%.*]] = call nofpclass(ninf nzero nsub nnorm) half @llvm.fabs.f16(half nofpclass(nan inf norm) [[ARG]]) #[[ATTR7]]
 ; CHECK-NEXT:    [[IS_SUBNORMAL:%.*]] = fcmp olt half [[FABS]], 0xH0400
 ; CHECK-NEXT:    call void @llvm.assume(i1 noundef [[IS_SUBNORMAL]]) #[[ATTR7]]
 ; CHECK-NEXT:    call void @extern.use.f16(half nofpclass(nan inf norm) [[ARG]])
 ; CHECK-NEXT:    ret half [[ARG]]
 ;
 entry:
   %fabs = call half @llvm.fabs.f16(half %arg)
   %is.subnormal = fcmp olt half %fabs, 0xH0400
entry:
   ret half %arg
 }
 
 ; Assume not subnormal or zero, and not infinity
 define half @fcmp_assume2_callsite_arg_return(half %arg) {
 ; CHECK-LABEL: define nofpclass(nan ninf zero sub norm) half @fcmp_assume2_callsite_arg_return
 ; CHECK-SAME: (half returned nofpclass(nan ninf zero sub norm) [[ARG:%.*]]) {
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[FABS:%.*]] = call nofpclass(nan zero sub norm) half @llvm.fabs.f16(half nofpclass(nan ninf zero sub norm) [[ARG]]) #[[ATTR7]]
+; CHECK-NEXT:    [[FABS:%.*]] = call nofpclass(nan ninf zero sub norm) half @llvm.fabs.f16(half nofpclass(nan ninf zero sub norm) [[ARG]]) #[[ATTR7]]
 ; CHECK-NEXT:    [[NOT_SUBNORMAL_OR_ZERO:%.*]] = fcmp oge half [[FABS]], 0xH0400
 ; CHECK-NEXT:    call void @llvm.assume(i1 noundef [[NOT_SUBNORMAL_OR_ZERO]]) #[[ATTR7]]
 ; CHECK-NEXT:    [[NOT_INF:%.*]] = fcmp oeq half [[ARG]], 0xH7C00
 ; CHECK-NEXT:    call void @llvm.assume(i1 noundef [[NOT_INF]]) #[[ATTR7]]
 ; CHECK-NEXT:    call void @extern.use.f16(half nofpclass(nan ninf zero sub norm) [[ARG]])
 ; CHECK-NEXT:    ret half [[ARG]]
 ;
 entry:

 }
 
 ; Make sure we don't get confused by looking at an unrelated assume
 ; based on the fabs of the value.
 define half @assume_fcmp_fabs_with_other_fabs_assume(half %arg) {
 ; CHECK-LABEL: define nofpclass(nan inf norm) half @assume_fcmp_fabs_with_other_fabs_assume
 ; CHECK-SAME: (half returned nofpclass(nan inf norm) [[ARG:%.*]]) {
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[FABS:%.*]] = call nofpclass(nan inf zero norm) half @llvm.fabs.f16(half nofpclass(nan inf norm) [[ARG]]) #[[ATTR7]]
+; CHECK-NEXT:    [[FABS:%.*]] = call nofpclass(nan inf zero nsub norm) half @llvm.fabs.f16(half nofpclass(nan inf norm) [[ARG]]) #[[ATTR7]]
 ; CHECK-NEXT:    [[UNRELATED_FABS:%.*]] = fcmp one half [[FABS]], 0xH0000
 ; CHECK-NEXT:    call void @llvm.assume(i1 noundef [[UNRELATED_FABS]]) #[[ATTR7]]
 ; CHECK-NEXT:    [[IS_SUBNORMAL:%.*]] = fcmp olt half [[FABS]], 0xH0400
 ; CHECK-NEXT:    call void @llvm.assume(i1 noundef [[IS_SUBNORMAL]]) #[[ATTR7]]
 ; CHECK-NEXT:    call void @extern.use.f16(half nofpclass(nan inf norm) [[ARG]])
-; CHECK-NEXT:    call void @extern.use.f16(half nofpclass(nan inf zero norm) [[FABS]])
+; CHECK-NEXT:    call void @extern.use.f16(half nofpclass(nan inf zero nsub norm) [[FABS]])
 ; CHECK-NEXT:    ret half [[ARG]]
 ;
 entry:
 
