// Copyright Contributors to the Open Shading Language project.
// SPDX-License-Identifier: BSD-3-Clause
// https://github.com/AcademySoftwareFoundation/OpenShadingLanguage

#pragma once

#include <OSL/oslconfig.h>

#include <unordered_set>
#include <vector>

#ifdef LLVM_NAMESPACE
namespace llvm = LLVM_NAMESPACE;
#endif

namespace llvm {
class BasicBlock;
class Constant;
class ConstantFolder;
class DIBuilder;
class DICompileUnit;
class DIFile;
class DILocation;
class DIScope;
class DISubprogram;
class DISubroutineType;
class ExecutionEngine;
class Function;
class FunctionType;
class SectionMemoryManager;
class JITEventListener;
class Linker;
class LLVMContext;
class Module;
class PointerType;
class StringRef;
class Type;
class Value;
class VectorType;

namespace legacy {
class FunctionPassManager;
class PassManager;
}  // namespace legacy
}  // namespace llvm



OSL_NAMESPACE_ENTER

namespace pvt {  // OSL::pvt


enum class TargetISA {
    UNKNOWN,
    NONE,
    x64,
    SSE4_2,
    AVX,
    AVX2,
    AVX2_noFMA,
    AVX512,
    AVX512_noFMA,
    HOST,
    COUNT
};



/// Wrapper class around LLVM functionality.  This handles all the
/// gory details of actually dealing with LLVM.  It should be sufficiently
/// generic that it would be useful for any LLVM-JITing app, and is not
/// tied to OSL internals at all.
class OSLEXECPUBLIC LLVM_Util {
public:
    struct OSLEXECPUBLIC PerThreadInfo {
        PerThreadInfo() {}
        ~PerThreadInfo();

    private:
        friend class LLVM_Util;
        struct Impl;
        mutable Impl* m_thread_info = nullptr;
        Impl* get() const;
    };

    LLVM_Util(const PerThreadInfo& per_thread_info, int debuglevel = 0,
              int vector_width = 4);
    ~LLVM_Util();

    // JIT'd code needs to exist with a longer lifetime than the LLVM_Util object.
    // To enable better cleanup at shutdown, the lifetime of all JIT'd code is
    // controlled by the the existence of ScopedJitMemoryUser objects.
    // When the last ScopedJitMemoryUser goes out of scope or is deleted,
    // then the underlying memory managers will be deleted
    struct OSLEXECPUBLIC ScopedJitMemoryUser {
        ScopedJitMemoryUser();
        ~ScopedJitMemoryUser();
    };

    /// Set debug level
    void debug(int d) { m_debug = d; }
    int debug() const { return m_debug; }
    void dumpasm(bool val) { m_dumpasm = val; }
    bool dumpasm() const { return m_dumpasm; }
    void jit_fma(bool val) { m_jit_fma = val; }
    bool jit_fma() const { return m_jit_fma; }
    void jit_aggressive(bool val) { m_jit_aggressive = val; }
    bool jit_aggressive() const { return m_jit_aggressive; }

    /// Return a reference to the current context.
    llvm::LLVMContext& context() const { return *m_llvm_context; }

    /// Return a pointer to the current module.  Make a new one if
    /// necessary.
    llvm::Module* module()
    {
        if (!m_llvm_module)
            m_llvm_module = new_module();
        return m_llvm_module;
    }

    /// Set the current module to m.
    void module(llvm::Module* m)
    {
        m_llvm_module       = m;
        m_ModuleIsFinalized = false;
        m_ModuleIsPruned    = false;
    }

    /// Create a new empty module.
    llvm::Module* new_module(const char* id = "default");

    /// Create a new module, populated with functions from the buffer
    /// bitcode[0..size-1].  The name identifies the buffer.  If err is not
    /// NULL, error messages will be stored there.
    llvm::Module* module_from_bitcode(const char* bitcode, size_t size,
                                      const std::string& name = std::string(),
                                      std::string* err        = NULL);

    bool debug_is_enabled() const;
    void debug_setup_compilation_unit(const char* compile_unit_name);
    void debug_push_function(const std::string& function_name,
                             OIIO::ustring sourcefile, int sourceline);
    void debug_pop_function();
    void debug_push_inlined_function(OIIO::ustring function_name,
                                     OIIO::ustring sourcefile, int sourceline);
    void debug_pop_inlined_function();
    void debug_set_location(OIIO::ustring sourcefile, int sourceline);

    /// Create a new function (that will later be populated with
    /// instructions) with up to 4 args.
    OSL_DEPRECATED("Use make_function flavor that takes a cspan (1.12)")
    llvm::Function* make_function(const std::string& name, bool fastcall,
                                  llvm::Type* rettype, llvm::Type* arg1 = NULL,
                                  llvm::Type* arg2 = NULL,
                                  llvm::Type* arg3 = NULL,
                                  llvm::Type* arg4 = NULL);

    /// Create a new function (that will later be populated with
    /// instructions) with a cspan of args.
    llvm::Function* make_function(const std::string& name, bool fastcall,
                                  llvm::Type* rettype,
                                  cspan<llvm::Type*> paramtypes,
                                  bool varargs = false);

    /// Add a global mapping of a function to its callable address
    /// explicitly instead of relying on dlsym.
    void add_function_mapping(llvm::Function* func, void* addr);

    /// Set up a new current function that subsequent basic blocks will
    /// be added to.
    void current_function(llvm::Function* func) { m_current_function = func; }

    /// Return a ptr to the current function we're generating.
    llvm::Function* current_function() const { return m_current_function; }

    /// Return the value ptr for the a-th argument of the current function.
    llvm::Value* current_function_arg(int a);


    /// Create a new IR builder with the given block as entry point. If
    /// block is NULL, a new basic block for the current function will be
    /// created.
    void new_builder(llvm::BasicBlock* block = NULL);

    /// End the current builder
    void end_builder();

