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3d57886267
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
82 lines
2.7 KiB
C++
82 lines
2.7 KiB
C++
//===-- InstrinsicInst.cpp - Intrinsic Instruction Wrappers ---------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements methods that make it really easy to deal with intrinsic
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// functions.
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//
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// All intrinsic function calls are instances of the call instruction, so these
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// are all subclasses of the CallInst class. Note that none of these classes
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// has state or virtual methods, which is an important part of this gross/neat
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// hack working.
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//
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// In some cases, arguments to intrinsics need to be generic and are defined as
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// type pointer to empty struct { }*. To access the real item of interest the
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// cast instruction needs to be stripped away.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/IR/IntrinsicInst.h"
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#include "llvm/IR/Constants.h"
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#include "llvm/IR/GlobalVariable.h"
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#include "llvm/IR/Metadata.h"
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using namespace llvm;
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//===----------------------------------------------------------------------===//
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/// DbgInfoIntrinsic - This is the common base class for debug info intrinsics
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///
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static Value *CastOperand(Value *C) {
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if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
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if (CE->isCast())
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return CE->getOperand(0);
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return nullptr;
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}
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Value *DbgInfoIntrinsic::StripCast(Value *C) {
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if (Value *CO = CastOperand(C)) {
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C = StripCast(CO);
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} else if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
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if (GV->hasInitializer())
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if (Value *CO = CastOperand(GV->getInitializer()))
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C = StripCast(CO);
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}
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return dyn_cast<GlobalVariable>(C);
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}
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static Value *getValueImpl(Value *Op) {
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auto *MD = cast<MetadataAsValue>(Op)->getMetadata();
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if (auto *V = dyn_cast<ValueAsMetadata>(MD))
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return V->getValue();
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// When the value goes to null, it gets replaced by an empty MDNode.
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assert(!cast<MDNode>(MD)->getNumOperands() && "Expected an empty MDNode");
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return nullptr;
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}
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//===----------------------------------------------------------------------===//
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/// DbgDeclareInst - This represents the llvm.dbg.declare instruction.
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///
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Value *DbgDeclareInst::getAddress() const {
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if (!getArgOperand(0))
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return nullptr;
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return getValueImpl(getArgOperand(0));
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}
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//===----------------------------------------------------------------------===//
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/// DbgValueInst - This represents the llvm.dbg.value instruction.
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///
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const Value *DbgValueInst::getValue() const {
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return const_cast<DbgValueInst *>(this)->getValue();
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}
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Value *DbgValueInst::getValue() { return getValueImpl(getArgOperand(0)); }
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