Update ARMISelLowering.cpp

Author: AZero13

llvm/lib/Target/ARM/ARMISelLowering.cpp

@@ -4840,25 +4840,24 @@ static bool isFloatingPointZero(SDValue Op) {
 }
 
 static bool shouldBeAdjustedToZero(SDValue LHS, APInt C, ISD::CondCode &CC) {
-  // TODO: Can we know ahead of time if we can use a MOVS?
+
+  // setlt and setge are changed to MI and PL for zero respectively, so it is
+  // safe.
+  if (C.isAllOnes() && (CC == ISD::SETLE || CC == ISD::SETGT)) {
+    CC = (CC == ISD::SETLE) ? ISD::SETLT : ISD::SETGE;
+    return true;
+  }
+
+  // On ARM, adds and subs set the V flags correctly, which means the optimizer
+  // can condense to a single adds/subs
   switch (LHS.getOpcode()) {
-  case ISD::AND:
-  case ISD::OR:
-  case ISD::XOR:
   case ISD::ADD:
   case ISD::SUB:
-  case ISD::MUL:
-    // In ARM, almost every instruction has a variant that sets flags.
     break;
   default:
     return false;
   }
 
-  if (C.isAllOnes() && (CC == ISD::SETLE || CC == ISD::SETGT)) {
-    CC = (CC == ISD::SETLE) ? ISD::SETLT : ISD::SETGE;
-    return true;
-  }
-
   if (C.isOne() && (CC == ISD::SETLT || CC == ISD::SETGE)) {
     CC = (CC == ISD::SETLT) ? ISD::SETLE : ISD::SETGT;
     return true;