[Strings] Add string.const (#4768)

This is more work than a typical instruction because it also adds a new section:
all the (string.const "foo") strings are put in a new "strings" section in the binary, and
the instructions refer to them by index.

1 files changed, 13 insertions, 1 deletions

diff --git a/src/wasm-binary.h b/src/wasm-binary.h
index c7ac7e7b7..c88aa3895 100644
--- a/src/wasm-binary.h
+++ b/src/wasm-binary.h
@@ -326,7 +326,8 @@ enum Section {
   Code = 10,
   Data = 11,
   DataCount = 12,
-  Tag = 13
+  Tag = 13,
+  Strings = 14,
 };
 
 // A passive segment is a segment that will not be automatically copied into a
@@ -1138,6 +1139,7 @@ enum ASTNodes {
   BrOnNonI31 = 0x65,
   StringNewWTF8 = 0x80,
   StringNewWTF16 = 0x81,
+  StringConst = 0x82,
 };
 
 enum MemoryAccess {
@@ -1280,6 +1282,7 @@ public:
   void writeFunctionSignatures();
   void writeExpression(Expression* curr);
   void writeFunctions();
+  void writeStrings();
   void writeGlobals();
   void writeExports();
   void writeDataCount();
@@ -1291,6 +1294,7 @@ public:
   uint32_t getGlobalIndex(Name name) const;
   uint32_t getTagIndex(Name name) const;
   uint32_t getTypeIndex(HeapType type) const;
+  uint32_t getStringIndex(Name string) const;
 
   void writeTableDeclarations();
   void writeElementSegments();
@@ -1381,6 +1385,9 @@ private:
   // info here, and then use it when writing the names.
   std::unordered_map<Name, MappedLocals> funcMappedLocals;
 
+  // Indexes in the string literal section of each StringConst in the wasm.
+  std::unordered_map<Name, Index> stringIndexes;
+
   void prepare();
 };
 
@@ -1534,6 +1541,10 @@ public:
   std::vector<Export*> exportOrder;
   void readExports();
 
+  // The strings in the strings section (which are referred to by StringConst).
+  std::vector<Name> strings;
+  void readStrings();
+
   Expression* readExpression();
   void readGlobals();
 
@@ -1710,6 +1721,7 @@ public:
   bool maybeVisitArrayLen(Expression*& out, uint32_t code);
   bool maybeVisitArrayCopy(Expression*& out, uint32_t code);
   bool maybeVisitStringNew(Expression*& out, uint32_t code);
+  bool maybeVisitStringConst(Expression*& out, uint32_t code);
   void visitSelect(Select* curr, uint8_t code);
   void visitReturn(Return* curr);
   void visitMemorySize(MemorySize* curr);