add global.get to as a valid elem expression

Author: martianboy

src/wasm/wasm-validator.cpp

@@ -799,7 +799,7 @@ void FunctionValidator::visitCallIndirect(CallIndirect* curr) {
     shouldBeTrue(!!table, curr, "call-indirect table must exist");
     shouldBeTrue(table->type.isFunction(),
                  curr,
-                 "call-indirect table type must be a funcref.");
+                 "call-indirect table must be of function type.");
   }
 
   validateCallParamsAndResult(curr, curr->sig);
@@ -2861,24 +2861,30 @@ static void validateTables(Module& module, ValidationInfo& info) {
       "table",
       "Non-nullable reference types are not yet supported for tables");
     if (!module.features.hasGC()) {
-      info.shouldBeTrue(
-        table->type.isFunction() || table->type == Type::externref,
-        "table",
-        "Only function reference types or externref are valid for table type");
+      info.shouldBeTrue(table->type.isFunction() ||
+                          table->type == Type::externref,
+                        "table",
+                        "Only function reference types or externref are valid "
+                        "for table type (when GC is disabled)");
     }
     if (!module.features.hasTypedFunctionReferences()) {
       info.shouldBeTrue(table->type == Type::funcref ||
                           table->type == Type::externref,
                         "table",
-                        "Only funcref and externref are valid for table type");
+                        "Only funcref and externref are valid for table type "
+                        "(when typed-function references are disabled)");
     }
   }
 
   for (auto& segment : module.elementSegments) {
-    info.shouldBeUnequal(segment->type,
-                         Type(Type::externref),
-                         "elem",
-                         "element segment type cannot be externref");
+    // Since element segment items need to be constant expressions, that leaves
+    // us with ref.null, ref.func and global.get. The GC proposal adds rtt.canon
+    // and rtt.sub to the list, but Binaryen doesn't consider RTTs as reference-
+    // types yet. As a result, the only possible type for element segments will
+    // be function references.
+    info.shouldBeTrue(segment->type.isFunction(),
+                      "elem",
+                      "element segment type must be of function type.");
     info.shouldBeTrue(
       segment->type.isNullable(),
       "elem",
@@ -2922,10 +2928,17 @@ static void validateTables(Module& module, ValidationInfo& info) {
     // Avoid double checking items
     if (module.features.hasReferenceTypes()) {
       for (auto* expr : segment->data) {
-        info.shouldBeTrue(
-          expr->is<RefFunc>() || expr->is<RefNull>(),
-          expr,
-          "element segment items must be either ref.func or ref.null func");
+        if (auto* globalExpr = expr->dynCast<GlobalGet>()) {
+          auto* global = module.getGlobal(globalExpr->name);
+          info.shouldBeFalse(
+            global->mutable_, expr, "expected a constant expression");
+        } else {
+          info.shouldBeTrue(expr->is<RefFunc>() || expr->is<RefNull>() ||
+                              expr->is<GlobalGet>(),
+                            expr,
+                            "element segment items must be one of global.get, "
+                            "ref.func, ref.null func");
+        }
         info.shouldBeSubType(expr->type,
                              segment->type,
                              expr,

test/multi-table.wast

@@ -1,5 +1,7 @@
 (module
   (type $none_=>_none (func))
+  (type $A (struct))
+  (global $g1 (ref null $none_=>_none) (ref.func $f))
   (import "a" "b" (table $t1 1 10 funcref))
   (table $t2 3 3 funcref)
   (table $t3 4 4 funcref)
@@ -17,7 +19,7 @@
 
   (elem $passive-1 func $f $g)
   (elem $passive-2 funcref (item ref.func $f) (item (ref.func $g)) (ref.null func))
-  (elem $passive-3 (ref null $none_=>_none) (item ref.func $f) (item (ref.func $g)) (ref.null $none_=>_none))
+  (elem $passive-3 (ref null $none_=>_none) (item ref.func $f) (item (ref.func $g)) (ref.null $none_=>_none) (global.get $g1))
   (elem $empty func)
   (elem $declarative declare func $h)
 

test/multi-table.wast.from-wast

@@ -11,8 +11,9 @@
  (table $textern 0 externref)
  (elem $passive-1 func $f $g)
  (elem $passive-2 funcref (ref.func $f) (ref.func $g) (ref.null func))
- (elem $passive-3 (ref null $none_=>_none) (ref.func $f) (ref.func $g) (ref.null $none_=>_none))
+ (elem $passive-3 (ref null $none_=>_none) (ref.func $f) (ref.func $g) (ref.null $none_=>_none) (global.get $g1))
  (elem declare func $h)
+ (global $g1 (ref null $none_=>_none) (ref.func $f))
  (func $f
   (drop
    (ref.func $h)

test/multi-table.wast.fromBinary

@@ -11,8 +11,9 @@
  (table $textern 0 externref)
  (elem $passive-1 func $f $g)
  (elem $passive-2 funcref (ref.func $f) (ref.func $g) (ref.null func))
- (elem $passive-3 (ref null $none_=>_none) (ref.func $f) (ref.func $g) (ref.null $none_=>_none))
+ (elem $passive-3 (ref null $none_=>_none) (ref.func $f) (ref.func $g) (ref.null $none_=>_none) (global.get $g1))
  (elem declare func $h)
+ (global $g1 (ref null $none_=>_none) (ref.func $f))
  (func $f
   (drop
    (ref.func $h)

test/multi-table.wast.fromBinary.noDebugInfo

@@ -11,8 +11,9 @@
  (table $2 0 externref)
  (elem func $0 $1)
  (elem funcref (ref.func $0) (ref.func $1) (ref.null func))
- (elem (ref null $none_=>_none) (ref.func $0) (ref.func $1) (ref.null $none_=>_none))
+ (elem (ref null $none_=>_none) (ref.func $0) (ref.func $1) (ref.null $none_=>_none) (global.get $global$0))
  (elem declare func $2)
+ (global $global$0 (ref null $none_=>_none) (ref.func $0))
  (func $0
   (drop
    (ref.func $2)