[PATCH] D124427: [Serialization] Pack Expr ObjectKind and ValueKind into one VBR.

[Sam McCall via Phabricator via cfe-commits]

sammccall created this revision.
sammccall added a reviewer: kadircet.
Herald added a subscriber: usaxena95.
Herald added a project: All.
sammccall requested review of this revision.
Herald added subscribers: cfe-commits, ilya-biryukov.
Herald added a project: clang.

Most Exprs are serialized unabbreviated, so this saves 6 bits per expr.
This is worth 0.3% on clangd --check=clangd/AST.cpp: 42276772 -> 42187128
Not terribly much but a trivial change...


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D124427

Files:
  clang/lib/Serialization/ASTReaderStmt.cpp
  clang/lib/Serialization/ASTWriterDecl.cpp
  clang/lib/Serialization/ASTWriterStmt.cpp


Index: clang/lib/Serialization/ASTWriterStmt.cpp
===================================================================
--- clang/lib/Serialization/ASTWriterStmt.cpp
+++ clang/lib/Serialization/ASTWriterStmt.cpp
@@ -544,8 +544,9 @@
   VisitStmt(E);
   Record.AddTypeRef(E->getType());
   Record.push_back(E->getDependence());
-  Record.push_back(E->getValueKind());
-  Record.push_back(E->getObjectKind());
+  // Stmt is often written unabbreviated.
+  // VK(2) + OK(3) fit together into a single VBR6 chunk.
+  Record.push_back(E->getValueKind() | E->getObjectKind() << 2);
 }
 
 void ASTStmtWriter::VisitConstantExpr(ConstantExpr *E) {
Index: clang/lib/Serialization/ASTWriterDecl.cpp
===================================================================
--- clang/lib/Serialization/ASTWriterDecl.cpp
+++ clang/lib/Serialization/ASTWriterDecl.cpp
@@ -2296,9 +2296,8 @@
   // Expr
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Type
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, ExprDependenceBits));
-  Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 3)); //GetValueKind
-  Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 3)); //GetObjectKind
-  //DeclRefExpr
+  Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 5)); // ValueKind, ObjectKind
+  // DeclRefExpr
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); //HasQualifier
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); //GetDeclFound
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); //ExplicitTemplateArgs
@@ -2316,9 +2315,8 @@
   // Expr
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Type
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, ExprDependenceBits));
-  Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 3)); //GetValueKind
-  Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 3)); //GetObjectKind
-  //Integer Literal
+  Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 5)); // ValueKind, ObjectKind
+  // Integer Literal
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Location
   Abv->Add(BitCodeAbbrevOp(32));                      // Bit Width
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Value
@@ -2331,9 +2329,8 @@
   // Expr
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Type
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, ExprDependenceBits));
-  Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 3)); //GetValueKind
-  Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 3)); //GetObjectKind
-  //Character Literal
+  Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 5)); // ValueKind, ObjectKind
+  // Character Literal
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // getValue
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Location
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 3)); // getKind
@@ -2346,8 +2343,7 @@
   // Expr
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Type
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, ExprDependenceBits));
-  Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 3)); //GetValueKind
-  Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 3)); //GetObjectKind
+  Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 5)); // ValueKind, ObjectKind
   // CastExpr
   Abv->Add(BitCodeAbbrevOp(0)); // PathSize
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // HasFPFeatures
Index: clang/lib/Serialization/ASTReaderStmt.cpp
===================================================================
--- clang/lib/Serialization/ASTReaderStmt.cpp
+++ clang/lib/Serialization/ASTReaderStmt.cpp
@@ -107,7 +107,7 @@
 
     /// The number of record fields required for the Expr class
     /// itself.
-    static const unsigned NumExprFields = NumStmtFields + 4;
+    static const unsigned NumExprFields = NumStmtFields + 3;
 
     /// Read and initialize a ExplicitTemplateArgumentList structure.
     void ReadTemplateKWAndArgsInfo(ASTTemplateKWAndArgsInfo &Args,
@@ -521,8 +521,9 @@
   VisitStmt(E);
   E->setType(Record.readType());
   E->setDependence(static_cast<ExprDependence>(Record.readInt()));
-  E->setValueKind(static_cast<ExprValueKind>(Record.readInt()));
-  E->setObjectKind(static_cast<ExprObjectKind>(Record.readInt()));
+  unsigned OKVK = Record.readInt();
+  E->setValueKind(static_cast<ExprValueKind>(OKVK & 0x3));
+  E->setObjectKind(static_cast<ExprObjectKind>(OKVK >> 2));
   assert(Record.getIdx() == NumExprFields &&
          "Incorrect expression field count");
 }


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