llvm-6502/lib/Transforms/Scalar
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
..
ADCE.cpp Update SetVector to rely on the underlying set's insert to return a pair<iterator, bool> 2014-11-19 07:49:26 +00:00
AlignmentFromAssumptions.cpp [AlignmentFromAssumptions] Don't crash just because the target is 32-bit 2014-09-11 08:40:17 +00:00
CMakeLists.txt Add an AlignmentFromAssumptions Pass 2014-09-07 20:05:11 +00:00
ConstantHoisting.cpp Remove unnecessary copying or replace it with moves in a bunch of places. 2014-10-04 16:55:56 +00:00
ConstantProp.cpp [C++] Use 'nullptr'. Transforms edition. 2014-04-25 05:29:35 +00:00
CorrelatedValuePropagation.cpp Make use of @llvm.assume from LazyValueInfo 2014-09-07 20:29:59 +00:00
DCE.cpp [Modules] Fix potential ODR violations by sinking the DEBUG_TYPE 2014-04-22 02:55:47 +00:00
DeadStoreElimination.cpp [DSE] Remove no-data-layout-only type-based overlap checking 2014-10-17 11:56:00 +00:00
EarlyCSE.cpp Tweak EarlyCSE to recognize series of dead stores 2014-11-18 17:46:32 +00:00
FlattenCFGPass.cpp [Modules] Fix potential ODR violations by sinking the DEBUG_TYPE 2014-04-22 02:55:47 +00:00
GVN.cpp Revert r222039 because of bot failure. 2014-11-19 00:13:26 +00:00
IndVarSimplify.cpp Update SetVector to rely on the underlying set's insert to return a pair<iterator, bool> 2014-11-19 07:49:26 +00:00
JumpThreading.cpp Revert r220349 to re-instate r220277 with a fix for PR21330 -- quite 2014-11-25 08:20:27 +00:00
LICM.cpp [LICM] Avoind store sinking if no preheader is available 2014-12-02 14:22:34 +00:00
LLVMBuild.txt ScalarOpts/LLVMBuild.txt: Prune unused dependency to IPA. 2014-09-09 15:00:38 +00:00
LoadCombine.cpp Use AA in LoadCombine 2014-11-03 23:19:16 +00:00
LoopDeletion.cpp Use range based for loops to avoid needing to re-mention SmallPtrSet size. 2014-08-24 23:23:06 +00:00
LoopIdiomRecognize.cpp Remove extra whitespace in function declaration. No functionality change. 2014-06-14 03:48:29 +00:00
LoopInstSimplify.cpp Update SetVector to rely on the underlying set's insert to return a pair<iterator, bool> 2014-11-19 07:49:26 +00:00
LoopRerollPass.cpp Reformat partially, where I touched for whitespace changes. 2014-10-28 11:54:52 +00:00
LoopRotation.cpp Do not simplifyLatch for loops where hoisting increments couldresult in extra live range interferance 2014-10-29 20:19:47 +00:00
LoopStrengthReduce.cpp Update SetVector to rely on the underlying set's insert to return a pair<iterator, bool> 2014-11-19 07:49:26 +00:00
LoopUnrollPass.cpp IR: Split Metadata from Value 2014-12-09 18:38:53 +00:00
LoopUnswitch.cpp Add functions for finding ephemeral values 2014-09-07 13:49:57 +00:00
LowerAtomic.cpp IR: add "cmpxchg weak" variant to support permitted failure. 2014-06-13 14:24:07 +00:00
Makefile
MemCpyOptimizer.cpp Allow call-slop optzn for destinations with a suitable dereferenceable attribute 2014-10-16 19:43:08 +00:00
MergedLoadStoreMotion.cpp Use Alias Analysis to hoist 2 loads from diamond to the common predecessor basic block. 2014-11-02 08:03:05 +00:00
PartiallyInlineLibCalls.cpp PartiallyInlineLibCalls: Check sqrt result type before transforming it. 2014-08-01 23:21:21 +00:00
Reassociate.cpp This Reassociate change unintentionally slipped in r222499 2014-11-21 02:37:38 +00:00
Reg2Mem.cpp [Modules] Fix potential ODR violations by sinking the DEBUG_TYPE 2014-04-22 02:55:47 +00:00
SampleProfile.cpp Update SetVector to rely on the underlying set's insert to return a pair<iterator, bool> 2014-11-19 07:49:26 +00:00
Scalar.cpp [C API] Make the 'lower switch' pass available via the C API. 2014-09-11 21:32:32 +00:00
Scalarizer.cpp Revert "IR: MDNode => Value" 2014-11-11 21:30:22 +00:00
ScalarReplAggregates.cpp IR: Split Metadata from Value 2014-12-09 18:38:53 +00:00
SCCP.cpp Update SetVector to rely on the underlying set's insert to return a pair<iterator, bool> 2014-11-19 07:49:26 +00:00
SeparateConstOffsetFromGEP.cpp [SeparateConstOffsetFromGEP] Allow SeparateConstOffsetFromGEP pass to lower GEPs. 2014-11-19 06:24:44 +00:00
SimplifyCFGPass.cpp [SimplifyCFG] threshold for folding branches with common destination 2014-09-30 22:23:38 +00:00
Sink.cpp Use range based for loops to avoid needing to re-mention SmallPtrSet size. 2014-08-24 23:23:06 +00:00
SROA.cpp IR: Split Metadata from Value 2014-12-09 18:38:53 +00:00
StructurizeCFG.cpp StructurizeCFG: Use LoopInfo analysis for better loop detection 2014-12-03 04:28:32 +00:00
TailRecursionElimination.cpp Fix tail recursion elimination 2014-11-19 13:32:51 +00:00