[DebugInfo] Refactor DIExpression [SZ]Ext creation into function [NFC]

[dstenb]

Summary

Split out from review of D70431.

Also, replace the SmallVector with a normal C array.

[vsk]

Thanks!

llvm/include/llvm/IR/DebugInfoMetadata.h

static int fragmentCmp(const FragmentInfo &A, const FragmentInfo &B) {
     if (r1 <= l2)
       return -1;
     else if (r2 <= l1)
       return 1;
     else
       return 0;
   }
 
+  /// Append a zero- or sign-extension to \p Expr. Converts the expression to a
+  /// stack value if it isn't one already.
+  static DIExpression *appendExt(const DIExpression *Expr, unsigned FromSize,
+                                 unsigned ToSize, bool Signed);
+
   /// Check if fragments overlap between a pair of FragmentInfos.
   static bool fragmentsOverlap(const FragmentInfo &A, const FragmentInfo &B) {
     return fragmentCmp(A, B) == 0;
   }
 
   /// Determine the relative position of the fragments described by this
   /// DIExpression and \p Other. Calls static fragmentCmp implementation.
   int fragmentCmp(const DIExpression *Other) const {

llvm/lib/IR/DebugInfoMetadata.cpp

bool DIExpression::isConstant() const {
   if (getElement(0) != dwarf::DW_OP_constu ||
       getElement(2) != dwarf::DW_OP_stack_value)
     return false;
   if (getNumElements() == 6 && getElement(3) != dwarf::DW_OP_LLVM_fragment)
     return false;
   return true;
 }
 
+DIExpression *DIExpression::appendExt(const DIExpression *Expr,
+                                      unsigned FromSize, unsigned ToSize,
+                                      bool Signed) {
+  dwarf::TypeKind TK = Signed ? dwarf::DW_ATE_signed : dwarf::DW_ATE_unsigned;
+  uint64_t Ops[] = {dwarf::DW_OP_LLVM_convert, FromSize, TK,
+                    dwarf::DW_OP_LLVM_convert, ToSize,   TK};
+  return appendToStack(Expr, Ops);
+}
+
 DIGlobalVariableExpression *
 DIGlobalVariableExpression::getImpl(LLVMContext &Context, Metadata *Variable,
                                     Metadata *Expression, StorageType Storage,
                                     bool ShouldCreate) {
   DEFINE_GETIMPL_LOOKUP(DIGlobalVariableExpression, (Variable, Expression));
   Metadata *Ops[] = {Variable, Expression};
   DEFINE_GETIMPL_STORE_NO_CONSTRUCTOR_ARGS(DIGlobalVariableExpression, Ops);
 }

llvm/lib/Transforms/Utils/Local.cpp

auto SignOrZeroExt = [&](DbgVariableIntrinsic &DII) -> DbgValReplacement {
       DILocalVariable *Var = DII.getVariable();
 
       // Without knowing signedness, sign/zero extension isn't possible.
       auto Signedness = Var->getSignedness();
       if (!Signedness)
         return None;
 
       bool Signed = *Signedness == DIBasicType::Signedness::Signed;
-      dwarf::TypeKind TK = Signed ? dwarf::DW_ATE_signed : dwarf::DW_ATE_unsigned;
-      SmallVector<uint64_t, 8> Ops({dwarf::DW_OP_LLVM_convert, ToBits, TK,
-                                   dwarf::DW_OP_LLVM_convert, FromBits, TK});
-      return DIExpression::appendToStack(DII.getExpression(), Ops);
+      return DIExpression::appendExt(DII.getExpression(), ToBits, FromBits,
+                                     Signed);
     };
     return rewriteDebugUsers(From, To, DomPoint, DT, SignOrZeroExt);
   }
 
   // TODO: Floating-point conversions, vectors.
   return false;
 }