   %fabs = call half @llvm.fabs.f16(half %arg)
   %unrelated.fabs = fcmp one half %fabs, 0.0
   call void @llvm.assume(i1 %unrelated.fabs)
   %is.subnormal = fcmp olt half %fabs, 0xH0400
;
   %alloca = alloca float
   store float %arg, ptr %alloca
   %ret = call float @returned_load(ptr %alloca)
   ret float %ret
 }
 
 define float @returned_fabs(float %x) {
 ; CHECK: Function Attrs: nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define float @returned_fabs
+; CHECK-LABEL: define nofpclass(ninf nzero nsub nnorm) float @returned_fabs
 ; CHECK-SAME: (float [[X:%.*]]) #[[ATTR2]] {
-; CHECK-NEXT:    [[FABS:%.*]] = call float @llvm.fabs.f32(float [[X]]) #[[ATTR7]]
+; CHECK-NEXT:    [[FABS:%.*]] = call nofpclass(ninf nzero nsub nnorm) float @llvm.fabs.f32(float [[X]]) #[[ATTR7]]
 ; CHECK-NEXT:    ret float [[FABS]]
 ;
   %fabs = call float @llvm.fabs.f32(float %x)
   ret float %fabs
 }
 
 define float @returned_fabs_nosnan(float nofpclass(snan) %x) {
 ; CHECK: Function Attrs: nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define nofpclass(snan) float @returned_fabs_nosnan
+; CHECK-LABEL: define nofpclass(snan ninf nzero nsub nnorm) float @returned_fabs_nosnan
 ; CHECK-SAME: (float nofpclass(snan) [[X:%.*]]) #[[ATTR2]] {
-; CHECK-NEXT:    [[FABS:%.*]] = call nofpclass(snan) float @llvm.fabs.f32(float nofpclass(snan) [[X]]) #[[ATTR7]]
+; CHECK-NEXT:    [[FABS:%.*]] = call nofpclass(snan ninf nzero nsub nnorm) float @llvm.fabs.f32(float nofpclass(snan) [[X]]) #[[ATTR7]]
 ; CHECK-NEXT:    ret float [[FABS]]
 ;
   %fabs = call float @llvm.fabs.f32(float %x)
   ret float %fabs
 }
 
 define float @returned_fabs_noqnan(float nofpclass(qnan) %x) {
 ; CHECK: Function Attrs: nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define nofpclass(qnan) float @returned_fabs_noqnan
+; CHECK-LABEL: define nofpclass(qnan ninf nzero nsub nnorm) float @returned_fabs_noqnan
 ; CHECK-SAME: (float nofpclass(qnan) [[X:%.*]]) #[[ATTR2]] {
-; CHECK-NEXT:    [[FABS:%.*]] = call nofpclass(qnan) float @llvm.fabs.f32(float nofpclass(qnan) [[X]]) #[[ATTR7]]
+; CHECK-NEXT:    [[FABS:%.*]] = call nofpclass(qnan ninf nzero nsub nnorm) float @llvm.fabs.f32(float nofpclass(qnan) [[X]]) #[[ATTR7]]
 ; CHECK-NEXT:    ret float [[FABS]]
 ;
   %fabs = call float @llvm.fabs.f32(float %x)
   ret float %fabs
 }
 
