[AMDGPU] Add address space based alias analysis pass

This is direct port of HSAILAliasAnalysis pass, just cleaned for
style and renamed.

Differential Revision: https://reviews.llvm.org/D31103

llvm-svn: 298172

5 files changed, 223 insertions, 0 deletions

diff --git a/llvm/lib/Target/AMDGPU/AMDGPU.h b/llvm/lib/Target/AMDGPU/AMDGPU.h
index 3e269fad71f..1cc68c7e242 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPU.h
+++ b/llvm/lib/Target/AMDGPU/AMDGPU.h
@@ -119,6 +119,9 @@ extern char &SIDebuggerInsertNopsID;
 void initializeSIInsertWaitsPass(PassRegistry&);
 extern char &SIInsertWaitsID;
 
+ImmutablePass *createAMDGPUAAWrapperPass();
+void initializeAMDGPUAAWrapperPassPass(PassRegistry&);
+
 Target &getTheAMDGPUTarget();
 Target &getTheGCNTarget();
 
diff --git a/llvm/lib/Target/AMDGPU/AMDGPUAliasAnalysis.cpp b/llvm/lib/Target/AMDGPU/AMDGPUAliasAnalysis.cpp
new file mode 100644
index 00000000000..127b2639794
--- /dev/null
+++ b/llvm/lib/Target/AMDGPU/AMDGPUAliasAnalysis.cpp
@@ -0,0 +1,117 @@
+//===- AMDGPUAliasAnalysis ---------------------------------------*- C++ -*-==//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+/// \file
+/// This is the AMGPU address space based alias analysis pass.
+//===----------------------------------------------------------------------===//
+
+#include "AMDGPU.h"
+#include "AMDGPUAliasAnalysis.h"
+#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/ValueTracking.h"
+#include "llvm/Analysis/Passes.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Pass.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "amdgpu-aa"
+
+// Register this pass...
+char AMDGPUAAWrapperPass::ID = 0;
+INITIALIZE_PASS(AMDGPUAAWrapperPass, "amdgpu-aa",
+                "AMDGPU Address space based Alias Analysis", false, true)
+
+ImmutablePass *llvm::createAMDGPUAAWrapperPass() {
+  return new AMDGPUAAWrapperPass();
+}
+
+void AMDGPUAAWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
+  AU.setPreservesAll();
+}
+
+AliasResult AMDGPUAAResult::alias(const MemoryLocation &LocA,
+                                  const MemoryLocation &LocB) {
+  // This array is indexed by the AMDGPUAS::AddressSpaces
+  // enum elements PRIVATE_ADDRESS ... to FLAT_ADDRESS
+  // see "llvm/Transforms/AMDSPIRUtils.h"
+  static const AliasResult ASAliasRules[5][5] = {
+ /*             Private    Global    Constant  Group     Flat */
+ /* Private  */ {MayAlias, NoAlias , NoAlias , NoAlias , MayAlias},
+ /* Global   */ {NoAlias , MayAlias, NoAlias , NoAlias , MayAlias},
+ /* Constant */ {NoAlias , NoAlias , MayAlias, NoAlias , MayAlias},
+ /* Group    */ {NoAlias , NoAlias , NoAlias , MayAlias, MayAlias},
+ /* Flat     */ {MayAlias, MayAlias, MayAlias, MayAlias, MayAlias}
+  };
+  unsigned asA = LocA.Ptr->getType()->getPointerAddressSpace();
+  unsigned asB = LocB.Ptr->getType()->getPointerAddressSpace();
+  if (asA > AMDGPUAS::AddressSpaces::FLAT_ADDRESS ||
+      asB > AMDGPUAS::AddressSpaces::FLAT_ADDRESS)
+    report_fatal_error("Pointer address space out of range");
+
+  AliasResult Result = ASAliasRules[asA][asB];
+  if (Result == NoAlias) return Result;
+
+  if (isa<Argument>(LocA.Ptr) && isa<Argument>(LocB.Ptr)) {
+    Type *T1 = cast<PointerType>(LocA.Ptr->getType())->getElementType();
+    Type *T2 = cast<PointerType>(LocB.Ptr->getType())->getElementType();
+
+    if ((T1->isVectorTy() && !T2->isVectorTy()) ||
+        (T2->isVectorTy() && !T1->isVectorTy()))
+      return NoAlias;
+  }
+  // Forward the query to the next alias analysis.
+  return AAResultBase::alias(LocA, LocB);
+}
+
+bool AMDGPUAAResult::pointsToConstantMemory(const MemoryLocation &Loc,
+                                            bool OrLocal) {
+  const Value *Base = GetUnderlyingObject(Loc.Ptr, DL);
+
+  if (Base->getType()->getPointerAddressSpace() ==
+     AMDGPUAS::AddressSpaces::CONSTANT_ADDRESS) {
+    return true;
+  }
+
+  if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(Base)) {
+    if (GV->isConstant())
+      return true;
+  } else if (const Argument *Arg = dyn_cast<Argument>(Base)) {
+    const Function *F = Arg->getParent();
+