    /// Create a new JITing ExecutionEngine and make it the current one.
    /// Return a pointer to the new engine.  If err is not NULL, put any
    /// errors there.
    /// Optionally enable debugging symbols (source file & line number)
    /// Optionally enable profiling events
    /// Optionally request a specific ISA for JIT on the host
    ///     ["x64", "SSE4.2", "AVX", "AVX2", "AVX512"]
    ///     (ignored if requested ISA not valid for host)
    /// Optionally enable debugging symbols (source file & line number)
    /// Optionally enable profiling events
    llvm::ExecutionEngine* make_jit_execengine(
        std::string* err = nullptr, TargetISA requestedISA = TargetISA::NONE,
        bool debugging_symbols = false, bool profiling_events = false);

    /// Report the host's TargetISA as chosen by the last call to
    /// make_jit_execengine() or to detect_cpu_features(). Don't call
    /// target_isa() unless one of those has previously been called.
    TargetISA target_isa() const { return m_target_isa; }

    // Check support for certain CPU ISA features. These are only valid
    // after detect_cpu_features() (or make_jit_execengine()) has been
    // called.
    bool supports_avx() const { return m_supports_avx; }
    bool supports_avx2() const { return m_supports_avx2; }
    bool supports_avx512f() const { return m_supports_avx512f; }
    bool supports_llvm_bit_masks_natively() const
    {
        return m_supports_llvm_bit_masks_natively;
    }
    bool supports_masked_stores() const { return m_supports_masked_stores; }

    // Does this host support the requested target ISA?
    static bool supports_isa(TargetISA target);

    // Look up the TargetISA enum by name. Special names: "host" means
    // figure out what this host is, "none" or "" mean to use the baseline
    // or no special ops not available on all flavors of this family of CPUs.
    static TargetISA lookup_isa_by_name(string_view target_name = "");

    // Name for this TargetISA enum.
    static const char* target_isa_name(TargetISA isa);

    /// Add a global mapping of a variable to its address
    /// explicitly instead of relying on dlsym.
    static void add_global_mapping(const char* global_var_name,
                                   void* global_var_addr);

    /// Check all external global variables to ensure they have
    /// been mapped to an address, a vector is populated with
    /// the names that are unmapped.
    void validate_global_mappings(
        std::vector<std::string>& names_of_unmapped_globals);

    // For CPU compilation, inventory the host CPU capabilities. You can
    // optionally request a specific ISA by name. If `no_fma` is true,
    // specifically pretend there is no FMA capability, even if the hardware
    // supports it. Return true if ok, false if it couldn't figure it out.
    bool detect_cpu_features(TargetISA requestedISA = TargetISA::UNKNOWN,
                             bool no_fma            = false);

    void dump_struct_data_layout(llvm::Type* Ty);
    void validate_struct_data_layout(
        llvm::Type* Ty,
        const std::vector<unsigned int>& expected_offset_by_index);


    /// Return a pointer to the current ExecutionEngine.  Create a JITing
    /// ExecutionEngine if one isn't already set up.
    llvm::ExecutionEngine* execengine()
    {
        if (!m_llvm_exec)
            make_jit_execengine();
        return m_llvm_exec;
    }

    /// Replace the ExecutionEngine (pass NULL to simply delete the
    /// current one).
    void execengine(llvm::ExecutionEngine* exec);

    enum class Linkage {
        External,  // Externally visible
        LinkOnceODR,  // One Definition Rule:  Inline version, but allow replacement by equivalent.
        Internal,  // Treat as static functions.
        Private    // Treat as static functions, but omit from symbol table.
    };

    /// Identify exactly which functions need to exist in the module based
    /// on actual usage from a set of external_functions. All unneeded
    /// functions are removed before we move to optimization which is much
    /// faster.  The external_functions will be set to have external linkage
    /// and the remaining functions set to internal linkage.
    void prune_and_internalize_module(
        std::unordered_set<llvm::Function*> external_functions,
        Linkage default_linkage = Linkage::Internal,
        std::string* out_err    = nullptr);

    // OLD, might deprecate later
    /// Change symbols in the module that are marked as having external
    /// linkage to an alternate linkage that allows them to be discarded if
    /// not used within the module. Only do this for functions that start
    /// with prefix, and that DON'T match anything in the two exceptions
    /// lists.
    void internalize_module_functions(
        const std::string& prefix, const std::vector<std::string>& exceptions,
        const std::vector<std::string>& moreexceptions);

    /// Setup LLVM optimization passes.
    /// if targetHost is true, passes to target the host will be added
    void setup_optimization_passes(int optlevel, bool target_host = true);

    /// Run the optimization passes.
    void do_optimize(std::string* err = NULL);

    /// Retrieve a callable pointer to the JITed version of a function.
    /// This will JIT the function if it hasn't already done so. Be sure
    /// you have already called do_optimize() if you want optimization.
    void* getPointerToFunction(llvm::Function* func);

    /// Wrap ExecutionEngine::InstallLazyFunctionCreator.
    void InstallLazyFunctionCreator(void* (*P)(const std::string&));


    /// Create a new LLVM basic block (for the current function) and return
    /// its handle.
    llvm::BasicBlock* new_basic_block(const std::string& name = std::string());

    /// Save the return block pointer when entering a function. If
    /// after==NULL, generate a new basic block for where to go after the
    /// function return.  Return the after BB.
    llvm::BasicBlock* push_function(llvm::BasicBlock* after = NULL);

    /// Pop basic return destination when exiting a function.  This includes
    /// resetting the IR insertion point to the block following the
    /// corresponding function call.
    void pop_function();

    /// Are we inside a function?
    bool inside_function() const;

