[clang][bytecode] Refactor Program::createGlobalString (#125467)

Remove unnecesary narrow() calls, rename a variable and initialize the
array as a whole instead of each element individually.

Author: tbaederr

clang/lib/AST/ByteCode/Program.cpp

@@ -35,6 +35,7 @@ const void *Program::getNativePointer(unsigned Idx) {
 unsigned Program::createGlobalString(const StringLiteral *S, const Expr *Base) {
   const size_t CharWidth = S->getCharByteWidth();
   const size_t BitWidth = CharWidth * Ctx.getCharBit();
+  unsigned StringLength = S->getLength();
 
   PrimType CharType;
   switch (CharWidth) {
@@ -55,15 +56,15 @@ unsigned Program::createGlobalString(const StringLiteral *S, const Expr *Base) {
     Base = S;
 
   // Create a descriptor for the string.
-  Descriptor *Desc = allocateDescriptor(Base, CharType, Descriptor::GlobalMD,
-                                        S->getLength() + 1,
-                                        /*isConst=*/true,
-                                        /*isTemporary=*/false,
-                                        /*isMutable=*/false);
+  Descriptor *Desc =
+      allocateDescriptor(Base, CharType, Descriptor::GlobalMD, StringLength + 1,
+                         /*isConst=*/true,
+                         /*isTemporary=*/false,
+                         /*isMutable=*/false);
 
   // Allocate storage for the string.
   // The byte length does not include the null terminator.
-  unsigned I = Globals.size();
+  unsigned GlobalIndex = Globals.size();
   unsigned Sz = Desc->getAllocSize();
   auto *G = new (Allocator, Sz) Global(Ctx.getEvalID(), Desc, /*isStatic=*/true,
                                        /*isExtern=*/false);
@@ -74,33 +75,32 @@ unsigned Program::createGlobalString(const StringLiteral *S, const Expr *Base) {
 
   // Construct the string in storage.
   const Pointer Ptr(G->block());
-  for (unsigned I = 0, N = S->getLength(); I <= N; ++I) {
-    Pointer Field = Ptr.atIndex(I).narrow();
-    const uint32_t CodePoint = I == N ? 0 : S->getCodeUnit(I);
+  for (unsigned I = 0; I <= StringLength; ++I) {
+    Pointer Field = Ptr.atIndex(I);
+    const uint32_t CodePoint = I == StringLength ? 0 : S->getCodeUnit(I);
     switch (CharType) {
     case PT_Sint8: {
       using T = PrimConv<PT_Sint8>::T;
       Field.deref<T>() = T::from(CodePoint, BitWidth);
-      Field.initialize();
       break;
     }
     case PT_Uint16: {
       using T = PrimConv<PT_Uint16>::T;
       Field.deref<T>() = T::from(CodePoint, BitWidth);
-      Field.initialize();
       break;
     }
     case PT_Uint32: {
       using T = PrimConv<PT_Uint32>::T;
       Field.deref<T>() = T::from(CodePoint, BitWidth);
-      Field.initialize();
       break;
     }
     default:
       llvm_unreachable("unsupported character type");
     }
   }
-  return I;
+  Ptr.initialize();
+
+  return GlobalIndex;
 }
 
 Pointer Program::getPtrGlobal(unsigned Idx) const {