+    // Only assume constant memory for arguments on kernels.
+    switch (F->getCallingConv()) {
+    default:
+      return AAResultBase::pointsToConstantMemory(Loc, OrLocal);
+    case CallingConv::AMDGPU_VS:
+    case CallingConv::AMDGPU_GS:
+    case CallingConv::AMDGPU_PS:
+    case CallingConv::AMDGPU_CS:
+    case CallingConv::AMDGPU_KERNEL:
+    case CallingConv::SPIR_KERNEL:
+      break;
+    }
+
+    unsigned ArgNo = Arg->getArgNo();
+    /* On an argument, ReadOnly attribute indicates that the function does
+       not write through this pointer argument, even though it may write
+       to the memory that the pointer points to.
+       On an argument, ReadNone attribute indicates that the function does
+       not dereference that pointer argument, even though it may read or write
+       the memory that the pointer points to if accessed through other pointers.
+     */
+    if (F->getAttributes().hasAttribute(ArgNo + 1, Attribute::NoAlias) &&
+          (F->getAttributes().hasAttribute(ArgNo + 1, Attribute::ReadNone) ||
+           F->getAttributes().hasAttribute(ArgNo + 1, Attribute::ReadOnly))) {
+      return true;
+    }
+  }
+  return AAResultBase::pointsToConstantMemory(Loc, OrLocal);
+}
diff --git a/llvm/lib/Target/AMDGPU/AMDGPUAliasAnalysis.h b/llvm/lib/Target/AMDGPU/AMDGPUAliasAnalysis.h
new file mode 100644
index 00000000000..943b4a68b25
--- /dev/null
+++ b/llvm/lib/Target/AMDGPU/AMDGPUAliasAnalysis.h
@@ -0,0 +1,86 @@
+//===- AMDGPUAliasAnalysis ---------------------------------------*- C++ -*-==//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+/// \file
+/// This is the AMGPU address space based alias analysis pass.
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ANALYSIS_AMDGPUALIASANALYSIS_H
+#define LLVM_ANALYSIS_AMDGPUALIASANALYSIS_H
+
+#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Pass.h"
+
+namespace llvm {
+
+/// A simple AA result that uses TBAA metadata to answer queries.
+class AMDGPUAAResult : public AAResultBase<AMDGPUAAResult> {
+  friend AAResultBase<AMDGPUAAResult>;
+
+  const DataLayout &DL;
+
+public:
+  explicit AMDGPUAAResult(const DataLayout &DL) : AAResultBase(), DL(DL) {}
+  AMDGPUAAResult(AMDGPUAAResult &&Arg)
+      : AAResultBase(std::move(Arg)), DL(Arg.DL){}
+
+  /// Handle invalidation events from the new pass manager.
+  ///
+  /// By definition, this result is stateless and so remains valid.
+  bool invalidate(Function &, const PreservedAnalyses &) { return false; }
+
+  AliasResult alias(const MemoryLocation &LocA, const MemoryLocation &LocB);
+  bool pointsToConstantMemory(const MemoryLocation &Loc, bool OrLocal);
+
+private:
+  bool Aliases(const MDNode *A, const MDNode *B) const;
+  bool PathAliases(const MDNode *A, const MDNode *B) const;
+};
+
+/// Analysis pass providing a never-invalidated alias analysis result.
+class AMDGPUAA : public AnalysisInfoMixin<AMDGPUAA> {
+  friend AnalysisInfoMixin<AMDGPUAA>;
+  static char PassID;
+
+public:
+  typedef AMDGPUAAResult Result;
+
+  AMDGPUAAResult run(Function &F, AnalysisManager<Function> &AM) {
+    return AMDGPUAAResult(F.getParent()->getDataLayout());
+  }
+};
+
+/// Legacy wrapper pass to provide the AMDGPUAAResult object.
+class AMDGPUAAWrapperPass : public ImmutablePass {
+  std::unique_ptr<AMDGPUAAResult> Result;
+
+public:
+  static char ID;
+
+  AMDGPUAAWrapperPass() : ImmutablePass(ID) {
+    initializeAMDGPUAAWrapperPassPass(*PassRegistry::getPassRegistry());
+  }
+
+  AMDGPUAAResult &getResult() { return *Result; }
+  const AMDGPUAAResult &getResult() const { return *Result; }
+
+  bool doInitialization(Module &M) override {
+    Result.reset(new AMDGPUAAResult(M.getDataLayout()));
+    return false;
+  }
+  bool doFinalization(Module &M) override {
+    Result.reset();
+    return false;
+  }
+  void getAnalysisUsage(AnalysisUsage &AU) const override;
+};
+
+}
+#endif // LLVM_ANALYSIS_AMDGPUALIASANALYSIS_H
diff --git a/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp b/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp
index 48442bcf2f1..33ba0883e30 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp
@@ -15,6 +15,7 @@
 
