PPC/s390: [wasm] Access "CEntryStub" from the root set.

Port 55643564

Original Commit Message:

    This removes a shortcut to a "CEntryStub" from the instance object and
    instead loads those values via the root set which is also referenced
    from the instance. It makes instance objects smaller.

R=mstarzinger@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=
LOG=N

Change-Id: I2ad2f3479431dae71f47af7ad5c722e46fd592d6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1716368Reviewed-by: Junliang Yan <jyan@ca.ibm.com>
Reviewed-by: Joran Siu <joransiu@ca.ibm.com>
Commit-Queue: Milad Farazmand <miladfar@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#62897}

src/builtins/ppc/builtins-ppc.cc

@@ -2599,7 +2599,10 @@ void Builtins::Generate_WasmCompileLazy(MacroAssembler* masm) {
     __ Push(kWasmInstanceRegister, kWasmCompileLazyFuncIndexRegister);
     // Load the correct CEntry builtin from the instance object.
     __ LoadP(r5, FieldMemOperand(kWasmInstanceRegister,
-                                 WasmInstanceObject::kCEntryStubOffset));
+                                 WasmInstanceObject::kIsolateRootOffset));
+    auto centry_id =
+        Builtins::kCEntry_Return1_DontSaveFPRegs_ArgvOnStack_NoBuiltinExit;
+    __ LoadP(r5, MemOperand(r5, IsolateData::builtin_slot_offset(centry_id)));
     // Initialize the JavaScript context with 0. CEntry will use it to
     // set the current context on the isolate.
     __ LoadSmiLiteral(cp, Smi::zero());

src/builtins/s390/builtins-s390.cc

@@ -2657,7 +2657,10 @@ void Builtins::Generate_WasmCompileLazy(MacroAssembler* masm) {
     __ Push(kWasmInstanceRegister, r7);
     // Load the correct CEntry builtin from the instance object.
     __ LoadP(r4, FieldMemOperand(kWasmInstanceRegister,
-                                 WasmInstanceObject::kCEntryStubOffset));
+                                 WasmInstanceObject::kIsolateRootOffset));
+    auto centry_id =
+        Builtins::kCEntry_Return1_DontSaveFPRegs_ArgvOnStack_NoBuiltinExit;
+    __ LoadP(r4, MemOperand(r4, IsolateData::builtin_slot_offset(centry_id)));
     // Initialize the JavaScript context with 0. CEntry will use it to
     // set the current context on the isolate.
     __ LoadSmiLiteral(cp, Smi::zero());