Index: llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -8196,6 +8196,27 @@
         return DAG.getNode(LogicOp, DL, ResultVT, IsFinite, IsNormal);
       }
     }
+
+    if (OrderedFPTestMask == (fcSubnormal | fcZero) && !IsOrdered) {
+      // TODO: Could handle ordered case, but it produces worse code for
+      // x86. Maybe handle ordered if fabs is free?
+
+      ISD::CondCode OrderedOp = IsInvertedFP ? ISD::SETUGE : ISD::SETOLT;
+      ISD::CondCode UnorderedOp = IsInvertedFP ? ISD::SETOGE : ISD::SETULT;
+
+      if (isCondCodeLegalOrCustom(IsOrdered ? OrderedOp : UnorderedOp,
+                                  OperandVT.getScalarType().getSimpleVT())) {
+        // (issubnormal(x) || iszero(x)) --> fabs(x) < smallest_normal
+
+        // TODO: Maybe only makes sense if fabs is free. Integer test of
+        // exponent bits seems better for x86.
+        SDValue Abs = DAG.getNode(ISD::FABS, DL, OperandVT, Op);
+        SDValue SmallestNormal = DAG.getConstantFP(
+            APFloat::getSmallestNormalized(Semantics), DL, OperandVT);
+        return DAG.getSetCC(DL, ResultVT, Abs, SmallestNormal,
+                            IsOrdered ? OrderedOp : UnorderedOp);
+      }
+    }
   }
 
   // Some checks may be represented as inversion of simpler check, for example
Index: llvm/test/CodeGen/X86/is_fpclass.ll
===================================================================
--- llvm/test/CodeGen/X86/is_fpclass.ll
+++ llvm/test/CodeGen/X86/is_fpclass.ll
@@ -2382,24 +2382,22 @@
 define i1 @issubnormal_or_zero_or_nan_f(float %x) {
 ; CHECK-32-LABEL: issubnormal_or_zero_or_nan_f:
 ; CHECK-32:       # %bb.0:
-; CHECK-32-NEXT:    movl {{[0-9]+}}(%esp), %eax
-; CHECK-32-NEXT:    testl $2139095040, %eax # imm = 0x7F800000
-; CHECK-32-NEXT:    sete %cl
-; CHECK-32-NEXT:    andl $2147483647, %eax # imm = 0x7FFFFFFF
-; CHECK-32-NEXT:    cmpl $2139095041, %eax # imm = 0x7F800001
-; CHECK-32-NEXT:    setge %al
-; CHECK-32-NEXT:    orb %cl, %al
+; CHECK-32-NEXT:    flds {{[0-9]+}}(%esp)
+; CHECK-32-NEXT:    fabs
+; CHECK-32-NEXT:    flds {{\.?LCPI[0-9]+_[0-9]+}}
+; CHECK-32-NEXT:    fxch %st(1)
+; CHECK-32-NEXT:    fucompp
+; CHECK-32-NEXT:    fnstsw %ax
+; CHECK-32-NEXT:    # kill: def $ah killed $ah killed $ax
+; CHECK-32-NEXT:    sahf
+; CHECK-32-NEXT:    setb %al
 ; CHECK-32-NEXT:    retl
 ;
 ; CHECK-64-LABEL: issubnormal_or_zero_or_nan_f:
 ; CHECK-64:       # %bb.0:
-; CHECK-64-NEXT:    movd %xmm0, %eax
-; CHECK-64-NEXT:    testl $2139095040, %eax # imm = 0x7F800000
-; CHECK-64-NEXT:    sete %cl
-; CHECK-64-NEXT:    andl $2147483647, %eax # imm = 0x7FFFFFFF
-; CHECK-64-NEXT:    cmpl $2139095041, %eax # imm = 0x7F800001
-; CHECK-64-NEXT:    setge %al
-; CHECK-64-NEXT:    orb %cl, %al
+; CHECK-64-NEXT:    andps {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0
+; CHECK-64-NEXT:    ucomiss {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0
+; CHECK-64-NEXT:    setb %al
 ; CHECK-64-NEXT:    retq
   %class = tail call i1 @llvm.is.fpclass.f32(float %x, i32 243)  ; 0xf0|0x3 = "subnormal|zero|nan"
   ret i1 %class
@@ -2524,24 +2522,22 @@
 define i1 @not_issubnormal_or_zero_or_nan_f(float %x) {
 ; CHECK-32-LABEL: not_issubnormal_or_zero_or_nan_f:
 ; CHECK-32:       # %bb.0:
-; CHECK-32-NEXT:    movl {{[0-9]+}}(%esp), %eax
-; CHECK-32-NEXT:    testl $2139095040, %eax # imm = 0x7F800000
-; CHECK-32-NEXT:    setne %cl
-; CHECK-32-NEXT:    andl $2147483647, %eax # imm = 0x7FFFFFFF
-; CHECK-32-NEXT:    cmpl $2139095041, %eax # imm = 0x7F800001
-; CHECK-32-NEXT:    setl %al
-; CHECK-32-NEXT:    andb %cl, %al
+; CHECK-32-NEXT:    flds {{[0-9]+}}(%esp)
+; CHECK-32-NEXT:    fabs
+; CHECK-32-NEXT:    flds {{\.?LCPI[0-9]+_[0-9]+}}
+; CHECK-32-NEXT:    fxch %st(1)
+; CHECK-32-NEXT:    fucompp
+; CHECK-32-NEXT:    fnstsw %ax
+; CHECK-32-NEXT:    # kill: def $ah killed $ah killed $ax
+; CHECK-32-NEXT:    sahf
+; CHECK-32-NEXT:    setae %al
 ; CHECK-32-NEXT:    retl
 ;
 ; CHECK-64-LABEL: not_issubnormal_or_zero_or_nan_f:
 ; CHECK-64:       # %bb.0:
-; CHECK-64-NEXT:    movd %xmm0, %eax
-; CHECK-64-NEXT:    testl $2139095040, %eax # imm = 0x7F800000
-; CHECK-64-NEXT:    setne %cl
-; CHECK-64-NEXT:    andl $2147483647, %eax # imm = 0x7FFFFFFF
-; CHECK-64-NEXT:    cmpl $2139095041, %eax # imm = 0x7F800001
-; CHECK-64-NEXT:    setl %al
-; CHECK-64-NEXT:    andb %cl, %al
+; CHECK-64-NEXT:    andps {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0
+; CHECK-64-NEXT:    ucomiss {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0
+; CHECK-64-NEXT:    setae %al
 ; CHECK-64-NEXT:    retq
   %class = tail call i1 @llvm.is.fpclass.f32(float %x, i32 780)  ; ~(0xf0|0x3) = ~"subnormal|zero|nan"
   ret i1 %class