 define float @returned_fabs_nonan(float nofpclass(nan) %x) {
 ; CHECK: Function Attrs: nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define nofpclass(nan) float @returned_fabs_nonan
+; CHECK-LABEL: define nofpclass(nan ninf nzero nsub nnorm) float @returned_fabs_nonan
 ; CHECK-SAME: (float nofpclass(nan) [[X:%.*]]) #[[ATTR2]] {
-; CHECK-NEXT:    [[FABS:%.*]] = call nofpclass(nan) float @llvm.fabs.f32(float nofpclass(nan) [[X]]) #[[ATTR7]]
+; CHECK-NEXT:    [[FABS:%.*]] = call nofpclass(nan ninf nzero nsub nnorm) float @llvm.fabs.f32(float nofpclass(nan) [[X]]) #[[ATTR7]]
 ; CHECK-NEXT:    ret float [[FABS]]
 ;
   %fabs = call float @llvm.fabs.f32(float %x)
   ret float %fabs
 }
 
 define float @returned_fabs_noinf(float nofpclass(inf) %x) {
 ; CHECK: Function Attrs: nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define nofpclass(inf) float @returned_fabs_noinf
+; CHECK-LABEL: define nofpclass(inf nzero nsub nnorm) float @returned_fabs_noinf
 ; CHECK-SAME: (float nofpclass(inf) [[X:%.*]]) #[[ATTR2]] {
-; CHECK-NEXT:    [[FABS:%.*]] = call nofpclass(inf) float @llvm.fabs.f32(float nofpclass(inf) [[X]]) #[[ATTR7]]
+; CHECK-NEXT:    [[FABS:%.*]] = call nofpclass(inf nzero nsub nnorm) float @llvm.fabs.f32(float nofpclass(inf) [[X]]) #[[ATTR7]]
 ; CHECK-NEXT:    ret float [[FABS]]
 ;
   %fabs = call float @llvm.fabs.f32(float %x)
   ret float %fabs
 }
 
 define float @returned_fneg(float %x) {
 ; CHECK: Function Attrs: nofree norecurse nosync nounwind willreturn memory(none)

 ; CHECK-NEXT:    ret float [[FNEG]]
 ;
   %fneg = fneg float %x
   ret float %fneg
 }
 
 define float @returned_fneg_fabs(float %x) {
 ; CHECK: Function Attrs: nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define float @returned_fneg_fabs
+; CHECK-LABEL: define nofpclass(pinf pzero psub pnorm) float @returned_fneg_fabs
 ; CHECK-SAME: (float [[X:%.*]]) #[[ATTR2]] {
-; CHECK-NEXT:    [[FABS:%.*]] = call float @llvm.fabs.f32(float [[X]]) #[[ATTR7]]
+; CHECK-NEXT:    [[FABS:%.*]] = call nofpclass(ninf nzero nsub nnorm) float @llvm.fabs.f32(float [[X]]) #[[ATTR7]]
 ; CHECK-NEXT:    [[FNEG_FABS:%.*]] = fneg float [[FABS]]
 ; CHECK-NEXT:    ret float [[FNEG_FABS]]
 ;
   %fabs = call float @llvm.fabs.f32(float %x)
   %fneg.fabs = fneg float %fabs
   ret float %fneg.fabs
 }
 
 define float @returned_fneg_fabs_nosnan(float nofpclass(snan) %x) {
 ; CHECK: Function Attrs: nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define nofpclass(snan) float @returned_fneg_fabs_nosnan
+; CHECK-LABEL: define nofpclass(snan pinf pzero psub pnorm) float @returned_fneg_fabs_nosnan
 ; CHECK-SAME: (float nofpclass(snan) [[X:%.*]]) #[[ATTR2]] {
-; CHECK-NEXT:    [[FABS:%.*]] = call nofpclass(snan) float @llvm.fabs.f32(float nofpclass(snan) [[X]]) #[[ATTR7]]
+; CHECK-NEXT:    [[FABS:%.*]] = call nofpclass(snan ninf nzero nsub nnorm) float @llvm.fabs.f32(float nofpclass(snan) [[X]]) #[[ATTR7]]
 ; CHECK-NEXT:    [[FNEG_FABS:%.*]] = fneg float [[FABS]]
 ; CHECK-NEXT:    ret float [[FNEG_FABS]]
 ;
   %fabs = call float @llvm.fabs.f32(float %x)
   %fneg.fabs = fneg float %fabs
   ret float %fneg.fabs
 }
 
