#ifndef HALIDE_CODEGEN_LLVM_H
#define HALIDE_CODEGEN_LLVM_H
/** \file
*
* Defines the base-class for all architecture-specific code
* generators that use llvm.
*/
namespace llvm {
class Value;
class Module;
class Function;
#if LLVM_VERSION >= 39
class IRBuilderDefaultInserter;
#else
template<bool> class IRBuilderDefaultInserter;
#endif
class ConstantFolder;
#if LLVM_VERSION >= 39
template<typename, typename> class IRBuilder;
#else
template<bool, typename, typename> class IRBuilder;
#endif
class LLVMContext;
class Type;
class StructType;
class Instruction;
class CallInst;
class ExecutionEngine;
class AllocaInst;
class Constant;
class Triple;
class MDNode;
class NamedMDNode;
class DataLayout;
class BasicBlock;
class GlobalVariable;
}
#include <map>
#include <string>
#include <vector>
#include <memory>
#include "IRVisitor.h"
#include "Module.h"
#include "Scope.h"
#include "ModulusRemainder.h"
#include "Target.h"
namespace Halide {
namespace Internal {
/** A code generator abstract base class. Actual code generators
* (e.g. CodeGen_X86) inherit from this. This class is responsible
* for taking a Halide Stmt and producing llvm bitcode, machine
* code in an object file, or machine code accessible through a
* function pointer.
*/
class CodeGen_LLVM : public IRVisitor {
public:
/** Create an instance of CodeGen_LLVM suitable for the target. */
static CodeGen_LLVM *new_for_target(const Target &target,
llvm::LLVMContext &context);
virtual ~CodeGen_LLVM();
/** Takes a halide Module and compiles it to an llvm Module. */
virtual std::unique_ptr<llvm::Module> compile(const Module &module);
/** The target we're generating code for */
const Target &get_target() const { return target; }
/** Tell the code generator which LLVM context to use. */
void set_context(llvm::LLVMContext &context);
/** Initialize internal llvm state for the enabled targets. */
static void initialize_llvm();
protected:
CodeGen_LLVM(Target t);
/** Compile a specific halide declaration into the llvm Module. */
// @{
virtual void compile_func(const LoweredFunc &func, const std::string &simple_name, const std::string &extern_name);
virtual void compile_buffer(const Buffer<> &buffer);
// @}
/** Helper functions for compiling Halide functions to llvm
* functions. begin_func performs all the work necessary to begin
* generating code for a function with a given argument list with
* the IRBuilder. A call to begin_func should be a followed by a
* call to end_func with the same arguments, to generate the
* appropriate cleanup code. */
// @{
virtual void begin_func(LoweredFunc::LinkageType linkage, const std::string &simple_name,
const std::string &extern_name, const std::vector<LoweredArgument> &args);
virtual void end_func(const std::vector<LoweredArgument> &args);
// @}
/** What should be passed as -mcpu, -mattrs, and related for
* compilation. The architecture-specific code generator should
* define these. */
// @{
virtual std::string mcpu() const = 0;
virtual std::string mattrs() const = 0;
virtual bool use_soft_float_abi() const = 0;
// @}
/** Should indexing math be promoted to 64-bit on platforms with
* 64-bit pointers? */
virtual bool promote_indices() const {return true;}
/** What's the natural vector bit-width to use for loads, stores, etc. */
virtual int native_vector_bits() const = 0;
/** State needed by llvm for code generation, including the
* current module, function, context, builder, and most recently
* generated llvm value. */
//@{
static bool llvm_initialized;
static bool llvm_X86_enabled;
static bool llvm_ARM_enabled;
static bool llvm_Hexagon_enabled;
static bool llvm_AArch64_enabled;
static bool llvm_NVPTX_enabled;
static bool llvm_Mips_enabled;
static bool llvm_PowerPC_enabled;
const Module *input_module;
std::unique_ptr<llvm::Module> module;
llvm::Function *function;
llvm::LLVMContext *context;
#if LLVM_VERSION >= 39
llvm::IRBuilder<llvm::ConstantFolder, llvm::IRBuilderDefaultInserter> *builder;
#else
