[wasm-c-api][ptr-compr] Fix call target caching

The previous pseudo-smi storage scheme for caching call target
addresses in a struct without requiring a custom visitor only
works on uncompressed 64-bit platforms. This patch fixes other
platforms (natural or compressed 32-bit) by boxing the address
in a Foreign.

Change-Id: I3c182c1d9ccae4858cac2757fc3daa40d1520998
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1771780
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63422}

src/builtins/base.tq

@@ -986,7 +986,7 @@ extern class WasmExportedFunctionData extends Struct {
   // The remaining fields are for fast calling from C++. The contract is
   // that they are lazily populated, and either all will be present or none.
   c_wrapper_code: Object;
-  wasm_call_target: Smi;  // Pseudo-smi: one-bit shift on all platforms.
+  wasm_call_target: Smi | Foreign;
   packed_args_size: Smi;
 }
 

src/wasm/c-api.cc

@@ -1354,6 +1354,26 @@ i::Handle<i::Object> WasmRefToV8(i::Isolate* isolate, const Ref* ref) {
   return impl(ref)->v8_object();
 }
 
+i::Handle<i::Object> CallTargetForCaching(i::Isolate* isolate,
+                                          i::Address real_call_target) {
+  if (i::kTaggedSize == i::kInt32Size) {
+    return isolate->factory()->NewForeign(real_call_target);
+  } else {
+    // 64-bit uncompressed platform.
+    return i::handle(i::Smi((real_call_target << i::kSmiTagSize) | i::kSmiTag),
+                     isolate);
+  }
+}
+
+i::Address CallTargetFromCache(i::Object cached_call_target) {
+  if (i::kTaggedSize == i::kInt32Size) {
+    return i::Foreign::cast(cached_call_target).foreign_address();
+  } else {
+    // 64-bit uncompressed platform.
+    return cached_call_target.ptr() >> i::kSmiTagSize;
+  }
+}
+
 void PrepareFunctionData(i::Isolate* isolate,
                          i::Handle<i::WasmExportedFunctionData> function_data,
                          i::wasm::FunctionSig* sig) {
@@ -1366,12 +1386,12 @@ void PrepareFunctionData(i::Isolate* isolate,
   // Compute packed args size.
   function_data->set_packed_args_size(
       i::wasm::CWasmArgumentsPacker::TotalSize(sig));
-  // Get call target (function table offset). This is an Address, we store
-  // it as a pseudo-Smi by shifting it by one bit, so the GC leaves it alone.
-  i::Address call_target =
-      function_data->instance().GetCallTarget(function_data->function_index());
-  i::Smi smi_target((call_target << i::kSmiTagSize) | i::kSmiTag);
-  function_data->set_wasm_call_target(smi_target);
+  // Get call target (function table offset), and wrap it as a cacheable object
+  // (pseudo-Smi or Foreign, depending on platform).
+  i::Handle<i::Object> call_target = CallTargetForCaching(
+      isolate,
+      function_data->instance().GetCallTarget(function_data->function_index()));
+  function_data->set_wasm_call_target(*call_target);
 }
 
 void PushArgs(i::wasm::FunctionSig* sig, const Val args[],
@@ -1495,7 +1515,7 @@ auto Func::call(const Val args[], Val results[]) const -> own<Trap> {
   i::Handle<i::Code> wrapper_code = i::Handle<i::Code>(
       i::Code::cast(function_data->c_wrapper_code()), isolate);
   i::Address call_target =
-      function_data->wasm_call_target().ptr() >> i::kSmiTagSize;
+      CallTargetFromCache(function_data->wasm_call_target());
 
   i::wasm::CWasmArgumentsPacker packer(function_data->packed_args_size());
   PushArgs(sig, args, &packer, store);

src/wasm/wasm-objects-inl.h

@@ -324,7 +324,7 @@ SMI_ACCESSORS(WasmExportedFunctionData, jump_table_offset,
               kJumpTableOffsetOffset)
 SMI_ACCESSORS(WasmExportedFunctionData, function_index, kFunctionIndexOffset)
 ACCESSORS(WasmExportedFunctionData, c_wrapper_code, Object, kCWrapperCodeOffset)
-ACCESSORS(WasmExportedFunctionData, wasm_call_target, Smi,
+ACCESSORS(WasmExportedFunctionData, wasm_call_target, Object,
           kWasmCallTargetOffset)
 SMI_ACCESSORS(WasmExportedFunctionData, packed_args_size, kPackedArgsSizeOffset)
 

src/wasm/wasm-objects.h

@@ -792,7 +792,7 @@ class WasmExportedFunctionData : public Struct {
   DECL_INT_ACCESSORS(jump_table_offset)
   DECL_INT_ACCESSORS(function_index)
   DECL_ACCESSORS(c_wrapper_code, Object)
-  DECL_ACCESSORS(wasm_call_target, Smi)
+  DECL_ACCESSORS(wasm_call_target, Object)
   DECL_INT_ACCESSORS(packed_args_size)
 
   DECL_CAST(WasmExportedFunctionData)