Index: llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -5773,8 +5773,10 @@
 
     // If we already have the use of the negated floating constant, it is free
     // to negate it even it has multiple uses.
-    if (!Op.hasOneUse() && CFP.use_empty())
+    if (!Op.hasOneUse() && CFP.use_empty()) {
+      RemoveDeadNode(CFP);
       break;
+    }
     Cost = NegatibleCost::Neutral;
     return CFP;
   }
@@ -5832,7 +5834,8 @@
     if (NegX && (CostX <= CostY)) {
       Cost = CostX;
       SDValue N = DAG.getNode(ISD::FSUB, DL, VT, NegX, Y, Flags);
-      RemoveDeadNode(NegY);
+      if (NegY != N)
+        RemoveDeadNode(NegY);
       return N;
     }
 
@@ -5840,7 +5843,8 @@
     if (NegY) {
       Cost = CostY;
       SDValue N = DAG.getNode(ISD::FSUB, DL, VT, NegY, X, Flags);
-      RemoveDeadNode(NegX);
+      if (NegX != N)
+        RemoveDeadNode(NegX);
       return N;
     }
     break;
@@ -5879,7 +5883,8 @@
     if (NegX && (CostX <= CostY)) {
       Cost = CostX;
       SDValue N = DAG.getNode(Opcode, DL, VT, NegX, Y, Flags);
-      RemoveDeadNode(NegY);
+      if (NegY != N)
+        RemoveDeadNode(NegY);
       return N;
     }
 
@@ -5892,7 +5897,8 @@
     if (NegY) {
       Cost = CostY;
       SDValue N = DAG.getNode(Opcode, DL, VT, X, NegY, Flags);
-      RemoveDeadNode(NegX);
+      if (NegX != N)
+        RemoveDeadNode(NegX);
       return N;
     }
     break;
@@ -5923,7 +5929,8 @@
     if (NegX && (CostX <= CostY)) {
       Cost = std::min(CostX, CostZ);
       SDValue N = DAG.getNode(Opcode, DL, VT, NegX, Y, NegZ, Flags);
-      RemoveDeadNode(NegY);
+      if (NegY != N)
+        RemoveDeadNode(NegY);
       return N;
     }
 
@@ -5931,7 +5938,8 @@
     if (NegY) {
       Cost = std::min(CostY, CostZ);
       SDValue N = DAG.getNode(Opcode, DL, VT, X, NegY, NegZ, Flags);
-      RemoveDeadNode(NegX);
+      if (NegX != N)
+        RemoveDeadNode(NegX);
       return N;
     }
     break;
Index: llvm/test/CodeGen/X86/pr47517.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/X86/pr47517.ll
@@ -0,0 +1,28 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple x86_64 < %s | FileCheck %s
+
+; To ensure unused floating point constant is correctly removed
+define float @test(float %src, float* %p) {
+; CHECK-LABEL: test:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    movq $0, (%rdi)
+; CHECK-NEXT:    xorps %xmm0, %xmm0
+; CHECK-NEXT:    retq
+entry:
+  %a0 = getelementptr inbounds float, float* %p, i32 0
+  %a1 = getelementptr inbounds float, float* %p, i32 1
+  store float 0.000000e+00, float* %a0
+  store float 0.000000e+00, float* %a1
+  %zero = load float, float* %a0
+  %fmul1 = fmul fast float %zero, %src
+  %fadd1 = fadd fast float %fmul1, %zero
+  %fmul2 = fmul fast float %fadd1, 2.000000e+00
+  %fmul3 = fmul fast float %fmul2, %fmul2
+  %fmul4 = fmul fast float %fmul2, 2.000000e+00
+  %fadd2 = fadd fast float %fmul4, -3.000000e+00
+  %fmul5 = fmul fast float %fadd2, %fmul2
+  %fadd3 = fadd fast float %fmul2, %src
+  %fadd4 = fadd fast float %fadd3, %fmul5
+  %fmul6 = fmul fast float %fmul3, %fadd4
+  ret float %fmul6
+}