Revert of PPC: [compiler] Drop the CompareNilIC. (patchset #1 id:1 of...

Revert of PPC: [compiler] Drop the CompareNilIC. (patchset #1 id:1 of https://codereview.chromium.org/1733663003/ )

Reason for revert:
Original commit reverted.

Original issue's description:
> PPC: [compiler] Drop the CompareNilIC.
>
> Port 666aec03
>
> Original commit message:
>     Since both null and undefined are also marked as undetectable now, we
>     can just test that bit instead of having the CompareNilIC try to collect
>     feedback to speed up the general case (without the undetectable bit
>     being used).
>
>     Drive-by-fix: Update the type system to match the new handling of
>     undetectable in the runtime.
>
> R=bmeurer@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
> BUG=
>
> Committed: https://crrev.com/546ea6b8393a894f07597ade5ec1c7db02c1e425
> Cr-Commit-Position: refs/heads/master@{#34266}

TBR=bmeurer@chromium.org,joransiu@ca.ibm.com,jyan@ca.ibm.com,michael_dawson@ca.ibm.com
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=

Review URL: https://codereview.chromium.org/1736253003

Cr-Commit-Position: refs/heads/master@{#34340}

src/full-codegen/ppc/full-codegen-ppc.cc

@@ -3994,11 +3994,10 @@ void FullCodeGenerator::EmitLiteralCompareNil(CompareOperation* expr,
     __ cmp(r3, r4);
     Split(eq, if_true, if_false, fall_through);
   } else {
-    __ JumpIfSmi(r3, if_false);
-    __ LoadP(r3, FieldMemOperand(r3, HeapObject::kMapOffset));
-    __ lbz(r4, FieldMemOperand(r3, Map::kBitFieldOffset));
-    __ andi(r0, r4, Operand(1 << Map::kIsUndetectable));
-    Split(ne, if_true, if_false, fall_through, cr0);
+    Handle<Code> ic = CompareNilICStub::GetUninitialized(isolate(), nil);
+    CallIC(ic, expr->CompareOperationFeedbackId());
+    __ CompareRoot(r3, Heap::kTrueValueRootIndex);
+    Split(eq, if_true, if_false, fall_through);
   }
   context()->Plug(if_true, if_false);
 }

src/ppc/interface-descriptors-ppc.cc

@@ -314,6 +314,13 @@ void CompareDescriptor::InitializePlatformSpecific(
 }
 
 
+void CompareNilDescriptor::InitializePlatformSpecific(
+    CallInterfaceDescriptorData* data) {
+  Register registers[] = {r3};
+  data->InitializePlatformSpecific(arraysize(registers), registers);
+}
+
+
 void ToBooleanDescriptor::InitializePlatformSpecific(
     CallInterfaceDescriptorData* data) {
   Register registers[] = {r3};