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comparison lib/Target/SystemZ/SystemZTDC.cpp @ 120:1172e4bd9c6f

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update 4.0.0
author mir3636
date Fri, 25 Nov 2016 19:14:25 +0900
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101:34baf5011add 120:1172e4bd9c6f
1 //===-- SystemZTDC.cpp - Utilize Test Data Class instruction --------------===//
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 looks for instructions that can be replaced by a Test Data Class
11 // instruction, and replaces them when profitable.
12 //
13 // Roughly, the following rules are recognized:
14 //
15 // 1: fcmp pred X, 0 -> tdc X, mask
16 // 2: fcmp pred X, +-inf -> tdc X, mask
17 // 3: fcmp pred X, +-minnorm -> tdc X, mask
18 // 4: tdc (fabs X), mask -> tdc X, newmask
19 // 5: icmp slt (bitcast float X to int), 0 -> tdc X, mask [ie. signbit]
20 // 6: icmp sgt (bitcast float X to int), -1 -> tdc X, mask
21 // 7: icmp ne/eq (call @llvm.s390.tdc.*(X, mask)) -> tdc X, mask/~mask
22 // 8: and i1 (tdc X, M1), (tdc X, M2) -> tdc X, (M1 & M2)
23 // 9: or i1 (tdc X, M1), (tdc X, M2) -> tdc X, (M1 | M2)
24 // 10: xor i1 (tdc X, M1), (tdc X, M2) -> tdc X, (M1 ^ M2)
25 //
26 // The pass works in 4 steps:
27 //
28 // 1. All fcmp and icmp instructions in a function are checked for a match
29 // with rules 1-3 and 5-7. Their TDC equivalents are stored in
30 // the ConvertedInsts mapping. If the operand of a fcmp instruction is
31 // a fabs, it's also folded according to rule 4.
32 // 2. All and/or/xor i1 instructions whose both operands have been already
33 // mapped are mapped according to rules 8-10. LogicOpsWorklist is used
34 // as a queue of instructions to check.
35 // 3. All mapped instructions that are considered worthy of conversion (ie.
36 // replacing them will actually simplify the final code) are replaced
37 // with a call to the s390.tdc intrinsic.
38 // 4. All intermediate results of replaced instructions are removed if unused.
39 //
40 // Instructions that match rules 1-3 are considered unworthy of conversion
41 // on their own (since a comparison instruction is superior), but are mapped
42 // in the hopes of folding the result using rules 4 and 8-10 (likely removing
43 // the original comparison in the process).
44 //
45 //===----------------------------------------------------------------------===//
46
47 #include "SystemZ.h"
48 #include "llvm/ADT/MapVector.h"
49 #include "llvm/IR/Constants.h"
50 #include "llvm/IR/Instructions.h"
51 #include "llvm/IR/InstIterator.h"
52 #include "llvm/IR/IntrinsicInst.h"
53 #include "llvm/IR/IRBuilder.h"
54 #include "llvm/IR/LegacyPassManager.h"
55 #include "llvm/IR/Module.h"
56 #include <deque>
57 #include <set>
58
59 using namespace llvm;
60
61 namespace llvm {
62 void initializeSystemZTDCPassPass(PassRegistry&);
63 }
64
65 namespace {
66
67 class SystemZTDCPass : public FunctionPass {
68 public:
69 static char ID;
70 SystemZTDCPass() : FunctionPass(ID) {
71 initializeSystemZTDCPassPass(*PassRegistry::getPassRegistry());
72 }
73
74 bool runOnFunction(Function &F) override;
75 private:
76 // Maps seen instructions that can be mapped to a TDC, values are
77 // (TDC operand, TDC mask, worthy flag) triples.
78 MapVector<Instruction *, std::tuple<Value *, int, bool>> ConvertedInsts;
79 // The queue of and/or/xor i1 instructions to be potentially folded.
80 std::vector<BinaryOperator *> LogicOpsWorklist;
81 // Instructions matched while folding, to be removed at the end if unused.
82 std::set<Instruction *> PossibleJunk;
83
84 // Tries to convert a fcmp instruction.
85 void convertFCmp(CmpInst &I);
86
87 // Tries to convert an icmp instruction.
88 void convertICmp(CmpInst &I);
89
90 // Tries to convert an i1 and/or/xor instruction, whose both operands
91 // have been already converted.
