1 //===-- AMDGPUAnnotateUniformValues.cpp - ---------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 /// \file
10 /// This pass adds amdgpu.uniform metadata to IR values so this information
11 /// can be used during instruction selection.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "AMDGPU.h"
16 #include "Utils/AMDGPUBaseInfo.h"
17 #include "Utils/AMDGPUMemoryUtils.h"
18 #include "llvm/Analysis/AliasAnalysis.h"
19 #include "llvm/Analysis/LegacyDivergenceAnalysis.h"
20 #include "llvm/Analysis/MemorySSA.h"
21 #include "llvm/IR/InstVisitor.h"
22 #include "llvm/InitializePasses.h"
23 
24 #define DEBUG_TYPE "amdgpu-annotate-uniform"
25 
26 using namespace llvm;
27 
28 namespace {
29 
30 class AMDGPUAnnotateUniformValues : public FunctionPass,
31                        public InstVisitor<AMDGPUAnnotateUniformValues> {
32   LegacyDivergenceAnalysis *DA;
33   MemorySSA *MSSA;
34   AliasAnalysis *AA;
35   bool isEntryFunc;
36   bool Changed;
37 
38   void setUniformMetadata(Instruction *I) {
39     I->setMetadata("amdgpu.uniform", MDNode::get(I->getContext(), {}));
40     Changed = true;
41   }
42 
43   void setNoClobberMetadata(Instruction *I) {
44     I->setMetadata("amdgpu.noclobber", MDNode::get(I->getContext(), {}));
45     Changed = true;
46   }
47 
48 public:
49   static char ID;
50   AMDGPUAnnotateUniformValues() :
51     FunctionPass(ID) { }
52   bool doInitialization(Module &M) override;
53   bool runOnFunction(Function &F) override;
54   StringRef getPassName() const override {
55     return "AMDGPU Annotate Uniform Values";
56   }
57   void getAnalysisUsage(AnalysisUsage &AU) const override {
58     AU.addRequired<LegacyDivergenceAnalysis>();
59     AU.addRequired<MemorySSAWrapperPass>();
60     AU.addRequired<AAResultsWrapperPass>();
61     AU.setPreservesAll();
62  }
63 
64   void visitBranchInst(BranchInst &I);
65   void visitLoadInst(LoadInst &I);
66 };
67 
68 } // End anonymous namespace
69 
70 INITIALIZE_PASS_BEGIN(AMDGPUAnnotateUniformValues, DEBUG_TYPE,
71                       "Add AMDGPU uniform metadata", false, false)
72 INITIALIZE_PASS_DEPENDENCY(LegacyDivergenceAnalysis)
73 INITIALIZE_PASS_DEPENDENCY(MemorySSAWrapperPass)
74 INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
75 INITIALIZE_PASS_END(AMDGPUAnnotateUniformValues, DEBUG_TYPE,
76                     "Add AMDGPU uniform metadata", false, false)
77 
78 char AMDGPUAnnotateUniformValues::ID = 0;
79 
80 void AMDGPUAnnotateUniformValues::visitBranchInst(BranchInst &I) {
81   if (DA->isUniform(&I))
82     setUniformMetadata(&I);
83 }
84 
85 void AMDGPUAnnotateUniformValues::visitLoadInst(LoadInst &I) {
86   Value *Ptr = I.getPointerOperand();
87   if (!DA->isUniform(Ptr))
88     return;
89   Instruction *PtrI = dyn_cast<Instruction>(Ptr);
90   if (PtrI)
91     setUniformMetadata(PtrI);
92 
93   // We're tracking up to the Function boundaries, and cannot go beyond because
94   // of FunctionPass restrictions. We can ensure that is memory not clobbered
95   // for memory operations that are live in to entry points only.
96   if (!isEntryFunc)
97     return;
98   bool GlobalLoad = I.getPointerAddressSpace() == AMDGPUAS::GLOBAL_ADDRESS;
99   if (GlobalLoad && !AMDGPU::isClobberedInFunction(&I, MSSA, AA))
100     setNoClobberMetadata(&I);
101 }
102 
103 bool AMDGPUAnnotateUniformValues::doInitialization(Module &M) {
104   return false;
105 }
106 
107 bool AMDGPUAnnotateUniformValues::runOnFunction(Function &F) {
108   if (skipFunction(F))
109     return false;
110 
111   DA = &getAnalysis<LegacyDivergenceAnalysis>();
112   MSSA = &getAnalysis<MemorySSAWrapperPass>().getMSSA();
113   AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
114   isEntryFunc = AMDGPU::isEntryFunctionCC(F.getCallingConv());
115 
116   Changed = false;
117   visit(F);
118   return Changed;
119 }
120 
121 FunctionPass *
122 llvm::createAMDGPUAnnotateUniformValues() {
123   return new AMDGPUAnnotateUniformValues();
124 }
125