[AIX][CodeGen] Storage Locations for Constant Pointers

This patch adds an `llc` option `-mroptr` to specify storage locations for constant pointers on AIX.

When the `-mroptr` option is specified, constant pointers, virtual function tables, and virtual type tables are placed in read-only storage. Otherwise, by default, pointers, virtual function tables, and virtual type tables are placed are placed in read/write storage.

https://reviews.llvm.org/D144190 enables the `-mroptr` option for `clang`.

Reviewed By: hubert.reinterpretcast, stephenpeckham, myhsu, MaskRay, serge-sans-paille

Differential Revision: https://reviews.llvm.org/D144189

1 files changed, 9 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/CommandFlags.cpp b/llvm/lib/CodeGen/CommandFlags.cpp
index 51d259c..5ef6507 100644
--- a/llvm/lib/CodeGen/CommandFlags.cpp
+++ b/llvm/lib/CodeGen/CommandFlags.cpp
@@ -103,6 +103,7 @@ CGOPT(bool, XRayOmitFunctionIndex)
 CGOPT(bool, DebugStrictDwarf)
 CGOPT(unsigned, AlignLoops)
 CGOPT(bool, JMCInstrument)
+CGOPT(bool, XCOFFReadOnlyPointers)
 
 codegen::RegisterCodeGenFlags::RegisterCodeGenFlags() {
 #define CGBINDOPT(NAME)                                                        \
@@ -478,6 +479,13 @@ codegen::RegisterCodeGenFlags::RegisterCodeGenFlags() {
       cl::init(false));
   CGBINDOPT(JMCInstrument);
 
+  static cl::opt<bool> XCOFFReadOnlyPointers(
+      "mroptr",
+      cl::desc("When set to true, const objects with relocatable address "
+               "values are put into the RO data section."),
+      cl::init(false));
+  CGBINDOPT(XCOFFReadOnlyPointers);
+
 #undef CGBINDOPT
 
   mc::RegisterMCTargetOptionsFlags();
@@ -554,6 +562,7 @@ codegen::InitTargetOptionsFromCodeGenFlags(const Triple &TheTriple) {
   Options.DebugStrictDwarf = getDebugStrictDwarf();
   Options.LoopAlignment = getAlignLoops();
   Options.JMCInstrument = getJMCInstrument();
+  Options.XCOFFReadOnlyPointers = getXCOFFReadOnlyPointers();
 
   Options.MCOptions = mc::InitMCTargetOptionsFromFlags();