92 void convertLogicOp(BinaryOperator &I);
93
94 // Marks an instruction as converted - adds it to ConvertedInsts and adds
95 // any and/or/xor i1 users to the queue.
96 void converted(Instruction *I, Value *V, int Mask, bool Worthy) {
97 ConvertedInsts[I] = std::make_tuple(V, Mask, Worthy);
98 auto &M = *I->getFunction()->getParent();
99 auto &Ctx = M.getContext();
100 for (auto *U : I->users()) {
101 auto *LI = dyn_cast<BinaryOperator>(U);
102 if (LI && LI->getType() == Type::getInt1Ty(Ctx) &&
103 (LI->getOpcode() == Instruction::And ||
104 LI->getOpcode() == Instruction::Or ||
105 LI->getOpcode() == Instruction::Xor)) {
106 LogicOpsWorklist.push_back(LI);
107 }
108 }
109 }
110 };
111
112 } // end anonymous namespace
113
114 char SystemZTDCPass::ID = 0;
115 INITIALIZE_PASS(SystemZTDCPass, "systemz-tdc",
116 "SystemZ Test Data Class optimization", false, false)
117
118 FunctionPass *llvm::createSystemZTDCPass() {
119 return new SystemZTDCPass();
120 }
121
122 void SystemZTDCPass::convertFCmp(CmpInst &I) {
123 Value *Op0 = I.getOperand(0);
124 auto *Const = dyn_cast<ConstantFP>(I.getOperand(1));
125 auto Pred = I.getPredicate();
126 // Only comparisons with consts are interesting.
127 if (!Const)
128 return;
129 // Compute the smallest normal number (and its negation).
130 auto &Sem = Op0->getType()->getFltSemantics();
131 APFloat Smallest = APFloat::getSmallestNormalized(Sem);
132 APFloat NegSmallest = Smallest;
133 NegSmallest.changeSign();
134 // Check if Const is one of our recognized consts.
135 int WhichConst;
136 if (Const->isZero()) {
137 // All comparisons with 0 can be converted.
138 WhichConst = 0;
139 } else if (Const->isInfinity()) {
140 // Likewise for infinities.
141 WhichConst = Const->isNegative() ? 2 : 1;
142 } else if (Const->isExactlyValue(Smallest)) {
143 // For Smallest, we cannot do EQ separately from GT.
144 if ((Pred & CmpInst::FCMP_OGE) != CmpInst::FCMP_OGE &&
145 (Pred & CmpInst::FCMP_OGE) != 0)
146 return;
147 WhichConst = 3;
148 } else if (Const->isExactlyValue(NegSmallest)) {
149 // Likewise for NegSmallest, we cannot do EQ separately from LT.
150 if ((Pred & CmpInst::FCMP_OLE) != CmpInst::FCMP_OLE &&
151 (Pred & CmpInst::FCMP_OLE) != 0)
152 return;
153 WhichConst = 4;
154 } else {
155 // Not one of our special constants.
156 return;
157 }
158 // Partial masks to use for EQ, GT, LT, UN comparisons, respectively.
159 static const int Masks[][4] = {
160 { // 0
161 SystemZ::TDCMASK_ZERO, // eq
162 SystemZ::TDCMASK_POSITIVE, // gt
163 SystemZ::TDCMASK_NEGATIVE, // lt
164 SystemZ::TDCMASK_NAN, // un
165 },
166 { // inf
167 SystemZ::TDCMASK_INFINITY_PLUS, // eq
168 0, // gt
169 (SystemZ::TDCMASK_ZERO |
170 SystemZ::TDCMASK_NEGATIVE |
171 SystemZ::TDCMASK_NORMAL_PLUS |
172 SystemZ::TDCMASK_SUBNORMAL_PLUS), // lt
173 SystemZ::TDCMASK_NAN, // un
174 },
175 { // -inf
176 SystemZ::TDCMASK_INFINITY_MINUS, // eq
177 (SystemZ::TDCMASK_ZERO |
178 SystemZ::TDCMASK_POSITIVE |
179 SystemZ::TDCMASK_NORMAL_MINUS |
180 SystemZ::TDCMASK_SUBNORMAL_MINUS), // gt
181 0, // lt
182 SystemZ::TDCMASK_NAN, // un
183 },
184 { // minnorm
185 0, // eq (unsupported)
186 (SystemZ::TDCMASK_NORMAL_PLUS |
187 SystemZ::TDCMASK_INFINITY_PLUS), // gt (actually ge)
188 (SystemZ::TDCMASK_ZERO |
189 SystemZ::TDCMASK_NEGATIVE |
190 SystemZ::TDCMASK_SUBNORMAL_PLUS), // lt
191 SystemZ::TDCMASK_NAN, // un
192 },
193 { // -minnorm
194 0, // eq (unsupported)
195 (SystemZ::TDCMASK_ZERO |
196 SystemZ::TDCMASK_POSITIVE |
197 SystemZ::TDCMASK_SUBNORMAL_MINUS), // gt
198 (SystemZ::TDCMASK_NORMAL_MINUS |
199 SystemZ::TDCMASK_INFINITY_MINUS), // lt (actually le)
200 SystemZ::TDCMASK_NAN, // un
201 }
202 };
203 // Construct the mask as a combination of the partial masks.
