================
@@ -1250,6 +1253,508 @@ getSafeRepackAttrs(Fortran::lower::AbstractConverter 
&converter) {
   return attrs.empty() ? mlir::ArrayAttr{} : builder.getArrayAttr(attrs);
 }
 
+//===----------------------------------------------------------------------===//
+// -finit-local= helpers
+//===----------------------------------------------------------------------===//
+
+/// Returns true if \p derived or any of its components (recursively) is a
+/// PowerPC vector type. fir::VectorType does not implement
+/// DataLayoutTypeInterface. Two pre-fix failure modes existed:
+///   - Direct vector local: silently initialized to zero regardless of mode
+///     (historical behavior); at the current head genByteSplatInit would
+///     hit llvm_unreachable instead.
+///   - Derived-type local with a vector component: crashed in record-size
+///     calculation when DataLayoutTypeInterface was queried.
+/// Excluding both cases at eligibility time avoids both failure modes.
+static bool
+containsVectorComponent(const Fortran::semantics::DerivedTypeSpec &derived) {
+  if (derived.IsVectorType())
+    return true;
+  const Fortran::semantics::Scope *scope = derived.GetScope();
+  if (!scope)
+    return false;
+  const Fortran::semantics::Symbol &typeSym = derived.typeSymbol();
+  const auto *details =
+      typeSym.detailsIf<Fortran::semantics::DerivedTypeDetails>();
+  if (!details)
+    return false;
+  for (const Fortran::semantics::SourceName &compName :
+       details->componentNames()) {
+    auto it = scope->find(compName);
+    if (it == scope->cend())
+      continue;
+    const Fortran::semantics::Symbol &comp = it->second.get();
+    if (const Fortran::semantics::DeclTypeSpec *compTy = comp.GetType())
+      if (const Fortran::semantics::DerivedTypeSpec *compDerived =
+              compTy->AsDerived())
+        if (containsVectorComponent(*compDerived))
+          return true;
+  }
+  return false;
+}
+
+/// Returns true when \p var is an automatic local variable eligible for
+/// -finit-local= initialization. Excluded: variables without a symbol,
+/// globals, dummy arguments, SAVE'd vars, ALLOCATABLE/POINTER, vars in
+/// an EQUIVALENCE set, vars with explicit or default initialization, and
+/// CUDA variables whose storage is always unreachable by a plain fir.store
+/// (constant, shared, usedevice). The Device case is deferred to genInitLocal
+/// which applies cuf::isCUDADeviceContext to distinguish cuf.alloc from
+/// fir.alloca storage.
+static bool shouldInitLocal(const Fortran::lower::pft::Variable &var) {
+  if (!var.hasSymbol() || var.isGlobal())
+    return false;
+  const Fortran::semantics::Symbol &sym = var.getSymbol();
+  if (Fortran::semantics::IsDummy(sym))
+    return false;
+  // Function result variables own the return-value storage and must not be
+  // pre-initialized: the function body is responsible for setting the result.
+  if (sym.IsFuncResult())
+    return false;
+  // Main-program locals have implicit SAVE semantics (Fortran 2018 8.5.16p4).
+  // IsSaved() does not catch this case because the SAVE attribute is implicit
+  // rather than explicit, so check the enclosing scope kind directly.
+  if (sym.owner().kind() == Fortran::semantics::Scope::Kind::MainProgram)
+    return false;
+  if (Fortran::semantics::IsSaved(sym))
+    return false;
+  if (Fortran::semantics::IsAllocatableOrPointer(sym))
+    return false;
+  if (Fortran::lower::hasDefaultInitialization(sym))
+    return false;
+  if (const auto *obj =
+          sym.detailsIf<Fortran::semantics::ObjectEntityDetails>())
+    if (obj->init())
+      return false;
+  if (Fortran::semantics::FindEquivalenceSet(sym))
+    return false;
+  // Cray pointees own no storage of their own; their FIR base is a
+  // pointer-box descriptor. Initializing it would overwrite the
+  // descriptor, not the pointee storage.
