[clang][bytecode][NFC] Avoid calling ASTContext::getTypeSize() (#119392)

In the case of primitive arrays, we can do this once and reuse the value
for all elements.

Author: tbaederr

clang/lib/AST/ByteCode/InterpBuiltinBitCast.cpp

@@ -33,8 +33,9 @@ using namespace clang::interp;
 //    bytes to/from the buffer.
 
 /// Used to iterate over pointer fields.
-using DataFunc = llvm::function_ref<bool(const Pointer &P, PrimType Ty,
-                                         Bits BitOffset, bool PackedBools)>;
+using DataFunc =
+    llvm::function_ref<bool(const Pointer &P, PrimType Ty, Bits BitOffset,
+                            Bits FullBitWidth, bool PackedBools)>;
 
 #define BITCAST_TYPE_SWITCH(Expr, B)                                           \
   do {                                                                         \
@@ -85,21 +86,25 @@ static bool enumerateData(const Pointer &P, const Context &Ctx, Bits Offset,
   assert(FieldDesc);
 
   // Primitives.
-  if (FieldDesc->isPrimitive())
-    return F(P, FieldDesc->getPrimType(), Offset, /*PackedBools=*/false);
+  if (FieldDesc->isPrimitive()) {
+    Bits FullBitWidth =
+        Bits(Ctx.getASTContext().getTypeSize(FieldDesc->getType()));
+    return F(P, FieldDesc->getPrimType(), Offset, FullBitWidth,
+             /*PackedBools=*/false);
+  }
 
   // Primitive arrays.
   if (FieldDesc->isPrimitiveArray()) {
     QualType ElemType = FieldDesc->getElemQualType();
-    size_t ElemSizeInBits = Ctx.getASTContext().getTypeSize(ElemType);
+    Bits ElemSize = Bits(Ctx.getASTContext().getTypeSize(ElemType));
     PrimType ElemT = *Ctx.classify(ElemType);
     // Special case, since the bools here are packed.
     bool PackedBools = FieldDesc->getType()->isExtVectorBoolType();
     unsigned NumElems = FieldDesc->getNumElems();
     bool Ok = true;
     for (unsigned I = P.getIndex(); I != NumElems; ++I) {
-      Ok = Ok && F(P.atIndex(I), ElemT, Offset, PackedBools);
-      Offset += PackedBools ? 1 : ElemSizeInBits;
+      Ok = Ok && F(P.atIndex(I), ElemT, Offset, ElemSize, PackedBools);
+      Offset += PackedBools ? Bits(1) : ElemSize;
       if (Offset >= BitsToRead)
         break;
     }
@@ -109,10 +114,10 @@ static bool enumerateData(const Pointer &P, const Context &Ctx, Bits Offset,
   // Composite arrays.
   if (FieldDesc->isCompositeArray()) {
     QualType ElemType = FieldDesc->getElemQualType();
-    size_t ElemSizeInBits = Ctx.getASTContext().getTypeSize(ElemType);
+    Bits ElemSize = Bits(Ctx.getASTContext().getTypeSize(ElemType));
     for (unsigned I = 0; I != FieldDesc->getNumElems(); ++I) {
       enumerateData(P.atIndex(I).narrow(), Ctx, Offset, BitsToRead, F);
-      Offset += ElemSizeInBits;
+      Offset += ElemSize;
       if (Offset >= BitsToRead)
         break;
     }
@@ -262,16 +267,14 @@ static bool readPointerToBuffer(const Context &Ctx, const Pointer &FromPtr,
 
   return enumeratePointerFields(
       FromPtr, Ctx, Buffer.size(),
-      [&](const Pointer &P, PrimType T, Bits BitOffset,
+      [&](const Pointer &P, PrimType T, Bits BitOffset, Bits FullBitWidth,
           bool PackedBools) -> bool {
-        CharUnits ObjectReprChars = ASTCtx.getTypeSizeInChars(P.getType());
-        Bits BitWidth = Bits(ASTCtx.toBits(ObjectReprChars));
-        Bits FullBitWidth = BitWidth;
+        Bits BitWidth = FullBitWidth;
 
-        if (const FieldDecl *FD = P.getField(); FD && FD->isBitField()) {
+        if (const FieldDecl *FD = P.getField(); FD && FD->isBitField())
           BitWidth = Bits(std::min(FD->getBitWidthValue(ASTCtx),
                                    (unsigned)FullBitWidth.getQuantity()));
-        } else if (T == PT_Bool && PackedBools)
+        else if (T == PT_Bool && PackedBools)
           BitWidth = Bits(1);
 
         if (BitWidth.isZero())
@@ -290,8 +293,7 @@ static bool readPointerToBuffer(const Context &Ctx, const Pointer &FromPtr,
         }
 
         assert(P.isInitialized());
-        auto Buff =
-            std::make_unique<std::byte[]>(ObjectReprChars.getQuantity());
+        auto Buff = std::make_unique<std::byte[]>(FullBitWidth.roundToBytes());
         // Work around floating point types that contain unused padding bytes.
         // This is really just `long double` on x86, which is the only
         // fundamental type with padding bytes.
@@ -386,11 +388,9 @@ bool clang::interp::DoBitCastPtr(InterpState &S, CodePtr OpPC,
       ASTCtx.getTargetInfo().isLittleEndian() ? Endian::Little : Endian::Big;
   bool Success = enumeratePointerFields(
       ToPtr, S.getContext(), Buffer.size(),
-      [&](const Pointer &P, PrimType T, Bits BitOffset,
+      [&](const Pointer &P, PrimType T, Bits BitOffset, Bits FullBitWidth,
           bool PackedBools) -> bool {
         QualType PtrType = P.getType();
-        CharUnits ObjectReprChars = ASTCtx.getTypeSizeInChars(PtrType);
-        Bits FullBitWidth = Bits(ASTCtx.toBits(ObjectReprChars));
         if (T == PT_Float) {
           const auto &Semantics = ASTCtx.getFloatTypeSemantics(PtrType);
           Bits NumBits = Bits(llvm::APFloatBase::getSizeInBits(Semantics));