    // Overview of masking strategy
    //
    // For if/then based on a conditional, the result of the conditional is
    // conditionals written to a symbol that is a wide boolean.  To handle
    // nesting we will keep a stack of conditional masks.  When a new
    // conditional mask is pushed, it is combined with the previous mask on
    // the top of the stack.  It is the top of the mask stack that is used
    // as the mask for any instructions requiring masking.  When a
    // conditional scope is exited, we just pop the top of the conditional
    // mask stack.
    //
    // Loops are handled by pushing their conditional result onto the
    // conditional mask stack, and popping it back off at the end of the
    // loop.
    //
    // Handling of early outs (exit, return, break, continue) is done by
    // storing a mask representing the lanes which are going to be
    // deactivated (or continue executing) to an allocated location in the
    // stack. We actually have to store these early out masks, so that we
    // can apply it to the conditional mask stack.  As that stack unwinds,
    // any early out masks are applied to the top of the conditional mask
    // stack.  As there are different types of early outs that apply to
    // different control flow scopes and multiple types can be present at
    // the same time for different data lanes, we must store these early
    // out masks at separate locations on the stack.
    //
    // To handle 'exit', we allocate a 'shader mask' that is initially
    // populated with a startMaskValue representing the active lanes in a
    // shader global batch.  For example perhaps only 7 of 16 data lanes
    // are populated, the startMaskValue would store that value and push it
    // onto the conditional mask stack.  We require a location on the stack
    // for this 'shader mask' in order for an 'exit' statement to modify it
    // and cause a subset of the lanes to be deactivated.  If an exit was
    // processed, the 'shader mask' is where it will be stored and pulled
    // from when applying to the unwinding conditional mask stack.
    //
    // To handle 'return', we allocate a 'function mask' that is initially
    // populated with a startMaskValue representing the active lanes when
    // an inlined function was called.  This startMaskValue should just be
    // value at the top of the conditional mask stack.  As function calls
    // can be nested, we maintain a stack of function masks.  We require a
    // location on the stack for each 'function mask' in order for a
    // 'return' statement to modify it and cause a subset of the lanes to
    // be deactivated.  If an return was processed, the 'return mask' is
    // where it will be stored and pulled from when applying to the
    // unwinding conditional mask stack. When a function scope is exited,
    // the function mask is popped so any return's processed would apply to
    // the outer function mask vs. the one just exited.
    //
    // To handle 'break', we use the condition symbol's location on the
    // stack to directly disable data lanes for the loop execution.  As we
    // already had a location to store the conditional symbol's mask, no
    // need to allocate or store a separate one.  However code will need to
    // reload the condition's value when a break 'could have been' called
    // vs. relying on a conditional result already in a register.
    //
    // To handle 'continue', we allocate a 'continue mask' that is
    // initially populated with a 0 representing the deactivated lanes by
    // 'continue' operations. We require a location on the stack for each
    // 'continue mask' in order for a 'continue' statement to modify it and
    // cause a subset of the lanes to be deactivated.  If an continue was
    // processed, the 'continue mask' is where it will be stored and pulled
    // from when applying to the unwinding conditional mask stack. When a
    // loop's scope is exited, the continue mask is popped so it wouldn't be
    // applied to an outer loop.
    //
    // The logic of when and how to actually apply these masks is handled
    // by the caller, tracking/storing the different stacks and masks is
    // handled here.  And queries exist to see how many early outs
    // operations have been processed, these counts can be used by the
    // caller to determine which to generate code to apply each of them.

    void push_function_mask(llvm::Value* startMaskValue);
    void pop_function_mask();

    void push_masked_loop(llvm::Value* location_of_control_mask,
                          llvm::Value* location_of_continue_mask);
    void pop_masked_loop();
    bool is_innermost_loop_masked() const;

    void push_shader_instance(llvm::Value* startMaskValue);
    void pop_shader_instance();

    // number of masked exits operations built inside the shader instance
    int masked_exit_count() const;

    // number of masked return operations inside the scope of the current
    // function mask
    int masked_return_count() const;

    // number of masked break operations inside the scope of the current
    // masked loop
    int masked_break_count() const;

    // number of masked continue operations inside the scope of the current
    // masked loop
    int masked_continue_count() const;

    // Push a mask onto the mask stack, which actually will AND the existing
    // top mask with the new mask and store that off. The mask must be of
    // type <16 x i1>,<8 x i1>, or <4 x i1> depending on vector_width
    void push_mask(llvm::Value* mask, bool negate = false,
                   bool absolute = false);
    void pop_mask();

    void apply_exit_to_mask_stack();
    void apply_return_to_mask_stack();
    void apply_break_to_mask_stack();
    void apply_continue_to_mask_stack();

    llvm::Value* current_mask();
    llvm::Value* apply_return_to(llvm::Value* existing_mask);

    // Shader level mask, should incorporate the batch size and any exits
    // processed up to this point.
    llvm::Value* shader_mask();

    void op_masked_break();
    void op_masked_continue();

    void op_masked_exit();
    void op_masked_return();

    void push_masked_return_block(llvm::BasicBlock* test_return);
    void pop_masked_return_block();
    bool has_masked_return_block() const;
    llvm::BasicBlock* masked_return_block() const;

    bool is_masking_required() const { return m_is_masking_required; }

    struct ScopedMasking {
        ScopedMasking() {}

        ScopedMasking(const ScopedMasking& other) = delete;

        ScopedMasking(ScopedMasking&& other)
            : m_util(other.m_util)
            , m_previous_masking_requirement(
                  other.m_previous_masking_requirement)
        {
            other.m_util = nullptr;
        }

        void release()
        {
            OSL_ASSERT(nullptr != m_util);
            m_util->set_masking_required(m_previous_masking_requirement);
            m_util = nullptr;
        }

        ScopedMasking& operator=(ScopedMasking&& other)
        {
            if (nullptr != m_util) {
                release();
            }
            m_util = other.m_util;
            m_previous_masking_requirement
                = other.m_previous_masking_requirement;
            other.m_util = nullptr;
            return *this;
        }

        ~ScopedMasking()
        {
            if (nullptr != m_util) {
                release();
            }
        }

    private:
        friend class LLVM_Util;
        ScopedMasking(LLVM_Util& util, bool enabled)
            : m_util(&util)
            , m_previous_masking_requirement(util.is_masking_required())
        {
            m_util->set_masking_required(enabled);
        }

        LLVM_Util* m_util                   = nullptr;
        bool m_previous_masking_requirement = false;
    };

    ScopedMasking create_masking_scope(bool enabled)
    {
        return ScopedMasking(*this, enabled);
    }

    /// Return the basic block where we go after returning from the current
    /// function.
    llvm::BasicBlock* return_block() const;

