[wasm][turbofan] Only use LoadImmutable for non-tagged values

Due to immutable loads being placed earlier during scheduling and
subsequently being spilled, the safepoint table of a function may grow
significantly. Until we implement an optimization to avoid spilling in
such cases, we disable immutable loads for tagged values.

Bug: chromium:1191540, v8:11510
Change-Id: Ia5c5d274e6d4b9145cd028828f9a328a65bed17f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2796953
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73743}

src/compiler/wasm-compiler.cc

@@ -84,10 +84,19 @@ MachineType assert_size(int expected_size, MachineType type) {
       assert_size(WASM_INSTANCE_OBJECT_SIZE(name), type), BuildLoadInstance(), \
       wasm::ObjectAccess::ToTagged(WasmInstanceObject::k##name##Offset))
 
+// TODO(11510): Using LoadImmutable for tagged values causes registers to be
+// spilled and added to the safepoint table, resulting in large code size
+// regressions. A possible solution would be to not spill the register at all,
+// but rather reload the value from memory. This will require non-trivial
+// changes in the register allocator and instuction selector.
 #define LOAD_INSTANCE_FIELD(name, type)                          \
-  gasm_->LoadImmutable(                                                        \
-      assert_size(WASM_INSTANCE_OBJECT_SIZE(name), type), BuildLoadInstance(), \
-      wasm::ObjectAccess::ToTagged(WasmInstanceObject::k##name##Offset))
+  (CanBeTaggedOrCompressedPointer((type).representation())       \
+       ? LOAD_MUTABLE_INSTANCE_FIELD(name, type)                 \
+       : gasm_->LoadImmutable(                                   \
+             assert_size(WASM_INSTANCE_OBJECT_SIZE(name), type), \
+             BuildLoadInstance(),                                \
+             wasm::ObjectAccess::ToTagged(                       \
+                 WasmInstanceObject::k##name##Offset)))
 
 #define LOAD_ROOT(root_name, factory_name)                   \
   (use_js_isolate_and_params()                               \