[NFC] Remove min/max functions from InstructionCost

[david-arm]

Summary

Removed the InstructionCost::min/max functions because it's
fine to use std::min/max instead.

[sdesmalen]

LGTM

llvm/include/llvm/Support/InstructionCost.h

bool operator<=(const CostType RHS) const {
     return *this <= RHS2;
   }
 
   bool operator>=(const CostType RHS) const {
     InstructionCost RHS2(RHS);
     return *this >= RHS2;
   }
 
-  static InstructionCost min(InstructionCost LHS, InstructionCost RHS) {
-    return LHS < RHS ? LHS : RHS;
-  }
-
-  static InstructionCost max(InstructionCost LHS, InstructionCost RHS) {
-    return LHS > RHS ? LHS : RHS;
-  }
-
   void print(raw_ostream &OS) const;
 };
 
 inline InstructionCost operator+(const InstructionCost &LHS,
                                  const InstructionCost &RHS) {
   InstructionCost LHS2(LHS);
   LHS2 += RHS;
   return LHS2;

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

for (unsigned I = NextInst; I < MaxInst; ++I) {
             UserCost += TTI->getVectorInstrCost(
                 Instruction::InsertElement, IE->getType(), CI->getZExtValue());
         }
         LLVM_DEBUG(dbgs() << "SLP: Compensate cost of users by: " << UserCost
                           << ".\n");
         Cost -= UserCost;
       }
 
-      MinCost = InstructionCost::min(MinCost, Cost);
+      MinCost = std::min(MinCost, Cost);
 
       if (Cost.isValid() && Cost < -SLPCostThreshold) {
         LLVM_DEBUG(dbgs() << "SLP: Vectorizing list at cost:" << Cost << ".\n");
         R.getORE()->emit(OptimizationRemark(SV_NAME, "VectorizedList",
                                                     cast<Instruction>(Ops[0]))
                                  << "SLP vectorized with cost " << ore::NV("Cost", Cost)
                                  << " and with tree size "
                                  << ore::NV("TreeSize", R.getTreeSize()));

llvm/unittests/Support/InstructionCostTest.cpp

TEST_F(CostTest, Operators) {
 
   TmpCost = VThree * IThreeA;
   EXPECT_FALSE(TmpCost.isValid());
 
   // Test value extraction
   EXPECT_EQ(*(VThree.getValue()), 3);
   EXPECT_EQ(IThreeA.getValue(), None);
 
-  EXPECT_EQ(InstructionCost::min(VThree, VNegTwo), -2);
-  EXPECT_EQ(InstructionCost::max(VThree, VSix), 6);
+  EXPECT_EQ(std::min(VThree, VNegTwo), -2);
+  EXPECT_EQ(std::max(VThree, VSix), 6);
 }