IR: RF_IgnoreMissingValues => RF_IgnoreMissingLocals, NFC

Clarify what this RemapFlag actually means.

  - Change the flag name to match its intended behaviour.
  - Clearly document that it's not supposed to affect globals.
  - Add a host of FIXMEs to indicate how to fix the behaviour to match
    the intent of the flag.

RF_IgnoreMissingLocals should only affect the behaviour of
RemapInstruction for function-local operands; namely, for operands of
type Argument, Instruction, and BasicBlock.  Currently, it is *only*
passed into RemapInstruction calls (and the transitive MapValue calls
that it makes).

When I split Metadata from Value I didn't understand the flag, and I
used it in a bunch of places for "global" metadata.

This commit doesn't have any functionality change, but prepares to
cleanup MapMetadata and MapValue.

llvm-svn: 265628

9 files changed, 25 insertions, 15 deletions

diff --git a/llvm/lib/CodeGen/WinEHPrepare.cpp b/llvm/lib/CodeGen/WinEHPrepare.cpp
index b2b3130e9f1..041fb7b912b 100644
--- a/llvm/lib/CodeGen/WinEHPrepare.cpp
+++ b/llvm/lib/CodeGen/WinEHPrepare.cpp
@@ -787,7 +787,7 @@ void WinEHPrepare::cloneCommonBlocks(Function &F) {
       // Loop over all instructions, fixing each one as we find it...
       for (Instruction &I : *BB)
         RemapInstruction(&I, VMap,
-                         RF_IgnoreMissingEntries | RF_NoModuleLevelChanges);
+                         RF_IgnoreMissingLocals | RF_NoModuleLevelChanges);
 
     // Catchrets targeting cloned blocks need to be updated separately from
     // the loop above because they are not in the current funclet.
diff --git a/llvm/lib/Linker/IRMover.cpp b/llvm/lib/Linker/IRMover.cpp
index 5351bd5948a..2958d96cbc7 100644
--- a/llvm/lib/Linker/IRMover.cpp
+++ b/llvm/lib/Linker/IRMover.cpp
@@ -997,7 +997,7 @@ bool IRLinker::linkFunctionBody(Function &Dst, Function &Src) {
     A.mutateType(TypeMap.get(A.getType()));
   for (BasicBlock &BB : Dst)
     for (Instruction &I : BB)
-      RemapInstruction(&I, ValueMap, RF_IgnoreMissingEntries | ValueMapperFlags,
+      RemapInstruction(&I, ValueMap, RF_IgnoreMissingLocals | ValueMapperFlags,
                        &TypeMap, &GValMaterializer);
 
   return false;
diff --git a/llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp b/llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
index 48ec2de5e56..8f283f92945 100644
--- a/llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
@@ -939,7 +939,7 @@ void LoopConstrainer::cloneLoop(LoopConstrainer::ClonedLoop &Result,
 
     for (Instruction &I : *ClonedBB)
       RemapInstruction(&I, Result.Map,
-                       RF_NoModuleLevelChanges | RF_IgnoreMissingEntries);
+                       RF_NoModuleLevelChanges | RF_IgnoreMissingLocals);
 
     // Exit blocks will now have one more predecessor and their PHI nodes need
     // to be edited to reflect that.  No phi nodes need to be introduced because
diff --git a/llvm/lib/Transforms/Scalar/LoopRotation.cpp b/llvm/lib/Transforms/Scalar/LoopRotation.cpp
index 1a9d1db1a53..b8148916295 100644
--- a/llvm/lib/Transforms/Scalar/LoopRotation.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopRotation.cpp
@@ -244,7 +244,7 @@ static bool rotateLoop(Loop *L, unsigned MaxHeaderSize, LoopInfo *LI,
 
     // Eagerly remap the operands of the instruction.
     RemapInstruction(C, ValueMap,
-                     RF_NoModuleLevelChanges|RF_IgnoreMissingEntries);
+                     RF_NoModuleLevelChanges | RF_IgnoreMissingLocals);
 
     // With the operands remapped, see if the instruction constant folds or is
     // otherwise simplifyable.  This commonly occurs because the entry from PHI
diff --git a/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp b/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp
index c3b941f46f6..955604f0507 100644
--- a/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp
@@ -1068,7 +1068,7 @@ void LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val,
     for (BasicBlock::iterator I = NewBlocks[i]->begin(),
            E = NewBlocks[i]->end(); I != E; ++I)
       RemapInstruction(&*I, VMap,
-                       RF_NoModuleLevelChanges | RF_IgnoreMissingEntries);
+                       RF_NoModuleLevelChanges | RF_IgnoreMissingLocals);
 
   // Rewrite the original preheader to select between versions of the loop.
   BranchInst *OldBR = cast<BranchInst>(loopPreheader->getTerminator());
diff --git a/llvm/lib/Transforms/Utils/CloneFunction.cpp b/llvm/lib/Transforms/Utils/CloneFunction.cpp
index 8e1715ac428..cf39ae955ad 100644
--- a/llvm/lib/Transforms/Utils/CloneFunction.cpp
+++ b/llvm/lib/Transforms/Utils/CloneFunction.cpp
@@ -694,7 +694,7 @@ void llvm::remapInstructionsInBlocks(
   for (auto *BB : Blocks)
     for (auto &Inst : *BB)
       RemapInstruction(&Inst, VMap,
-                       RF_NoModuleLevelChanges | RF_IgnoreMissingEntries);
+                       RF_NoModuleLevelChanges | RF_IgnoreMissingLocals);
 }
 