    /// Save the basic block pointers when entering a loop.
    void push_loop(llvm::BasicBlock* step, llvm::BasicBlock* after);

    /// Pop basic block pointers when exiting a loop.
    void pop_loop();

    /// Return the basic block of the current loop's 'step' instructions.
    llvm::BasicBlock* loop_step_block() const;

    /// Return the basic block of the current loop's exit point.
    llvm::BasicBlock* loop_after_block() const;


    llvm::Type* type_float() const { return m_llvm_type_float; }
    llvm::Type* type_double() const { return m_llvm_type_double; }
    llvm::Type* type_int() const { return m_llvm_type_int; }
    llvm::Type* type_int8() const { return m_llvm_type_int8; }
    llvm::Type* type_int16() const { return m_llvm_type_int16; }
    llvm::Type* type_addrint() const { return m_llvm_type_addrint; }
    llvm::Type* type_bool() const { return m_llvm_type_bool; }
    llvm::Type* type_char() const { return m_llvm_type_char; }
    llvm::Type* type_longlong() const { return m_llvm_type_longlong; }
    llvm::Type* type_void() const { return m_llvm_type_void; }
    llvm::Type* type_triple() const { return m_llvm_type_triple; }
    llvm::Type* type_matrix() const { return m_llvm_type_matrix; }
    llvm::Type* type_typedesc() const { return m_llvm_type_longlong; }
    llvm::PointerType* type_void_ptr() const { return m_llvm_type_void_ptr; }
    llvm::PointerType* type_string() { return m_llvm_type_char_ptr; }
    llvm::PointerType* type_ustring_ptr() const
    {
        return m_llvm_type_ustring_ptr;
    }
    llvm::PointerType* type_char_ptr() const { return m_llvm_type_char_ptr; }
    llvm::PointerType* type_bool_ptr() const { return m_llvm_type_bool_ptr; }
    llvm::PointerType* type_int_ptr() const { return m_llvm_type_int_ptr; }
    llvm::PointerType* type_float_ptr() const { return m_llvm_type_float_ptr; }
    llvm::PointerType* type_longlong_ptr() const
    {
        return m_llvm_type_longlong_ptr;
    }
    llvm::PointerType* type_triple_ptr() const
    {
        return m_llvm_type_triple_ptr;
    }
    llvm::PointerType* type_matrix_ptr() const
    {
        return m_llvm_type_matrix_ptr;
    }
    llvm::PointerType* type_double_ptr() const
    {
        return m_llvm_type_double_ptr;
    }

    llvm::Type* type_wide_float() const { return m_llvm_type_wide_float; }
    llvm::Type* type_wide_double() const { return m_llvm_type_wide_double; }
    llvm::Type* type_wide_int() const { return m_llvm_type_wide_int; }
    llvm::Type* type_wide_bool() const { return m_llvm_type_wide_bool; }
    llvm::Type* type_wide_char() const { return m_llvm_type_wide_char; }
    llvm::Type* type_wide_longlong() const { return m_llvm_type_wide_longlong; }
    llvm::Type* type_wide_triple() const { return m_llvm_type_wide_triple; }
    llvm::Type* type_wide_matrix() const { return m_llvm_type_wide_matrix; }
    llvm::Type* type_wide_void_ptr() const { return m_llvm_type_wide_void_ptr; }
    llvm::Type* type_wide_string() const
    {
        return m_llvm_type_wide_ustring_ptr;
    }
    llvm::PointerType* type_wide_char_ptr() const
    {
        return m_llvm_type_wide_char_ptr;
    }
    llvm::PointerType* type_wide_bool_ptr() const
    {
        return m_llvm_type_wide_bool_ptr;
    }
    llvm::PointerType* type_wide_int_ptr() const
    {
        return m_llvm_type_wide_int_ptr;
    }
    llvm::PointerType* type_wide_float_ptr() const
    {
        return m_llvm_type_wide_float_ptr;
    }

    // Different ISA's may have different representations of a mask from
    // llvm's vector of bits that comparison operations emit. And we need
    // varying boolean symbols to have the correct data type (size) on the
    // stack and in data structures.
    llvm::Type* type_native_mask() const { return m_llvm_type_native_mask; }

    /// Generate the appropriate llvm type definition for a TypeDesc
    /// (this is the actual type, for example when we allocate it).
    llvm::Type* llvm_type(const OIIO::TypeDesc& typedesc);

    /// Generate the appropriate llvm vector type definition for a TypeDesc
    /// (this is the actual type, for example when we allocate it).
    llvm::Type* llvm_vector_type(const OIIO::TypeDesc& typedesc);

    // Wrapper for llvm::VectorType::get() that handles LLVM 11 API change
    static llvm::VectorType* llvm_vector_type(llvm::Type* elementtype,
                                              unsigned numelements);

    /// This will return a llvm::Type that is the same as a C union of
    /// the given types[].
    llvm::Type* type_union(cspan<llvm::Type*> types);

    /// This will return a llvm::Type that is the same as a C struct
    /// comprised fields of the given types[], in order.
    llvm::Type* type_struct(cspan<llvm::Type*> types,
                            const std::string& name = "",
                            bool is_packed          = false);

    /// Return the llvm::Type that is a pointer to the given llvm type.
    llvm::Type* type_ptr(llvm::Type* type);

    /// Return the llvm::Type that is the wide version of the given llvm type
    llvm::Type* type_wide(llvm::Type* type);

    /// Return the llvm::Type that is an array of n elements of the given
    /// llvm type.
    llvm::Type* type_array(llvm::Type* type, int n);

    /// Return an llvm::FunctionType that describes a function with the
    /// given return types, parameter types (in a cspan), and whether it
    /// uses varargs conventions.
    llvm::FunctionType* type_function(llvm::Type* rettype,
                                      cspan<llvm::Type*> params,
                                      bool varargs = false);

    /// Return a llvm::PointerType that's a pointer to the described
    /// kind of function.
    llvm::PointerType* type_function_ptr(llvm::Type* rettype,
                                         cspan<llvm::Type*> params,
                                         bool varargs = false);

