1 //===-- NVPTXImageOptimizer.cpp - Image optimization pass -----------------===//
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 // This pass implements IR-level optimizations of image access code,
10 // including:
11 //
12 // 1. Eliminate istypep intrinsics when image access qualifier is known
13 //
14 //===----------------------------------------------------------------------===//
15
16 #include "NVPTX.h"
17 #include "NVPTXUtilities.h"
18 #include "llvm/Analysis/ConstantFolding.h"
19 #include "llvm/IR/Instructions.h"
20 #include "llvm/IR/Intrinsics.h"
21 #include "llvm/IR/IntrinsicsNVPTX.h"
22 #include "llvm/IR/Module.h"
23 #include "llvm/Pass.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
getPassName() const38 StringRef getPassName() const override { return "NVPTX Image Optimizer"; }
39
40 private:
41 bool replaceIsTypePSampler(Instruction &I);
42 bool replaceIsTypePSurface(Instruction &I);
43 bool replaceIsTypePTexture(Instruction &I);
44 Value *cleanupValue(Value *V);
45 void replaceWith(Instruction *From, ConstantInt *To);
46 };
47 }
48
49 char NVPTXImageOptimizer::ID = 0;
50
NVPTXImageOptimizer()51 NVPTXImageOptimizer::NVPTXImageOptimizer()
52 : FunctionPass(ID) {}
53
runOnFunction(Function & F)54 bool NVPTXImageOptimizer::runOnFunction(Function &F) {
55 if (skipFunction(F))
56 return false;
57
58 bool Changed = false;
59 InstrToDelete.clear();
60
61 // Look for call instructions in the function
62 for (BasicBlock &BB : F) {
63 for (Instruction &Instr : BB) {
64 if (CallInst *CI = dyn_cast<CallInst>(&Instr)) {
65 Function *CalledF = CI->getCalledFunction();
66 if (CalledF && CalledF->isIntrinsic()) {
67 // This is an intrinsic function call, check if its an istypep
68 switch (CalledF->getIntrinsicID()) {
69 default: break;
70 case Intrinsic::nvvm_istypep_sampler:
71 Changed |= replaceIsTypePSampler(Instr);
72 break;
73 case Intrinsic::nvvm_istypep_surface:
74 Changed |= replaceIsTypePSurface(Instr);
75 break;
76 case Intrinsic::nvvm_istypep_texture:
77 Changed |= replaceIsTypePTexture(Instr);
78 break;
79 }
80 }
81 }
82 }
83 }
84
85 // Delete any istypep instances we replaced in the IR
86 for (Instruction *I : InstrToDelete)
87 I->eraseFromParent();
88
89 return Changed;
90 }
91
replaceIsTypePSampler(Instruction & I)92 bool NVPTXImageOptimizer::replaceIsTypePSampler(Instruction &I) {
93 Value *TexHandle = cleanupValue(I.getOperand(0));
94 if (isSampler(*TexHandle)) {
95 // This is an OpenCL sampler, so it must be a samplerref
96 replaceWith(&I, ConstantInt::getTrue(I.getContext()));
97 return true;
98 } else if (isImage(*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 (Use &U : From->uses()) {
151 if (BranchInst *BI = dyn_cast<BranchInst>(U)) {
152 if (BI->isUnconditional()) continue;
153 BasicBlock *Dest;
154 if (To->isZero())
155 // Get false block
156 Dest = BI->getSuccessor(1);
157 else
158 // Get true block
159 Dest = BI->getSuccessor(0);
160 BranchInst::Create(Dest, BI->getIterator());
161 InstrToDelete.push_back(BI);
162 }
163 }
164 From->replaceAllUsesWith(To);
165 InstrToDelete.push_back(From);
166 }
167
cleanupValue(Value * V)168 Value *NVPTXImageOptimizer::cleanupValue(Value *V) {
169 if (ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(V)) {
170 return cleanupValue(EVI->getAggregateOperand());
171 }
172 return V;
173 }
174
createNVPTXImageOptimizerPass()175 FunctionPass *llvm::createNVPTXImageOptimizerPass() {
176 return new NVPTXImageOptimizer();
177 }
178