PPC: Fix offset calculation on AIX when not using a

function descriptor

Change-Id: I439bac759cb363f35f6aa23a699b6ef1d9079684
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1925027Reviewed-by: Junliang Yan <jyan@ca.ibm.com>
Commit-Queue: Milad Farazmand <miladfar@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#65052}

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

@@ -1940,6 +1940,7 @@ void TurboAssembler::CallCFunctionHelper(Register function,
     LoadP(ip, MemOperand(function, 0));
     dest = ip;
   } else if (ABI_CALL_VIA_IP) {
+    // pLinux and Simualtor, not AIX
     Move(ip, function);
     dest = ip;
   }

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

@@ -1031,17 +1031,18 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
       Label start_call;
       bool isWasmCapiFunction =
           linkage()->GetIncomingDescriptor()->IsWasmCapiFunction();
+      int offset = 9 * kInstrSize;
 #if defined(_AIX)
       // AIX/PPC64BE Linux uses a function descriptor
       int kNumParametersMask = kHasFunctionDescriptorBitMask - 1;
       num_parameters = kNumParametersMask & misc_field;
       has_function_descriptor =
           (misc_field & kHasFunctionDescriptorBitMask) != 0;
-      // AIX emits 2 extra Load instructions under CallCFunctionHelper
+      // AIX may emit 2 extra Load instructions under CallCFunctionHelper
       // due to having function descriptor.
-      constexpr int offset = 11 * kInstrSize;
-#else
-      constexpr int offset = 9 * kInstrSize;
+      if (has_function_descriptor) {
+        offset = 11 * kInstrSize;
+      }
 #endif
       if (isWasmCapiFunction) {
         __ mflr(r0);