204 int Mask = 0;
205 if (Pred & CmpInst::FCMP_OEQ)
206 Mask |= Masks[WhichConst][0];
207 if (Pred & CmpInst::FCMP_OGT)
208 Mask |= Masks[WhichConst][1];
209 if (Pred & CmpInst::FCMP_OLT)
210 Mask |= Masks[WhichConst][2];
211 if (Pred & CmpInst::FCMP_UNO)
212 Mask |= Masks[WhichConst][3];
213 // A lone fcmp is unworthy of tdc conversion on its own, but may become
214 // worthy if combined with fabs.
215 bool Worthy = false;
216 if (CallInst *CI = dyn_cast<CallInst>(Op0)) {
217 Function *F = CI->getCalledFunction();
218 if (F && F->getIntrinsicID() == Intrinsic::fabs) {
219 // Fold with fabs - adjust the mask appropriately.
220 Mask &= SystemZ::TDCMASK_PLUS;
221 Mask |= Mask >> 1;
222 Op0 = CI->getArgOperand(0);
223 // A combination of fcmp with fabs is a win, unless the constant
224 // involved is 0 (which is handled by later passes).
225 Worthy = WhichConst != 0;
226 PossibleJunk.insert(CI);
227 }
228 }
229 converted(&I, Op0, Mask, Worthy);
230 }
231
232 void SystemZTDCPass::convertICmp(CmpInst &I) {
233 Value *Op0 = I.getOperand(0);
234 auto *Const = dyn_cast<ConstantInt>(I.getOperand(1));
235 auto Pred = I.getPredicate();
236 // All our icmp rules involve comparisons with consts.
237 if (!Const)
238 return;
239 if (auto *Cast = dyn_cast<BitCastInst>(Op0)) {
240 // Check for icmp+bitcast used for signbit.
241 if (!Cast->getSrcTy()->isFloatTy() &&
242 !Cast->getSrcTy()->isDoubleTy() &&
243 !Cast->getSrcTy()->isFP128Ty())
244 return;
245 Value *V = Cast->getOperand(0);
246 int Mask;
247 if (Pred == CmpInst::ICMP_SLT && Const->isZero()) {
248 // icmp slt (bitcast X), 0 - set if sign bit true
249 Mask = SystemZ::TDCMASK_MINUS;
250 } else if (Pred == CmpInst::ICMP_SGT && Const->isMinusOne()) {
251 // icmp sgt (bitcast X), -1 - set if sign bit false
252 Mask = SystemZ::TDCMASK_PLUS;
253 } else {
254 // Not a sign bit check.
255 return;
256 }
257 PossibleJunk.insert(Cast);
258 converted(&I, V, Mask, true);
259 } else if (auto *CI = dyn_cast<CallInst>(Op0)) {
260 // Check if this is a pre-existing call of our tdc intrinsic.
261 Function *F = CI->getCalledFunction();
262 if (!F || F->getIntrinsicID() != Intrinsic::s390_tdc)
263 return;
264 if (!Const->isZero())
265 return;
266 Value *V = CI->getArgOperand(0);
267 auto *MaskC = dyn_cast<ConstantInt>(CI->getArgOperand(1));
268 // Bail if the mask is not a constant.