llvm::IRBuilder<true, llvm::ConstantFolder, llvm::IRBuilderDefaultInserter<true>> *builder;
#endif
llvm::Value *value;
llvm::MDNode *very_likely_branch;
std::vector<LoweredArgument> current_function_args;
//@}
/** The target we're generating code for */
Halide::Target target;
/** Grab all the context specific internal state. */
virtual void init_context();
/** Initialize the CodeGen_LLVM internal state to compile a fresh
* module. This allows reuse of one CodeGen_LLVM object to compiled
* multiple related modules (e.g. multiple device kernels). */
virtual void init_module();
/** Add external_code entries to llvm module. */
void add_external_code(const Module &halide_module);
/** Run all of llvm's optimization passes on the module. */
void optimize_module();
/** Add an entry to the symbol table, hiding previous entries with
* the same name. Call this when new values come into scope. */
void sym_push(const std::string &name, llvm::Value *value);
/** Remove an entry for the symbol table, revealing any previous
* entries with the same name. Call this when values go out of
* scope. */
void sym_pop(const std::string &name);
/** Fetch an entry from the symbol table. If the symbol is not
* found, it either errors out (if the second arg is true), or
* returns nullptr. */
llvm::Value* sym_get(const std::string &name,
bool must_succeed = true) const;
/** Test if an item exists in the symbol table. */
bool sym_exists(const std::string &name) const;
/** Some useful llvm types */
// @{
llvm::Type *void_t, *i1_t, *i8_t, *i16_t, *i32_t, *i64_t, *f16_t, *f32_t, *f64_t;
llvm::StructType *buffer_t_type,
*type_t_type,
*dimension_t_type,
*metadata_t_type,
*argument_t_type,
*scalar_value_t_type,
*device_interface_t_type;
// @}
/** Some useful llvm types for subclasses */
// @{
llvm::Type *i8x8, *i8x16, *i8x32;
llvm::Type *i16x4, *i16x8, *i16x16;
llvm::Type *i32x2, *i32x4, *i32x8;
llvm::Type *i64x2, *i64x4;
llvm::Type *f32x2, *f32x4, *f32x8;
llvm::Type *f64x2, *f64x4;
// @}
/** Some wildcard variables used for peephole optimizations in
* subclasses */
// @{
Expr wild_i8x8, wild_i16x4, wild_i32x2; // 64-bit signed ints
Expr wild_u8x8, wild_u16x4, wild_u32x2; // 64-bit unsigned ints
Expr wild_i8x16, wild_i16x8, wild_i32x4, wild_i64x2; // 128-bit signed ints
Expr wild_u8x16, wild_u16x8, wild_u32x4, wild_u64x2; // 128-bit unsigned ints
Expr wild_i8x32, wild_i16x16, wild_i32x8, wild_i64x4; // 256-bit signed ints
Expr wild_u8x32, wild_u16x16, wild_u32x8, wild_u64x4; // 256-bit unsigned ints
Expr wild_f32x2; // 64-bit floats
Expr wild_f32x4, wild_f64x2; // 128-bit floats
Expr wild_f32x8, wild_f64x4; // 256-bit floats
// Wildcards for a varying number of lanes.
Expr wild_u1x_, wild_i8x_, wild_u8x_, wild_i16x_, wild_u16x_;
Expr wild_i32x_, wild_u32x_, wild_i64x_, wild_u64x_;
Expr wild_f32x_, wild_f64x_;
Expr min_i8, max_i8, max_u8;
Expr min_i16, max_i16, max_u16;
Expr min_i32, max_i32, max_u32;
Expr min_i64, max_i64, max_u64;
Expr min_f32, max_f32, min_f64, max_f64;
// @}
/** Emit code that evaluates an expression, and return the llvm
* representation of the result of the expression. */
llvm::Value *codegen(Expr);
/** Emit code that runs a statement. */
void codegen(Stmt);
/** Codegen a vector Expr by codegenning each lane and combining. */
void scalarize(Expr);
/** Some destructors should always be called. Others should only
* be called if the pipeline is exiting with an error code. */
enum DestructorType {Always, OnError, OnSuccess};
/* Call this at the location of object creation to register how an
* object should be destroyed. This does three things:
* 1) Emits code here that puts the object in a unique
* null-initialized stack slot
* 2) Adds an instruction to the destructor block that calls the
* destructor on that stack slot if it's not null.
* 3) Returns that stack slot, so you can neuter the destructor
* (by storing null to the stack slot) or destroy the object early
* (by calling trigger_destructor).
