[AMDGPU] Add amdgpu-unify-metadata pass

Multiple metadata values for records such as opencl.ocl.version, llvm.ident
and similar are created after linking several modules. For some of them, notably
opencl.ocl.version, this creates semantic problem because we cannot tell which
version of OpenCL the composite module conforms.

Moreover, such repetitions of identical values often create a huge list of
unneeded metadata, which grows bitcode size both in memory and stored on disk.
It can go up to several Mb when linked against our OpenCL library. Lastly, such
long lists obscure reading of dumped IR.

The pass unifies metadata after linking.

Differential Revision: https://reviews.llvm.org/D25381

llvm-svn: 289092

llvm/lib/Target/AMDGPU/AMDGPU.h

@@ -90,6 +90,10 @@ ModulePass *createAMDGPUAlwaysInlinePass();
 ModulePass *createAMDGPUOpenCLImageTypeLoweringPass();
 FunctionPass *createAMDGPUAnnotateUniformValues();
 
+FunctionPass* createAMDGPUUnifyMetadataPass();
+void initializeAMDGPUUnifyMetadataPass(PassRegistry&);
+extern char &AMDGPUUnifyMetadataID;
+
 void initializeSIFixControlFlowLiveIntervalsPass(PassRegistry&);
 extern char &SIFixControlFlowLiveIntervalsID;
 

llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp

@@ -34,6 +34,7 @@
 #include "llvm/Transforms/Scalar.h"
 #include "llvm/Transforms/Scalar/GVN.h"
 #include "llvm/Transforms/Vectorize.h"
+#include "llvm/IR/LegacyPassManager.h"
 
 using namespace llvm;
 
@@ -85,6 +86,7 @@ extern "C" void LLVMInitializeAMDGPUTarget() {
   initializeAMDGPUAnnotateUniformValuesPass(*PR);
   initializeAMDGPUPromoteAllocaPass(*PR);
   initializeAMDGPUCodeGenPreparePass(*PR);
+  initializeAMDGPUUnifyMetadataPass(*PR);
   initializeSIAnnotateControlFlowPass(*PR);
   initializeSIInsertWaitsPass(*PR);
   initializeSIWholeQuadModePass(*PR);
@@ -189,6 +191,10 @@ StringRef AMDGPUTargetMachine::getFeatureString(const Function &F) const {
     FSAttr.getValueAsString();
 }
 
+void AMDGPUTargetMachine::addEarlyAsPossiblePasses(PassManagerBase &PM) {
+  PM.add(llvm::createAMDGPUUnifyMetadataPass());
+}
+
 //===----------------------------------------------------------------------===//
 // R600 Target Machine (R600 -> Cayman)
 //===----------------------------------------------------------------------===//

llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.h

@@ -50,6 +50,7 @@ public:
   TargetLoweringObjectFile *getObjFileLowering() const override {
     return TLOF.get();
   }
+  void addEarlyAsPossiblePasses(PassManagerBase &PM) override;
 };
 
