1 //===-- NVPTXImageOptimizer.cpp - Image optimization pass -----------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This pass implements IR-level optimizations of image access code,
11 // including:
12 //
13 // 1. Eliminate istypep intrinsics when image access qualifier is known
14 //
15 //===----------------------------------------------------------------------===//
16
17 #include "NVPTX.h"
18 #include "NVPTXUtilities.h"
19 #include "llvm/IR/Instructions.h"
20 #include "llvm/IR/Intrinsics.h"
21 #include "llvm/IR/Module.h"
22 #include "llvm/Pass.h"
23 #include "llvm/Analysis/ConstantFolding.h"
24
25 using namespace llvm;
26
27 namespace {
28 class NVPTXImageOptimizer : public FunctionPass {
29 private:
30 static char ID;
31 SmallVector<Instruction*, 4> InstrToDelete;
32
33 public:
34 NVPTXImageOptimizer();
35
36 bool runOnFunction(Function &F) override;
37
38 private:
39 bool replaceIsTypePSampler(Instruction &I);
40 bool replaceIsTypePSurface(Instruction &I);
41 bool replaceIsTypePTexture(Instruction &I);
42 Value *cleanupValue(Value *V);
43 void replaceWith(Instruction *From, ConstantInt *To);
44 };
45 }
46
47 char NVPTXImageOptimizer::ID = 0;
48
NVPTXImageOptimizer()49 NVPTXImageOptimizer::NVPTXImageOptimizer()
50 : FunctionPass(ID) {}
51
runOnFunction(Function & F)52 bool NVPTXImageOptimizer::runOnFunction(Function &F) {
53 bool Changed = false;
54 InstrToDelete.clear();
55
56 // Look for call instructions in the function
57 for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE;
58 ++BI) {
59 for (BasicBlock::iterator I = (*BI).begin(), E = (*BI).end();
60 I != E; ++I) {
61 Instruction &Instr = *I;
62 if (CallInst *CI = dyn_cast<CallInst>(I)) {
63 Function *CalledF = CI->getCalledFunction();
64 if (CalledF && CalledF->isIntrinsic()) {
65 // This is an intrinsic function call, check if its an istypep
66 switch (CalledF->getIntrinsicID()) {
67 default: break;
68 case Intrinsic::nvvm_istypep_sampler:
69 Changed |= replaceIsTypePSampler(Instr);
70 break;
71 case Intrinsic::nvvm_istypep_surface:
72 Changed |= replaceIsTypePSurface(Instr);
73 break;
74 case Intrinsic::nvvm_istypep_texture:
75 Changed |= replaceIsTypePTexture(Instr);
76 break;
77 }
78 }
79 }
80 }
81 }
82
83 // Delete any istypep instances we replaced in the IR
84 for (unsigned i = 0, e = InstrToDelete.size(); i != e; ++i)
85 InstrToDelete[i]->eraseFromParent();
86
87 return Changed;
88 }
89
replaceIsTypePSampler(Instruction & I)90 bool NVPTXImageOptimizer::replaceIsTypePSampler(Instruction &I) {
91 Value *TexHandle = cleanupValue(I.getOperand(0));
92 if (isSampler(*TexHandle)) {
93 // This is an OpenCL sampler, so it must be a samplerref
94 replaceWith(&I, ConstantInt::getTrue(I.getContext()));
95 return true;
96 } else if (isImageWriteOnly(*TexHandle) ||
97 isImageReadWrite(*TexHandle) ||
98 isImageReadOnly(*TexHandle)) {
99 // This is an OpenCL image, so it cannot be a samplerref
100 replaceWith(&I, ConstantInt::getFalse(I.getContext()));
101 return true;
102 } else {
103 // The image type is unknown, so we cannot eliminate the intrinsic
104 return false;
105 }
106 }
107
replaceIsTypePSurface(Instruction & I)108 bool NVPTXImageOptimizer::replaceIsTypePSurface(Instruction &I) {
109 Value *TexHandle = cleanupValue(I.getOperand(0));
110 if (isImageReadWrite(*TexHandle) ||
111 isImageWriteOnly(*TexHandle)) {
112 // This is an OpenCL read-only/read-write image, so it must be a surfref
113 replaceWith(&I, ConstantInt::getTrue(I.getContext()));
114 return true;
115 } else if (isImageReadOnly(*TexHandle) ||
116 isSampler(*TexHandle)) {
117 // This is an OpenCL read-only/ imageor sampler, so it cannot be
118 // a surfref
119 replaceWith(&I, ConstantInt::getFalse(I.getContext()));
120 return true;
121 } else {
122 // The image type is unknown, so we cannot eliminate the intrinsic
123 return false;
124 }
125 }
126
replaceIsTypePTexture(Instruction & I)127 bool NVPTXImageOptimizer::replaceIsTypePTexture(Instruction &I) {
128 Value *TexHandle = cleanupValue(I.getOperand(0));
129 if (isImageReadOnly(*TexHandle)) {
130 // This is an OpenCL read-only image, so it must be a texref
131 replaceWith(&I, ConstantInt::getTrue(I.getContext()));
132 return true;
133 } else if (isImageWriteOnly(*TexHandle) ||
134 isImageReadWrite(*TexHandle) ||
135 isSampler(*TexHandle)) {
136 // This is an OpenCL read-write/write-only image or a sampler, so it
137 // cannot be a texref
138 replaceWith(&I, ConstantInt::getFalse(I.getContext()));
139 return true;
140 } else {
141 // The image type is unknown, so we cannot eliminate the intrinsic
142 return false;
143 }
144 }
145
replaceWith(Instruction * From,ConstantInt * To)146 void NVPTXImageOptimizer::replaceWith(Instruction *From, ConstantInt *To) {
147 // We implement "poor man's DCE" here to make sure any code that is no longer
148 // live is actually unreachable and can be trivially eliminated by the
149 // unreachable block elimination pass.
150 for (CallInst::use_iterator UI = From->use_begin(), UE = From->use_end();
151 UI != UE; ++UI) {
152 if (BranchInst *BI = dyn_cast<BranchInst>(*UI)) {
153 if (BI->isUnconditional()) continue;
154 BasicBlock *Dest;
155 if (To->isZero())
156 // Get false block
157 Dest = BI->getSuccessor(1);
158 else
159 // Get true block
160 Dest = BI->getSuccessor(0);
161 BranchInst::Create(Dest, BI);
162 InstrToDelete.push_back(BI);
163 }
164 }
165 From->replaceAllUsesWith(To);
166 InstrToDelete.push_back(From);
167 }
168
cleanupValue(Value * V)169 Value *NVPTXImageOptimizer::cleanupValue(Value *V) {
170 if (ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(V)) {
171 return cleanupValue(EVI->getAggregateOperand());
172 }
173 return V;
174 }
175
createNVPTXImageOptimizerPass()176 FunctionPass *llvm::createNVPTXImageOptimizerPass() {
177 return new NVPTXImageOptimizer();
178 }
179