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
diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index 2e67011..0de929e 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -737,44 +737,79 @@
return Flags;
}
+static void WriteValueAsMetadataImpl(const ValueAsMetadata *MD,
+ const ValueEnumerator &VE,
+ BitstreamWriter &Stream,
+ SmallVectorImpl<uint64_t> &Record,
+ unsigned Code) {
+ // Mimic an MDNode with a value as one operand.
+ Value *V = MD->getValue();
+ Record.push_back(VE.getTypeID(V->getType()));
+ Record.push_back(VE.getValueID(V));
+ Stream.EmitRecord(Code, Record, 0);
+ Record.clear();
+}
+
+static void WriteLocalAsMetadata(const LocalAsMetadata *MD,
+ const ValueEnumerator &VE,
+ BitstreamWriter &Stream,
+ SmallVectorImpl<uint64_t> &Record) {
+ WriteValueAsMetadataImpl(MD, VE, Stream, Record, bitc::METADATA_FN_NODE);
+}
+
+static void WriteConstantAsMetadata(const ConstantAsMetadata *MD,
+ const ValueEnumerator &VE,
+ BitstreamWriter &Stream,
+ SmallVectorImpl<uint64_t> &Record) {
+ WriteValueAsMetadataImpl(MD, VE, Stream, Record, bitc::METADATA_NODE);
+}
+
static void WriteMDNode(const MDNode *N,
const ValueEnumerator &VE,
BitstreamWriter &Stream,
SmallVectorImpl<uint64_t> &Record) {
for (unsigned i = 0, e = N->getNumOperands(); i != e; ++i) {
- if (N->getOperand(i)) {
- Record.push_back(VE.getTypeID(N->getOperand(i)->getType()));
- Record.push_back(VE.getValueID(N->getOperand(i)));
- } else {
+ Metadata *MD = N->getOperand(i);
+ if (!MD) {
Record.push_back(VE.getTypeID(Type::getVoidTy(N->getContext())));
Record.push_back(0);
+ continue;
}
+ if (auto *V = dyn_cast<ConstantAsMetadata>(MD)) {
+ Record.push_back(VE.getTypeID(V->getValue()->getType()));
+ Record.push_back(VE.getValueID(V->getValue()));
+ continue;
+ }
+ assert(!isa<LocalAsMetadata>(MD) && "Unexpected function-local metadata");
+ Record.push_back(VE.getTypeID(Type::getMetadataTy(N->getContext())));
+ Record.push_back(VE.getMetadataID(MD));
}
- unsigned MDCode = N->isFunctionLocal() ? bitc::METADATA_FN_NODE :
- bitc::METADATA_NODE;
- Stream.EmitRecord(MDCode, Record, 0);
+ Stream.EmitRecord(bitc::METADATA_NODE, Record, 0);
Record.clear();
}
static void WriteModuleMetadata(const Module *M,
const ValueEnumerator &VE,
BitstreamWriter &Stream) {
- const auto &Vals = VE.getMDValues();
+ const auto &MDs = VE.getMDs();
bool StartedMetadataBlock = false;
unsigned MDSAbbrev = 0;
SmallVector<uint64_t, 64> Record;
- for (unsigned i = 0, e = Vals.size(); i != e; ++i) {
-
- if (const MDNode *N = dyn_cast<MDNode>(Vals[i])) {
- if (!N->isFunctionLocal() || !N->getFunction()) {
- if (!StartedMetadataBlock) {
- Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);
- StartedMetadataBlock = true;
- }
- WriteMDNode(N, VE, Stream, Record);
+ for (unsigned i = 0, e = MDs.size(); i != e; ++i) {
+ if (const MDNode *N = dyn_cast<MDNode>(MDs[i])) {
+ if (!StartedMetadataBlock) {
+ Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);
+ StartedMetadataBlock = true;
}
- } else if (const MDString *MDS = dyn_cast<MDString>(Vals[i])) {
- if (!StartedMetadataBlock) {
+ WriteMDNode(N, VE, Stream, Record);
+ } else if (const auto *MDC = dyn_cast<ConstantAsMetadata>(MDs[i])) {
+ if (!StartedMetadataBlock) {
+ Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);
+ StartedMetadataBlock = true;
+ }
+ WriteConstantAsMetadata(MDC, VE, Stream, Record);
+ } else if (const MDString *MDS = dyn_cast<MDString>(MDs[i])) {
+ if (!StartedMetadataBlock) {
Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);
// Abbrev for METADATA_STRING.
@@ -813,7 +848,7 @@
// Write named metadata operands.
for (unsigned i = 0, e = NMD->getNumOperands(); i != e; ++i)
- Record.push_back(VE.getValueID(NMD->getOperand(i)));
+ Record.push_back(VE.getMetadataID(NMD->getOperand(i)));
Stream.EmitRecord(bitc::METADATA_NAMED_NODE, Record, 0);
Record.clear();
}
@@ -827,16 +862,16 @@
BitstreamWriter &Stream) {
bool StartedMetadataBlock = false;
SmallVector<uint64_t, 64> Record;
- const SmallVectorImpl<const MDNode *> &Vals = VE.getFunctionLocalMDValues();
- for (unsigned i = 0, e = Vals.size(); i != e; ++i)
- if (const MDNode *N = Vals[i])
- if (N->isFunctionLocal() && N->getFunction() == &F) {
- if (!StartedMetadataBlock) {
- Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);
- StartedMetadataBlock = true;
- }
- WriteMDNode(N, VE, Stream, Record);
- }
+ const SmallVectorImpl<const LocalAsMetadata *> &MDs =
+ VE.getFunctionLocalMDs();
+ for (unsigned i = 0, e = MDs.size(); i != e; ++i) {
+ assert(MDs[i] && "Expected valid function-local metadata");
+ if (!StartedMetadataBlock) {
+ Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);
+ StartedMetadataBlock = true;
+ }
+ WriteLocalAsMetadata(MDs[i], VE, Stream, Record);
+ }
if (StartedMetadataBlock)
Stream.ExitBlock();
@@ -866,7 +901,7 @@
for (unsigned i = 0, e = MDs.size(); i != e; ++i) {
Record.push_back(MDs[i].first);
- Record.push_back(VE.getValueID(MDs[i].second));
+ Record.push_back(VE.getMetadataID(MDs[i].second));
}
Stream.EmitRecord(bitc::METADATA_ATTACHMENT, Record, 0);
Record.clear();
@@ -1686,11 +1721,12 @@
} else {
MDNode *Scope, *IA;
DL.getScopeAndInlinedAt(Scope, IA, I->getContext());
+ assert(Scope && "Expected valid scope");
Vals.push_back(DL.getLine());
Vals.push_back(DL.getCol());
- Vals.push_back(Scope ? VE.getValueID(Scope)+1 : 0);
- Vals.push_back(IA ? VE.getValueID(IA)+1 : 0);
+ Vals.push_back(Scope ? VE.getMetadataID(Scope) + 1 : 0);
+ Vals.push_back(IA ? VE.getMetadataID(IA) + 1 : 0);
Stream.EmitRecord(bitc::FUNC_CODE_DEBUG_LOC, Vals);
Vals.clear();