1 //===----- SVEIntrinsicOpts - SVE ACLE Intrinsics Opts --------------------===//
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 // Performs general IR level optimizations on SVE intrinsics.
11 //
12 // The main goal of this pass is to remove unnecessary reinterpret
13 // intrinsics (llvm.aarch64.sve.convert.[to|from].svbool), e.g:
14 //
15 // %1 = @llvm.aarch64.sve.convert.to.svbool.nxv4i1(<vscale x 4 x i1> %a)
16 // %2 = @llvm.aarch64.sve.convert.from.svbool.nxv4i1(<vscale x 16 x i1> %1)
17 //
18 // This pass also looks for ptest intrinsics & phi instructions where the
19 // operands are being needlessly converted to and from svbool_t.
20 //
21 //===----------------------------------------------------------------------===//
22
23 #include "Utils/AArch64BaseInfo.h"
24 #include "llvm/ADT/PostOrderIterator.h"
25 #include "llvm/ADT/SetVector.h"
26 #include "llvm/IR/Constants.h"
27 #include "llvm/IR/Dominators.h"
28 #include "llvm/IR/IRBuilder.h"
29 #include "llvm/IR/Instructions.h"
30 #include "llvm/IR/IntrinsicInst.h"
31 #include "llvm/IR/IntrinsicsAArch64.h"
32 #include "llvm/IR/LLVMContext.h"
33 #include "llvm/IR/PatternMatch.h"
34 #include "llvm/InitializePasses.h"
35 #include "llvm/Support/Debug.h"
36
37 using namespace llvm;
38 using namespace llvm::PatternMatch;
39
40 #define DEBUG_TYPE "aarch64-sve-intrinsic-opts"
41
42 namespace llvm {
43 void initializeSVEIntrinsicOptsPass(PassRegistry &);
44 }
45
46 namespace {
47 struct SVEIntrinsicOpts : public ModulePass {
48 static char ID; // Pass identification, replacement for typeid
SVEIntrinsicOpts__anonfbba781d0111::SVEIntrinsicOpts49 SVEIntrinsicOpts() : ModulePass(ID) {
50 initializeSVEIntrinsicOptsPass(*PassRegistry::getPassRegistry());
51 }
52
53 bool runOnModule(Module &M) override;
54 void getAnalysisUsage(AnalysisUsage &AU) const override;
55
56 private:
57 static IntrinsicInst *isReinterpretToSVBool(Value *V);
58
59 static bool optimizeIntrinsic(Instruction *I);
60
61 bool optimizeFunctions(SmallSetVector<Function *, 4> &Functions);
62
63 static bool optimizeConvertFromSVBool(IntrinsicInst *I);
64 static bool optimizePTest(IntrinsicInst *I);
65
66 static bool processPhiNode(IntrinsicInst *I);
67 };
68 } // end anonymous namespace
69
getAnalysisUsage(AnalysisUsage & AU) const70 void SVEIntrinsicOpts::getAnalysisUsage(AnalysisUsage &AU) const {
71 AU.addRequired<DominatorTreeWrapperPass>();
72 AU.setPreservesCFG();
73 }
74
75 char SVEIntrinsicOpts::ID = 0;
76 static const char *name = "SVE intrinsics optimizations";
77 INITIALIZE_PASS_BEGIN(SVEIntrinsicOpts, DEBUG_TYPE, name, false, false)
78 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass);
79 INITIALIZE_PASS_END(SVEIntrinsicOpts, DEBUG_TYPE, name, false, false)
80
81 namespace llvm {
createSVEIntrinsicOptsPass()82 ModulePass *createSVEIntrinsicOptsPass() { return new SVEIntrinsicOpts(); }
83 } // namespace llvm
84
85 /// Returns V if it's a cast from <n x 16 x i1> (aka svbool_t), nullptr
86 /// otherwise.
isReinterpretToSVBool(Value * V)87 IntrinsicInst *SVEIntrinsicOpts::isReinterpretToSVBool(Value *V) {
88 IntrinsicInst *I = dyn_cast<IntrinsicInst>(V);
89 if (!I)
90 return nullptr;
91
92 if (I->getIntrinsicID() != Intrinsic::aarch64_sve_convert_to_svbool)
93 return nullptr;
94
95 return I;
96 }
97
98 /// The function will remove redundant reinterprets casting in the presence
99 /// of the control flow
processPhiNode(IntrinsicInst * X)100 bool SVEIntrinsicOpts::processPhiNode(IntrinsicInst *X) {
101
102 SmallVector<Instruction *, 32> Worklist;
103 auto RequiredType = X->getType();
104
105 auto *PN = dyn_cast<PHINode>(X->getArgOperand(0));
106 assert(PN && "Expected Phi Node!");
107
108 // Don't create a new Phi unless we can remove the old one.