 //===----------------------------------------------------------------------===//

llvm/lib/Target/AMDGPU/AMDGPUUnifyMetadata.cpp

@@ -0,0 +1,147 @@
+//===-- AMDGPUUnifyMetadata.cpp - Unify OpenCL metadata -------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// \file
+// \brief This pass that unifies multiple OpenCL metadata due to linking.
+//
+//===----------------------------------------------------------------------===//
+
+#include "AMDGPU.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Pass.h"
+
+using namespace llvm;
+
+namespace {
+  namespace kOCLMD {
+    const char SpirVer[]            = "opencl.spir.version";
+    const char OCLVer[]             = "opencl.ocl.version";
+    const char UsedExt[]            = "opencl.used.extensions";
+    const char UsedOptCoreFeat[]    = "opencl.used.optional.core.features";
+    const char CompilerOptions[]    = "opencl.compiler.options";
+    const char LLVMIdent[]          = "llvm.ident";
+  }
+
+  /// \brief Unify multiple OpenCL metadata due to linking.
+  class AMDGPUUnifyMetadata : public FunctionPass {
+  public:
+    static char ID;
+    explicit AMDGPUUnifyMetadata() : FunctionPass(ID) {};
+
+  private:
+    // This should really be a module pass but we have to run it as early
+    // as possible, so given function passes are executed first and
+    // TargetMachine::addEarlyAsPossiblePasses() expects only function passes
+    // it has to be a function pass.
+    virtual bool runOnModule(Module &M);
+
+    // \todo: Convert to a module pass.
+    virtual bool runOnFunction(Function &F);
+
+    /// \brief Unify version metadata.
+    /// \return true if changes are made.
+    /// Assume the named metadata has operands each of which is a pair of
+    /// integer constant, e.g.
+    /// !Name = {!n1, !n2}
+    /// !n1 = {i32 1, i32 2}
+    /// !n2 = {i32 2, i32 0}
+    /// Keep the largest version as the sole operand if PickFirst is false.
+    /// Otherwise pick it from the first value, representing kernel module.
+    bool unifyVersionMD(Module &M, StringRef Name, bool PickFirst) {
+      auto NamedMD = M.getNamedMetadata(Name);
+      if (!NamedMD || NamedMD->getNumOperands() <= 1)
+        return false;
+      MDNode *MaxMD = nullptr;
+      auto MaxVer = 0U;
+      for (const auto &VersionMD : NamedMD->operands()) {
+        assert(VersionMD->getNumOperands() == 2);
+        auto CMajor = mdconst::extract<ConstantInt>(VersionMD->getOperand(0));
+        auto VersionMajor = CMajor->getZExtValue();
+        auto CMinor = mdconst::extract<ConstantInt>(VersionMD->getOperand(1));
+        auto VersionMinor = CMinor->getZExtValue();
+        auto Ver = (VersionMajor * 100) + (VersionMinor * 10);
+        if (Ver > MaxVer) {
+          MaxVer = Ver;
+          MaxMD = VersionMD;
+        }
+        if (PickFirst)
+          break;
+      }
+      NamedMD->eraseFromParent();
+      NamedMD = M.getOrInsertNamedMetadata(Name);
+      NamedMD->addOperand(MaxMD);
+      return true;
+    }
+
+  /// \brief Unify version metadata.
+  /// \return true if changes are made.
+  /// Assume the named metadata has operands each of which is a list e.g.
+  /// !Name = {!n1, !n2}
+  /// !n1 = !{!"cl_khr_fp16", {!"cl_khr_fp64"}}
+  /// !n2 = !{!"cl_khr_image"}
+  /// Combine it into a single list with unique operands.
+  bool unifyExtensionMD(Module &M, StringRef Name) {
+    auto NamedMD = M.getNamedMetadata(Name);
+    if (!NamedMD || NamedMD->getNumOperands() == 1)
+      return false;
+
+    SmallVector<Metadata *, 4> All;
+    for (const auto &MD : NamedMD->operands())
+      for (const auto &Op : MD->operands())
+        if (std::find(All.begin(), All.end(), Op.get()) == All.end())
+          All.push_back(Op.get());
+
+    NamedMD->eraseFromParent();
+    NamedMD = M.getOrInsertNamedMetadata(Name);
+    NamedMD->addOperand(MDNode::get(M.getContext(), All));
+    return true;
+  }
+};
+
+} // end anonymous namespace
+
+char AMDGPUUnifyMetadata::ID = 0;
+
+char &llvm::AMDGPUUnifyMetadataID = AMDGPUUnifyMetadata::ID;
+
+INITIALIZE_PASS(AMDGPUUnifyMetadata, "amdgpu-unify-metadata",
+                "Unify multiple OpenCL metadata due to linking",
+                false, false)
+
+FunctionPass* llvm::createAMDGPUUnifyMetadataPass() {
+  return new AMDGPUUnifyMetadata();
+}
+
+bool AMDGPUUnifyMetadata::runOnModule(Module &M) {
+  const char* Vers[] = {
+      kOCLMD::SpirVer,
+      kOCLMD::OCLVer
+  };
+  const char* Exts[] = {
+      kOCLMD::UsedExt,
+      kOCLMD::UsedOptCoreFeat,
+      kOCLMD::CompilerOptions,
+      kOCLMD::LLVMIdent
+  };
+
+  bool Changed = false;
+
+  for (auto &I:Vers)
+    Changed |= unifyVersionMD(M, I, true);
+
+  for (auto &I:Exts)
+    Changed |= unifyExtensionMD(M, I);
+
+  return Changed;
+}
+
+bool AMDGPUUnifyMetadata::runOnFunction(Function &F) {
+  return runOnModule(*F.getParent());
+}

llvm/lib/Target/AMDGPU/CMakeLists.txt

@@ -41,6 +41,7 @@ add_llvm_target(AMDGPUCodeGen
   AMDGPUISelDAGToDAG.cpp
   AMDGPUMCInstLower.cpp
   AMDGPUMachineFunction.cpp
+  AMDGPUUnifyMetadata.cpp
   AMDGPUOpenCLImageTypeLoweringPass.cpp
   AMDGPUSubtarget.cpp
   AMDGPUTargetMachine.cpp

llvm/test/CodeGen/AMDGPU/unify-metadata.ll

@@ -0,0 +1,26 @@
+; RUN: opt -mtriple=amdgcn--amdhsa -amdgpu-unify-metadata -S < %s | FileCheck -check-prefix=ALL %s
+
+; This test check that we have a singe metadata value after linking several
+; modules for records such as opencl.ocl.version, llvm.ident and similar.
+
+; ALL-DAG: !opencl.ocl.version = !{![[OCL_VER:[0-9]+]]}
+; ALL-DAG: !llvm.ident = !{![[LLVM_IDENT:[0-9]+]]}
+; ALL-DAG: !opencl.used.extensions = !{![[USED_EXT:[0-9]+]]}
+; ALL-DAG: ![[OCL_VER]] = !{i32 1, i32 2}
+; ALL-DAG: ![[LLVM_IDENT]] = !{!"clang version 4.0 "}
+; ALL-DAG: ![[USED_EXT]] = !{!"cl_images", !"cl_khr_fp16", !"cl_doubles"}
+
+define void @test() {
+   ret void
+}
+
+!opencl.ocl.version = !{!1, !0, !0, !0}
+!llvm.ident = !{!2, !2, !2, !2}
+!opencl.used.extensions = !{!3, !3, !4, !5}
+
+!0 = !{i32 2, i32 0}
+!1 = !{i32 1, i32 2}
+!2 = !{!"clang version 4.0 "}
+!3 = !{!"cl_images", !"cl_khr_fp16"}
+!4 = !{!"cl_images", !"cl_doubles"}
+!5 = !{}