 #include "AMDGPUTargetMachine.h"
 #include "AMDGPU.h"
+#include "AMDGPUAliasAnalysis.h"
 #include "AMDGPUCallLowering.h"
 #include "AMDGPUInstructionSelector.h"
 #include "AMDGPULegalizerInfo.h"
@@ -93,6 +94,11 @@ static cl::opt<bool> InternalizeSymbols(
   cl::init(false),
   cl::Hidden);
 
+// Enable address space based alias analysis
+static cl::opt<bool> EnableAMDGPUAliasAnalysis("enable-amdgpu-aa", cl::Hidden,
+  cl::desc("Enable AMDGPU Alias Analysis"),
+  cl::init(true));
+
 extern "C" void LLVMInitializeAMDGPUTarget() {
   // Register the target
   RegisterTargetMachine<R600TargetMachine> X(getTheAMDGPUTarget());
@@ -119,6 +125,7 @@ extern "C" void LLVMInitializeAMDGPUTarget() {
   initializeSIInsertSkipsPass(*PR);
   initializeSIDebuggerInsertNopsPass(*PR);
   initializeSIOptimizeExecMaskingPass(*PR);
+  initializeAMDGPUAAWrapperPassPass(*PR);
 }
 
 static std::unique_ptr<TargetLoweringObjectFile> createTLOF(const Triple &TT) {
@@ -507,6 +514,15 @@ void AMDGPUPassConfig::addIRPasses() {
       addPass(createSROAPass());
 
     addStraightLineScalarOptimizationPasses();
+
+    if (EnableAMDGPUAliasAnalysis) {
+      addPass(createAMDGPUAAWrapperPass());
+      addPass(createExternalAAWrapperPass([](Pass &P, Function &,
+                                             AAResults &AAR) {
+        if (auto *WrapperPass = P.getAnalysisIfAvailable<AMDGPUAAWrapperPass>())
+          AAR.addAAResult(WrapperPass->getResult());
+        }));
+    }
   }
 
   TargetPassConfig::addIRPasses();
diff --git a/llvm/lib/Target/AMDGPU/CMakeLists.txt b/llvm/lib/Target/AMDGPU/CMakeLists.txt
index a1c263c8764..7b550e8f2b5 100644
--- a/llvm/lib/Target/AMDGPU/CMakeLists.txt
+++ b/llvm/lib/Target/AMDGPU/CMakeLists.txt
@@ -36,6 +36,7 @@ endif()
 
 add_llvm_target(AMDGPUCodeGen
   AMDILCFGStructurizer.cpp
+  AMDGPUAliasAnalysis.cpp
   AMDGPUAlwaysInlinePass.cpp
   AMDGPUAnnotateKernelFeatures.cpp
   AMDGPUAnnotateUniformValues.cpp