[llvm] r248453 - [IR] Teach `llvm::User` to co-allocate a descriptor.
Sanjoy Das via llvm-commits
llvm-commits at lists.llvm.org
Wed Sep 23 18:00:49 PDT 2015
Author: sanjoy
Date: Wed Sep 23 20:00:49 2015
New Revision: 248453
URL: http://llvm.org/viewvc/llvm-project?rev=248453&view=rev
Log:
[IR] Teach `llvm::User` to co-allocate a descriptor.
Summary:
With this change, subclasses of `llvm::User` will be able to co-allocate
a variable number of bytes (called a "descriptor") with the `llvm::User`
instance. The co-allocated descriptor can later be accessed using
`llvm::User::getDescriptor`. This will be used in later changes to
implement operand bundles.
This change steals one bit from `NumUserOperands`, but given that it is
still 28 bits wide I don't think this will be a practical issue.
This change does not allow allocating hung off uses with descriptors.
This only for simplicity, not for any fundamental reason; and we can
easily add this functionality later if needed.
Reviewers: reames, chandlerc, dexonsmith, kmod, majnemer, pete, JosephTremoulet
Subscribers: pete, sanjoy, llvm-commits
Differential Revision: http://reviews.llvm.org/D12455
Modified:
llvm/trunk/include/llvm/IR/User.h
llvm/trunk/include/llvm/IR/Value.h
llvm/trunk/lib/IR/User.cpp
Modified: llvm/trunk/include/llvm/IR/User.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/User.h?rev=248453&r1=248452&r2=248453&view=diff
==============================================================================
--- llvm/trunk/include/llvm/IR/User.h (original)
+++ llvm/trunk/include/llvm/IR/User.h Wed Sep 23 20:00:49 2015
@@ -19,6 +19,7 @@
#ifndef LLVM_IR_USER_H
#define LLVM_IR_USER_H
+#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/iterator.h"
#include "llvm/ADT/iterator_range.h"
#include "llvm/IR/Value.h"
@@ -39,6 +40,9 @@ class User : public Value {
friend struct HungoffOperandTraits;
virtual void anchor();
+ LLVM_ATTRIBUTE_ALWAYS_INLINE inline static void *
+ allocateFixedOperandUser(size_t, unsigned, unsigned);
+
protected:
/// Allocate a User with an operand pointer co-allocated.
///
@@ -51,6 +55,16 @@ protected:
/// This is used for subclasses which have a fixed number of operands.
void *operator new(size_t Size, unsigned Us);
+ /// Allocate a User with the operands co-allocated. If DescBytes is non-zero
+ /// then allocate an additional DescBytes bytes before the operands. These
+ /// bytes can be accessed by calling getDescriptor.
+ ///
+ /// DescBytes needs to be divisible by sizeof(void *). The allocated
+ /// descriptor, if any, is aligned to sizeof(void *) bytes.
+ ///
+ /// This is used for subclasses which have a fixed number of operands.
+ void *operator new(size_t Size, unsigned Us, unsigned DescBytes);
+
User(Type *ty, unsigned vty, Use *OpList, unsigned NumOps)
: Value(ty, vty) {
assert(NumOps < (1u << NumUserOperandsBits) && "Too many operands");
@@ -137,6 +151,12 @@ public:
unsigned getNumOperands() const { return NumUserOperands; }
+ /// Returns the descriptor co-allocated with this User instance.
+ ArrayRef<const uint8_t> getDescriptor() const;
+
+ /// Returns the descriptor co-allocated with this User instance.
+ MutableArrayRef<uint8_t> getDescriptor();
+
/// Set the number of operands on a GlobalVariable.
///
/// GlobalVariable always allocates space for a single operands, but
Modified: llvm/trunk/include/llvm/IR/Value.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/Value.h?rev=248453&r1=248452&r2=248453&view=diff
==============================================================================
--- llvm/trunk/include/llvm/IR/Value.h (original)
+++ llvm/trunk/include/llvm/IR/Value.h Wed Sep 23 20:00:49 2015
@@ -104,12 +104,13 @@ protected:
///
/// Note, this should *NOT* be used directly by any class other than User.
/// User uses this value to find the Use list.
- enum : unsigned { NumUserOperandsBits = 29 };
+ enum : unsigned { NumUserOperandsBits = 28 };
unsigned NumUserOperands : NumUserOperandsBits;
bool IsUsedByMD : 1;
bool HasName : 1;
bool HasHungOffUses : 1;
+ bool HasDescriptor : 1;
private:
template <typename UseT> // UseT == 'Use' or 'const Use'
Modified: llvm/trunk/lib/IR/User.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/User.cpp?rev=248453&r1=248452&r2=248453&view=diff
==============================================================================
--- llvm/trunk/lib/IR/User.cpp (original)
+++ llvm/trunk/lib/IR/User.cpp Wed Sep 23 20:00:49 2015
@@ -87,22 +87,70 @@ void User::growHungoffUses(unsigned NewN
Use::zap(OldOps, OldOps + OldNumUses, true);
}
+
+// This is a private struct used by `User` to track the co-allocated descriptor
+// section.
