PPC/s390: handle kExternalRef case

R=joransiu@ca.ibm.com

Change-Id: Iace9b8bf40d416b2c7c56c383d00b4f0a6501de1
Reviewed-on: https://chromium-review.googlesource.com/1236973Reviewed-by: Muntasir Mallick <mmallick@ca.ibm.com>
Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#56103}

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

@@ -74,6 +74,7 @@ class PPCOperandConverter final : public InstructionOperandConverter {
         return Operand(constant.ToInt64());
 #endif
       case Constant::kExternalReference:
+        return Operand(constant.ToExternalReference());
       case Constant::kDelayedStringConstant:
         return Operand::EmbeddedStringConstant(
             constant.ToDelayedStringConstant());

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

@@ -67,6 +67,7 @@ class S390OperandConverter final : public InstructionOperandConverter {
         return Operand(constant.ToInt64());
 #endif
       case Constant::kExternalReference:
+        return Operand(constant.ToExternalReference());
       case Constant::kDelayedStringConstant:
         return Operand::EmbeddedStringConstant(
             constant.ToDelayedStringConstant());