    /// Return the human-readable name of the type of the llvm type.
    std::string llvm_typename(llvm::Type* type) const;

    /// Return the llvm::Type of the llvm value.
    llvm::Type* llvm_typeof(llvm::Value* val) const;

    /// Return the human-readable name of the type of the llvm value.
    std::string llvm_typenameof(llvm::Value* val) const;

    /// Return an llvm::Constant holding the given floating point constant.
    llvm::Constant* constant(float f);

    /// Return an llvm::Constant holding the given integer constant.
    llvm::Constant* constant(int i);

    /// Return an llvm::Constant holding the given integer constant.
    llvm::Constant* constant8(int i);
    llvm::Constant* constant16(uint16_t i);
    llvm::Constant* constant64(uint64_t i);
    llvm::Constant* constant128(uint64_t i);
    llvm::Constant* constant128(uint64_t left, uint64_t right);

    // Return an llvm::Constant holding an explicit signed int64_t constant.
    llvm::Constant* constanti64(int64_t i);

    /// Return an llvm::Constant holding the given size_t constant.
    llvm::Constant* constant(size_t i);

    /// Return an llvm::Constant holding the given bool constant.
    /// Change the name so it doesn't get mixed up with int.
    llvm::Constant* constant_bool(bool b);

    /// Return a constant void pointer to the given constant address.
    /// If the type specified is NULL, it will make a 'void *'.
    llvm::Value* constant_ptr(void* p, llvm::PointerType* type = NULL);

    /// Return an llvm::Value holding the given string constant.
    llvm::Value* constant(ustring s);
    llvm::Value* constant(string_view s) { return constant(ustring(s)); }

    llvm::Value* llvm_mask_to_native(llvm::Value* llvm_mask);
    llvm::Value* native_to_llvm_mask(llvm::Value* native_mask);

    llvm::Value* mask_as_int(llvm::Value* mask);
    llvm::Value* mask_as_int8(llvm::Value* mask);
    llvm::Value* mask4_as_int8(llvm::Value* mask);
    llvm::Value* mask_as_int16(llvm::Value* mask);
    llvm::Value* int_as_mask(llvm::Value* value);
    llvm::Value* test_if_mask_is_non_zero(llvm::Value* mask);

    llvm::Value* test_mask_lane(llvm::Value* mask, int lane_index);
    llvm::Value* test_mask_lane(llvm::Value* mask, llvm::Value* lane_index);
    llvm::Value* widen_value(llvm::Value* val);
    llvm::Value* negate_mask(llvm::Value* mask);

    /// Return an llvm::Value for a long long that is a packed
    /// representation of a TypeDesc.
    llvm::Constant* constant(const OIIO::TypeDesc& type);

    // Return "wide" (SIMD vector) constants of various types, with
    // vector_width.
    llvm::Constant* wide_constant(float f);
    llvm::Constant* wide_constant(int i);
    llvm::Constant* wide_constant(size_t i);
    llvm::Constant* wide_constant_bool(bool b);
    llvm::Value* wide_constant(ustring s);
    llvm::Value* wide_constant(string_view s)
    {
        return wide_constant(ustring(s));
    }

    /// Return an llvm::Value holding wide version of the given scalar
    /// constant.
    llvm::Constant* wide_constant(llvm::Constant* constant_val);

    // Return wide (SIMD vector) constant with arbitrary width.
    llvm::Constant* wide_constant(int width, int value);
    llvm::Constant* wide_constant(int width, float value);

    /// Return an llvm::Value for a void* variable with value NULL.
    llvm::Constant* void_ptr_null();

    /// Cast the pointer variable specified by val to the kind of pointer
    /// described by type (as an llvm pointer type).
    llvm::Value* ptr_cast(llvm::Value* val, llvm::Type* type,
                          const std::string& llname = {});
    llvm::Value* ptr_cast(llvm::Value* val, llvm::PointerType* type,
                          const std::string& llname = {})
    {
        return ptr_cast(val, (llvm::Type*)type, llname);
    }

    /// Cast the pointer variable specified by val to a pointer to the type
    /// described by type (as an llvm data type).
    llvm::Value* ptr_to_cast(llvm::Value* val, llvm::Type* type,
                             const std::string& llname = {});

    /// Cast the pointer variable specified by val to a pointer to the given
    /// data type, return the llvm::Value of the new pointer.
    llvm::Value* ptr_cast(llvm::Value* val, const OIIO::TypeDesc& type,
                          const std::string& llname = {});

    llvm::Value* wide_ptr_cast(llvm::Value* val, const OIIO::TypeDesc& type);

    /// Cast the variable specified by val to a pointer of type void*,
    /// return the llvm::Value of the new pointer.
    llvm::Value* int_to_ptr_cast(llvm::Value* val);

    /// Cast the pointer variable specified by val to a pointer of type
    /// void* return the llvm::Value of the new pointer.
    llvm::Value* void_ptr(llvm::Value* val, const std::string& llname = {});

    /// Generate a pointer that is (ptrtype)((char *)ptr + offset).
    /// If ptrtype is NULL, just return a void*.
    llvm::Value* offset_ptr(llvm::Value* ptr, int offset,
                            llvm::Type* ptrtype = NULL);

    /// Generate a pointer that is (ptrtype)((char *)ptr + offset).
    /// If ptrtype is NULL, just return a void*.
    llvm::Value* offset_ptr(llvm::Value* ptr, llvm::Value* offset,
                            llvm::Type* ptrtype = nullptr);

    void assume_ptr_is_aligned(llvm::Value* ptr, unsigned alignment);

    /// Generate an alloca instruction to allocate space for n copies of the
    /// given llvm type, and return its pointer.
    llvm::Value* op_alloca(llvm::Type* llvmtype, int n = 1,
                           const std::string& name = std::string(),
                           int align               = 0);
    llvm::Value* op_alloca(llvm::PointerType* llvmtype, int n = 1,
                           const std::string& name = std::string(),
                           int align               = 0)
    {
        return op_alloca((llvm::Type*)llvmtype, n, name);
    }

