LLParser: Handle BlockAddresses on-the-fly

Previously all `blockaddress()` constants were treated as forward
references.  They were resolved twice:  once at the end of the function
in question, and again at the end of the module.  Furthermore, if the
same blockaddress was referenced N times, the parser created N distinct
`GlobalVariable`s (one for each reference).

Instead, resolve all block addresses at the beginning of the function,
creating the standard `BasicBlock` forward references used for all other
basic block references.  After the function, all references can be
resolved immediately.  To check for the condition of parsing block
addresses from within the same function, I created a reference to the
current per-function-state in `BlockAddressPFS`.

Also, create only one forward-reference per basic block.  Because
forward references to block addresses are rare, the data structure here
shouldn't matter.  If somehow it does someday, this can be pretty easily
changed to a `DenseMap<std::pair<ValID, ValID>, GV>`.

This is part of PR20515.

llvm-svn: 215952

1 files changed, 12 insertions, 10 deletions

diff --git a/llvm/lib/AsmParser/LLParser.h b/llvm/lib/AsmParser/LLParser.h
index a3eb8d3ed38..556b385c3c4 100644
--- a/llvm/lib/AsmParser/LLParser.h
+++ b/llvm/lib/AsmParser/LLParser.h
@@ -128,17 +128,21 @@ namespace llvm {
 
     // References to blockaddress.  The key is the function ValID, the value is
     // a list of references to blocks in that function.
-    std::map<ValID, std::vector<std::pair<ValID, GlobalValue*> > >
-      ForwardRefBlockAddresses;
+    std::map<ValID, std::map<ValID, GlobalValue *>> ForwardRefBlockAddresses;
+    class PerFunctionState;
+    /// Reference to per-function state to allow basic blocks to be
+    /// forward-referenced by blockaddress instructions within the same
+    /// function.
+    PerFunctionState *BlockAddressPFS;
 
     // Attribute builder reference information.
     std::map<Value*, std::vector<unsigned> > ForwardRefAttrGroups;
     std::map<unsigned, AttrBuilder> NumberedAttrBuilders;
 
   public:
-    LLParser(StringRef F, SourceMgr &SM, SMDiagnostic &Err, Module *m) :
-      Context(m->getContext()), Lex(F, SM, Err, m->getContext()),
-      M(m) {}
+    LLParser(StringRef F, SourceMgr &SM, SMDiagnostic &Err, Module *m)
+        : Context(m->getContext()), Lex(F, SM, Err, m->getContext()), M(m),
+          BlockAddressPFS(nullptr) {}
     bool Run();
 
     LLVMContext &getContext() { return Context; }
@@ -327,6 +331,8 @@ namespace llvm {
       /// unnamed.  If there is an error, this returns null otherwise it returns
       /// the block being defined.
       BasicBlock *DefineBB(const std::string &Name, LocTy Loc);
+
+      bool resolveForwardRefBlockAddresses();
     };
 
     bool ConvertValIDToValue(Type *Ty, ValID &ID, Value *&V,
@@ -372,7 +378,7 @@ namespace llvm {
     bool ParseValID(ValID &ID, PerFunctionState *PFS = nullptr);
     bool ParseGlobalValue(Type *Ty, Constant *&V);
     bool ParseGlobalTypeAndValue(Constant *&V);
-    bool ParseGlobalValueVector(SmallVectorImpl<Constant*> &Elts);
+    bool ParseGlobalValueVector(SmallVectorImpl<Constant *> &Elts);
     bool parseOptionalComdat(Comdat *&C);
     bool ParseMetadataListValue(ValID &ID, PerFunctionState *PFS);
     bool ParseMetadataValue(ValID &ID, PerFunctionState *PFS);
@@ -432,10 +438,6 @@ namespace llvm {
     int ParseGetElementPtr(Instruction *&I, PerFunctionState &PFS);
     int ParseExtractValue(Instruction *&I, PerFunctionState &PFS);
     int ParseInsertValue(Instruction *&I, PerFunctionState &PFS);
-
-    bool ResolveForwardRefBlockAddresses(Function *TheFn,
-                             std::vector<std::pair<ValID, GlobalValue*> > &Refs,
-                                         PerFunctionState *PFS);
   };
 } // End llvm namespace