[Strings] string.concat (#4777)

Author: kripken

scripts/gen-s-parser.py

@@ -621,6 +621,7 @@
     ("string.measure_wtf16", "makeStringMeasure(s, StringMeasureWTF16)"),
     ("string.encode_wtf8",   "makeStringEncode(s, StringEncodeWTF8)"),
     ("string.encode_wtf16",  "makeStringEncode(s, StringEncodeWTF16)"),
+    ("string.concat",        "makeStringConcat(s)"),
 ]
 
 

src/gen-s-parser.inc

@@ -3129,9 +3129,17 @@ switch (op[0]) {
         switch (op[3]) {
           case 'i': {
             switch (op[7]) {
-              case 'c':
-                if (strcmp(op, "string.const") == 0) { return makeStringConst(s); }
-                goto parse_error;
+              case 'c': {
+                switch (op[10]) {
+                  case 'c':
+                    if (strcmp(op, "string.concat") == 0) { return makeStringConcat(s); }
+                    goto parse_error;
+                  case 's':
+                    if (strcmp(op, "string.const") == 0) { return makeStringConst(s); }
+                    goto parse_error;
+                  default: goto parse_error;
+                }
+              }
               case 'e': {
                 switch (op[17]) {
                   case '1':

src/ir/ReFinalize.cpp

@@ -176,6 +176,7 @@ void ReFinalize::visitStringNew(StringNew* curr) { curr->finalize(); }
 void ReFinalize::visitStringConst(StringConst* curr) { curr->finalize(); }
 void ReFinalize::visitStringMeasure(StringMeasure* curr) { curr->finalize(); }
 void ReFinalize::visitStringEncode(StringEncode* curr) { curr->finalize(); }
+void ReFinalize::visitStringConcat(StringConcat* curr) { curr->finalize(); }
 
 void ReFinalize::visitFunction(Function* curr) {
   // we may have changed the body from unreachable to none, which might be bad

src/ir/cost.h

@@ -681,6 +681,9 @@ struct CostAnalyzer : public OverriddenVisitor<CostAnalyzer, CostType> {
   CostType visitStringEncode(StringEncode* curr) {
     return 6 + visit(curr->ref) + visit(curr->ptr);
   }
+  CostType visitStringConcat(StringConcat* curr) {
+    return 10 + visit(curr->left) + visit(curr->right);
+  }
 
 private:
   CostType nullCheckCost(Expression* ref) {

src/ir/effects.h

@@ -742,6 +742,10 @@ class EffectAnalyzer {
       // traps when ref is null or we write out of bounds.
       parent.implicitTrap = true;
     }
+    void visitStringConcat(StringConcat* curr) {
+      // traps when an input is null.
+      parent.implicitTrap = true;
+    }
   };
 
 public:

src/ir/possible-contents.cpp

@@ -689,6 +689,10 @@ struct InfoCollector
     // TODO: optimize when possible
     addRoot(curr);
   }
+  void visitStringConcat(StringConcat* curr) {
+    // TODO: optimize when possible
+    addRoot(curr);
+  }
 
   // TODO: Model which throws can go to which catches. For now, anything thrown
   //       is sent to the location of that tag, and any catch of that tag can

src/passes/Print.cpp

@@ -2272,6 +2272,9 @@ struct PrintExpressionContents
         WASM_UNREACHABLE("invalid string.encode*");
     }
   }
+  void visitStringConcat(StringConcat* curr) {
+    printMedium(o, "string.concat");
+  }
 };
 
 // Prints an expression in s-expr format, including both the

src/wasm-binary.h

@@ -1144,6 +1144,7 @@ enum ASTNodes {
   StringMeasureWTF16 = 0x85,
   StringEncodeWTF8 = 0x86,
   StringEncodeWTF16 = 0x87,
+  StringConcat = 0x88,
 };
 
 enum MemoryAccess {
@@ -1728,6 +1729,7 @@ class WasmBinaryBuilder {
   bool maybeVisitStringConst(Expression*& out, uint32_t code);
   bool maybeVisitStringMeasure(Expression*& out, uint32_t code);
   bool maybeVisitStringEncode(Expression*& out, uint32_t code);
+  bool maybeVisitStringConcat(Expression*& out, uint32_t code);
   void visitSelect(Select* curr, uint8_t code);
   void visitReturn(Return* curr);
   void visitMemorySize(MemorySize* curr);

src/wasm-builder.h

@@ -1020,6 +1020,13 @@ class Builder {
     ret->finalize();
     return ret;
   }
+  StringConcat* makeStringConcat(Expression* left, Expression* right) {
+    auto* ret = wasm.allocator.alloc<StringConcat>();
+    ret->left = left;
+    ret->right = right;
+    ret->finalize();
+    return ret;
+  }
 
   // Additional helpers
 

src/wasm-delegations-fields.def

@@ -742,6 +742,13 @@ switch (DELEGATE_ID) {
     DELEGATE_END(StringEncode);
     break;
   }
+  case Expression::Id::StringConcatId: {
+    DELEGATE_START(StringConcat);
+    DELEGATE_FIELD_CHILD(StringConcat, right);
+    DELEGATE_FIELD_CHILD(StringConcat, left);
+    DELEGATE_END(StringConcat);
+    break;
+  }
 }
 
 #undef DELEGATE_ID