+  if (sym.test(Fortran::semantics::Symbol::Flag::CrayPointee))
+    return false;
+  // PowerPC vector types (vector(real(4)) etc.) lower to fir::VectorType
+  // which does not implement DataLayoutTypeInterface at the HLFIR level.
+  // Without this guard:
+  //   - A direct vector local would hit llvm_unreachable in genByteSplatInit
+  //     (historically it silently fell back to zero before that assert was
+  //     added).
+  //   - A derived-type local with a vector component would crash in
+  //     record-size calculation when DataLayoutTypeInterface was queried.
+  // Exclude both cases by walking components recursively.
+  if (const Fortran::semantics::DeclTypeSpec *declTy = sym.GetType())
+    if (const Fortran::semantics::DerivedTypeSpec *derived =
+            declTy->AsDerived())
+      if (containsVectorComponent(*derived))
+        return false;
+  // CUDA storage accessibility:
+  //   constant / shared / usedevice: always unreachable by a plain fir.store
+  //     from the host -- skip.
+  //   device: the allocation choice (cuf.alloc vs fir.alloca) depends on
+  //     whether the insertion point is in a device context; that check
+  //     requires the MLIR builder and is deferred to genInitLocal, which
+  //     calls cuf::isCUDADeviceContext(builder.getRegion()) after this
+  //     predicate returns true.
+  //   managed / unified / pinned: host-accessible unified memory -- 
initialize.
+  if (auto cudaAttr = Fortran::semantics::GetCUDADataAttr(&sym)) {
+    switch (*cudaAttr) {
+    case Fortran::common::CUDADataAttr::Constant:
+    case Fortran::common::CUDADataAttr::Shared:
+    case Fortran::common::CUDADataAttr::UseDevice:
+      return false;
+    default:
+      break;
+    }
+  }
+  return true;
+}
+
+/// Build a constant whose every byte equals \p bytePat.
+/// Handles: integer, float (bitcast from integer splat), complex (both parts),
+/// and logical (raw integer, stored via bitcasted address by the caller).
+/// Character, derived-type, and sequence types are all intercepted by
+/// genInitLocalStore or initAddr before this function is called and must
+/// not reach it. fir::VectorType (PowerPC vector types, direct or as a
+/// derived-type component) is excluded upstream by shouldInitLocal via
+/// containsVectorComponent and will never reach this function.
+static mlir::Value genByteSplatInit(fir::FirOpBuilder &builder,
+                                    mlir::Location loc, mlir::Type ty,
+                                    uint8_t bytePat) {
+  mlir::Type eleTy = fir::unwrapSequenceType(ty);
+
+  // Build a signless integer constant from a byte splat.  arith.constant
+  // requires a signless integer type; callers that need a non-signless result
+  // (e.g. unsigned ui32) must fir.convert the returned value themselves.
+  auto makeIntCst = [&](unsigned bits) -> mlir::Value {
+    llvm::APInt byteVal(8, bytePat);
+    llvm::APInt splat = llvm::APInt::getSplat(bits, byteVal);
+    mlir::Type intTy = builder.getIntegerType(bits);
+    return mlir::arith::ConstantOp::create(
+        builder, loc, intTy, builder.getIntegerAttr(intTy, splat));
+  };
+
+  if (auto fpTy = mlir::dyn_cast<mlir::FloatType>(eleTy)) {
+    mlir::Value intCst = makeIntCst(fpTy.getWidth());
+    return mlir::arith::BitcastOp::create(builder, loc, fpTy, intCst);
+  }
+  if (auto intTy = mlir::dyn_cast<mlir::IntegerType>(eleTy)) {
+    mlir::Value cst = makeIntCst(intTy.getWidth());
+    // arith.constant only supports signless integers; fir.convert reinterprets
+    // the bit pattern into the declared signed or unsigned type without
+    // changing any bits, satisfying FIR verification for !fir.ref<ui32> etc.