    /// Generate an alloca instruction to allocate space for n copies of the
    /// given type, and return its pointer.
    llvm::Value* op_alloca(const OIIO::TypeDesc& type, int n = 1,
                           const std::string& name = std::string(),
                           int align               = 0);

    /// Generate an alloca instruction to allocate space for n copies of the
    /// given type, and return its pointer.
    llvm::Value* wide_op_alloca(const OIIO::TypeDesc& type, int n = 1,
                                const std::string& name = std::string(),
                                int align               = 0);

    /// Generate code for a call to the function pointer, with the given
    /// arg list.  Return an llvm::Value* corresponding to the return
    /// value of the function, if any.
    llvm::Value* call_function(llvm::Value* func, cspan<llvm::Value*> args);
    /// Generate code for a call to the named function with the given arg
    /// list.  Return an llvm::Value* corresponding to the return value of
    /// the function, if any.
    llvm::Value* call_function(const char* name, cspan<llvm::Value*> args);

    llvm::Value* call_function(const char* name, llvm::Value* arg0)
    {
        return call_function(name, cspan<llvm::Value*>(&arg0, 1));
    }
    llvm::Value* call_function(const char* name, llvm::Value* arg0,
                               llvm::Value* arg1)
    {
        return call_function(name, { arg0, arg1 });
    }
    llvm::Value* call_function(const char* name, llvm::Value* arg0,
                               llvm::Value* arg1, llvm::Value* arg2)
    {
        return call_function(name, { arg0, arg1, arg2 });
    }
    llvm::Value* call_function(const char* name, llvm::Value* arg0,
                               llvm::Value* arg1, llvm::Value* arg2,
                               llvm::Value* arg3)
    {
        return call_function(name, { arg0, arg1, arg2, arg3 });
    }

    /// Mark the function call to pass the pointer to the structure
    /// to be used as the return value.
    void mark_structure_return_value(llvm::Value* funccall);

    /// Mark the function call (which MUST be the value returned by a
    /// call_function()) as using the 'fast' calling convention.
    void mark_fast_func_call(llvm::Value* funccall);

    /// Set the code insertion point for subsequent ops to block.
    void set_insert_point(llvm::BasicBlock* block);

    /// Return op from a void function.  If retval is NULL, we are returning
    /// from a void function.
    void op_return(llvm::Value* retval = NULL);

    /// Create a branch instruction to block and establish that as the as
    /// the new code insertion point.
    void op_branch(llvm::BasicBlock* block);

    /// Create a conditional branch instruction to trueblock if cond is
    /// true, to falseblock if cond is false, and establish trueblock as the
    /// new insertion point).
    void op_branch(llvm::Value* cond, llvm::BasicBlock* trueblock,
                   llvm::BasicBlock* falseblock);

    /// Generate code for a memset.
    void op_memset(llvm::Value* ptr, int val, int len, int align = 1);

    /// Generate code for variable size memset
    void op_memset(llvm::Value* ptr, int val, llvm::Value* len, int align = 1);

    /// Generate code for a memcpy.
    void op_memcpy(llvm::Value* dst, llvm::Value* src, int len, int align = 1);

    /// Generate code for a memcpy.
    void op_memcpy(llvm::Value* dst, int dstalign, llvm::Value* src,
                   int srcalign, int len);

    /// Dereference a pointer:  return *ptr
    /// type is the type of the thing being pointed to.
    llvm::Value* op_load(llvm::Type* type, llvm::Value* ptr,
                         const std::string& llname = {});
    // Blind pointer version that's deprecated as of LLVM13:
    llvm::Value* op_load(llvm::Value* ptr, const std::string& llname = {});

    llvm::Value* op_gather(llvm::Value* ptr, llvm::Value* index);

    /// Store to a dereferenced pointer
    /// respecting the current mask & masking_enabled flag:   *ptr = val
    void op_store(llvm::Value* val, llvm::Value* ptr);

    /// Store to a dereferenced pointer with no masking:   *ptr = val
    void op_unmasked_store(llvm::Value* val, llvm::Value* ptr);

    /// Dereference a pointer of a native mask
    /// converting it to a llvm mask (vector of bits):  return native_to_llvm_mask(*ptr)
    llvm::Value* op_load_mask(llvm::Value* native_mask_ptr);

    /// Store to a dereferenced pointer of a llvm mask
    /// converting it to the native mask type for storage:   *ptr = llvm_mask_to_native(val);
    void op_store_mask(llvm::Value* llvm_mask, llvm::Value* native_mask_ptr);

    void op_scatter(llvm::Value* wide_val, llvm::Value* ptr,
                    llvm::Value* wide_index);

    // N.B. "GEP" -- GetElementPointer -- is a particular LLVM-ism that is
    // the means for retrieving elements from some kind of aggregate: the
    // i-th field in a struct, the i-th element of an array.  They can be
    // chained together, to get at items in a recursive hierarchy.

    /// Generate a GEP (get element pointer) where the element index is an
    /// llvm::Value, which can be generated from either a constant or a
    /// runtime-computed integer element index. `type` is the type of the data
    /// we're retrieving.
    llvm::Value* GEP(llvm::Type* type, llvm::Value* ptr, llvm::Value* elem,
                     const std::string& llname = {});
    // Blind pointer version that's deprecated as of LLVM13:
    llvm::Value* GEP(llvm::Value* ptr, llvm::Value* elem,
                     const std::string& llname = {});

    /// Generate a GEP (get element pointer) with an integer element
    /// offset. `type` is the type of the data we're retrieving.
    llvm::Value* GEP(llvm::Type* type, llvm::Value* ptr, int elem,
                     const std::string& llname = {});
    // Blind pointer version that's deprecated as of LLVM13:
    llvm::Value* GEP(llvm::Value* ptr, int elem,
                     const std::string& llname = {});