 define float @returned_fneg_fabs_noqnan(float nofpclass(qnan) %x) {
 ; CHECK: Function Attrs: nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define nofpclass(qnan) float @returned_fneg_fabs_noqnan
+; CHECK-LABEL: define nofpclass(qnan pinf pzero psub pnorm) float @returned_fneg_fabs_noqnan
 ; CHECK-SAME: (float nofpclass(qnan) [[X:%.*]]) #[[ATTR2]] {
-; CHECK-NEXT:    [[FABS:%.*]] = call nofpclass(qnan) float @llvm.fabs.f32(float nofpclass(qnan) [[X]]) #[[ATTR7]]
+; CHECK-NEXT:    [[FABS:%.*]] = call nofpclass(qnan ninf nzero nsub nnorm) float @llvm.fabs.f32(float nofpclass(qnan) [[X]]) #[[ATTR7]]
 ; CHECK-NEXT:    [[FNEG_FABS:%.*]] = fneg float [[FABS]]
 ; CHECK-NEXT:    ret float [[FNEG_FABS]]
 ;
   %fabs = call float @llvm.fabs.f32(float %x)
   %fneg.fabs = fneg float %fabs
   ret float %fneg.fabs
 }
 
 define float @returned_fneg_fabs_nonan(float nofpclass(nan) %x) {
 ; CHECK: Function Attrs: nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define nofpclass(nan) float @returned_fneg_fabs_nonan
+; CHECK-LABEL: define nofpclass(nan pinf pzero psub pnorm) float @returned_fneg_fabs_nonan
 ; CHECK-SAME: (float nofpclass(nan) [[X:%.*]]) #[[ATTR2]] {
-; CHECK-NEXT:    [[FABS:%.*]] = call nofpclass(nan) float @llvm.fabs.f32(float nofpclass(nan) [[X]]) #[[ATTR7]]
+; CHECK-NEXT:    [[FABS:%.*]] = call nofpclass(nan ninf nzero nsub nnorm) float @llvm.fabs.f32(float nofpclass(nan) [[X]]) #[[ATTR7]]
 ; CHECK-NEXT:    [[FNEG_FABS:%.*]] = fneg float [[FABS]]
 ; CHECK-NEXT:    ret float [[FNEG_FABS]]
 ;
   %fabs = call float @llvm.fabs.f32(float %x)
   %fneg.fabs = fneg float %fabs
   ret float %fneg.fabs
 }
 
 define float @returned_fneg_fabs_noneg(float nofpclass(ninf nsub nnorm nzero) %x) {
 ; CHECK: Function Attrs: nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define float @returned_fneg_fabs_noneg
+; CHECK-LABEL: define nofpclass(pinf pzero psub pnorm) float @returned_fneg_fabs_noneg
 ; CHECK-SAME: (float nofpclass(ninf nzero nsub nnorm) [[X:%.*]]) #[[ATTR2]] {
-; CHECK-NEXT:    [[FABS:%.*]] = call float @llvm.fabs.f32(float nofpclass(ninf nzero nsub nnorm) [[X]]) #[[ATTR7]]
+; CHECK-NEXT:    [[FABS:%.*]] = call nofpclass(ninf nzero nsub nnorm) float @llvm.fabs.f32(float nofpclass(ninf nzero nsub nnorm) [[X]]) #[[ATTR7]]
 ; CHECK-NEXT:    [[FNEG_FABS:%.*]] = fneg float [[FABS]]
 ; CHECK-NEXT:    ret float [[FNEG_FABS]]
 ;
   %fabs = call float @llvm.fabs.f32(float %x)
   %fneg.fabs = fneg float %fabs
   ret float %fneg.fabs
 }
 
