Add "PIE Level" metadata to module flags

[tmsriram]

Summary

Currently, with -fPIC,

We see this:

!llvm.module.flags = !{!0}
!0 = !{i32 1, !"PIC Level", i32 2}

and module.getPICLevel() is used to query PIC. I am doing the same for PIE.

I will follow this up with patches to:

• Set PIE Level in LLVM in Clang and delete llvm::TargetOptions::PositionIndependentExecutable target member.
• Use Module::getPIELevel to check for PIE.

[rnk]

lgtm

[• rafael]

Out of curiosity. What is the relationship of this and

enum Model { Default, Static, PIC_, DynamicNoPIC };

Is the enum something we should deprecate and eventually remove? The
medata is used only on The powerpc backend right now.

Cheers,
Rafael

[tmsriram]

267911

include/llvm/IR/Module.h

/// @{
 
   /// \brief Returns the PIC level (small or large model)
   PICLevel::Level getPICLevel() const;
 
   /// \brief Set the PIC level (small or large model)
   void setPICLevel(PICLevel::Level PL);
 /// @}
 
+/// @}
+/// @name Utility functions for querying and setting PIE level
+/// @{
+
+  /// \brief Returns the PIE level (small or large model)
+  PIELevel::Level getPIELevel() const;
+
+  /// \brief Set the PIE level (small or large model)
+  void setPIELevel(PIELevel::Level PL);
+/// @}
+
   /// @name Utility functions for querying and setting PGO summary
   /// @{
 
   /// \brief Set maximum function count in PGO mode
   void setMaximumFunctionCount(uint64_t);
 
   /// \brief Returns maximum function count in PGO mode
   Optional<uint64_t> getMaximumFunctionCount();

include/llvm/Support/CodeGen.h

namespace CodeModel {
     // Sync changes with CodeGenCWrappers.h.
     enum Model { Default, JITDefault, Small, Kernel, Medium, Large };
   }
 
   namespace PICLevel {
     enum Level { Default=0, Small=1, Large=2 };
   }
 
+  namespace PIELevel {
+    enum Level { Default=0, Small=1, Large=2 };
+  }
+
   // TLS models.
   namespace TLSModel {
     enum Model {
       GeneralDynamic,
       LocalDynamic,
       InitialExec,
       LocalExec
     };

lib/IR/Module.cpp

PICLevel::Level Module::getPICLevel() const {
   return static_cast<PICLevel::Level>(
       cast<ConstantInt>(Val->getValue())->getZExtValue());
 }
 
 void Module::setPICLevel(PICLevel::Level PL) {
   addModuleFlag(ModFlagBehavior::Error, "PIC Level", PL);
 }
 
+PIELevel::Level Module::getPIELevel() const {
+  auto *Val = cast_or_null<ConstantAsMetadata>(getModuleFlag("PIE Level"));
+
+  if (!Val)
+    return PIELevel::Default;
+
+  return static_cast<PIELevel::Level>(
+      cast<ConstantInt>(Val->getValue())->getZExtValue());
+}
+
+void Module::setPIELevel(PIELevel::Level PL) {
+  addModuleFlag(ModFlagBehavior::Error, "PIE Level", PL);
+}
+
 void Module::setMaximumFunctionCount(uint64_t Count) {
   addModuleFlag(ModFlagBehavior::Error, "MaxFunctionCount", Count);
 }
 
 Optional<uint64_t> Module::getMaximumFunctionCount() {
   auto *Val =
       cast_or_null<ConstantAsMetadata>(getModuleFlag("MaxFunctionCount"));
   if (!Val)