+    if (!intTy.isSignless())
+      cst = builder.createConvert(loc, intTy, cst);
+    return cst;
+  }
+  // Complex: apply the byte pattern to each (real, imag) part.
+  if (auto cplxTy = mlir::dyn_cast<mlir::ComplexType>(eleTy)) {
+    mlir::Type partTy = cplxTy.getElementType();
+    mlir::Value partVal = genByteSplatInit(builder, loc, partTy, bytePat);
+    return mlir::complex::CreateOp::create(builder, loc, cplxTy, partVal,
+                                           partVal);
+  }
+  // LOGICAL(k) has a fixed size of k bytes under the default kind mapping,
+  // but a non-default mapping (e.g. --kind-mapping=l4:8) may map LOGICAL(4)
+  // to a single byte.  Use KindMapping::getLogicalBitsize so the constant
+  // width matches the actual allocation size.
+  // The caller stores it via a bitcasted address to preserve the bit pattern
+  // (fir.convert from integer to !fir.logical normalizes nonzero -> true).
+  if (auto logTy = mlir::dyn_cast<fir::LogicalType>(eleTy)) {
+    return 
makeIntCst(builder.getKindMap().getLogicalBitsize(logTy.getFKind()));
+  }
+  // All types that pass shouldInitLocal and reach genInitLocalStore are
+  // handled explicitly above (integer, float, complex, logical) or are
+  // intercepted before this call (character, record, sequence).
+  // PowerPC vector types (direct or as a derived-type component) are excluded
+  // by shouldInitLocal via containsVectorComponent and never reach here.
+  // A silent zero for an unhandled type would violate the hex-mode contract,
+  // so assert rather than fall back silently.
+  llvm_unreachable("genByteSplatInit: unhandled type in hex mode");
+}
+
+/// Emit a store of the -finit-local= pattern for a single scalar address.
+/// Fixed-length CHARACTER in hex mode: byte-loop over every byte of storage.
+/// LOGICAL stores via a bitcasted integer address to preserve the raw bit
+/// pattern past fir.convert normalization.
+/// All byte-view and coordinate types carry the source address volatility so
+/// that final stores are emitted as "store volatile" when the variable is
+/// volatile.
+static void genInitLocalStore(fir::FirOpBuilder &builder, mlir::Location loc,
+                              mlir::Type ty, mlir::Value addr,
+                              Fortran::lower::InitLocalKind mode,
+                              uint8_t hexByte) {
+  // Fixed-length CHARACTER: for hex mode emit a compile-time byte-loop so
+  // every code-unit gets the requested pattern. Zero falls through to
+  // fir.zero_bits below.
+  if (auto charTy = mlir::dyn_cast<fir::CharacterType>(ty)) {
+    // CHARACTER(0) has zero-length storage -- nothing to initialize.
+    if (charTy.getLen() == 0)
+      return;
+    if (mode == Fortran::lower::InitLocalKind::Hex) {
+      // Loop over every byte of the character storage. For kind=1 each
+      // code unit is one byte; for kind=2/4 (UTF-16/32) each code unit is
+      // kind bytes wide. We use a kind=1 singleton as the view element so
+      // fir.coordinate_of advances exactly one byte per step, and iterate
+      // nUnits * kindBytes times to cover all bytes.  Use KindMapping to
+      // get the true byte width under any --kind-mapping override.
+      int64_t nUnits = charTy.hasConstantLen() ? charTy.getLen() : 0;
+      int64_t kindBytes =
+          builder.getKindMap().getCharacterBitsize(charTy.getFKind()) / 8;
----------------
MattPD wrote:

Confirmed. Both paths keep their writes inside the allocation under 
`--kind-mapping=a1:16`.

https://github.com/llvm/llvm-project/pull/216164
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