diff --git a/llvm/lib/CodeGen/CodeGenCommonISel.cpp b/llvm/lib/CodeGen/CodeGenCommonISel.cpp
index d985751e2be0b..4cd2f6ae2fdb1 100644
--- a/llvm/lib/CodeGen/CodeGenCommonISel.cpp
+++ b/llvm/lib/CodeGen/CodeGenCommonISel.cpp
@@ -202,6 +202,8 @@ FPClassTest llvm::invertFPClassTestIfSimpler(FPClassTest Test, bool UseFCmp) {
   case fcSubnormal | fcZero | fcNan:
     return InvertedTest;
   case fcInf | fcNan:
+  case fcPosInf | fcNan:
+  case fcNegInf | fcNan:
     // If we're trying to use fcmp, we can take advantage of the nan check
     // behavior of the compare (but this is more instructions in the integer
     // expansion).
diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index c3affabb19d37..2b41b8a9a810e 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -8754,6 +8754,22 @@ SDValue TargetLowering::expandIS_FPCLASS(EVT ResultVT, SDValue Op,
                           IsOrderedInf ? OrderedCmpOpcode : UnorderedCmpOpcode);
     }
 
+    if ((OrderedFPTestMask == fcPosInf || OrderedFPTestMask == fcNegInf) &&
+        isCondCodeLegalOrCustom(IsOrdered ? OrderedCmpOpcode
+                                          : UnorderedCmpOpcode,
+                                OperandVT.getSimpleVT())) {
+      // isposinf(x) --> x == inf
+      // isneginf(x) --> x == -inf
+      // isposinf(x) || nan --> x u== inf
+      // isneginf(x) || nan --> x u== -inf
+
+      SDValue Inf = DAG.getConstantFP(
+          APFloat::getInf(Semantics, OrderedFPTestMask == fcNegInf), DL,
+          OperandVT);
+      return DAG.getSetCC(DL, ResultVT, Op, Inf,
+                          IsOrdered ? OrderedCmpOpcode : UnorderedCmpOpcode);
+    }
+
     if (OrderedFPTestMask == (fcSubnormal | fcZero) && !IsOrdered) {
       // TODO: Could handle ordered case, but it produces worse code for
       // x86. Maybe handle ordered if fabs is free?
diff --git a/llvm/test/CodeGen/X86/is_fpclass.ll b/llvm/test/CodeGen/X86/is_fpclass.ll
index cc4d4c4543a51..97136dafa6c2c 100644
--- a/llvm/test/CodeGen/X86/is_fpclass.ll
+++ b/llvm/test/CodeGen/X86/is_fpclass.ll
@@ -2116,24 +2116,19 @@ entry:
 define i1 @is_plus_inf_or_nan_f(float %x) {
 ; X86-LABEL: is_plus_inf_or_nan_f:
 ; X86:       # %bb.0:
-; X86-NEXT:    movl {{[0-9]+}}(%esp), %eax
-; X86-NEXT:    cmpl $2139095040, %eax # imm = 0x7F800000
-; X86-NEXT:    sete %cl
-; X86-NEXT:    andl $2147483647, %eax # imm = 0x7FFFFFFF
-; X86-NEXT:    cmpl $2139095041, %eax # imm = 0x7F800001
-; X86-NEXT:    setge %al
-; X86-NEXT:    orb %cl, %al
+; X86-NEXT:    flds {{[0-9]+}}(%esp)
+; X86-NEXT:    flds {{\.?LCPI[0-9]+_[0-9]+}}
+; X86-NEXT:    fucompp
+; X86-NEXT:    fnstsw %ax
+; X86-NEXT:    # kill: def $ah killed $ah killed $ax
+; X86-NEXT:    sahf
+; X86-NEXT:    sete %al
 ; X86-NEXT:    retl
 ;
 ; X64-LABEL: is_plus_inf_or_nan_f:
 ; X64:       # %bb.0:
-; X64-NEXT:    movd %xmm0, %eax
-; X64-NEXT:    cmpl $2139095040, %eax # imm = 0x7F800000
-; X64-NEXT:    sete %cl
-; X64-NEXT:    andl $2147483647, %eax # imm = 0x7FFFFFFF
-; X64-NEXT:    cmpl $2139095041, %eax # imm = 0x7F800001
-; X64-NEXT:    setge %al
-; X64-NEXT:    orb %cl, %al
+; X64-NEXT:    ucomiss {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0
+; X64-NEXT:    sete %al
 ; X64-NEXT:    retq
   %class = tail call i1 @llvm.is.fpclass.f32(float %x, i32 515)  ; 0x200|0x3 = "+inf|nan"
   ret i1 %class
@@ -2142,24 +2137,19 @@ define i1 @is_plus_inf_or_nan_f(float %x) {
 define i1 @is_minus_inf_or_nan_f(float %x) {
 ; X86-LABEL: is_minus_inf_or_nan_f:
 ; X86:       # %bb.0:
-; X86-NEXT:    movl {{[0-9]+}}(%esp), %eax
-; X86-NEXT:    cmpl $-8388608, %eax # imm = 0xFF800000
-; X86-NEXT:    sete %cl
