PPC: fix aix function descriptor issue on builtins

bug: v8:8828
Change-Id: I271f8cd4282f52fbcc573f6ccbe67b1111f62c7f
Reviewed-on: https://chromium-review.googlesource.com/c/1448711
Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59556}

src/builtins/ppc/builtins-ppc.cc

@@ -554,9 +554,6 @@ void Generate_JSEntryVariant(MacroAssembler* masm, StackFrame::Type type,
 
   Label invoke, handler_entry, exit;
 
-  // Called from C
-  __ function_descriptor();
-
   {
     NoRootArrayScope no_root_array(masm);
 
@@ -2603,16 +2600,6 @@ void Builtins::Generate_CEntry(MacroAssembler* masm, int result_size,
   __ Move(isolate_reg, ExternalReference::isolate_address(masm->isolate()));
 
   Register target = r15;
-  if (ABI_USES_FUNCTION_DESCRIPTORS) {
-    // AIX/PPC64BE Linux use a function descriptor.
-    __ LoadP(ToRegister(ABI_TOC_REGISTER), MemOperand(r15, kPointerSize));
-    __ LoadP(ip, MemOperand(r15, 0));  // Instruction address
-    target = ip;
-  } else if (ABI_CALL_VIA_IP) {
-    __ Move(ip, r15);
-    target = ip;
-  }
-
   __ StoreReturnAddressAndCall(target);
 
   // If return value is on the stack, pop it to registers.

src/compiler/backend/ppc/code-generator-ppc.cc

@@ -2287,7 +2287,6 @@ void CodeGenerator::AssembleConstructFrame() {
   auto call_descriptor = linkage()->GetIncomingDescriptor();
   if (frame_access_state()->has_frame()) {
     if (call_descriptor->IsCFunctionCall()) {
-      __ function_descriptor();
       __ mflr(r0);
       if (FLAG_enable_embedded_constant_pool) {
         __ Push(r0, fp, kConstantPoolRegister);

src/regexp/ppc/regexp-macro-assembler-ppc.cc

@@ -109,9 +109,6 @@ RegExpMacroAssemblerPPC::RegExpMacroAssemblerPPC(Isolate* isolate, Zone* zone,
       internal_failure_label_() {
   DCHECK_EQ(0, registers_to_save % 2);
 
-// Called from C
-  __ function_descriptor();
-
   __ b(&entry_label_);  // We'll write the entry code later.
   // If the code gets too big or corrupted, an internal exception will be
   // raised, and we will exit right away.

src/simulator.h

@@ -121,7 +121,19 @@ class GeneratedCode {
 #else
   DISABLE_CFI_ICALL Return Call(Args... args) {
     // When running without a simulator we call the entry directly.
+#if V8_OS_AIX
+    // AIX ABI requires function descriptors (FD).  Artificially create a pseudo
+    // FD to ensure correct dispatch to generated code.  The 'volatile'
+    // declaration is required to avoid the compiler from not observing the
+    // alias of the pseudo FD to the function pointer, and hence, optimizing the
+    // pseudo FD declaration/initialization away.
+    volatile Address function_desc[] = {reinterpret_cast<Address>(fn_ptr_), 0,
+                                        0};
+    Signature* fn = reinterpret_cast<Signature*>(function_desc);
+    return fn(args...);
+#else
     return fn_ptr_(args...);
+#endif  // V8_OS_AIX
   }
 #endif