PPC/s390: Reland "[ptr-compr] New RelocInfo for compressed pointers."

Port 18c29ab9

Original Commit Message:

    Port ed319e84

    Original Commit Message:

        Failure addressed by not exposing the new test to the jitless environment.
        (jgruber@ on TBR).

        New enum RelocInfo::COMPRESSED_EMBEDDED_OBJECT created to support
        compressed pointers in generated code. Enum name EMBEDDED_OBJECT
        changed to FULL_EMBEDDED_OBJECT.

        RelocInfo::[set_]target_object() abstract away the difference between
        FULL_EMBEDDED_OBJECT and COMPRESSED_EMBEDDED_OBJECT.

        Compressed embedded objects can only be created at this time on
        x64 with pointer compression turned on. Arm64 constant pools don't
        support compressed objects at this time.

R=miladfar@ca.ibm.com, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=
LOG=N

Change-Id: I97ef9b7394f384c2a1b97aab9fdac0eeb80eb734
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1591993Reviewed-by: Junliang Yan <jyan@ca.ibm.com>
Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
Commit-Queue: Milad Farazmand <miladfar@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#61143}

src/ppc/assembler-ppc-inl.h

@@ -178,7 +178,7 @@ Handle<HeapObject> RelocInfo::target_object_handle(Assembler* origin) {
 void RelocInfo::set_target_object(Heap* heap, HeapObject target,
                                   WriteBarrierMode write_barrier_mode,
                                   ICacheFlushMode icache_flush_mode) {
-  DCHECK(IsCodeTarget(rmode_) || rmode_ == EMBEDDED_OBJECT);
+  DCHECK(IsCodeTarget(rmode_) || rmode_ == FULL_EMBEDDED_OBJECT);
   Assembler::set_target_address_at(pc_, constant_pool_, target->ptr(),
                                    icache_flush_mode);
   if (write_barrier_mode == UPDATE_WRITE_BARRIER && !host().is_null()) {