PPC/s390: Fix undefined behaviour on CommentOperator

Port 19953355

Original Commit Message:

    The {CommentOperator}, used for implementing the --code-comments flag,
    is not UBSan-safe. This CL fixes this and adds a test which uses code
    comments.

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

Change-Id: Ia7976ec9a726fdeb7d8bfbb99c8a16d473aa0da4
Reviewed-on: https://chromium-review.googlesource.com/1157230Reviewed-by: Muntasir Mallick <mmallick@ca.ibm.com>
Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#54828}

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

@@ -1057,11 +1057,13 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
     case kArchPrepareTailCall:
       AssemblePrepareTailCall();
       break;
-    case kArchComment: {
-      Address comment_string = i.InputExternalReference(0).address();
-      __ RecordComment(reinterpret_cast<const char*>(comment_string));
+    case kArchComment:
+#ifdef V8_TARGET_ARCH_PPC64
+      __ RecordComment(reinterpret_cast<const char*>(i.InputInt64(0)));
+#else
+      __ RecordComment(reinterpret_cast<const char*>(i.InputInt32(0)));
+#endif
       break;
-    }
     case kArchCallCFunction: {
       int const num_parameters = MiscField::decode(instr->opcode());
       if (instr->InputAt(0)->IsImmediate()) {

src/compiler/s390/code-generator-s390.cc

@@ -1348,11 +1348,13 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
   ArchOpcode opcode = ArchOpcodeField::decode(instr->opcode());
 
   switch (opcode) {
-    case kArchComment: {
-      Address comment_string = i.InputExternalReference(0).address();
-      __ RecordComment(reinterpret_cast<const char*>(comment_string));
+    case kArchComment:
+#ifdef V8_TARGET_ARCH_S390X
+      __ RecordComment(reinterpret_cast<const char*>(i.InputInt64(0)));
+#else
+      __ RecordComment(reinterpret_cast<const char*>(i.InputInt32(0)));
+#endif
       break;
-    }
     case kArchCallCodeObject: {
       if (HasRegisterInput(instr, 0)) {
         Register reg = i.InputRegister(0);