[wasm] WasmModuleBuilder should emit 'end' after an init. expr.

WriteInitializerExpressions did not emit the final 'end' opcode, and
expected call sites to do so, which they did not do consistently.
We move this functionality to WriteInitializerExpression.

Change-Id: Idf42272a3dbdfd0d7f22675731e193584f75c41f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3122159
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76532}

src/wasm/wasm-module-builder.cc

@@ -454,7 +454,8 @@ void WasmModuleBuilder::SetMaxMemorySize(uint32_t value) {
 void WasmModuleBuilder::SetHasSharedMemory() { has_shared_memory_ = true; }
 
 namespace {
-void WriteInitializerExpression(ZoneBuffer* buffer, const WasmInitExpr& init,
+void WriteInitializerExpressionWithEnd(ZoneBuffer* buffer,
+                                       const WasmInitExpr& init,
                                        ValueType type) {
   switch (init.kind()) {
     case WasmInitExpr::kI32Const:
@@ -534,7 +535,7 @@ void WriteInitializerExpression(ZoneBuffer* buffer, const WasmInitExpr& init,
     case WasmInitExpr::kStructNewWithRtt:
       STATIC_ASSERT((kExprStructNewWithRtt >> 8) == kGCPrefix);
       for (const WasmInitExpr& operand : init.operands()) {
-        WriteInitializerExpression(buffer, operand, kWasmBottom);
+        WriteInitializerExpressionWithEnd(buffer, operand, kWasmBottom);
       }
       buffer->write_u8(kGCPrefix);
       buffer->write_u8(static_cast<uint8_t>(kExprStructNewWithRtt));
@@ -543,7 +544,7 @@ void WriteInitializerExpression(ZoneBuffer* buffer, const WasmInitExpr& init,
     case WasmInitExpr::kArrayInit:
       STATIC_ASSERT((kExprArrayInit >> 8) == kGCPrefix);
       for (const WasmInitExpr& operand : init.operands()) {
-        WriteInitializerExpression(buffer, operand, kWasmBottom);
+        WriteInitializerExpressionWithEnd(buffer, operand, kWasmBottom);
       }
       buffer->write_u8(kGCPrefix);
       buffer->write_u8(static_cast<uint8_t>(kExprArrayInit));
@@ -559,7 +560,8 @@ void WriteInitializerExpression(ZoneBuffer* buffer, const WasmInitExpr& init,
     case WasmInitExpr::kRttSub:
     case WasmInitExpr::kRttFreshSub:
       // The operand to rtt.sub must be emitted first.
-      WriteInitializerExpression(buffer, init.operands()[0], kWasmBottom);
+      WriteInitializerExpressionWithEnd(buffer, init.operands()[0],
+                                        kWasmBottom);
       STATIC_ASSERT((kExprRttSub >> 8) == kGCPrefix);
       STATIC_ASSERT((kExprRttFreshSub >> 8) == kGCPrefix);
       buffer->write_u8(kGCPrefix);
@@ -571,6 +573,11 @@ void WriteInitializerExpression(ZoneBuffer* buffer, const WasmInitExpr& init,
   }
 }
 
+void WriteInitializerExpression(ZoneBuffer* buffer, const WasmInitExpr& init,
+                                ValueType type) {
+  WriteInitializerExpressionWithEnd(buffer, init, type);
+  buffer->write_u8(kExprEnd);
+}
 }  // namespace
 
 void WasmModuleBuilder::WriteTo(ZoneBuffer* buffer) const {
@@ -705,7 +712,6 @@ void WasmModuleBuilder::WriteTo(ZoneBuffer* buffer) const {
       WriteValueType(buffer, global.type);
       buffer->write_u8(global.mutability ? 1 : 0);
       WriteInitializerExpression(buffer, global.init, global.type);
-      buffer->write_u8(kExprEnd);
     }
     FixupSection(buffer, start);
   }