*/
llvm::Value *register_destructor(llvm::Function *destructor_fn, llvm::Value *obj, DestructorType when);
/** Call a destructor early. Pass in the value returned by register destructor. */
void trigger_destructor(llvm::Function *destructor_fn, llvm::Value *stack_slot);
/** Retrieves the block containing the error handling
* code. Creates it if it doesn't already exist for this
* function. */
llvm::BasicBlock *get_destructor_block();
/** Codegen an assertion. If false, returns the error code (if not
* null), or evaluates and returns the message, which must be an
* Int(32) expression. */
// @{
void create_assertion(llvm::Value *condition, Expr message, llvm::Value *error_code = nullptr);
// @}
/** Return the the pipeline with the given error code. Will run
* the destructor block. */
void return_with_error_code(llvm::Value *error_code);
/** Put a string constant in the module as a global variable and return a pointer to it. */
llvm::Constant *create_string_constant(const std::string &str);
/** Put a binary blob in the module as a global variable and return a pointer to it. */
llvm::Constant *create_binary_blob(const std::vector<char> &data, const std::string &name, bool constant = true);
/** Widen an llvm scalar into an llvm vector with the given number of lanes. */
llvm::Value *create_broadcast(llvm::Value *, int lanes);
/** Generate a pointer into a named buffer at a given index, of a
* given type. The index counts according to the scalar type of
* the type passed in. */
// @{
llvm::Value *codegen_buffer_pointer(std::string buffer, Type type, llvm::Value *index);
llvm::Value *codegen_buffer_pointer(std::string buffer, Type type, Expr index);
llvm::Value *codegen_buffer_pointer(llvm::Value *base_address, Type type, Expr index);
llvm::Value *codegen_buffer_pointer(llvm::Value *base_address, Type type, llvm::Value *index);
// @}
/** Turn a Halide Type into an llvm::Value representing a constant halide_type_t */
llvm::Value *make_halide_type_t(Type);
/** Mark a load or store with type-based-alias-analysis metadata
* so that llvm knows it can reorder loads and stores across
* different buffers */
void add_tbaa_metadata(llvm::Instruction *inst, std::string buffer, Expr index);
/** Get a unique name for the actual block of memory that an
* allocate node uses. Used so that alias analysis understands
* when multiple Allocate nodes shared the same memory. */
virtual std::string get_allocation_name(const std::string &n) {return n;}
/** Helpers for implementing fast integer division. */
// @{
// Compute high_half(a*b) >> shr. Note that this is a shift in
// addition to the implicit shift due to taking the upper half of
// the multiply result.
virtual Expr mulhi_shr(Expr a, Expr b, int shr);
// Compute (a+b)/2, assuming a < b.
virtual Expr sorted_avg(Expr a, Expr b);
// @}
using IRVisitor::visit;
/** Generate code for various IR nodes. These can be overridden by
* architecture-specific code to perform peephole
* optimizations. The result of each is stored in \ref value */
// @{
virtual void visit(const IntImm *);
virtual void visit(const UIntImm *);
virtual void visit(const FloatImm *);
virtual void visit(const StringImm *);
virtual void visit(const Cast *);
virtual void visit(const Variable *);
virtual void visit(const Add *);
virtual void visit(const Sub *);
virtual void visit(const Mul *);
virtual void visit(const Div *);
virtual void visit(const Mod *);
virtual void visit(const Min *);
virtual void visit(const Max *);
virtual void visit(const EQ *);
virtual void visit(const NE *);
virtual void visit(const LT *);
virtual void visit(const LE *);
virtual void visit(const GT *);
virtual void visit(const GE *);
virtual void visit(const And *);
virtual void visit(const Or *);
virtual void visit(const Not *);
virtual void visit(const Select *);
virtual void visit(const Load *);
virtual void visit(const Ramp *);
virtual void visit(const Broadcast *);
virtual void visit(const Call *);
virtual void visit(const Let *);
virtual void visit(const LetStmt *);
virtual void visit(const AssertStmt *);
virtual void visit(const ProducerConsumer *);
virtual void visit(const For *);
virtual void visit(const Store *);
virtual void visit(const Block *);
virtual void visit(const IfThenElse *);
virtual void visit(const Evaluate *);
virtual void visit(const Shuffle *);
virtual void visit(const Prefetch *);
// @}
/** Generate code for an allocate node. It has no default
* implementation - it must be handled in an architecture-specific
* way. */
virtual void visit(const Allocate *) = 0;
/** Generate code for a free node. It has no default
* implementation and must be handled in an architecture-specific
* way. */
virtual void visit(const Free *) = 0;
