Index: llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -834,6 +834,13 @@
     return replaceInstUsesWith(II, FCmp);
   }
 
+  if (Mask == (~fcNan & fcAllFlags) && !IsStrict) {
+    // Equivalent of !isnan. Replace with standard fcmp.
+    Value *FCmp = Builder.CreateFCmpORD(Src0, Src0);
+    FCmp->takeName(&II);
+    return replaceInstUsesWith(II, FCmp);
+  }
+
   if (Mask == fcZero && !IsStrict) {
     // Equivalent of == 0.
     Value *FCmp =
@@ -843,14 +850,26 @@
     return replaceInstUsesWith(II, FCmp);
   }
 
+  if (Mask == (~fcZero & fcAllFlags) && !IsStrict) {
+    // Equivalent of !(x == 0).
+    Value *FCmp =
+        Builder.CreateFCmpUNE(Src0, ConstantFP::get(Src0->getType(), 0.0));
+
+    FCmp->takeName(&II);
+    return replaceInstUsesWith(II, FCmp);
+  }
+
   // fp_class (nnan x), qnan|snan|other -> fp_class (nnan x), other
   if ((Mask & fcNan) && isKnownNeverNaN(Src0, &getTargetLibraryInfo())) {
     return replaceOperand(II, 1,
                           ConstantInt::get(Src1->getType(), Mask & ~fcNan));
   }
 
-  // TODO: Handle inverted mask cases, e.g.
   // fp_class (nnan x), ~(qnan|snan) -> true
+  if (Mask == (~fcNan & fcAllFlags) &&
+      isKnownNeverNaN(Src0, &getTargetLibraryInfo())) {
+    return replaceInstUsesWith(II, ConstantInt::get(II.getType(), true));
+  }
 
   // fp_class (ninf x), ninf|pinf|other -> fp_class (ninf x), other
   if ((Mask & fcInf) && isKnownNeverInfinity(Src0, &getTargetLibraryInfo())) {
@@ -858,6 +877,12 @@
                           ConstantInt::get(Src1->getType(), Mask & ~fcInf));
   }
 
+  // fp_class (ninf x), ~(ninf|pinf) -> true
+  if (Mask == (~fcInf & fcAllFlags) &&
+      isKnownNeverInfinity(Src0, &getTargetLibraryInfo())) {
+    return replaceInstUsesWith(II, ConstantInt::get(II.getType(), true));
+  }
+
   // Clamp mask to used bits
   if ((Mask & fcAllFlags) != Mask) {
     CallInst *NewCall = Builder.CreateCall(
Index: llvm/test/Transforms/InstCombine/is_fpclass.ll
===================================================================
--- llvm/test/Transforms/InstCombine/is_fpclass.ll
+++ llvm/test/Transforms/InstCombine/is_fpclass.ll
@@ -125,7 +125,7 @@
 
 define i1 @test_class_is_not_p0_n0_f32(float %x) {
 ; CHECK-LABEL: @test_class_is_not_p0_n0_f32(
-; CHECK-NEXT:    [[VAL:%.*]] = call i1 @llvm.is.fpclass.f32(float [[X:%.*]], i32 927)
+; CHECK-NEXT:    [[VAL:%.*]] = fcmp une float [[X:%.*]], 0.000000e+00
 ; CHECK-NEXT:    ret i1 [[VAL]]
 ;
   %val = call i1 @llvm.is.fpclass.f32(float %x, i32 927) ; ~fcZero & fcAllFlags
@@ -143,7 +143,7 @@
 
 define i1 @test_class_is_not_p0_n0_f32_daz(float %x) "denormal-fp-math"="ieee,preserve-sign" {
 ; CHECK-LABEL: @test_class_is_not_p0_n0_f32_daz(
-; CHECK-NEXT:    [[VAL:%.*]] = call i1 @llvm.is.fpclass.f32(float [[X:%.*]], i32 927)
+; CHECK-NEXT:    [[VAL:%.*]] = fcmp une float [[X:%.*]], 0.000000e+00
 ; CHECK-NEXT:    ret i1 [[VAL]]
 ;
   %val = call i1 @llvm.is.fpclass.f32(float %x, i32 927) ; ~fcZero & fcAllFlags
@@ -447,9 +447,7 @@
 ; Fold test of is not nan
 define i1 @test_class_is_not_nan_nnan_src(float %x) {
 ; CHECK-LABEL: @test_class_is_not_nan_nnan_src(
-; CHECK-NEXT:    [[NNAN:%.*]] = fadd nnan float [[X:%.*]], 1.000000e+00
-; CHECK-NEXT:    [[CLASS:%.*]] = call i1 @llvm.is.fpclass.f32(float [[NNAN]], i32 1020)
-; CHECK-NEXT:    ret i1 [[CLASS]]
+; CHECK-NEXT:    ret i1 true
 ;
   %nnan = fadd nnan float %x, 1.0
   %class = call i1 @llvm.is.fpclass.f32(float %nnan, i32 1020) ; ~fcNan & fcAllFlags
@@ -458,9 +456,7 @@
 
 define i1 @test_class_is_not_nan_nnan_src_strict(float %x) {
 ; CHECK-LABEL: @test_class_is_not_nan_nnan_src_strict(
-; CHECK-NEXT:    [[NNAN:%.*]] = fadd nnan float [[X:%.*]], 1.000000e+00
-; CHECK-NEXT:    [[CLASS:%.*]] = call i1 @llvm.is.fpclass.f32(float [[NNAN]], i32 1020) #[[ATTR3]]
-; CHECK-NEXT:    ret i1 [[CLASS]]
+; CHECK-NEXT:    ret i1 true
 ;
   %nnan = fadd nnan float %x, 1.0
   %class = call i1 @llvm.is.fpclass.f32(float %nnan, i32 1020) strictfp ; ~fcNan & fcAllFlags
@@ -511,9 +507,7 @@
 
 define i1 @test_class_is_not_inf_ninf_src(float %x) {
 ; CHECK-LABEL: @test_class_is_not_inf_ninf_src(
-; CHECK-NEXT:    [[NINF:%.*]] = fadd ninf float [[X:%.*]], 1.000000e+00
-; CHECK-NEXT:    [[CLASS:%.*]] = call i1 @llvm.is.fpclass.f32(float [[NINF]], i32 507)
-; CHECK-NEXT:    ret i1 [[CLASS]]
+; CHECK-NEXT:    ret i1 true
 ;
   %ninf = fadd ninf float %x, 1.0
   %class = call i1 @llvm.is.fpclass.f32(float %ninf, i32 507) ; ~fcInf & fcAllFlags
@@ -522,9 +516,7 @@
 
 define i1 @test_class_is_not_inf_ninf_src_strict(float %x) {
 ; CHECK-LABEL: @test_class_is_not_inf_ninf_src_strict(
-; CHECK-NEXT:    [[NINF:%.*]] = fadd ninf float [[X:%.*]], 1.000000e+00
-; CHECK-NEXT:    [[CLASS:%.*]] = call i1 @llvm.is.fpclass.f32(float [[NINF]], i32 507) #[[ATTR3]]
-; CHECK-NEXT:    ret i1 [[CLASS]]
+; CHECK-NEXT:    ret i1 true
 ;
   %ninf = fadd ninf float %x, 1.0
   %class = call i1 @llvm.is.fpclass.f32(float %ninf, i32 507) strictfp ; ~fcInf & fcAllFlags