1 files changed, 182 insertions, 0 deletions
diff --git a/contrib/llvm-project/llvm/lib/Target/AMDGPU/AMDGPUAnnotateUniformValues.cpp b/contrib/llvm-project/llvm/lib/Target/AMDGPU/AMDGPUAnnotateUniformValues.cpp
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index 000000000000..71121ade0a49
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+++ b/contrib/llvm-project/llvm/lib/Target/AMDGPU/AMDGPUAnnotateUniformValues.cpp
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+//===-- AMDGPUAnnotateUniformValues.cpp - ---------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+/// \file
+/// This pass adds amdgpu.uniform metadata to IR values so this information
+/// can be used during instruction selection.
+//
+//===----------------------------------------------------------------------===//
+
+#include "AMDGPU.h"
+#include "llvm/ADT/SetVector.h"
+#include "llvm/Analysis/LegacyDivergenceAnalysis.h"
+#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/Analysis/MemoryDependenceAnalysis.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/InstVisitor.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+
+#define DEBUG_TYPE "amdgpu-annotate-uniform"
+
+using namespace llvm;
+
+namespace {
+
+class AMDGPUAnnotateUniformValues : public FunctionPass,
+                       public InstVisitor<AMDGPUAnnotateUniformValues> {
+  LegacyDivergenceAnalysis *DA;
+  MemoryDependenceResults *MDR;
+  LoopInfo *LI;
+  DenseMap<Value*, GetElementPtrInst*> noClobberClones;
+  bool isKernelFunc;
+
+public:
+  static char ID;
+  AMDGPUAnnotateUniformValues() :
+    FunctionPass(ID) { }
+  bool doInitialization(Module &M) override;
+  bool runOnFunction(Function &F) override;
+  StringRef getPassName() const override {
+    return "AMDGPU Annotate Uniform Values";
+  }
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.addRequired<LegacyDivergenceAnalysis>();
+    AU.addRequired<MemoryDependenceWrapperPass>();
+    AU.addRequired<LoopInfoWrapperPass>();
+    AU.setPreservesAll();
+ }
+
+  void visitBranchInst(BranchInst &I);
+  void visitLoadInst(LoadInst &I);
+  bool isClobberedInFunction(LoadInst * Load);
+};
+
+} // End anonymous namespace
+
+INITIALIZE_PASS_BEGIN(AMDGPUAnnotateUniformValues, DEBUG_TYPE,
+                      "Add AMDGPU uniform metadata", false, false)
+INITIALIZE_PASS_DEPENDENCY(LegacyDivergenceAnalysis)
+INITIALIZE_PASS_DEPENDENCY(MemoryDependenceWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
+INITIALIZE_PASS_END(AMDGPUAnnotateUniformValues, DEBUG_TYPE,
+                    "Add AMDGPU uniform metadata", false, false)
+
+char AMDGPUAnnotateUniformValues::ID = 0;
+
+static void setUniformMetadata(Instruction *I) {
+  I->setMetadata("amdgpu.uniform", MDNode::get(I->getContext(), {}));
+}
+static void setNoClobberMetadata(Instruction *I) {
+  I->setMetadata("amdgpu.noclobber", MDNode::get(I->getContext(), {}));
+}
+
+static void DFS(BasicBlock *Root, SetVector<BasicBlock*> & Set) {
+  for (auto I : predecessors(Root))
+    if (Set.insert(I))
+      DFS(I, Set);
+}
+
+bool AMDGPUAnnotateUniformValues::isClobberedInFunction(LoadInst * Load) {
+  // 1. get Loop for the Load->getparent();
+  // 2. if it exists, collect all the BBs from the most outer
+  // loop and check for the writes. If NOT - start DFS over all preds.
+  // 3. Start DFS over all preds from the most outer loop header.
+  SetVector<BasicBlock *> Checklist;
+  BasicBlock *Start = Load->getParent();
+  Checklist.insert(Start);
+  const Value *Ptr = Load->getPointerOperand();
+  const Loop *L = LI->getLoopFor(Start);
+  if (L) {
+    const Loop *P = L;
+    do {
+      L = P;
+      P = P->getParentLoop();
+    } while (P);
+    Checklist.insert(L->block_begin(), L->block_end());
+    Start = L->getHeader();
+  }
+
+  DFS(Start, Checklist);
+  for (auto &BB : Checklist) {
+    BasicBlock::iterator StartIt = (!L && (BB == Load->getParent())) ?
+      BasicBlock::iterator(Load) : BB->end();
+    auto Q = MDR->getPointerDependencyFrom(MemoryLocation(Ptr), true,
+                                           StartIt, BB, Load);
+    if (Q.isClobber() || Q.isUnknown())
+      return true;
+  }
+  return false;
+}
+
+void AMDGPUAnnotateUniformValues::visitBranchInst(BranchInst &I) {
+  if (DA->isUniform(&I))
+    setUniformMetadata(I.getParent()->getTerminator());
+}
+
+void AMDGPUAnnotateUniformValues::visitLoadInst(LoadInst &I) {
+  Value *Ptr = I.getPointerOperand();
+  if (!DA->isUniform(Ptr))
+    return;
+  auto isGlobalLoad = [&](LoadInst &Load)->bool {
+    return Load.getPointerAddressSpace() == AMDGPUAS::GLOBAL_ADDRESS;
+  };
+  // We're tracking up to the Function boundaries
+  // We cannot go beyond because of FunctionPass restrictions
+  // Thus we can ensure that memory not clobbered for memory
+  // operations that live in kernel only.
+  bool NotClobbered = isKernelFunc &&   !isClobberedInFunction(&I);
+  Instruction *PtrI = dyn_cast<Instruction>(Ptr);
+  if (!PtrI && NotClobbered && isGlobalLoad(I)) {
+    if (isa<Argument>(Ptr) || isa<GlobalValue>(Ptr)) {
+      // Lookup for the existing GEP
+      if (noClobberClones.count(Ptr)) {
+        PtrI = noClobberClones[Ptr];
+      } else {
+        // Create GEP of the Value
+        Function *F = I.getParent()->getParent();
+        Value *Idx = Constant::getIntegerValue(
+          Type::getInt32Ty(Ptr->getContext()), APInt(64, 0));
+        // Insert GEP at the entry to make it dominate all uses
+        PtrI = GetElementPtrInst::Create(
+          Ptr->getType()->getPointerElementType(), Ptr,
+          ArrayRef<Value*>(Idx), Twine(""), F->getEntryBlock().getFirstNonPHI());
+      }
+      I.replaceUsesOfWith(Ptr, PtrI);
+    }
+  }
+
+  if (PtrI) {
+    setUniformMetadata(PtrI);
+    if (NotClobbered)
+      setNoClobberMetadata(PtrI);
+  }
+}
+
+bool AMDGPUAnnotateUniformValues::doInitialization(Module &M) {
+  return false;
+}
+
+bool AMDGPUAnnotateUniformValues::runOnFunction(Function &F) {
+  if (skipFunction(F))
+    return false;
+
+  DA  = &getAnalysis<LegacyDivergenceAnalysis>();
+  MDR = &getAnalysis<MemoryDependenceWrapperPass>().getMemDep();
+  LI  = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
+  isKernelFunc = F.getCallingConv() == CallingConv::AMDGPU_KERNEL;
+
+  visit(F);
+  noClobberClones.clear();
+  return true;
+}
+
+FunctionPass *
+llvm::createAMDGPUAnnotateUniformValues() {
+  return new AMDGPUAnnotateUniformValues();
+}