[Strings] Implement string.encode_wtf16_array (#6402)

Author: kripken

src/wasm-interpreter.h

@@ -1919,7 +1919,43 @@ class ExpressionRunner : public OverriddenVisitor<SubType, Flow> {
     }
     return Literal(int32_t(data->values.size()));
   }
-  Flow visitStringEncode(StringEncode* curr) { return Flow(NONCONSTANT_FLOW); }
+  Flow visitStringEncode(StringEncode* curr) {
+    // For now we only support JS-style strings into arrays.
+    if (curr->op != StringEncodeWTF16Array) {
+      return Flow(NONCONSTANT_FLOW);
+    }
+
+    Flow ref = visit(curr->ref);
+    if (ref.breaking()) {
+      return ref;
+    }
+    Flow ptr = visit(curr->ptr);
+    if (ptr.breaking()) {
+      return ptr;
+    }
+    Flow start = visit(curr->start);
+    if (start.breaking()) {
+      return start;
+    }
+
+    auto refData = ref.getSingleValue().getGCData();
+    auto ptrData = ptr.getSingleValue().getGCData();
+    if (!refData || !ptrData) {
+      trap("null ref");
+    }
+    auto startVal = start.getSingleValue().getInteger();
+    auto& refValues = refData->values;
+    auto& ptrValues = ptrData->values;
+    if (startVal + refValues.size() > ptrValues.size()) {
+      trap("oob");
+    }
+
+    for (Index i = 0; i < refValues.size(); i++) {
+      ptrValues[startVal + i] = refValues[i];
+    }
+
+    return Literal(int32_t(refData->values.size()));
+  }
   Flow visitStringConcat(StringConcat* curr) { return Flow(NONCONSTANT_FLOW); }
   Flow visitStringEq(StringEq* curr) {
     NOTE_ENTER("StringEq");

test/lit/exec/strings.wast

@@ -4,8 +4,11 @@
 
 (module
   (type $array16 (array (mut i16)))
+
   (memory 1 1)
 
+  (import "fuzzing-support" "log" (func $log (param i32)))
+
   ;; CHECK:      [fuzz-exec] calling new_wtf16_array
   ;; CHECK-NEXT: [fuzz-exec] note result: new_wtf16_array => string("ello")
   (func $new_wtf16_array (export "new_wtf16_array") (result stringref)
@@ -185,6 +188,62 @@
       )
     )
   )
+
+  ;; CHECK:      [fuzz-exec] calling encode
+  ;; CHECK-NEXT: [LoggingExternalInterface logging 3]
+  ;; CHECK-NEXT: [LoggingExternalInterface logging 0]
+  ;; CHECK-NEXT: [LoggingExternalInterface logging 97]
+  ;; CHECK-NEXT: [LoggingExternalInterface logging 98]
+  ;; CHECK-NEXT: [LoggingExternalInterface logging 99]
+  ;; CHECK-NEXT: [LoggingExternalInterface logging 0]
+  (func $encode (export "encode")
+    (local $array16 (ref $array16))
+    (local.set $array16
+      (array.new_default $array16
+        (i32.const 10)
+      )
+    )
+    ;; Log out that we wrote 3 things.
+    (call $log
+      (string.encode_wtf16_array
+        (string.const "abc")
+        (local.get $array16)
+        (i32.const 4)
+      )
+    )
+    ;; We wrote 3 things at offset 4. Log out the values at 3,4,5,6,7 (the first
+    ;; and last should be 0, and "abc" in between).
+    (call $log
+      (array.get $array16
+        (local.get $array16)
+        (i32.const 3)
+      )
+    )
+    (call $log
+      (array.get $array16
+        (local.get $array16)
+        (i32.const 4)
+      )
+    )
+    (call $log
+      (array.get $array16
+        (local.get $array16)
+        (i32.const 5)
+      )
+    )
+    (call $log
+      (array.get $array16
+        (local.get $array16)
+        (i32.const 6)
+      )
+    )
+    (call $log
+      (array.get $array16
+        (local.get $array16)
+        (i32.const 7)
+      )
+    )
+  )
 )
 ;; CHECK:      [fuzz-exec] calling new_wtf16_array
 ;; CHECK-NEXT: [fuzz-exec] note result: new_wtf16_array => string("ello")
@@ -242,6 +301,14 @@
 
 ;; CHECK:      [fuzz-exec] calling get_length
 ;; CHECK-NEXT: [fuzz-exec] note result: get_length => 7
+
+;; CHECK:      [fuzz-exec] calling encode
+;; CHECK-NEXT: [LoggingExternalInterface logging 3]
+;; CHECK-NEXT: [LoggingExternalInterface logging 0]
+;; CHECK-NEXT: [LoggingExternalInterface logging 97]
+;; CHECK-NEXT: [LoggingExternalInterface logging 98]
+;; CHECK-NEXT: [LoggingExternalInterface logging 99]
+;; CHECK-NEXT: [LoggingExternalInterface logging 0]
 ;; CHECK-NEXT: [fuzz-exec] comparing compare.1
 ;; CHECK-NEXT: [fuzz-exec] comparing compare.10
 ;; CHECK-NEXT: [fuzz-exec] comparing compare.2
@@ -253,6 +320,7 @@
 ;; CHECK-NEXT: [fuzz-exec] comparing compare.8
 ;; CHECK-NEXT: [fuzz-exec] comparing compare.9
 ;; CHECK-NEXT: [fuzz-exec] comparing const
+;; CHECK-NEXT: [fuzz-exec] comparing encode
 ;; CHECK-NEXT: [fuzz-exec] comparing eq.1
 ;; CHECK-NEXT: [fuzz-exec] comparing eq.2
 ;; CHECK-NEXT: [fuzz-exec] comparing eq.3