109 if (!PN->hasOneUse())
110 return false;
111
112 for (Value *IncValPhi : PN->incoming_values()) {
113 auto *Reinterpret = isReinterpretToSVBool(IncValPhi);
114 if (!Reinterpret ||
115 RequiredType != Reinterpret->getArgOperand(0)->getType())
116 return false;
117 }
118
119 // Create the new Phi
120 LLVMContext &Ctx = PN->getContext();
121 IRBuilder<> Builder(Ctx);
122 Builder.SetInsertPoint(PN);
123 PHINode *NPN = Builder.CreatePHI(RequiredType, PN->getNumIncomingValues());
124 Worklist.push_back(PN);
125
126 for (unsigned I = 0; I < PN->getNumIncomingValues(); I++) {
127 auto *Reinterpret = cast<Instruction>(PN->getIncomingValue(I));
128 NPN->addIncoming(Reinterpret->getOperand(0), PN->getIncomingBlock(I));
129 Worklist.push_back(Reinterpret);
130 }
131
132 // Cleanup Phi Node and reinterprets
133 X->replaceAllUsesWith(NPN);
134 X->eraseFromParent();
135
136 for (auto &I : Worklist)
137 if (I->use_empty())
138 I->eraseFromParent();
139
140 return true;
141 }
142
optimizePTest(IntrinsicInst * I)143 bool SVEIntrinsicOpts::optimizePTest(IntrinsicInst *I) {
144 IntrinsicInst *Op1 = dyn_cast<IntrinsicInst>(I->getArgOperand(0));
145 IntrinsicInst *Op2 = dyn_cast<IntrinsicInst>(I->getArgOperand(1));
146
147 if (Op1 && Op2 &&
148 Op1->getIntrinsicID() == Intrinsic::aarch64_sve_convert_to_svbool &&
149 Op2->getIntrinsicID() == Intrinsic::aarch64_sve_convert_to_svbool &&
150 Op1->getArgOperand(0)->getType() == Op2->getArgOperand(0)->getType()) {
151
152 Value *Ops[] = {Op1->getArgOperand(0), Op2->getArgOperand(0)};
153 Type *Tys[] = {Op1->getArgOperand(0)->getType()};
154 Module *M = I->getParent()->getParent()->getParent();
155
156 auto Fn = Intrinsic::getDeclaration(M, I->getIntrinsicID(), Tys);
157 auto CI = CallInst::Create(Fn, Ops, I->getName(), I);
158
159 I->replaceAllUsesWith(CI);
160 I->eraseFromParent();
161 if (Op1->use_empty())
162 Op1->eraseFromParent();
163 if (Op1 != Op2 && Op2->use_empty())
164 Op2->eraseFromParent();
165
166 return true;
167 }
168
169 return false;
170 }
171
optimizeConvertFromSVBool(IntrinsicInst * I)172 bool SVEIntrinsicOpts::optimizeConvertFromSVBool(IntrinsicInst *I) {
173 assert(I->getIntrinsicID() == Intrinsic::aarch64_sve_convert_from_svbool &&
174 "Unexpected opcode");
175
176 // If the reinterpret instruction operand is a PHI Node
177 if (isa<PHINode>(I->getArgOperand(0)))
178 return processPhiNode(I);
179
180 SmallVector<Instruction *, 32> CandidatesForRemoval;
181 Value *Cursor = I->getOperand(0), *EarliestReplacement = nullptr;
182
183 const auto *IVTy = cast<VectorType>(I->getType());
184
185 // Walk the chain of conversions.
186 while (Cursor) {
187 // If the type of the cursor has fewer lanes than the final result, zeroing
188 // must take place, which breaks the equivalence chain.
