[IR] Remove uses of the oddly named ConstantFP::getZeroValueForNegati…

…on in integer code.

Confusingly ConstantFP's getZeroValueForNegation intentionally
handles non-FP constants. It calls getNullValue in Constant.

Nearly all uses in tree are for integers rather than FP. Maybe due
to replacing FSub -0.0, X idiom with an FNeg instructions a few
years ago.

This patch replaces all the integer uses in tree with ConstantInt::get(0, Ty).

The one remaining use is in clang with a FIXME that it should use fneg.
I'll fix that next and then delete ConstantFP::getZeroValueForNegation.

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D147492

llvm/lib/IR/Constants.cpp

@@ -2601,8 +2601,7 @@ Constant *ConstantExpr::getShuffleVector(Constant *V1, Constant *V2,
 Constant *ConstantExpr::getNeg(Constant *C, bool HasNUW, bool HasNSW) {
   assert(C->getType()->isIntOrIntVectorTy() &&
          "Cannot NEG a nonintegral value!");
-  return getSub(ConstantFP::getZeroValueForNegation(C->getType()),
-                C, HasNUW, HasNSW);
+  return getSub(ConstantInt::get(C->getType(), 0), C, HasNUW, HasNSW);
 }
 
 Constant *ConstantExpr::getNot(Constant *C) {

llvm/lib/IR/Instructions.cpp

@@ -3073,42 +3073,42 @@ BinaryOperator *BinaryOperator::Create(BinaryOps Op, Value *S1, Value *S2,
 
 BinaryOperator *BinaryOperator::CreateNeg(Value *Op, const Twine &Name,
                                           Instruction *InsertBefore) {
-  Value *zero = ConstantFP::getZeroValueForNegation(Op->getType());
+  Value *Zero = ConstantInt::get(Op->getType(), 0);
   return new BinaryOperator(Instruction::Sub,
-                            zero, Op,
+                            Zero, Op,
                             Op->getType(), Name, InsertBefore);
 }
 
 BinaryOperator *BinaryOperator::CreateNeg(Value *Op, const Twine &Name,
                                           BasicBlock *InsertAtEnd) {
-  Value *zero = ConstantFP::getZeroValueForNegation(Op->getType());
+  Value *Zero = ConstantInt::get(Op->getType(), 0);
   return new BinaryOperator(Instruction::Sub,
-                            zero, Op,
+                            Zero, Op,
                             Op->getType(), Name, InsertAtEnd);
 }
 
 BinaryOperator *BinaryOperator::CreateNSWNeg(Value *Op, const Twine &Name,
                                              Instruction *InsertBefore) {
-  Value *zero = ConstantFP::getZeroValueForNegation(Op->getType());
-  return BinaryOperator::CreateNSWSub(zero, Op, Name, InsertBefore);
+  Value *Zero = ConstantInt::get(Op->getType(), 0);
+  return BinaryOperator::CreateNSWSub(Zero, Op, Name, InsertBefore);
 }
 
 BinaryOperator *BinaryOperator::CreateNSWNeg(Value *Op, const Twine &Name,
                                              BasicBlock *InsertAtEnd) {
-  Value *zero = ConstantFP::getZeroValueForNegation(Op->getType());
-  return BinaryOperator::CreateNSWSub(zero, Op, Name, InsertAtEnd);
+  Value *Zero = ConstantInt::get(Op->getType(), 0);
+  return BinaryOperator::CreateNSWSub(Zero, Op, Name, InsertAtEnd);
 }
 
 BinaryOperator *BinaryOperator::CreateNUWNeg(Value *Op, const Twine &Name,
                                              Instruction *InsertBefore) {
-  Value *zero = ConstantFP::getZeroValueForNegation(Op->getType());
-  return BinaryOperator::CreateNUWSub(zero, Op, Name, InsertBefore);
+  Value *Zero = ConstantInt::get(Op->getType(), 0);
+  return BinaryOperator::CreateNUWSub(Zero, Op, Name, InsertBefore);
 }
 
 BinaryOperator *BinaryOperator::CreateNUWNeg(Value *Op, const Twine &Name,
                                              BasicBlock *InsertAtEnd) {
-  Value *zero = ConstantFP::getZeroValueForNegation(Op->getType());
-  return BinaryOperator::CreateNUWSub(zero, Op, Name, InsertAtEnd);
+  Value *Zero = ConstantInt::get(Op->getType(), 0);
+  return BinaryOperator::CreateNUWSub(Zero, Op, Name, InsertAtEnd);
 }
 
 BinaryOperator *BinaryOperator::CreateNot(Value *Op, const Twine &Name,