 /// \brief Clones a loop \p OrigLoop.  Returns the loop and the blocks in \p
diff --git a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
index 5e128541fb2..8f32e0093b9 100644
--- a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
@@ -636,7 +636,7 @@ bool llvm::UnrollRuntimeLoopRemainder(Loop *L, unsigned Count,
   for (BasicBlock *BB : NewBlocks) {
     for (Instruction &I : *BB) {
       RemapInstruction(&I, VMap,
-                       RF_NoModuleLevelChanges | RF_IgnoreMissingEntries);
+                       RF_NoModuleLevelChanges | RF_IgnoreMissingLocals);
     }
   }
 
diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index f750509a5e8..8284d6bf626 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -2236,7 +2236,7 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI, unsigned BonusInstThreshold) {
         continue;
       Instruction *NewBonusInst = BonusInst->clone();
       RemapInstruction(NewBonusInst, VMap,
-                       RF_NoModuleLevelChanges | RF_IgnoreMissingEntries);
+                       RF_NoModuleLevelChanges | RF_IgnoreMissingLocals);
       VMap[&*BonusInst] = NewBonusInst;
 
       // If we moved a load, we cannot any longer claim any knowledge about
@@ -2255,7 +2255,7 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI, unsigned BonusInstThreshold) {
     // two conditions together.
     Instruction *New = Cond->clone();
     RemapInstruction(New, VMap,
-                     RF_NoModuleLevelChanges | RF_IgnoreMissingEntries);
+                     RF_NoModuleLevelChanges | RF_IgnoreMissingLocals);
     PredBlock->getInstList().insert(PBI->getIterator(), New);
     New->takeName(Cond);
     Cond->setName(New->getName() + ".old");
diff --git a/llvm/lib/Transforms/Utils/ValueMapper.cpp b/llvm/lib/Transforms/Utils/ValueMapper.cpp
index 0c2954fdd32..25c90b17d66 100644
--- a/llvm/lib/Transforms/Utils/ValueMapper.cpp
+++ b/llvm/lib/Transforms/Utils/ValueMapper.cpp
@@ -274,9 +274,11 @@ Value *Mapper::mapValue(const Value *V) {
   // are using the identity mapping.
   if (isa<GlobalValue>(V)) {
     if (Flags & RF_NullMapMissingGlobalValues) {
-      assert(!(Flags & RF_IgnoreMissingEntries) &&
+      // FIXME: Remove this assertion.  RF_IgnoreMissingLocals is unrelated to
+      // RF_NullMapMissingGlobalValues.
+      assert(!(Flags & RF_IgnoreMissingLocals) &&
              "Illegal to specify both RF_NullMapMissingGlobalValues and "
-             "RF_IgnoreMissingEntries");
+             "RF_IgnoreMissingLocals");
       return nullptr;
     }
     return VM[V] = const_cast<Value*>(V);
@@ -303,8 +305,11 @@ Value *Mapper::mapValue(const Value *V) {
     if (!isa<LocalAsMetadata>(MD) && (Flags & RF_NoModuleLevelChanges))
       return VM[V] = const_cast<Value *>(V);
 
+    // FIXME: be consistent with function-local values for LocalAsMetadata by
+    // returning nullptr when LocalAsMetadata is missing.  Adding a mapping is
+    // expensive.
     auto *MappedMD = mapMetadata(MD);
-    if (MD == MappedMD || (!MappedMD && (Flags & RF_IgnoreMissingEntries)))
+    if (MD == MappedMD || (!MappedMD && (Flags & RF_IgnoreMissingLocals)))
       return VM[V] = const_cast<Value *>(V);
 
     return VM[V] = MetadataAsValue::get(V->getContext(), MappedMD);
@@ -628,14 +633,17 @@ Optional<Metadata *> Mapper::mapSimpleMetadata(const Metadata *MD) {
     if ((Flags & RF_NoModuleLevelChanges))
       return mapToSelf(MD);
 
+  // FIXME: Assert that this is not LocalAsMetadata.  It should be handled
+  // elsewhere.
   if (const auto *VMD = dyn_cast<ValueAsMetadata>(MD)) {
     // Disallow recursion into metadata mapping through mapValue.
     VM.disableMapMetadata();
     Value *MappedV = mapValue(VMD->getValue());
     VM.enableMapMetadata();
 
+    // FIXME: Always use "ignore" behaviour.  There should only be globals here.
     if (VMD->getValue() == MappedV ||
-        (!MappedV && (Flags & RF_IgnoreMissingEntries)))
+        (!MappedV && (Flags & RF_IgnoreMissingLocals)))
       return mapToSelf(MD);
 
     return mapToMetadata(MD, MappedV ? ValueAsMetadata::get(MappedV) : nullptr);
@@ -658,6 +666,8 @@ Metadata *llvm::MapMetadata(const Metadata *MD, ValueToValueMapTy &VM,
 }
 
 Metadata *Mapper::mapMetadata(const Metadata *MD) {
+  // FIXME: First check for and deal with LocalAsMetadata, so that
+  // mapSimpleMetadata() doesn't need to deal with it.
   if (Optional<Metadata *> NewMD = mapSimpleMetadata(MD))
     return *NewMD;
 
@@ -703,7 +713,7 @@ void llvm::RemapInstruction(Instruction *I, ValueToValueMapTy &VMap,
     if (V)
       *op = V;
     else
-      assert((Flags & RF_IgnoreMissingEntries) &&
+      assert((Flags & RF_IgnoreMissingLocals) &&
              "Referenced value not in value map!");
   }
 
@@ -715,7 +725,7 @@ void llvm::RemapInstruction(Instruction *I, ValueToValueMapTy &VMap,
       if (V)
         PN->setIncomingBlock(i, cast<BasicBlock>(V));
       else
-        assert((Flags & RF_IgnoreMissingEntries) &&
+        assert((Flags & RF_IgnoreMissingLocals) &&
                "Referenced block not in value map!");
     }
   }