[ConstantFolding] Constify ConstantFoldInstOperands and ConstantFoldInstruction argument. NFC (#138108)

I tried to use these with a const reference in a separate patch, but the
pointers weren't marked as const. It turns out that these don't mutate
the instruction.

Author: lukel97

llvm/include/llvm/Analysis/ConstantFolding.h

@@ -53,7 +53,7 @@ bool IsConstantOffsetFromGlobal(Constant *C, GlobalValue *&GV, APInt &Offset,
 /// Note that this fails if not all of the operands are constant.  Otherwise,
 /// this function can only fail when attempting to fold instructions like loads
 /// and stores, which have no constant expression form.
-Constant *ConstantFoldInstruction(Instruction *I, const DataLayout &DL,
+Constant *ConstantFoldInstruction(const Instruction *I, const DataLayout &DL,
                                   const TargetLibraryInfo *TLI = nullptr);
 
 /// ConstantFoldConstant - Fold the constant using the specified DataLayout.
@@ -74,7 +74,8 @@ Constant *ConstantFoldConstant(const Constant *C, const DataLayout &DL,
 /// all uses of the original operation are replaced by the constant-folded
 /// result. The \p AllowNonDeterministic parameter controls whether this is
 /// allowed.
-Constant *ConstantFoldInstOperands(Instruction *I, ArrayRef<Constant *> Ops,
+Constant *ConstantFoldInstOperands(const Instruction *I,
+                                   ArrayRef<Constant *> Ops,
                                    const DataLayout &DL,
                                    const TargetLibraryInfo *TLI = nullptr,
                                    bool AllowNonDeterministic = true);

llvm/lib/Analysis/ConstantFolding.cpp

@@ -1123,7 +1123,8 @@ ConstantFoldConstantImpl(const Constant *C, const DataLayout &DL,
 
 } // end anonymous namespace
 
-Constant *llvm::ConstantFoldInstruction(Instruction *I, const DataLayout &DL,
+Constant *llvm::ConstantFoldInstruction(const Instruction *I,
+                                        const DataLayout &DL,
                                         const TargetLibraryInfo *TLI) {
   // Handle PHI nodes quickly here...
   if (auto *PN = dyn_cast<PHINode>(I)) {
@@ -1156,7 +1157,7 @@ Constant *llvm::ConstantFoldInstruction(Instruction *I, const DataLayout &DL,
 
   // Scan the operand list, checking to see if they are all constants, if so,
   // hand off to ConstantFoldInstOperandsImpl.
-  if (!all_of(I->operands(), [](Use &U) { return isa<Constant>(U); }))
+  if (!all_of(I->operands(), [](const Use &U) { return isa<Constant>(U); }))
     return nullptr;
 
   SmallDenseMap<Constant *, Constant *> FoldedOps;
@@ -1177,7 +1178,7 @@ Constant *llvm::ConstantFoldConstant(const Constant *C, const DataLayout &DL,
   return ConstantFoldConstantImpl(C, DL, TLI, FoldedOps);
 }
 
-Constant *llvm::ConstantFoldInstOperands(Instruction *I,
+Constant *llvm::ConstantFoldInstOperands(const Instruction *I,
                                          ArrayRef<Constant *> Ops,
                                          const DataLayout &DL,
                                          const TargetLibraryInfo *TLI,