PPC: Disable constantpool before calling Stub without frame

    Constantpool register is being used with no frame, and
    therefore it points to its parent stub's constantpool
    causing segfault.
    Disable constantpool before CallStub if frame not set.

R=joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, mbrandy@us.ibm.com

BUG=
LOG=N

Review-Url: https://codereview.chromium.org/2106493002
Cr-Commit-Position: refs/heads/master@{#37300}

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

@@ -216,7 +216,12 @@ class OutOfLineRecordWrite final : public OutOfLineCode {
       DCHECK_EQ(0, offset_immediate_);
       __ add(scratch1_, object_, offset_);
     }
+    if (must_save_lr_ && FLAG_enable_embedded_constant_pool) {
+      ConstantPoolUnavailableScope constant_pool_unavailable(masm());
+      __ CallStub(&stub);
+    } else {
       __ CallStub(&stub);
+    }
     if (must_save_lr_) {
       // We need to save and restore lr if the frame was elided.
       __ Pop(scratch1_);