diff --git a/llvm/lib/Target/PowerPC/PPCTargetMachine.cpp b/llvm/lib/Target/PowerPC/PPCTargetMachine.cpp
--- a/llvm/lib/Target/PowerPC/PPCTargetMachine.cpp
+++ b/llvm/lib/Target/PowerPC/PPCTargetMachine.cpp
@@ -223,6 +223,10 @@
 
 static Reloc::Model getEffectiveRelocModel(const Triple &TT,
                                            Optional<Reloc::Model> RM) {
+  // AIX only supports PIC, RM option is ignored.
+  if (TT.isOSAIX())
+    return Reloc::PIC_;
+
   if (RM.hasValue())
     return *RM;
 
diff --git a/llvm/unittests/CodeGen/AIXRelocModelTest.cpp b/llvm/unittests/CodeGen/AIXRelocModelTest.cpp
new file mode 100644
--- /dev/null
+++ b/llvm/unittests/CodeGen/AIXRelocModelTest.cpp
@@ -0,0 +1,25 @@
+#include "llvm/ADT/Triple.h"
+#include "llvm/Support/TargetRegistry.h"
+#include "llvm/Target/TargetMachine.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+TEST(AIXRelocModelTest, ForceDefalutToPIC) {
+  Triple TheTriple(/*ArchStr*/ "powerpc", /*VendorStr*/ "", /*OSStr*/ "aix");
+  std::string Error;
+  const Target *TheTarget = TargetRegistry::lookupTarget("", TheTriple, Error);
+  ASSERT_TRUE(TheTarget) << Error;
+
+  TargetOptions Options;
+  // Create a TargetMachine for powerpc-aix target, and deliberately try to set
+  // its relocation model to static.
+  std::unique_ptr<TargetMachine> Target(TheTarget->createTargetMachine(
+      /*TT*/ TheTriple.getTriple(), /*CPU*/ "", /*Features*/ "",
+      /*Options*/ Options, /*RM*/ Reloc::Static, /*CM*/ None,
+      /*OL*/ CodeGenOpt::Default));
+  ASSERT_TRUE(Target) << "Could not allocate target machine!";
+
+  // The relocation model on AIX should be force to PIC regardeless.
+  EXPECT_TRUE(Target->getRelocationModel() == Reloc::PIC_);
+}
diff --git a/llvm/unittests/CodeGen/CMakeLists.txt b/llvm/unittests/CodeGen/CMakeLists.txt
--- a/llvm/unittests/CodeGen/CMakeLists.txt
+++ b/llvm/unittests/CodeGen/CMakeLists.txt
@@ -14,6 +14,7 @@
 
 add_llvm_unittest(CodeGenTests
   AArch64SelectionDAGTest.cpp
+  AIXRelocModelTest.cpp
   DIEHashTest.cpp
   LowLevelTypeTest.cpp
   MachineInstrBundleIteratorTest.cpp