llvm/lib/IR/ValueSymbolTable.cpp
Duncan P. N. Exon Smith dad20b2ae2 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.)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223802 91177308-0d34-0410-b5e6-96231b3b80d8
2014-12-09 18:38:53 +00:00

116 lines
3.9 KiB
C++

//===-- ValueSymbolTable.cpp - Implement the ValueSymbolTable class -------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the ValueSymbolTable class for the IR library.
//
//===----------------------------------------------------------------------===//
#include "llvm/IR/ValueSymbolTable.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/IR/GlobalValue.h"
#include "llvm/IR/Type.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
#define DEBUG_TYPE "valuesymtab"
// Class destructor
ValueSymbolTable::~ValueSymbolTable() {
#ifndef NDEBUG // Only do this in -g mode...
for (iterator VI = vmap.begin(), VE = vmap.end(); VI != VE; ++VI)
dbgs() << "Value still in symbol table! Type = '"
<< *VI->getValue()->getType() << "' Name = '"
<< VI->getKeyData() << "'\n";
assert(vmap.empty() && "Values remain in symbol table!");
#endif
}
// Insert a value into the symbol table with the specified name...
//
void ValueSymbolTable::reinsertValue(Value* V) {
assert(V->hasName() && "Can't insert nameless Value into symbol table");
// Try inserting the name, assuming it won't conflict.
if (vmap.insert(V->getValueName())) {
//DEBUG(dbgs() << " Inserted value: " << V->getValueName() << ": " << *V << "\n");
return;
}
// Otherwise, there is a naming conflict. Rename this value.
SmallString<256> UniqueName(V->getName().begin(), V->getName().end());
// The name is too already used, just free it so we can allocate a new name.
V->getValueName()->Destroy();
unsigned BaseSize = UniqueName.size();
while (1) {
// Trim any suffix off and append the next number.
UniqueName.resize(BaseSize);
raw_svector_ostream(UniqueName) << ++LastUnique;
// Try insert the vmap entry with this suffix.
auto IterBool = vmap.insert(std::make_pair(UniqueName, V));
if (IterBool.second) {
// Newly inserted name. Success!
V->setValueName(&*IterBool.first);
//DEBUG(dbgs() << " Inserted value: " << UniqueName << ": " << *V << "\n");
return;
}
}
}
void ValueSymbolTable::removeValueName(ValueName *V) {
//DEBUG(dbgs() << " Removing Value: " << V->getKeyData() << "\n");
// Remove the value from the symbol table.
vmap.remove(V);
}
/// createValueName - This method attempts to create a value name and insert
/// it into the symbol table with the specified name. If it conflicts, it
/// auto-renames the name and returns that instead.
ValueName *ValueSymbolTable::createValueName(StringRef Name, Value *V) {
// In the common case, the name is not already in the symbol table.
auto IterBool = vmap.insert(std::make_pair(Name, V));
if (IterBool.second) {
//DEBUG(dbgs() << " Inserted value: " << Entry.getKeyData() << ": "
// << *V << "\n");
return &*IterBool.first;
}
// Otherwise, there is a naming conflict. Rename this value.
SmallString<256> UniqueName(Name.begin(), Name.end());
while (1) {
// Trim any suffix off and append the next number.
UniqueName.resize(Name.size());
raw_svector_ostream(UniqueName) << ++LastUnique;
// Try insert the vmap entry with this suffix.
auto IterBool = vmap.insert(std::make_pair(UniqueName, V));
if (IterBool.second) {
// DEBUG(dbgs() << " Inserted value: " << UniqueName << ": " << *V <<
// "\n");
return &*IterBool.first;
}
}
}
// dump - print out the symbol table
//
void ValueSymbolTable::dump() const {
//DEBUG(dbgs() << "ValueSymbolTable:\n");
for (const_iterator I = begin(), E = end(); I != E; ++I) {
//DEBUG(dbgs() << " '" << I->getKeyData() << "' = ");
I->getValue()->dump();
//DEBUG(dbgs() << "\n");
}
}