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

7 files changed, 30 insertions, 19 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp
index cca5f229c2f..8cfaba68d20 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp
@@ -64,7 +64,7 @@ static void srcMgrDiagHandler(const SMDiagnostic &Diag, void *diagInfo) {
 
     if (LocInfo->getNumOperands() != 0)
       if (const ConstantInt *CI =
-          dyn_cast<ConstantInt>(LocInfo->getOperand(ErrorLine)))
+              mdconst::dyn_extract<ConstantInt>(LocInfo->getOperand(ErrorLine)))
         LocCookie = CI->getZExtValue();
   }
 
@@ -467,7 +467,8 @@ void AsmPrinter::EmitInlineAsm(const MachineInstr *MI) const {
     if (MI->getOperand(i-1).isMetadata() &&
         (LocMD = MI->getOperand(i-1).getMetadata()) &&
         LocMD->getNumOperands() != 0) {
-      if (const ConstantInt *CI = dyn_cast<ConstantInt>(LocMD->getOperand(0))) {
+      if (const ConstantInt *CI =
+              mdconst::dyn_extract<ConstantInt>(LocMD->getOperand(0))) {
         LocCookie = CI->getZExtValue();
         break;
       }
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
index 76ba663bb84..6c5a630edb1 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
@@ -1192,10 +1192,10 @@ DwarfUnit::constructTemplateValueParameterDIE(DIE &Buffer,
     addType(ParamDIE, resolve(VP.getType()));
   if (!VP.getName().empty())
     addString(ParamDIE, dwarf::DW_AT_name, VP.getName());
-  if (Value *Val = VP.getValue()) {
-    if (ConstantInt *CI = dyn_cast<ConstantInt>(Val))
+  if (Metadata *Val = VP.getValue()) {
+    if (ConstantInt *CI = mdconst::dyn_extract<ConstantInt>(Val))
       addConstantValue(ParamDIE, CI, resolve(VP.getType()));
-    else if (GlobalValue *GV = dyn_cast<GlobalValue>(Val)) {
+    else if (GlobalValue *GV = mdconst::dyn_extract<GlobalValue>(Val)) {
       // For declaration non-type template parameters (such as global values and
       // functions)
       DIELoc *Loc = new (DIEValueAllocator) DIELoc();
diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp
index 96e2d3d74de..577c048ba60 100644
--- a/llvm/lib/CodeGen/CodeGenPrepare.cpp
+++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp
@@ -3810,8 +3810,10 @@ static bool extractBranchMetadata(BranchInst *BI,
   if (!ProfileData || ProfileData->getNumOperands() != 3)
     return false;
 
-  const auto *CITrue = dyn_cast<ConstantInt>(ProfileData->getOperand(1));
-  const auto *CIFalse = dyn_cast<ConstantInt>(ProfileData->getOperand(2));
+  const auto *CITrue =
+      mdconst::dyn_extract<ConstantInt>(ProfileData->getOperand(1));
+  const auto *CIFalse =
+      mdconst::dyn_extract<ConstantInt>(ProfileData->getOperand(2));
   if (!CITrue || !CIFalse)
     return false;
 
diff --git a/llvm/lib/CodeGen/MachineInstr.cpp b/llvm/lib/CodeGen/MachineInstr.cpp
index 7ad0d9426ef..968ec2c68e8 100644
--- a/llvm/lib/CodeGen/MachineInstr.cpp
+++ b/llvm/lib/CodeGen/MachineInstr.cpp
@@ -397,7 +397,7 @@ void MachineOperand::print(raw_ostream &OS, const TargetMachine *TM) const {
     break;
   case MachineOperand::MO_Metadata:
     OS << '<';
-    getMetadata()->printAsOperand(OS, /*PrintType=*/false);
+    getMetadata()->printAsOperand(OS);
     OS << '>';
     break;
   case MachineOperand::MO_MCSymbol:
@@ -537,7 +537,7 @@ raw_ostream &llvm::operator<<(raw_ostream &OS, const MachineMemOperand &MMO) {
   if (const MDNode *TBAAInfo = MMO.getAAInfo().TBAA) {
     OS << "(tbaa=";
     if (TBAAInfo->getNumOperands() > 0)
-      TBAAInfo->getOperand(0)->printAsOperand(OS, /*PrintType=*/false);
+      TBAAInfo->getOperand(0)->printAsOperand(OS);
     else
       OS << "<unknown>";
     OS << ")";
@@ -548,7 +548,7 @@ raw_ostream &llvm::operator<<(raw_ostream &OS, const MachineMemOperand &MMO) {
     OS << "(alias.scope=";
     if (ScopeInfo->getNumOperands() > 0)
       for (unsigned i = 0, ie = ScopeInfo->getNumOperands(); i != ie; ++i) {
-        ScopeInfo->getOperand(i)->printAsOperand(OS, /*PrintType=*/false);
+        ScopeInfo->getOperand(i)->printAsOperand(OS);
         if (i != ie-1)
           OS << ",";
       }
@@ -562,7 +562,7 @@ raw_ostream &llvm::operator<<(raw_ostream &OS, const MachineMemOperand &MMO) {
     OS << "(noalias=";
     if (NoAliasInfo->getNumOperands() > 0)
       for (unsigned i = 0, ie = NoAliasInfo->getNumOperands(); i != ie; ++i) {
-        NoAliasInfo->getOperand(i)->printAsOperand(OS, /*PrintType=*/false);
+        NoAliasInfo->getOperand(i)->printAsOperand(OS);
         if (i != ie-1)
           OS << ",";
       }
@@ -599,6 +599,8 @@ MachineInstr::MachineInstr(MachineFunction &MF, const MCInstrDesc &tid,
   : MCID(&tid), Parent(nullptr), Operands(nullptr), NumOperands(0),
     Flags(0), AsmPrinterFlags(0),
     NumMemRefs(0), MemRefs(nullptr), debugLoc(dl) {
+  assert(debugLoc.hasTrivialDestructor() && "Expected trivial destructor");
+
   // Reserve space for the expected number of operands.
   if (unsigned NumOps = MCID->getNumOperands() +
     MCID->getNumImplicitDefs() + MCID->getNumImplicitUses()) {
@@ -617,6 +619,8 @@ MachineInstr::MachineInstr(MachineFunction &MF, const MachineInstr &MI)
     Flags(0), AsmPrinterFlags(0),
     NumMemRefs(MI.NumMemRefs), MemRefs(MI.MemRefs),
     debugLoc(MI.getDebugLoc()) {
+  assert(debugLoc.hasTrivialDestructor() && "Expected trivial destructor");
+
   CapOperands = OperandCapacity::get(MI.getNumOperands());
   Operands = MF.allocateOperandArray(CapOperands);
 
