diff --git a/llvm/lib/Analysis/TargetTransformInfo.cpp b/llvm/lib/Analysis/TargetTransformInfo.cpp
--- a/llvm/lib/Analysis/TargetTransformInfo.cpp
+++ b/llvm/lib/Analysis/TargetTransformInfo.cpp
@@ -1043,6 +1043,16 @@
     return getArithmeticInstrCost(I->getOpcode(), I->getType(), Op1VK, Op2VK,
                                   Op1VP, Op2VP, Operands);
   }
+  case Instruction::FNeg: {
+    TargetTransformInfo::OperandValueKind Op1VK, Op2VK;
+    TargetTransformInfo::OperandValueProperties Op1VP, Op2VP;
+    Op1VK = getOperandInfo(I->getOperand(0), Op1VP);
+    Op2VK = OK_AnyValue;
+    Op2VP = OP_None;
+    SmallVector<const Value *, 2> Operands(I->operand_values());
+    return getArithmeticInstrCost(I->getOpcode(), I->getType(), Op1VK, Op2VK,
+                                  Op1VP, Op2VP, Operands);
+  }
   case Instruction::Select: {
     const SelectInst *SI = cast<SelectInst>(I);
     Type *CondTy = SI->getCondition()->getType();
diff --git a/llvm/test/Analysis/CostModel/X86/arith-fp.ll b/llvm/test/Analysis/CostModel/X86/arith-fp.ll
--- a/llvm/test/Analysis/CostModel/X86/arith-fp.ll
+++ b/llvm/test/Analysis/CostModel/X86/arith-fp.ll
@@ -354,48 +354,92 @@
 }
 
 define i32 @fneg(i32 %arg) {
-; CHECK-LABEL: 'fneg'
-; CHECK-NEXT:  Cost Model: Unknown cost for instruction: %F32 = fneg float undef
-; CHECK-NEXT:  Cost Model: Unknown cost for instruction: %V4F32 = fneg <4 x float> undef
-; CHECK-NEXT:  Cost Model: Unknown cost for instruction: %V8F32 = fneg <8 x float> undef
-; CHECK-NEXT:  Cost Model: Unknown cost for instruction: %V16F32 = fneg <16 x float> undef
-; CHECK-NEXT:  Cost Model: Unknown cost for instruction: %F64 = fneg double undef
-; CHECK-NEXT:  Cost Model: Unknown cost for instruction: %V2F64 = fneg <2 x double> undef
-; CHECK-NEXT:  Cost Model: Unknown cost for instruction: %V4F64 = fneg <4 x double> undef
-; CHECK-NEXT:  Cost Model: Unknown cost for instruction: %V8F64 = fneg <8 x double> undef
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: ret i32 undef
+; SSE1-LABEL: 'fneg'
+; SSE1-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %F32 = fneg float undef
+; SSE1-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V4F32 = fneg <4 x float> undef
+; SSE1-NEXT:  Cost Model: Found an estimated cost of 8 for instruction: %V8F32 = fneg <8 x float> undef
+; SSE1-NEXT:  Cost Model: Found an estimated cost of 16 for instruction: %V16F32 = fneg <16 x float> undef
+; SSE1-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %F64 = fneg double undef
+; SSE1-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V2F64 = fneg <2 x double> undef
+; SSE1-NEXT:  Cost Model: Found an estimated cost of 8 for instruction: %V4F64 = fneg <4 x double> undef
+; SSE1-NEXT:  Cost Model: Found an estimated cost of 16 for instruction: %V8F64 = fneg <8 x double> undef
+; SSE1-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: ret i32 undef
+;
+; SSE2-LABEL: 'fneg'
+; SSE2-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %F32 = fneg float undef
+; SSE2-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V4F32 = fneg <4 x float> undef
+; SSE2-NEXT:  Cost Model: Found an estimated cost of 8 for instruction: %V8F32 = fneg <8 x float> undef
+; SSE2-NEXT:  Cost Model: Found an estimated cost of 16 for instruction: %V16F32 = fneg <16 x float> undef
+; SSE2-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %F64 = fneg double undef
+; SSE2-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V2F64 = fneg <2 x double> undef
+; SSE2-NEXT:  Cost Model: Found an estimated cost of 8 for instruction: %V4F64 = fneg <4 x double> undef
+; SSE2-NEXT:  Cost Model: Found an estimated cost of 16 for instruction: %V8F64 = fneg <8 x double> undef