189 const auto *CursorVTy = cast<VectorType>(Cursor->getType());
190 if (CursorVTy->getElementCount().getKnownMinValue() <
191 IVTy->getElementCount().getKnownMinValue())
192 break;
193
194 // If the cursor has the same type as I, it is a viable replacement.
195 if (Cursor->getType() == IVTy)
196 EarliestReplacement = Cursor;
197
198 auto *IntrinsicCursor = dyn_cast<IntrinsicInst>(Cursor);
199
200 // If this is not an SVE conversion intrinsic, this is the end of the chain.
201 if (!IntrinsicCursor || !(IntrinsicCursor->getIntrinsicID() ==
202 Intrinsic::aarch64_sve_convert_to_svbool ||
203 IntrinsicCursor->getIntrinsicID() ==
204 Intrinsic::aarch64_sve_convert_from_svbool))
205 break;
206
207 CandidatesForRemoval.insert(CandidatesForRemoval.begin(), IntrinsicCursor);
208 Cursor = IntrinsicCursor->getOperand(0);
209 }
210
211 // If no viable replacement in the conversion chain was found, there is
212 // nothing to do.
213 if (!EarliestReplacement)
214 return false;
215
216 I->replaceAllUsesWith(EarliestReplacement);
217 I->eraseFromParent();
218
219 while (!CandidatesForRemoval.empty()) {
220 Instruction *Candidate = CandidatesForRemoval.pop_back_val();
221 if (Candidate->use_empty())
222 Candidate->eraseFromParent();
223 }
224 return true;
225 }
226
optimizeIntrinsic(Instruction * I)227 bool SVEIntrinsicOpts::optimizeIntrinsic(Instruction *I) {
228 IntrinsicInst *IntrI = dyn_cast<IntrinsicInst>(I);
229 if (!IntrI)
230 return false;
231
232 switch (IntrI->getIntrinsicID()) {
233 case Intrinsic::aarch64_sve_convert_from_svbool:
234 return optimizeConvertFromSVBool(IntrI);
235 case Intrinsic::aarch64_sve_ptest_any:
236 case Intrinsic::aarch64_sve_ptest_first:
237 case Intrinsic::aarch64_sve_ptest_last:
238 return optimizePTest(IntrI);
239 default:
240 return false;
241 }
242
243 return true;
244 }
245
optimizeFunctions(SmallSetVector<Function *,4> & Functions)246 bool SVEIntrinsicOpts::optimizeFunctions(
247 SmallSetVector<Function *, 4> &Functions) {
248 bool Changed = false;
249 for (auto *F : Functions) {
250 DominatorTree *DT = &getAnalysis<DominatorTreeWrapperPass>(*F).getDomTree();
251
252 // Traverse the DT with an rpo walk so we see defs before uses, allowing
253 // simplification to be done incrementally.
254 BasicBlock *Root = DT->getRoot();
255 ReversePostOrderTraversal<BasicBlock *> RPOT(Root);
256 for (auto *BB : RPOT)
257 for (Instruction &I : make_early_inc_range(*BB))
258 Changed |= optimizeIntrinsic(&I);
259 }
260 return Changed;
261 }
262
runOnModule(Module & M)263 bool SVEIntrinsicOpts::runOnModule(Module &M) {
264 bool Changed = false;
265 SmallSetVector<Function *, 4> Functions;
266
267 // Check for SVE intrinsic declarations first so that we only iterate over
268 // relevant functions. Where an appropriate declaration is found, store the
269 // function(s) where it is used so we can target these only.
270 for (auto &F : M.getFunctionList()) {
271 if (!F.isDeclaration())
272 continue;
273
274 switch (F.getIntrinsicID()) {
275 case Intrinsic::aarch64_sve_convert_from_svbool:
276 case Intrinsic::aarch64_sve_ptest_any:
277 case Intrinsic::aarch64_sve_ptest_first:
278 case Intrinsic::aarch64_sve_ptest_last:
279 for (User *U : F.users())
280 Functions.insert(cast<Instruction>(U)->getFunction());
281 break;
282 default:
283 break;
284 }
285 }
286
287 if (!Functions.empty())
288 Changed |= optimizeFunctions(Functions);
289
290 return Changed;
291 }
292