    /// Generate a GEP (get element pointer) with two integer element
    /// offsets.  This is just a special (and common) case of GEP where
    /// we have a 2-level hierarchy and we have fixed element indices
    /// that are known at compile time.  `type` is the type of the data we're
    /// retrieving.
    llvm::Value* GEP(llvm::Type* type, llvm::Value* ptr, int elem1, int elem2,
                     const std::string& llname = {});
    // Blind pointer version that's deprecated as of LLVM13:
    llvm::Value* GEP(llvm::Value* ptr, int elem1, int elem2,
                     const std::string& llname = {});

    // Arithmetic ops.  It auto-detects the type (int vs float).
    // ...
    llvm::Value* op_add(llvm::Value* a, llvm::Value* b);
    llvm::Value* op_sub(llvm::Value* a, llvm::Value* b);
    llvm::Value* op_neg(llvm::Value* a);
    llvm::Value* op_mul(llvm::Value* a, llvm::Value* b);
    llvm::Value* op_div(llvm::Value* a, llvm::Value* b);
    llvm::Value* op_mod(llvm::Value* a, llvm::Value* b);
    llvm::Value* op_float_to_int(llvm::Value* a);
    llvm::Value* op_int_to_float(llvm::Value* a);
    llvm::Value* op_bool_to_int(llvm::Value* a);
    llvm::Value* op_bool_to_float(llvm::Value* a);
    llvm::Value* op_int_to_bool(llvm::Value* a);
    llvm::Value* op_float_to_double(llvm::Value* a);
    llvm::Value* op_int_to_longlong(llvm::Value* a);

    llvm::Value* op_and(llvm::Value* a, llvm::Value* b);
    llvm::Value* op_or(llvm::Value* a, llvm::Value* b);
    llvm::Value* op_xor(llvm::Value* a, llvm::Value* b);
    llvm::Value* op_shl(llvm::Value* a, llvm::Value* b);
    llvm::Value* op_shr(llvm::Value* a, llvm::Value* b);
    llvm::Value* op_not(llvm::Value* a);

    /// Generate IR for (cond ? a : b).  Cond should be a bool.
    llvm::Value* op_select(llvm::Value* cond, llvm::Value* a, llvm::Value* b);
    llvm::Value* op_zero_if(llvm::Value* cond, llvm::Value* a);

    llvm::Value* op_1st_active_lane_of(llvm::Value* mask);
    llvm::Value* op_lanes_that_match_masked(llvm::Value* scalar_value,
                                            llvm::Value* wide_value,
                                            llvm::Value* mask);

    /// Extracts a scalar value from a vector type
    llvm::Value* op_extract(llvm::Value* a, int index);
    llvm::Value* op_extract(llvm::Value* a, llvm::Value* index);
    llvm::Value* op_insert(llvm::Value* v, llvm::Value* a, int index);

    // Comparison ops.  It auto-detects the type (int vs float).
    // ordered only applies to float comparisons -- ordered means the
    // comparison will succeed only if neither arg is NaN.
    // ...
    llvm::Value* op_eq(llvm::Value* a, llvm::Value* b, bool ordered = false);
    llvm::Value* op_ne(llvm::Value* a, llvm::Value* b, bool ordered = false);
    llvm::Value* op_gt(llvm::Value* a, llvm::Value* b, bool ordered = false);
    llvm::Value* op_lt(llvm::Value* a, llvm::Value* b, bool ordered = false);
    llvm::Value* op_ge(llvm::Value* a, llvm::Value* b, bool ordered = false);
    llvm::Value* op_le(llvm::Value* a, llvm::Value* b, bool ordered = false);

    llvm::Value* op_fabs(llvm::Value* v);
    llvm::Value* op_is_not_finite(llvm::Value* v);

    /// Write the module's bitcode (after compilation/optimization) to a
    /// file.  If err is not NULL, errors will be deposited there.
    void write_bitcode_file(const char* filename, std::string* err = NULL);

    /// Insert bitcode from another module into the current Module
    /// returns true if successful, false otherwise.
    /// Ownership of the other_module is transferred.
    bool absorb_module(std::unique_ptr<llvm::Module> other_module);

    /// Generate PTX for the current Module and return it as a string
    bool ptx_compile_group(llvm::Module* lib_module, const std::string& name,
                           std::string& out);

    /// Convert all functions in module's bitcode to a string.
    std::string bitcode_string(llvm::Module* module);

    /// Convert one function's bitcode to a string.
    std::string bitcode_string(llvm::Function* func);

    /// Convert entire module's bitcode to a string.
    std::string module_string();

    /// Delete the IR for the body of the given function to reclaim its
    /// memory (only helpful if we know we won't use it again).
    void delete_func_body(llvm::Function* func);

    /// Is the function empty, except for simply a ret statement?
    bool func_is_empty(llvm::Function* func);

    std::string func_name(llvm::Function* f);

    static size_t total_jit_memory_held();

private:
    class MemoryManager;
    class IRBuilder;

    void SetupLLVM();
    IRBuilder& builder();

    int m_debug;
    bool m_dumpasm        = false;
    bool m_jit_fma        = false;
    bool m_jit_aggressive = false;
    PerThreadInfo::Impl* m_thread;
    llvm::LLVMContext* m_llvm_context;
    llvm::Module* m_llvm_module;
    IRBuilder* m_builder;
    llvm::SectionMemoryManager* m_llvm_jitmm;
    llvm::Function* m_current_function;
    llvm::legacy::PassManager* m_llvm_module_passes;
    llvm::legacy::FunctionPassManager* m_llvm_func_passes;
    llvm::ExecutionEngine* m_llvm_exec;
    TargetISA m_target_isa = TargetISA::UNKNOWN;

    std::vector<llvm::BasicBlock*> m_return_block;      // stack for func call
    std::vector<llvm::BasicBlock*> m_loop_after_block;  // stack for break
    std::vector<llvm::BasicBlock*> m_loop_step_block;   // stack for continue