+; SSE2-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: ret i32 undef
+;
+; SSE42-LABEL: 'fneg'
+; SSE42-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %F32 = fneg float undef
+; SSE42-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V4F32 = fneg <4 x float> undef
+; SSE42-NEXT:  Cost Model: Found an estimated cost of 8 for instruction: %V8F32 = fneg <8 x float> undef
+; SSE42-NEXT:  Cost Model: Found an estimated cost of 16 for instruction: %V16F32 = fneg <16 x float> undef
+; SSE42-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %F64 = fneg double undef
+; SSE42-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V2F64 = fneg <2 x double> undef
+; SSE42-NEXT:  Cost Model: Found an estimated cost of 8 for instruction: %V4F64 = fneg <4 x double> undef
+; SSE42-NEXT:  Cost Model: Found an estimated cost of 16 for instruction: %V8F64 = fneg <8 x double> undef
+; SSE42-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: ret i32 undef
+;
+; AVX-LABEL: 'fneg'
+; AVX-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %F32 = fneg float undef
+; AVX-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V4F32 = fneg <4 x float> undef
+; AVX-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V8F32 = fneg <8 x float> undef
+; AVX-NEXT:  Cost Model: Found an estimated cost of 8 for instruction: %V16F32 = fneg <16 x float> undef
+; AVX-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %F64 = fneg double undef
+; AVX-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V2F64 = fneg <2 x double> undef
+; AVX-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V4F64 = fneg <4 x double> undef
+; AVX-NEXT:  Cost Model: Found an estimated cost of 8 for instruction: %V8F64 = fneg <8 x double> undef
+; AVX-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: ret i32 undef
+;
+; AVX512-LABEL: 'fneg'
+; AVX512-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %F32 = fneg float undef
+; AVX512-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V4F32 = fneg <4 x float> undef
+; AVX512-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V8F32 = fneg <8 x float> undef
+; AVX512-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V16F32 = fneg <16 x float> undef
+; AVX512-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %F64 = fneg double undef
+; AVX512-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V2F64 = fneg <2 x double> undef
+; AVX512-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V4F64 = fneg <4 x double> undef
+; AVX512-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V8F64 = fneg <8 x double> undef
+; AVX512-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: ret i32 undef
 ;
 ; SLM-LABEL: 'fneg'
-; SLM-NEXT:  Cost Model: Unknown cost for instruction: %F32 = fneg float undef
-; SLM-NEXT:  Cost Model: Unknown cost for instruction: %V4F32 = fneg <4 x float> undef
-; SLM-NEXT:  Cost Model: Unknown cost for instruction: %V8F32 = fneg <8 x float> undef
-; SLM-NEXT:  Cost Model: Unknown cost for instruction: %V16F32 = fneg <16 x float> undef
-; SLM-NEXT:  Cost Model: Unknown cost for instruction: %F64 = fneg double undef
-; SLM-NEXT:  Cost Model: Unknown cost for instruction: %V2F64 = fneg <2 x double> undef
-; SLM-NEXT:  Cost Model: Unknown cost for instruction: %V4F64 = fneg <4 x double> undef
-; SLM-NEXT:  Cost Model: Unknown cost for instruction: %V8F64 = fneg <8 x double> undef
+; SLM-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %F32 = fneg float undef
+; SLM-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V4F32 = fneg <4 x float> undef
+; SLM-NEXT:  Cost Model: Found an estimated cost of 8 for instruction: %V8F32 = fneg <8 x float> undef
