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llvm-mirror/include/llvm/IR/Argument.h
Reid Kleckner 73e1a13fdc [IR] De-virtualize ~Value to save a vptr
Summary:
Implements PR889

Removing the virtual table pointer from Value saves 1% of RSS when doing
LTO of llc on Linux. The impact on time was positive, but too noisy to
conclusively say that performance improved. Here is a link to the
spreadsheet with the original data:

https://docs.google.com/spreadsheets/d/1F4FHir0qYnV0MEp2sYYp_BuvnJgWlWPhWOwZ6LbW7W4/edit?usp=sharing

This change makes it invalid to directly delete a Value, User, or
Instruction pointer. Instead, such code can be rewritten to a null check
and a call Value::deleteValue(). Value objects tend to have their
lifetimes managed through iplist, so for the most part, this isn't a big
deal.  However, there are some places where LLVM deletes values, and
those places had to be migrated to deleteValue.  I have also created
llvm::unique_value, which has a custom deleter, so it can be used in
place of std::unique_ptr<Value>.

I had to add the "DerivedUser" Deleter escape hatch for MemorySSA, which
derives from User outside of lib/IR. Code in IR cannot include MemorySSA
headers or call the MemoryAccess object destructors without introducing
a circular dependency, so we need some level of indirection.
Unfortunately, no class derived from User may have any virtual methods,
because adding a virtual method would break User::getHungOffOperands(),
which assumes that it can find the use list immediately prior to the
User object. I've added a static_assert to the appropriate OperandTraits
templates to help people avoid this trap.

Reviewers: chandlerc, mehdi_amini, pete, dberlin, george.burgess.iv

Reviewed By: chandlerc

Subscribers: krytarowski, eraman, george.burgess.iv, mzolotukhin, Prazek, nlewycky, hans, inglorion, pcc, tejohnson, dberlin, llvm-commits

Differential Revision: https://reviews.llvm.org/D31261

llvm-svn: 303362
2017-05-18 17:24:10 +00:00

131 lines
4.2 KiB
C++

//===-- llvm/Argument.h - Definition of the Argument class ------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file declares the Argument class.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_IR_ARGUMENT_H
#define LLVM_IR_ARGUMENT_H
#include "llvm/ADT/Twine.h"
#include "llvm/ADT/ilist_node.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/Value.h"
namespace llvm {
/// This class represents an incoming formal argument to a Function. A formal
/// argument, since it is ``formal'', does not contain an actual value but
/// instead represents the type, argument number, and attributes of an argument
/// for a specific function. When used in the body of said function, the
/// argument of course represents the value of the actual argument that the
/// function was called with.
class Argument final : public Value {
Function *Parent;
unsigned ArgNo;
friend class Function;
void setParent(Function *parent);
public:
/// Argument constructor.
explicit Argument(Type *Ty, const Twine &Name = "", Function *F = nullptr,
unsigned ArgNo = 0);
inline const Function *getParent() const { return Parent; }
inline Function *getParent() { return Parent; }
/// Return the index of this formal argument in its containing function.
///
/// For example in "void foo(int a, float b)" a is 0 and b is 1.
unsigned getArgNo() const {
assert(Parent && "can't get number of unparented arg");
return ArgNo;
}
/// Return true if this argument has the nonnull attribute. Also returns true
/// if at least one byte is known to be dereferenceable and the pointer is in
/// addrspace(0).
bool hasNonNullAttr() const;
/// If this argument has the dereferenceable attribute, return the number of
/// bytes known to be dereferenceable. Otherwise, zero is returned.
uint64_t getDereferenceableBytes() const;
/// If this argument has the dereferenceable_or_null attribute, return the
/// number of bytes known to be dereferenceable. Otherwise, zero is returned.
uint64_t getDereferenceableOrNullBytes() const;
/// Return true if this argument has the byval attribute.
bool hasByValAttr() const;
/// Return true if this argument has the swiftself attribute.
bool hasSwiftSelfAttr() const;
/// Return true if this argument has the swifterror attribute.
bool hasSwiftErrorAttr() const;
/// Return true if this argument has the byval attribute or inalloca
/// attribute. These attributes represent arguments being passed by value.
bool hasByValOrInAllocaAttr() const;
/// If this is a byval or inalloca argument, return its alignment.
unsigned getParamAlignment() const;
/// Return true if this argument has the nest attribute.
bool hasNestAttr() const;
/// Return true if this argument has the noalias attribute.
bool hasNoAliasAttr() const;
/// Return true if this argument has the nocapture attribute.
bool hasNoCaptureAttr() const;
/// Return true if this argument has the sret attribute.
bool hasStructRetAttr() const;
/// Return true if this argument has the returned attribute.
bool hasReturnedAttr() const;
/// Return true if this argument has the readonly or readnone attribute.
bool onlyReadsMemory() const;
/// Return true if this argument has the inalloca attribute.
bool hasInAllocaAttr() const;
/// Return true if this argument has the zext attribute.
bool hasZExtAttr() const;
/// Return true if this argument has the sext attribute.
bool hasSExtAttr() const;
/// Add attributes to an argument.
void addAttrs(AttrBuilder &B);
void addAttr(Attribute::AttrKind Kind);
void addAttr(Attribute Attr);
/// Remove attributes from an argument.
void removeAttr(Attribute::AttrKind Kind);
/// Check if an argument has a given attribute.
bool hasAttribute(Attribute::AttrKind Kind) const;
/// Method for support type inquiry through isa, cast, and dyn_cast.
static inline bool classof(const Value *V) {
return V->getValueID() == ArgumentVal;
}
};
} // End llvm namespace
#endif