 define float @returned_fneg_fabs_nopos(float nofpclass(pinf psub pnorm pzero) %x) {
 ; CHECK: Function Attrs: nofree norecurse nosync nounwind willreturn memory(none)
 ; CHECK-LABEL: define nofpclass(inf zero sub norm) float @returned_fneg_fabs_nopos
 ; CHECK-SAME: (float nofpclass(pinf pzero psub pnorm) [[X:%.*]]) #[[ATTR2]] {
 ; CHECK-NEXT:    [[FABS:%.*]] = call nofpclass(inf zero sub norm) float @llvm.fabs.f32(float nofpclass(pinf pzero psub pnorm) [[X]]) #[[ATTR7]]
 ; CHECK-NEXT:    [[FNEG_FABS:%.*]] = fneg float [[FABS]]
 ; CHECK-NEXT:    ret float [[FNEG_FABS]]
 ;
   %fabs = call float @llvm.fabs.f32(float %x)
   %fneg.fabs = fneg float %fabs
   ret float %fneg.fabs
 }
 
 define float @returned_fneg_fabs_mixed(float nofpclass(psub nnorm nzero qnan ninf) %x) {
 ; CHECK: Function Attrs: nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define nofpclass(qnan sub) float @returned_fneg_fabs_mixed
+; CHECK-LABEL: define nofpclass(qnan pinf pzero sub pnorm) float @returned_fneg_fabs_mixed
 ; CHECK-SAME: (float nofpclass(qnan ninf nzero psub nnorm) [[X:%.*]]) #[[ATTR2]] {
-; CHECK-NEXT:    [[FABS:%.*]] = call nofpclass(qnan sub) float @llvm.fabs.f32(float nofpclass(qnan ninf nzero psub nnorm) [[X]]) #[[ATTR7]]
+; CHECK-NEXT:    [[FABS:%.*]] = call nofpclass(qnan ninf nzero sub nnorm) float @llvm.fabs.f32(float nofpclass(qnan ninf nzero psub nnorm) [[X]]) #[[ATTR7]]
 ; CHECK-NEXT:    [[FNEG_FABS:%.*]] = fneg float [[FABS]]
 ; CHECK-NEXT:    ret float [[FNEG_FABS]]
 ;
   %fabs = call float @llvm.fabs.f32(float %x)
   %fneg.fabs = fneg float %fabs
   ret float %fneg.fabs
 }
 
 define float @returned_fneg_fabs_ninf_flag_fabs(float %x) {
 ; CHECK: Function Attrs: nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define nofpclass(inf) float @returned_fneg_fabs_ninf_flag_fabs
+; CHECK-LABEL: define nofpclass(inf pzero psub pnorm) float @returned_fneg_fabs_ninf_flag_fabs
 ; CHECK-SAME: (float [[X:%.*]]) #[[ATTR2]] {
-; CHECK-NEXT:    [[FABS:%.*]] = call ninf nofpclass(inf) float @llvm.fabs.f32(float [[X]]) #[[ATTR7]]
+; CHECK-NEXT:    [[FABS:%.*]] = call ninf nofpclass(inf nzero nsub nnorm) float @llvm.fabs.f32(float [[X]]) #[[ATTR7]]
 ; CHECK-NEXT:    [[FNEG_FABS:%.*]] = fneg float [[FABS]]
 ; CHECK-NEXT:    ret float [[FNEG_FABS]]
 ;
   %fabs = call ninf float @llvm.fabs.f32(float %x)
   %fneg.fabs = fneg float %fabs
   ret float %fneg.fabs
 }
 