+struct DescriptorInfo {
+ intptr_t SizeInBytes;
+};
+
+ArrayRef<const uint8_t> User::getDescriptor() const {
+ auto MutableARef = const_cast<User *>(this)->getDescriptor();
+ return {MutableARef.begin(), MutableARef.end()};
+}
+
+MutableArrayRef<uint8_t> User::getDescriptor() {
+ assert(HasDescriptor && "Don't call otherwise!");
+ assert(!HasHungOffUses && "Invariant!");
+
+ auto *DI = reinterpret_cast<DescriptorInfo *>(getIntrusiveOperands()) - 1;
+ assert(DI->SizeInBytes != 0 && "Should not have had a descriptor otherwise!");
+
+ return MutableArrayRef<uint8_t>(
+ reinterpret_cast<uint8_t *>(DI) - DI->SizeInBytes, DI->SizeInBytes);
+}
+
//===----------------------------------------------------------------------===//
// User operator new Implementations
//===----------------------------------------------------------------------===//
-void *User::operator new(size_t Size, unsigned Us) {
+void *User::allocateFixedOperandUser(size_t Size, unsigned Us,
+ unsigned DescBytes) {
assert(Us < (1u << NumUserOperandsBits) && "Too many operands");
- void *Storage = ::operator new(Size + sizeof(Use) * Us);
- Use *Start = static_cast<Use*>(Storage);
+
+ static_assert(sizeof(DescriptorInfo) % sizeof(void *) == 0, "Required below");
+
+ unsigned DescBytesToAllocate =
+ DescBytes == 0 ? 0 : (DescBytes + sizeof(DescriptorInfo));
+ assert(DescBytesToAllocate % sizeof(void *) == 0 &&
+ "We need this to satisfy alignment constraints for Uses");
+
+ uint8_t *Storage = static_cast<uint8_t *>(
+ ::operator new(Size + sizeof(Use) * Us + DescBytesToAllocate));
+ Use *Start = reinterpret_cast<Use *>(Storage + DescBytesToAllocate);
Use *End = Start + Us;
User *Obj = reinterpret_cast<User*>(End);
Obj->NumUserOperands = Us;
Obj->HasHungOffUses = false;
+ Obj->HasDescriptor = DescBytes != 0;
Use::initTags(Start, End);
+
+ if (DescBytes != 0) {
+ auto *DescInfo = reinterpret_cast<DescriptorInfo *>(Storage + DescBytes);
+ DescInfo->SizeInBytes = DescBytes;
+ }
+
return Obj;
}
+void *User::operator new(size_t Size, unsigned Us) {
+ return allocateFixedOperandUser(Size, Us, 0);
+}
+
+void *User::operator new(size_t Size, unsigned Us, unsigned DescBytes) {
+ return allocateFixedOperandUser(Size, Us, DescBytes);
+}
+
void *User::operator new(size_t Size) {
// Allocate space for a single Use*
void *Storage = ::operator new(Size + sizeof(Use *));
@@ -110,6 +158,7 @@ void *User::operator new(size_t Size) {
User *Obj = reinterpret_cast<User *>(HungOffOperandList + 1);
Obj->NumUserOperands = 0;
Obj->HasHungOffUses = true;
+ Obj->HasDescriptor = false;
*HungOffOperandList = nullptr;
return Obj;
}
@@ -123,11 +172,20 @@ void User::operator delete(void *Usr) {
// use a Use[] allocated prior to the user.
User *Obj = static_cast<User *>(Usr);
if (Obj->HasHungOffUses) {
+ assert(!Obj->HasDescriptor && "not supported!");
+
Use **HungOffOperandList = static_cast<Use **>(Usr) - 1;
// drop the hung off uses.
Use::zap(*HungOffOperandList, *HungOffOperandList + Obj->NumUserOperands,
/* Delete */ true);
::operator delete(HungOffOperandList);
+ } else if (Obj->HasDescriptor) {
+ Use *UseBegin = static_cast<Use *>(Usr) - Obj->NumUserOperands;
+ Use::zap(UseBegin, UseBegin + Obj->NumUserOperands, /* Delete */ false);
+
+ auto *DI = reinterpret_cast<DescriptorInfo *>(UseBegin) - 1;
+ uint8_t *Storage = reinterpret_cast<uint8_t *>(DI) - DI->SizeInBytes;
+ ::operator delete(Storage);
} else {
Use *Storage = static_cast<Use *>(Usr) - Obj->NumUserOperands;
Use::zap(Storage, Storage + Obj->NumUserOperands,
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