Index: lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -1748,7 +1748,7 @@
   // E.g. (icmp sgt x, n) | (icmp slt x, 0) --> icmp ugt x, n
   if (Value *V = simplifyRangeCheck(RHS, LHS, /*Inverted=*/true))
     return V;
- 
+
   // This only handles icmp of constants: (icmp1 A, C1) | (icmp2 B, C2).
   if (!LHSCst || !RHSCst) return nullptr;
 
@@ -2748,5 +2748,17 @@
       }
   }
 
+  // If we are XORing the sign bit of a floating-point value, convert
+  // this to fsub from -0.0, then cast back to integer.
+  ConstantInt *CI;
+  if (CastInst *Op0C = dyn_cast<CastInst>(Op0)) {
+    if (isa<BitCastInst>(Op0C) && Op0->getType()->isFloatingPointTy() &&
+          match(Op1, m_ConstantInt(CI)) && CI->isMinValue(true)) {
+        Value *Call = Builder->CreateFSub(
+            ConstantFP::getNegativeZero(Op0->getType()), Op0);
+        return CastInst::CreateBitOrPointerCast(Call, I.getType());
+    }
+  }
+
   return Changed ? &I : nullptr;
 }