 define float @returned_fneg_fabs_ninf_flag_fneg(float %x) {
 ; CHECK: Function Attrs: nofree norecurse nosync nounwind willreturn memory(none)
-; CHECK-LABEL: define nofpclass(inf) float @returned_fneg_fabs_ninf_flag_fneg
+; CHECK-LABEL: define nofpclass(inf pzero psub pnorm) float @returned_fneg_fabs_ninf_flag_fneg
 ; CHECK-SAME: (float [[X:%.*]]) #[[ATTR2]] {
-; CHECK-NEXT:    [[FABS:%.*]] = call float @llvm.fabs.f32(float [[X]]) #[[ATTR7]]
+; CHECK-NEXT:    [[FABS:%.*]] = call nofpclass(ninf nzero nsub nnorm) float @llvm.fabs.f32(float [[X]]) #[[ATTR7]]
 ; CHECK-NEXT:    [[FNEG_FABS:%.*]] = fneg ninf float [[FABS]]
 ; CHECK-NEXT:    ret float [[FNEG_FABS]]
 ;
   %fabs = call float @llvm.fabs.f32(float %x)
   %fneg.fabs = fneg ninf float %fabs
   ret float %fneg.fabs
 }
 

llvm/unittests/Analysis/ValueTrackingTest.cpp

 
 TEST_F(ComputeKnownFPClassTest, FabsUnknown) {
   parseAssembly(
       "declare float @llvm.fabs.f32(float)"
       "define float @test(float %arg) {\n"
       "  %A = call float @llvm.fabs.f32(float %arg)"
       "  ret float %A\n"
       "}\n");
-  expectKnownFPClass(fcAllFlags, false);
+  expectKnownFPClass(fcPositive | fcNan, false);
 }
 
 TEST_F(ComputeKnownFPClassTest, FNegFabsUnknown) {
   parseAssembly(
       "declare float @llvm.fabs.f32(float)"
       "define float @test(float %arg) {\n"
       "  %fabs = call float @llvm.fabs.f32(float %arg)"
       "  %A = fneg float %fabs"
       "  ret float %A\n"
       "}\n");
-  expectKnownFPClass(fcAllFlags, true);
+  expectKnownFPClass(fcNegative | fcNan, true);
 }
 
 TEST_F(ComputeKnownFPClassTest, NegFabsNInf) {
   parseAssembly(
       "declare float @llvm.fabs.f32(float)"
       "define float @test(float %arg) {\n"
       "  %fabs = call ninf float @llvm.fabs.f32(float %arg)"
       "  %A = fneg float %fabs"
       "  ret float %A\n"
       "}\n");
-  expectKnownFPClass(~fcInf, true);
+  expectKnownFPClass((fcNegative & ~fcNegInf) | fcNan, true);
 }
 
 TEST_F(ComputeKnownFPClassTest, FNegFabsNNaN) {
   parseAssembly(
       "declare float @llvm.fabs.f32(float)"
       "define float @test(float %arg) {\n"
       "  %fabs = call nnan float @llvm.fabs.f32(float %arg)"
       "  %A = fneg float %fabs"
       "  ret float %A\n"
       "}\n");
-  expectKnownFPClass(~fcNan, true);
+  expectKnownFPClass(fcNegative, true);
 }
 
 TEST_F(ComputeKnownFPClassTest, CopySignNNanSrc0) {
   parseAssembly(
       "declare float @llvm.fabs.f32(float)\n"
       "declare float @llvm.copysign.f32(float, float)\n"
       "define float @test(float %arg0, float %arg1) {\n"
       "  %fabs = call nnan float @llvm.fabs.f32(float %arg0)"
       "  %A = call float @llvm.copysign.f32(float %fabs, float %arg1)"
       "  ret float %A\n"
       "}\n");
-  expectKnownFPClass(~fcNan, std::nullopt);
+  expectKnownFPClass(fcPositive, std::nullopt);
 }
 
 TEST_F(ComputeKnownFPClassTest, CopySignNInfSrc0_NegSign) {
   parseAssembly(
       "declare float @llvm.log.f32(float)\n"
       "declare float @llvm.copysign.f32(float, float)\n"
       "define float @test(float %arg0, float %arg1) {\n"
       "  %ninf = call ninf float @llvm.log.f32(float %arg0)"