    llvm::Type* m_llvm_type_float;
    llvm::Type* m_llvm_type_double;
    llvm::Type* m_llvm_type_int;
    llvm::Type* m_llvm_type_int8;
    llvm::Type* m_llvm_type_int16;
    llvm::Type* m_llvm_type_addrint;
    llvm::Type* m_llvm_type_bool;
    llvm::Type* m_llvm_type_char;
    llvm::Type* m_llvm_type_longlong;
    llvm::Type* m_llvm_type_void;
    llvm::Type* m_llvm_type_triple;
    llvm::Type* m_llvm_type_matrix;
    llvm::PointerType* m_llvm_type_void_ptr;
    llvm::PointerType* m_llvm_type_ustring_ptr;
    llvm::PointerType* m_llvm_type_char_ptr;
    llvm::PointerType* m_llvm_type_bool_ptr;
    llvm::PointerType* m_llvm_type_int_ptr;
    llvm::PointerType* m_llvm_type_float_ptr;
    llvm::PointerType* m_llvm_type_longlong_ptr;
    llvm::PointerType* m_llvm_type_triple_ptr;
    llvm::PointerType* m_llvm_type_matrix_ptr;
    llvm::PointerType* m_llvm_type_double_ptr;

    int m_vector_width;
    llvm::Type* m_llvm_type_wide_float;
    llvm::Type* m_llvm_type_wide_double;
    llvm::Type* m_llvm_type_wide_int;
    llvm::Type* m_llvm_type_wide_bool;
    llvm::Type* m_llvm_type_wide_char;
    llvm::Type* m_llvm_type_wide_longlong;
    llvm::Type* m_llvm_type_wide_triple;
    llvm::Type* m_llvm_type_wide_matrix;
    llvm::Type* m_llvm_type_wide_void_ptr;
    llvm::Type* m_llvm_type_wide_ustring_ptr;
    llvm::PointerType* m_llvm_type_wide_char_ptr;
    llvm::PointerType* m_llvm_type_wide_int_ptr;
    llvm::PointerType* m_llvm_type_wide_bool_ptr;
    llvm::PointerType* m_llvm_type_wide_float_ptr;
    llvm::Type* m_llvm_type_native_mask;

    bool m_supports_masked_stores           = false;
    bool m_supports_llvm_bit_masks_natively = false;
    bool m_supports_avx512f                 = false;
    bool m_supports_avx2                    = false;
    bool m_supports_avx                     = false;

    // Profiling Info
    llvm::JITEventListener* mVTuneNotifier;

    // Debug Info
    llvm::DIFile* getOrCreateDebugFileFor(const std::string& file_name);
    llvm::DIScope* getCurrentDebugScope() const;
    llvm::DILocation* getCurrentInliningSite() const;

    llvm::DIBuilder* m_llvm_debug_builder;
    llvm::DICompileUnit* mDebugCU;
    std::vector<llvm::DIScope*> mLexicalBlocks;

    typedef std::unordered_map<std::string, llvm::DIFile*> FileByNameType;
    FileByNameType mDebugFileByName;
    std::vector<llvm::DILocation*> mInliningSites;
    llvm::DISubroutineType* mSubTypeForInlinedFunction;
    bool m_ModuleIsFinalized;
    bool m_ModuleIsPruned;

    // Additional tracking for masked conditionals, shaders, subroutines, and loop flow control
    struct MaskInfo {
        llvm::Value* mask;
        bool negate;
        int applied_return_mask_count;
    };
    std::vector<MaskInfo>
        m_mask_stack;  // stack for masks that all stores should use when enabled

    bool m_is_masking_required;
    int m_masked_exit_count = 0;

    struct MaskedLoopContext {
        llvm::Value* location_of_control_mask;
        llvm::Value* location_of_continue_mask;
        int break_count;
        int continue_count;
    };
    std::vector<MaskedLoopContext>
        m_masked_loop_stack;  // stack to track loop condition & break count

    void set_masking_required(bool required)
    {
        m_is_masking_required = required;
    }

    // For each pushed inlined function call, keep a slot for modified masks
    // to be stored from code blocks that might be branched over
    struct MaskedSubroutineContext {
        llvm::Value* location_of_mask;
        int return_count;
        // stack for masked returns to return to, maybe not the same the regular return block
        // because there could have been other active data lanes in the function
        // not traveling the masked conditional path which encounters a return
        std::vector<llvm::BasicBlock*> return_block_stack;
    };

    std::vector<MaskedSubroutineContext> m_masked_subroutine_stack;
    MaskedSubroutineContext& masked_function_context()
    {
        OSL_ASSERT(false == m_masked_subroutine_stack.empty());
        return m_masked_subroutine_stack.back();
    }
    const MaskedSubroutineContext& masked_function_context() const
    {
        OSL_ASSERT(false == m_masked_subroutine_stack.empty());
        return m_masked_subroutine_stack.back();
    }
    MaskedSubroutineContext& masked_shader_context()
    {
        OSL_ASSERT(false == m_masked_subroutine_stack.empty());
        return m_masked_subroutine_stack.front();
    }
    bool inside_of_inlined_masked_function_call() const
    {
        return (m_masked_subroutine_stack.size() > size_t(1));
    }

    MaskedLoopContext& masked_loop_context()
    {
        OSL_ASSERT(false == m_masked_loop_stack.empty());
        return m_masked_loop_stack.back();
    }
    const MaskedLoopContext& masked_loop_context() const
    {
        OSL_ASSERT(false == m_masked_loop_stack.empty());
        return m_masked_loop_stack.back();
    }
    bool inside_of_masked_loop() const
    {
        return (false == m_masked_loop_stack.empty());
    }

    llvm::Value* op_linearize_16x_indices(llvm::Value* wide_index);
    llvm::Value* op_linearize_8x_indices(llvm::Value* wide_index);
    std::array<llvm::Value*, 2> op_split_16x(llvm::Value* vector_val);
    std::array<llvm::Value*, 2> op_split_8x(llvm::Value* vector_val);
    std::array<llvm::Value*, 4> op_quarter_16x(llvm::Value* vector_val);
    llvm::Value* op_combine_8x_vectors(llvm::Value* half_vec_1,
                                       llvm::Value* half_vec_2);
    llvm::Value* op_combine_4x_vectors(llvm::Value* half_vec_1,
                                       llvm::Value* half_vec_2);
};



};  // namespace pvt
OSL_NAMESPACE_EXIT
