llvm-mirror/lib/IR/MDBuilder.cpp
Duncan P. N. Exon Smith 3d57886267 IR: Split Metadata from Value
Split `Metadata` away from the `Value` class hierarchy, as part of
PR21532.  Assembly and bitcode changes are in the wings, but this is the
bulk of the change for the IR C++ API.

I have a follow-up patch prepared for `clang`.  If this breaks other
sub-projects, I apologize in advance :(.  Help me compile it on Darwin
I'll try to fix it.  FWIW, the errors should be easy to fix, so it may
be simpler to just fix it yourself.

This breaks the build for all metadata-related code that's out-of-tree.
Rest assured the transition is mechanical and the compiler should catch
almost all of the problems.

Here's a quick guide for updating your code:

  - `Metadata` is the root of a class hierarchy with three main classes:
    `MDNode`, `MDString`, and `ValueAsMetadata`.  It is distinct from
    the `Value` class hierarchy.  It is typeless -- i.e., instances do
    *not* have a `Type`.

  - `MDNode`'s operands are all `Metadata *` (instead of `Value *`).

  - `TrackingVH<MDNode>` and `WeakVH` referring to metadata can be
    replaced with `TrackingMDNodeRef` and `TrackingMDRef`, respectively.

    If you're referring solely to resolved `MDNode`s -- post graph
    construction -- just use `MDNode*`.

  - `MDNode` (and the rest of `Metadata`) have only limited support for
    `replaceAllUsesWith()`.

    As long as an `MDNode` is pointing at a forward declaration -- the
    result of `MDNode::getTemporary()` -- it maintains a side map of its
    uses and can RAUW itself.  Once the forward declarations are fully
    resolved RAUW support is dropped on the ground.  This means that
    uniquing collisions on changing operands cause nodes to become
    "distinct".  (This already happened fairly commonly, whenever an
    operand went to null.)

    If you're constructing complex (non self-reference) `MDNode` cycles,
    you need to call `MDNode::resolveCycles()` on each node (or on a
    top-level node that somehow references all of the nodes).  Also,
    don't do that.  Metadata cycles (and the RAUW machinery needed to
    construct them) are expensive.

  - An `MDNode` can only refer to a `Constant` through a bridge called
    `ConstantAsMetadata` (one of the subclasses of `ValueAsMetadata`).

    As a side effect, accessing an operand of an `MDNode` that is known
    to be, e.g., `ConstantInt`, takes three steps: first, cast from
    `Metadata` to `ConstantAsMetadata`; second, extract the `Constant`;
    third, cast down to `ConstantInt`.

    The eventual goal is to introduce `MDInt`/`MDFloat`/etc. and have
    metadata schema owners transition away from using `Constant`s when
    the type isn't important (and they don't care about referring to
    `GlobalValue`s).

    In the meantime, I've added transitional API to the `mdconst`
    namespace that matches semantics with the old code, in order to
    avoid adding the error-prone three-step equivalent to every call
    site.  If your old code was:

        MDNode *N = foo();
        bar(isa             <ConstantInt>(N->getOperand(0)));
        baz(cast            <ConstantInt>(N->getOperand(1)));
        bak(cast_or_null    <ConstantInt>(N->getOperand(2)));
        bat(dyn_cast        <ConstantInt>(N->getOperand(3)));
        bay(dyn_cast_or_null<ConstantInt>(N->getOperand(4)));

    you can trivially match its semantics with:

        MDNode *N = foo();
        bar(mdconst::hasa               <ConstantInt>(N->getOperand(0)));
        baz(mdconst::extract            <ConstantInt>(N->getOperand(1)));
        bak(mdconst::extract_or_null    <ConstantInt>(N->getOperand(2)));
        bat(mdconst::dyn_extract        <ConstantInt>(N->getOperand(3)));
        bay(mdconst::dyn_extract_or_null<ConstantInt>(N->getOperand(4)));

    and when you transition your metadata schema to `MDInt`:

        MDNode *N = foo();
        bar(isa             <MDInt>(N->getOperand(0)));
        baz(cast            <MDInt>(N->getOperand(1)));
        bak(cast_or_null    <MDInt>(N->getOperand(2)));
        bat(dyn_cast        <MDInt>(N->getOperand(3)));
        bay(dyn_cast_or_null<MDInt>(N->getOperand(4)));

  - A `CallInst` -- specifically, intrinsic instructions -- can refer to
    metadata through a bridge called `MetadataAsValue`.  This is a
    subclass of `Value` where `getType()->isMetadataTy()`.

    `MetadataAsValue` is the *only* class that can legally refer to a
    `LocalAsMetadata`, which is a bridged form of non-`Constant` values
    like `Argument` and `Instruction`.  It can also refer to any other
    `Metadata` subclass.

(I'll break all your testcases in a follow-up commit, when I propagate
this change to assembly.)

