Reapply "AMDGPU: Add 32-bit constant address space"

This reverts r324494 and reapplies r324487.

llvm-svn: 324747
diff --git a/llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.cpp b/llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.cpp
index 6292a4e..c3e96f9 100644
--- a/llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.cpp
@@ -447,7 +447,8 @@
 }
 
 bool isReadOnlySegment(const GlobalValue *GV) {
-  return GV->getType()->getAddressSpace() == AMDGPUAS::CONSTANT_ADDRESS;
+  return GV->getType()->getAddressSpace() == AMDGPUAS::CONSTANT_ADDRESS ||
+         GV->getType()->getAddressSpace() == AMDGPUAS::CONSTANT_ADDRESS_32BIT;
 }
 
 bool shouldEmitConstantsToTextSection(const Triple &TT) {