@@ -1960,7 +1964,8 @@ void MachineInstr::emitError(StringRef Msg) const {
     if (getOperand(i-1).isMetadata() &&
         (LocMD = getOperand(i-1).getMetadata()) &&
         LocMD->getNumOperands() != 0) {
-      if (const ConstantInt *CI = dyn_cast<ConstantInt>(LocMD->getOperand(0))) {
+      if (const ConstantInt *CI =
+              mdconst::dyn_extract<ConstantInt>(LocMD->getOperand(0))) {
         LocCookie = CI->getZExtValue();
         break;
       }
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index cab3cbf8ab5..c573339c7bf 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -4714,7 +4714,8 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
     return nullptr;
   case Intrinsic::read_register: {
     Value *Reg = I.getArgOperand(0);
-    SDValue RegName = DAG.getMDNode(cast<MDNode>(Reg));
+    SDValue RegName =
+        DAG.getMDNode(cast<MDNode>(cast<MetadataAsValue>(Reg)->getMetadata()));
     EVT VT = TLI.getValueType(I.getType());
     setValue(&I, DAG.getNode(ISD::READ_REGISTER, sdl, VT, RegName));
     return nullptr;
@@ -4723,7 +4724,8 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
     Value *Reg = I.getArgOperand(0);
     Value *RegValue = I.getArgOperand(1);
     SDValue Chain = getValue(RegValue).getOperand(0);
-    SDValue RegName = DAG.getMDNode(cast<MDNode>(Reg));
+    SDValue RegName =
+        DAG.getMDNode(cast<MDNode>(cast<MetadataAsValue>(Reg)->getMetadata()));
     DAG.setRoot(DAG.getNode(ISD::WRITE_REGISTER, sdl, MVT::Other, Chain,
                             RegName, getValue(RegValue)));
     return nullptr;
diff --git a/llvm/lib/CodeGen/StackColoring.cpp b/llvm/lib/CodeGen/StackColoring.cpp
index dcf1b448a91..faf94b67fe7 100644
--- a/llvm/lib/CodeGen/StackColoring.cpp
+++ b/llvm/lib/CodeGen/StackColoring.cpp
@@ -463,7 +463,8 @@ void StackColoring::remapInstructions(DenseMap<int, int> &SlotRemap) {
     if (!VI.Var)
       continue;
     if (SlotRemap.count(VI.Slot)) {
-      DEBUG(dbgs()<<"Remapping debug info for ["<<VI.Var->getName()<<"].\n");
+      DEBUG(dbgs() << "Remapping debug info for ["
+                   << DIVariable(VI.Var).getName() << "].\n");
       VI.Slot = SlotRemap[VI.Slot];
       FixedDbg++;
     }
diff --git a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
index e52552af5e4..55cc016cc98 100644
--- a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -464,15 +464,15 @@ emitModuleFlags(MCStreamer &Streamer,
       continue;
 
     StringRef Key = MFE.Key->getString();
-    Value *Val = MFE.Val;
+    Metadata *Val = MFE.Val;
 
     if (Key == "Objective-C Image Info Version") {
-      VersionVal = cast<ConstantInt>(Val)->getZExtValue();
+      VersionVal = mdconst::extract<ConstantInt>(Val)->getZExtValue();
     } else if (Key == "Objective-C Garbage Collection" ||
                Key == "Objective-C GC Only" ||
                Key == "Objective-C Is Simulated" ||
                Key == "Objective-C Image Swift Version") {
-      ImageInfoFlags |= cast<ConstantInt>(Val)->getZExtValue();
+      ImageInfoFlags |= mdconst::extract<ConstantInt>(Val)->getZExtValue();
     } else if (Key == "Objective-C Image Info Section") {
       SectionVal = cast<MDString>(Val)->getString();
     } else if (Key == "Linker Options") {
@@ -966,7 +966,7 @@ emitModuleFlags(MCStreamer &Streamer,
        i = ModuleFlags.begin(), e = ModuleFlags.end(); i != e; ++i) {
     const Module::ModuleFlagEntry &MFE = *i;
     StringRef Key = MFE.Key->getString();
-    Value *Val = MFE.Val;
+    Metadata *Val = MFE.Val;
     if (Key == "Linker Options") {
       LinkerOptions = cast<MDNode>(Val);
       break;