[InstCombine] Preserve Instruction name when converting select to max/min/abs.

[RKSimon]

Any there test files that you can regenerate so the varname regexs change?

[nikic]

D140192 for a more thorough solution to this problem.

[craig.topper]

Fixed by D140192

llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp

 //===- InstCombineSelect.cpp ----------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
bool IntMinIsPoison = SPF == SelectPatternFlavor::SPF_ABS &&
                           match(RHS, m_NSWNeg(m_Specific(LHS)));
     Constant *IntMinIsPoisonC =
         ConstantInt::get(Type::getInt1Ty(Sel.getContext()), IntMinIsPoison);
     Instruction *Abs =
         IC.Builder.CreateBinaryIntrinsic(Intrinsic::abs, LHS, IntMinIsPoisonC);
 
     if (SPF == SelectPatternFlavor::SPF_NABS)
       return BinaryOperator::CreateNeg(Abs); // Always without NSW flag!
+    Abs->takeName(&Sel);
     return IC.replaceInstUsesWith(Sel, Abs);
   }
 
   if (SelectPatternResult::isMinOrMax(SPF)) {
     Intrinsic::ID IntrinsicID;
     switch (SPF) {
     case SelectPatternFlavor::SPF_UMIN:
       IntrinsicID = Intrinsic::umin;
       break;
     case SelectPatternFlavor::SPF_UMAX:
       IntrinsicID = Intrinsic::umax;
       break;
     case SelectPatternFlavor::SPF_SMIN:
       IntrinsicID = Intrinsic::smin;
       break;
     case SelectPatternFlavor::SPF_SMAX:
       IntrinsicID = Intrinsic::smax;
       break;
     default:
       llvm_unreachable("Unexpected SPF");
     }
-    return IC.replaceInstUsesWith(
-        Sel, IC.Builder.CreateBinaryIntrinsic(IntrinsicID, LHS, RHS));
+    Instruction *MinMax = IC.Builder.CreateBinaryIntrinsic(IntrinsicID, LHS, RHS);
+    MinMax->takeName(&Sel);
+    return IC.replaceInstUsesWith(Sel, MinMax);
   }
 
   return nullptr;
 }
 
 /// If we have a select with an equality comparison, then we know the value in
 /// one of the arms of the select. See if substituting this value into an arm
 /// and simplifying the result yields the same value as the other arm.