llvm-svn: 223802
2014-12-09 18:38:53 +00:00

163 lines
6.0 KiB
C++

//===---- llvm/MDBuilder.cpp - Builder for LLVM metadata ------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the MDBuilder class, which is used as a convenient way to
// create LLVM metadata with a consistent and simplified interface.
//
//===----------------------------------------------------------------------===//
#include "llvm/IR/MDBuilder.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/Metadata.h"
using namespace llvm;
MDString *MDBuilder::createString(StringRef Str) {
return MDString::get(Context, Str);
}
ConstantAsMetadata *MDBuilder::createConstant(Constant *C) {
return ConstantAsMetadata::get(C);
}
MDNode *MDBuilder::createFPMath(float Accuracy) {
if (Accuracy == 0.0)
return nullptr;
assert(Accuracy > 0.0 && "Invalid fpmath accuracy!");
auto *Op =
createConstant(ConstantFP::get(Type::getFloatTy(Context), Accuracy));
return MDNode::get(Context, Op);
}
MDNode *MDBuilder::createBranchWeights(uint32_t TrueWeight,
uint32_t FalseWeight) {
uint32_t Weights[] = {TrueWeight, FalseWeight};
return createBranchWeights(Weights);
}
MDNode *MDBuilder::createBranchWeights(ArrayRef<uint32_t> Weights) {
assert(Weights.size() >= 2 && "Need at least two branch weights!");
SmallVector<Metadata *, 4> Vals(Weights.size() + 1);
Vals[0] = createString("branch_weights");
Type *Int32Ty = Type::getInt32Ty(Context);
for (unsigned i = 0, e = Weights.size(); i != e; ++i)
Vals[i + 1] = createConstant(ConstantInt::get(Int32Ty, Weights[i]));
return MDNode::get(Context, Vals);
}
MDNode *MDBuilder::createRange(const APInt &Lo, const APInt &Hi) {
assert(Lo.getBitWidth() == Hi.getBitWidth() && "Mismatched bitwidths!");
// If the range is everything then it is useless.
if (Hi == Lo)
return nullptr;
// Return the range [Lo, Hi).
Type *Ty = IntegerType::get(Context, Lo.getBitWidth());
Metadata *Range[2] = {createConstant(ConstantInt::get(Ty, Lo)),
createConstant(ConstantInt::get(Ty, Hi))};
return MDNode::get(Context, Range);
}
MDNode *MDBuilder::createAnonymousAARoot(StringRef Name, MDNode *Extra) {
// To ensure uniqueness the root node is self-referential.
MDNode *Dummy = MDNode::getTemporary(Context, None);
SmallVector<Metadata *, 3> Args(1, Dummy);
if (Extra)
Args.push_back(Extra);
if (!Name.empty())
Args.push_back(createString(Name));
MDNode *Root = MDNode::get(Context, Args);
// At this point we have
// !0 = metadata !{} <- dummy
// !1 = metadata !{metadata !0} <- root
// Replace the dummy operand with the root node itself and delete the dummy.
Root->replaceOperandWith(0, Root);
MDNode::deleteTemporary(Dummy);
// We now have
// !1 = metadata !{metadata !1} <- self-referential root
return Root;
}
MDNode *MDBuilder::createTBAARoot(StringRef Name) {
return MDNode::get(Context, createString(Name));
}
/// \brief Return metadata for a non-root TBAA node with the given name,
/// parent in the TBAA tree, and value for 'pointsToConstantMemory'.
MDNode *MDBuilder::createTBAANode(StringRef Name, MDNode *Parent,
bool isConstant) {
if (isConstant) {
Constant *Flags = ConstantInt::get(Type::getInt64Ty(Context), 1);
Metadata *Ops[3] = {createString(Name), Parent, createConstant(Flags)};
return MDNode::get(Context, Ops);
} else {
Metadata *Ops[2] = {createString(Name), Parent};
return MDNode::get(Context, Ops);
}
}
MDNode *MDBuilder::createAliasScopeDomain(StringRef Name) {
return MDNode::get(Context, createString(Name));
}
MDNode *MDBuilder::createAliasScope(StringRef Name, MDNode *Domain) {
Metadata *Ops[2] = {createString(Name), Domain};
return MDNode::get(Context, Ops);
}
/// \brief Return metadata for a tbaa.struct node with the given
/// struct field descriptions.
MDNode *MDBuilder::createTBAAStructNode(ArrayRef<TBAAStructField> Fields) {
SmallVector<Metadata *, 4> Vals(Fields.size() * 3);
Type *Int64 = Type::getInt64Ty(Context);
for (unsigned i = 0, e = Fields.size(); i != e; ++i) {
Vals[i * 3 + 0] = createConstant(ConstantInt::get(Int64, Fields[i].Offset));
Vals[i * 3 + 1] = createConstant(ConstantInt::get(Int64, Fields[i].Size));
Vals[i * 3 + 2] = Fields[i].TBAA;
}
return MDNode::get(Context, Vals);
}
/// \brief Return metadata for a TBAA struct node in the type DAG
/// with the given name, a list of pairs (offset, field type in the type DAG).
MDNode *MDBuilder::createTBAAStructTypeNode(
StringRef Name, ArrayRef<std::pair<MDNode *, uint64_t>> Fields) {
SmallVector<Metadata *, 4> Ops(Fields.size() * 2 + 1);
Type *Int64 = Type::getInt64Ty(Context);
Ops[0] = createString(Name);
for (unsigned i = 0, e = Fields.size(); i != e; ++i) {
Ops[i * 2 + 1] = Fields[i].first;
Ops[i * 2 + 2] = createConstant(ConstantInt::get(Int64, Fields[i].second));
}
return MDNode::get(Context, Ops);
}
/// \brief Return metadata for a TBAA scalar type node with the
/// given name, an offset and a parent in the TBAA type DAG.
MDNode *MDBuilder::createTBAAScalarTypeNode(StringRef Name, MDNode *Parent,
uint64_t Offset) {
ConstantInt *Off = ConstantInt::get(Type::getInt64Ty(Context), Offset);
Metadata *Ops[3] = {createString(Name), Parent, createConstant(Off)};
return MDNode::get(Context, Ops);
}
/// \brief Return metadata for a TBAA tag node with the given
/// base type, access type and offset relative to the base type.
MDNode *MDBuilder::createTBAAStructTagNode(MDNode *BaseType, MDNode *AccessType,
uint64_t Offset) {
Type *Int64 = Type::getInt64Ty(Context);
Metadata *Ops[3] = {BaseType, AccessType,
createConstant(ConstantInt::get(Int64, Offset))};
return MDNode::get(Context, Ops);
}