+; SLM-NEXT:  Cost Model: Found an estimated cost of 16 for instruction: %V16F32 = fneg <16 x float> undef
+; SLM-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %F64 = fneg double undef
+; SLM-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V2F64 = fneg <2 x double> undef
+; SLM-NEXT:  Cost Model: Found an estimated cost of 8 for instruction: %V4F64 = fneg <4 x double> undef
+; SLM-NEXT:  Cost Model: Found an estimated cost of 16 for instruction: %V8F64 = fneg <8 x double> undef
 ; SLM-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: ret i32 undef
 ;
 ; GLM-LABEL: 'fneg'
-; GLM-NEXT:  Cost Model: Unknown cost for instruction: %F32 = fneg float undef
-; GLM-NEXT:  Cost Model: Unknown cost for instruction: %V4F32 = fneg <4 x float> undef
-; GLM-NEXT:  Cost Model: Unknown cost for instruction: %V8F32 = fneg <8 x float> undef
-; GLM-NEXT:  Cost Model: Unknown cost for instruction: %V16F32 = fneg <16 x float> undef
-; GLM-NEXT:  Cost Model: Unknown cost for instruction: %F64 = fneg double undef
-; GLM-NEXT:  Cost Model: Unknown cost for instruction: %V2F64 = fneg <2 x double> undef
-; GLM-NEXT:  Cost Model: Unknown cost for instruction: %V4F64 = fneg <4 x double> undef
-; GLM-NEXT:  Cost Model: Unknown cost for instruction: %V8F64 = fneg <8 x double> undef
+; GLM-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %F32 = fneg float undef
+; GLM-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V4F32 = fneg <4 x float> undef
+; GLM-NEXT:  Cost Model: Found an estimated cost of 8 for instruction: %V8F32 = fneg <8 x float> undef
+; GLM-NEXT:  Cost Model: Found an estimated cost of 16 for instruction: %V16F32 = fneg <16 x float> undef
+; GLM-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %F64 = fneg double undef
+; GLM-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V2F64 = fneg <2 x double> undef
+; GLM-NEXT:  Cost Model: Found an estimated cost of 8 for instruction: %V4F64 = fneg <4 x double> undef
+; GLM-NEXT:  Cost Model: Found an estimated cost of 16 for instruction: %V8F64 = fneg <8 x double> undef
 ; GLM-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: ret i32 undef
 ;
 ; BTVER2-LABEL: 'fneg'
-; BTVER2-NEXT:  Cost Model: Unknown cost for instruction: %F32 = fneg float undef
-; BTVER2-NEXT:  Cost Model: Unknown cost for instruction: %V4F32 = fneg <4 x float> undef
-; BTVER2-NEXT:  Cost Model: Unknown cost for instruction: %V8F32 = fneg <8 x float> undef
-; BTVER2-NEXT:  Cost Model: Unknown cost for instruction: %V16F32 = fneg <16 x float> undef
-; BTVER2-NEXT:  Cost Model: Unknown cost for instruction: %F64 = fneg double undef
-; BTVER2-NEXT:  Cost Model: Unknown cost for instruction: %V2F64 = fneg <2 x double> undef
-; BTVER2-NEXT:  Cost Model: Unknown cost for instruction: %V4F64 = fneg <4 x double> undef
-; BTVER2-NEXT:  Cost Model: Unknown cost for instruction: %V8F64 = fneg <8 x double> undef
+; BTVER2-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %F32 = fneg float undef
+; BTVER2-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V4F32 = fneg <4 x float> undef
+; BTVER2-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V8F32 = fneg <8 x float> undef
+; BTVER2-NEXT:  Cost Model: Found an estimated cost of 8 for instruction: %V16F32 = fneg <16 x float> undef
+; BTVER2-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %F64 = fneg double undef
+; BTVER2-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V2F64 = fneg <2 x double> undef
+; BTVER2-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V4F64 = fneg <4 x double> undef
+; BTVER2-NEXT:  Cost Model: Found an estimated cost of 8 for instruction: %V8F64 = fneg <8 x double> undef
 ; BTVER2-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: ret i32 undef
 ;
   %F32 = fneg float undef