/** These IR nodes should have been removed during
* lowering. CodeGen_LLVM will error out if they are present */
// @{
virtual void visit(const Provide *);
virtual void visit(const Realize *);
// @}
/** If we have to bail out of a pipeline midway, this should
* inject the appropriate target-specific cleanup code. */
virtual void prepare_for_early_exit() {}
/** Get the llvm type equivalent to the given halide type in the
* current context. */
llvm::Type *llvm_type_of(Type);
/** Perform an alloca at the function entrypoint. Will be cleaned
* on function exit. */
llvm::Value *create_alloca_at_entry(llvm::Type *type, int n,
bool zero_initialize = false,
const std::string &name = "");
/** Which buffers came in from the outside world (and so we can't
* guarantee their alignment) */
std::set<std::string> external_buffer;
/** The user_context argument. May be a constant null if the
* function is being compiled without a user context. */
llvm::Value *get_user_context() const;
/** Implementation of the intrinsic call to
* interleave_vectors. This implementation allows for interleaving
* an arbitrary number of vectors.*/
virtual llvm::Value *interleave_vectors(const std::vector<llvm::Value *> &);
/** Generate a call to a vector intrinsic or runtime inlined
* function. The arguments are sliced up into vectors of the width
* given by 'intrin_lanes', the intrinsic is called on each
* piece, then the results (if any) are concatenated back together
* into the original type 't'. For the version that takes an
* llvm::Type *, the type may be void, so the vector width of the
* arguments must be specified explicitly as
* 'called_lanes'. */
// @{
llvm::Value *call_intrin(Type t, int intrin_lanes,
const std::string &name, std::vector<Expr>);
llvm::Value *call_intrin(llvm::Type *t, int intrin_lanes,
const std::string &name, std::vector<llvm::Value *>);
// @}
/** Take a slice of lanes out of an llvm vector. Pads with undefs
* if you ask for more lanes than the vector has. */
virtual llvm::Value *slice_vector(llvm::Value *vec, int start, int extent);
/** Concatenate a bunch of llvm vectors. Must be of the same type. */
virtual llvm::Value *concat_vectors(const std::vector<llvm::Value *> &);
/** Create an LLVM shuffle vectors instruction. */
virtual llvm::Value *shuffle_vectors(llvm::Value *a, llvm::Value *b,
const std::vector<int> &indices);
/** Shorthand for shuffling a vector with an undef vector. */
llvm::Value *shuffle_vectors(llvm::Value *v, const std::vector<int> &indices);
/** Go looking for a vector version of a runtime function. Will
* return the best match. Matches in the following order:
*
* 1) The requested vector width.
*
* 2) The width which is the smallest power of two
* greater than or equal to the vector width.
*
* 3) All the factors of 2) greater than one, in decreasing order.
*
* 4) The smallest power of two not yet tried.
*
* So for a 5-wide vector, it tries: 5, 8, 4, 2, 16.
*
* If there's no match, returns (nullptr, 0).
*/
std::pair<llvm::Function *, int> find_vector_runtime_function(const std::string &name, int lanes);
/** Get the result of modulus-remainder analysis for a given expr. */
ModulusRemainder get_alignment_info(Expr e);
private:
/** All the values in scope at the current code location during
* codegen. Use sym_push and sym_pop to access. */
Scope<llvm::Value *> symbol_table;
/** Alignment info for Int(32) variables in scope. */
Scope<ModulusRemainder> alignment_info;
/** String constants already emitted to the module. Tracked to
* prevent emitting the same string many times. */
std::map<std::string, llvm::Constant *> string_constants;
/** A basic block to branch to on error that triggers all
* destructors. As destructors are registered, code gets added
* to this block. */
llvm::BasicBlock *destructor_block;
/** Embed an instance of halide_filter_metadata_t in the code, using
* the given name (by convention, this should be ${FUNCTIONNAME}_metadata)
* as extern "C" linkage. Note that the return value is a function-returning-
* pointer-to-constant-data.
*/
llvm::Function* embed_metadata_getter(const std::string &metadata_getter_name,
const std::string &function_name, const std::vector<LoweredArgument> &args);
/** Embed a constant expression as a global variable. */
llvm::Constant *embed_constant_expr(Expr e);
llvm::Function *add_argv_wrapper(const std::string &name);
llvm::Value *codegen_dense_vector_load(const Load *load, llvm::Value *vpred = nullptr);
virtual void codegen_predicated_vector_load(const Load *op);
virtual void codegen_predicated_vector_store(const Store *op);
};
}
/** Given a Halide module, generate an llvm::Module. */
EXPORT std::unique_ptr<llvm::Module> codegen_llvm(const Module &module,
llvm::LLVMContext &context);
}
#endif