269 if (!MaskC)
270 return;
271 int Mask = MaskC->getZExtValue();
272 Mask &= SystemZ::TDCMASK_ALL;
273 if (Pred == CmpInst::ICMP_NE) {
274 // icmp ne (call llvm.s390.tdc(...)), 0 -> simple TDC
275 } else if (Pred == CmpInst::ICMP_EQ) {
276 // icmp eq (call llvm.s390.tdc(...)), 0 -> TDC with inverted mask
277 Mask ^= SystemZ::TDCMASK_ALL;
278 } else {
279 // An unknown comparison - ignore.
280 return;
281 }
282 PossibleJunk.insert(CI);
283 converted(&I, V, Mask, false);
284 }
285 }
286
287 void SystemZTDCPass::convertLogicOp(BinaryOperator &I) {
288 Value *Op0, *Op1;
289 int Mask0, Mask1;
290 bool Worthy0, Worthy1;
291 std::tie(Op0, Mask0, Worthy0) = ConvertedInsts[cast<Instruction>(I.getOperand(0))];
292 std::tie(Op1, Mask1, Worthy1) = ConvertedInsts[cast<Instruction>(I.getOperand(1))];
293 if (Op0 != Op1)
294 return;
295 int Mask;
296 switch (I.getOpcode()) {
297 case Instruction::And:
298 Mask = Mask0 & Mask1;
299 break;
300 case Instruction::Or:
301 Mask = Mask0 | Mask1;
302 break;
303 case Instruction::Xor:
304 Mask = Mask0 ^ Mask1;
305 break;
306 default:
307 llvm_unreachable("Unknown op in convertLogicOp");
308 }
309 converted(&I, Op0, Mask, true);
310 }
311
312 bool SystemZTDCPass::runOnFunction(Function &F) {
313 ConvertedInsts.clear();
314 LogicOpsWorklist.clear();
315 PossibleJunk.clear();
316
317 // Look for icmp+fcmp instructions.
318 for (auto &I : instructions(F)) {
319 if (I.getOpcode() == Instruction::FCmp)
320 convertFCmp(cast<CmpInst>(I));
321 else if (I.getOpcode() == Instruction::ICmp)
322 convertICmp(cast<CmpInst>(I));
323 }
324
325 // If none found, bail already.
326 if (ConvertedInsts.empty())
327 return false;
328
329 // Process the queue of logic instructions.
330 while (!LogicOpsWorklist.empty()) {
331 BinaryOperator *Op = LogicOpsWorklist.back();
332 LogicOpsWorklist.pop_back();
333 // If both operands mapped, and the instruction itself not yet mapped,
334 // convert it.
335 if (ConvertedInsts.count(dyn_cast<Instruction>(Op->getOperand(0))) &&
336 ConvertedInsts.count(dyn_cast<Instruction>(Op->getOperand(1))) &&
337 !ConvertedInsts.count(Op))
338 convertLogicOp(*Op);
339 }
340
341 // Time to actually replace the instructions. Do it in the reverse order
342 // of finding them, since there's a good chance the earlier ones will be
343 // unused (due to being folded into later ones).
344 Module &M = *F.getParent();
345 auto &Ctx = M.getContext();
346 Value *Zero32 = ConstantInt::get(Type::getInt32Ty(Ctx), 0);
347 bool MadeChange = false;
348 for (auto &It : reverse(ConvertedInsts)) {
349 Instruction *I = It.first;
350 Value *V;
351 int Mask;
352 bool Worthy;
353 std::tie(V, Mask, Worthy) = It.second;
354 if (!I->user_empty()) {
355 // If used and unworthy of conversion, skip it.
356 if (!Worthy)
357 continue;
358 // Call the intrinsic, compare result with 0.
359 Value *TDCFunc = Intrinsic::getDeclaration(&M, Intrinsic::s390_tdc,
360 V->getType());
361 IRBuilder<> IRB(I);
362 Value *MaskVal = ConstantInt::get(Type::getInt64Ty(Ctx), Mask);
363 Instruction *TDC = IRB.CreateCall(TDCFunc, {V, MaskVal});
364 Value *ICmp = IRB.CreateICmp(CmpInst::ICMP_NE, TDC, Zero32);
365 I->replaceAllUsesWith(ICmp);
366 }
367 // If unused, or used and converted, remove it.
368 I->eraseFromParent();
369 MadeChange = true;
370 }
371
372 if (!MadeChange)
373 return false;
374
375 // We've actually done something - now clear misc accumulated junk (fabs,
376 // bitcast).
377 for (auto *I : PossibleJunk)
378 if (I->user_empty())
379 I->eraseFromParent();
380
381 return true;
382 }