-; X86-NEXT:    andl $2147483647, %eax # imm = 0x7FFFFFFF
-; X86-NEXT:    cmpl $2139095041, %eax # imm = 0x7F800001
-; X86-NEXT:    setge %al
-; X86-NEXT:    orb %cl, %al
+; X86-NEXT:    flds {{[0-9]+}}(%esp)
+; X86-NEXT:    flds {{\.?LCPI[0-9]+_[0-9]+}}
+; X86-NEXT:    fucompp
+; X86-NEXT:    fnstsw %ax
+; X86-NEXT:    # kill: def $ah killed $ah killed $ax
+; X86-NEXT:    sahf
+; X86-NEXT:    sete %al
 ; X86-NEXT:    retl
 ;
 ; X64-LABEL: is_minus_inf_or_nan_f:
 ; X64:       # %bb.0:
-; X64-NEXT:    movd %xmm0, %eax
-; X64-NEXT:    cmpl $-8388608, %eax # imm = 0xFF800000
-; X64-NEXT:    sete %cl
-; X64-NEXT:    andl $2147483647, %eax # imm = 0x7FFFFFFF
-; X64-NEXT:    cmpl $2139095041, %eax # imm = 0x7F800001
-; X64-NEXT:    setge %al
-; X64-NEXT:    orb %cl, %al
+; X64-NEXT:    ucomiss {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0
+; X64-NEXT:    sete %al
 ; X64-NEXT:    retq
   %class = tail call i1 @llvm.is.fpclass.f32(float %x, i32 7)  ; "-inf|nan"
   ret i1 %class
@@ -2168,24 +2158,19 @@ define i1 @is_minus_inf_or_nan_f(float %x) {
 define i1 @not_is_plus_inf_or_nan_f(float %x) {
 ; X86-LABEL: not_is_plus_inf_or_nan_f:
 ; X86:       # %bb.0:
-; X86-NEXT:    movl {{[0-9]+}}(%esp), %eax
-; X86-NEXT:    cmpl $-8388608, %eax # imm = 0xFF800000
-; X86-NEXT:    sete %cl
-; X86-NEXT:    andl $2147483647, %eax # imm = 0x7FFFFFFF
-; X86-NEXT:    cmpl $2139095040, %eax # imm = 0x7F800000
-; X86-NEXT:    setl %al
-; X86-NEXT:    orb %cl, %al
+; X86-NEXT:    flds {{[0-9]+}}(%esp)
+; X86-NEXT:    flds {{\.?LCPI[0-9]+_[0-9]+}}
+; X86-NEXT:    fucompp
+; X86-NEXT:    fnstsw %ax
+; X86-NEXT:    # kill: def $ah killed $ah killed $ax
+; X86-NEXT:    sahf
+; X86-NEXT:    setne %al
 ; X86-NEXT:    retl
 ;
 ; X64-LABEL: not_is_plus_inf_or_nan_f:
 ; X64:       # %bb.0:
-; X64-NEXT:    movd %xmm0, %eax
-; X64-NEXT:    cmpl $-8388608, %eax # imm = 0xFF800000
-; X64-NEXT:    sete %cl
-; X64-NEXT:    andl $2147483647, %eax # imm = 0x7FFFFFFF
-; X64-NEXT:    cmpl $2139095040, %eax # imm = 0x7F800000
-; X64-NEXT:    setl %al
-; X64-NEXT:    orb %cl, %al
+; X64-NEXT:    ucomiss {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0
+; X64-NEXT:    setne %al
 ; X64-NEXT:    retq
   %class = tail call i1 @llvm.is.fpclass.f32(float %x, i32 508)  ; ~(0x200|0x3) = "~(+inf|nan)"
   ret i1 %class
@@ -2194,24 +2179,19 @@ define i1 @not_is_plus_inf_or_nan_f(float %x) {
 define i1 @not_is_minus_inf_or_nan_f(float %x) {
 ; X86-LABEL: not_is_minus_inf_or_nan_f:
 ; X86:       # %bb.0:
-; X86-NEXT:    movl {{[0-9]+}}(%esp), %eax
-; X86-NEXT:    cmpl $2139095040, %eax # imm = 0x7F800000
-; X86-NEXT:    sete %cl
-; X86-NEXT:    andl $2147483647, %eax # imm = 0x7FFFFFFF
-; X86-NEXT:    cmpl $2139095040, %eax # imm = 0x7F800000
-; X86-NEXT:    setl %al
-; X86-NEXT:    orb %cl, %al
+; X86-NEXT:    flds {{[0-9]+}}(%esp)
+; X86-NEXT:    flds {{\.?LCPI[0-9]+_[0-9]+}}
+; X86-NEXT:    fucompp
+; X86-NEXT:    fnstsw %ax
+; X86-NEXT:    # kill: def $ah killed $ah killed $ax
+; X86-NEXT:    sahf
+; X86-NEXT:    setne %al
 ; X86-NEXT:    retl
 ;
 ; X64-LABEL: not_is_minus_inf_or_nan_f:
 ; X64:       # %bb.0:
-; X64-NEXT:    movd %xmm0, %eax
-; X64-NEXT:    cmpl $2139095040, %eax # imm = 0x7F800000
-; X64-NEXT:    sete %cl
-; X64-NEXT:    andl $2147483647, %eax # imm = 0x7FFFFFFF
-; X64-NEXT:    cmpl $2139095040, %eax # imm = 0x7F800000
-; X64-NEXT:    setl %al
-; X64-NEXT:    orb %cl, %al
+; X64-NEXT:    ucomiss {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0
+; X64-NEXT:    setne %al
 ; X64-NEXT:    retq
   %class = tail call i1 @llvm.is.fpclass.f32(float %x, i32 1016)  ; "~(-inf|nan)"
   ret i1 %class