[Draft] Use Module to get Triple in getDefaultSubtargetFeatures

Module can be used to query target-abi (follow up patch) which
can be used to populate default subtarget features.
It is currently not possible to provide any reasonable
target-features for compiler generated functions (See: #69780)
Having a target-abi will provide a way to add minimal
requirements for target-features like `+d` for RISC-V.

Author: hiraditya

llvm/include/llvm/LTO/legacy/ThinLTOCodeGenerator.h

@@ -40,7 +40,7 @@ struct TargetMachineBuilder {
   std::optional<Reloc::Model> RelocModel;
   CodeGenOptLevel CGOptLevel = CodeGenOptLevel::Aggressive;
 
-  std::unique_ptr<TargetMachine> create() const;
+  std::unique_ptr<TargetMachine> create(const Module &M) const;
 };
 
 /// This class define an interface similar to the LTOCodeGenerator, but adapted

llvm/include/llvm/TargetParser/SubtargetFeature.h

@@ -20,6 +20,7 @@
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/IR/Module.h"
 #include "llvm/Support/MathExtras.h"
 #include <array>
 #include <initializer_list>
@@ -195,7 +196,7 @@ class SubtargetFeatures {
   void dump() const;
 
   /// Adds the default features for the specified target triple.
-  void getDefaultSubtargetFeatures(const Triple& Triple);
+  void getDefaultSubtargetFeatures(const Module &M);
 
   /// Determine if a feature has a flag; '+' or '-'
   static bool hasFlag(StringRef Feature) {

llvm/lib/LTO/LTOBackend.cpp

@@ -201,7 +201,7 @@ static std::unique_ptr<TargetMachine>
 createTargetMachine(const Config &Conf, const Target *TheTarget, Module &M) {
   StringRef TheTriple = M.getTargetTriple();
   SubtargetFeatures Features;
-  Features.getDefaultSubtargetFeatures(Triple(TheTriple));
+  Features.getDefaultSubtargetFeatures(M);
   for (const std::string &A : Conf.MAttrs)
     Features.AddFeature(A);
 

llvm/lib/LTO/LTOCodeGenerator.cpp

@@ -406,7 +406,7 @@ bool LTOCodeGenerator::determineTarget() {
   // Construct LTOModule, hand over ownership of module and target. Use MAttr as
   // the default set of features.
   SubtargetFeatures Features(join(Config.MAttrs, ""));
-  Features.getDefaultSubtargetFeatures(Triple);
+  Features.getDefaultSubtargetFeatures(*MergedModule);
   FeatureStr = Features.getString();
   if (Config.CPU.empty())
     Config.CPU = lto::getThinLTODefaultCPU(Triple);

llvm/lib/LTO/LTOModule.cpp

@@ -213,7 +213,7 @@ LTOModule::makeLTOModule(MemoryBufferRef Buffer, const TargetOptions &options,
 
   // construct LTOModule, hand over ownership of module and target
   SubtargetFeatures Features;
-  Features.getDefaultSubtargetFeatures(Triple);
+  Features.getDefaultSubtargetFeatures(*M.get());
   std::string FeatureStr = Features.getString();
   // Set a default CPU for Darwin triples.
   std::string CPU;

llvm/lib/LTO/ThinLTOCodeGenerator.cpp

@@ -582,7 +582,7 @@ void ThinLTOCodeGenerator::crossReferenceSymbol(StringRef Name) {
 }
 
 // TargetMachine factory
-std::unique_ptr<TargetMachine> TargetMachineBuilder::create() const {
+std::unique_ptr<TargetMachine> TargetMachineBuilder::create(const Module &M) const {
   std::string ErrMsg;
   const Target *TheTarget =
       TargetRegistry::lookupTarget(TheTriple.str(), ErrMsg);
@@ -592,7 +592,7 @@ std::unique_ptr<TargetMachine> TargetMachineBuilder::create() const {
 
   // Use MAttr as the default set of features.
   SubtargetFeatures Features(MAttr);
-  Features.getDefaultSubtargetFeatures(TheTriple);
+  Features.getDefaultSubtargetFeatures(M);
   std::string FeatureStr = Features.getString();
 
   std::unique_ptr<TargetMachine> TM(
@@ -920,7 +920,7 @@ void ThinLTOCodeGenerator::optimize(Module &TheModule) {
   initTMBuilder(TMBuilder, Triple(TheModule.getTargetTriple()));
 
   // Optimize now
-  optimizeModule(TheModule, *TMBuilder.create(), OptLevel, Freestanding,
+  optimizeModule(TheModule, *TMBuilder.create(TheModule), OptLevel, Freestanding,
                  DebugPassManager, nullptr);
 }
 
@@ -997,7 +997,8 @@ void ThinLTOCodeGenerator::run() {
                                              /*IsImporting*/ false);
 
         // CodeGen
-        auto OutputBuffer = codegenModule(*TheModule, *TMBuilder.create());
+        TargetMachine &TM = *TMBuilder.create(*TheModule);
+        auto OutputBuffer = codegenModule(*TheModule, TM);
         if (SavedObjectsDirectoryPath.empty())
           ProducedBinaries[count] = std::move(OutputBuffer);
         else
@@ -1185,9 +1186,10 @@ void ThinLTOCodeGenerator::run() {
         saveTempBitcode(*TheModule, SaveTempsDir, count, ".0.original.bc");
 
         auto &ImportList = ImportLists[ModuleIdentifier];
+        TargetMachine &TM = *TMBuilder.create(*TheModule);
         // Run the main process now, and generates a binary
         auto OutputBuffer = ProcessThinLTOModule(
-            *TheModule, *Index, ModuleMap, *TMBuilder.create(), ImportList,
+            *TheModule, *Index, ModuleMap, TM, ImportList,
             ExportList, GUIDPreservedSymbols,
             ModuleToDefinedGVSummaries[ModuleIdentifier], CacheOptions,
             DisableCodeGen, SaveTempsDir, Freestanding, OptLevel, count,

llvm/lib/TargetParser/SubtargetFeature.cpp

@@ -68,7 +68,8 @@ LLVM_DUMP_METHOD void SubtargetFeatures::dump() const {
 }
 #endif
 
-void SubtargetFeatures::getDefaultSubtargetFeatures(const Triple& Triple) {
+void SubtargetFeatures::getDefaultSubtargetFeatures(const Module &M) {
+  llvm::Triple Triple(M.getTargetTriple());
   // FIXME: This is an inelegant way of specifying the features of a
   // subtarget. It would be better if we could encode this information
   // into the IR.