1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469
|
//===----- SVEIntrinsicOpts - SVE ACLE Intrinsics Opts --------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// Performs general IR level optimizations on SVE intrinsics.
//
// This pass performs the following optimizations:
//
// - removes unnecessary ptrue intrinsics (llvm.aarch64.sve.ptrue), e.g:
// %1 = @llvm.aarch64.sve.ptrue.nxv4i1(i32 31)
// %2 = @llvm.aarch64.sve.ptrue.nxv8i1(i32 31)
// ; (%1 can be replaced with a reinterpret of %2)
//
// - optimizes ptest intrinsics where the operands are being needlessly
// converted to and from svbool_t.
//
//===----------------------------------------------------------------------===//
#include "AArch64.h"
#include "Utils/AArch64BaseInfo.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/IntrinsicsAArch64.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/InitializePasses.h"
#include "llvm/Support/Debug.h"
using namespace llvm;
using namespace llvm::PatternMatch;
#define DEBUG_TYPE "aarch64-sve-intrinsic-opts"
namespace {
struct SVEIntrinsicOpts : public ModulePass {
static char ID; // Pass identification, replacement for typeid
SVEIntrinsicOpts() : ModulePass(ID) {
initializeSVEIntrinsicOptsPass(*PassRegistry::getPassRegistry());
}
bool runOnModule(Module &M) override;
void getAnalysisUsage(AnalysisUsage &AU) const override;
private:
bool coalescePTrueIntrinsicCalls(BasicBlock &BB,
SmallSetVector<IntrinsicInst *, 4> &PTrues);
bool optimizePTrueIntrinsicCalls(SmallSetVector<Function *, 4> &Functions);
bool optimizePredicateStore(Instruction *I);
bool optimizePredicateLoad(Instruction *I);
bool optimizeInstructions(SmallSetVector<Function *, 4> &Functions);
/// Operates at the function-scope. I.e., optimizations are applied local to
/// the functions themselves.
bool optimizeFunctions(SmallSetVector<Function *, 4> &Functions);
};
} // end anonymous namespace
void SVEIntrinsicOpts::getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<DominatorTreeWrapperPass>();
AU.setPreservesCFG();
}
char SVEIntrinsicOpts::ID = 0;
static const char *name = "SVE intrinsics optimizations";
INITIALIZE_PASS_BEGIN(SVEIntrinsicOpts, DEBUG_TYPE, name, false, false)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass);
INITIALIZE_PASS_END(SVEIntrinsicOpts, DEBUG_TYPE, name, false, false)
ModulePass *llvm::createSVEIntrinsicOptsPass() {
return new SVEIntrinsicOpts();
}
/// Checks if a ptrue intrinsic call is promoted. The act of promoting a
/// ptrue will introduce zeroing. For example:
///
/// %1 = <vscale x 4 x i1> call @llvm.aarch64.sve.ptrue.nxv4i1(i32 31)
/// %2 = <vscale x 16 x i1> call @llvm.aarch64.sve.convert.to.svbool.nxv4i1(<vscale x 4 x i1> %1)
/// %3 = <vscale x 8 x i1> call @llvm.aarch64.sve.convert.from.svbool.nxv8i1(<vscale x 16 x i1> %2)
///
/// %1 is promoted, because it is converted:
///
/// <vscale x 4 x i1> => <vscale x 16 x i1> => <vscale x 8 x i1>
///
/// via a sequence of the SVE reinterpret intrinsics convert.{to,from}.svbool.
static bool isPTruePromoted(IntrinsicInst *PTrue) {
// Find all users of this intrinsic that are calls to convert-to-svbool
// reinterpret intrinsics.
SmallVector<IntrinsicInst *, 4> ConvertToUses;
for (User *User : PTrue->users()) {
if (match(User, m_Intrinsic<Intrinsic::aarch64_sve_convert_to_svbool>())) {
ConvertToUses.push_back(cast<IntrinsicInst>(User));
}
}
// If no such calls were found, this is ptrue is not promoted.
if (ConvertToUses.empty())
return false;
// Otherwise, try to find users of the convert-to-svbool intrinsics that are
// calls to the convert-from-svbool intrinsic, and would result in some lanes
// being zeroed.
const auto *PTrueVTy = cast<ScalableVectorType>(PTrue->getType());
for (IntrinsicInst *ConvertToUse : ConvertToUses) {
for (User *User : ConvertToUse->users()) {
auto *IntrUser = dyn_cast<IntrinsicInst>(User);
if (IntrUser && IntrUser->getIntrinsicID() ==
Intrinsic::aarch64_sve_convert_from_svbool) {
const auto *IntrUserVTy = cast<ScalableVectorType>(IntrUser->getType());
// Would some lanes become zeroed by the conversion?
if (IntrUserVTy->getElementCount().getKnownMinValue() >
PTrueVTy->getElementCount().getKnownMinValue())
// This is a promoted ptrue.
return true;
}
}
}
// If no matching calls were found, this is not a promoted ptrue.
return false;
}
/// Attempts to coalesce ptrues in a basic block.
bool SVEIntrinsicOpts::coalescePTrueIntrinsicCalls(
BasicBlock &BB, SmallSetVector<IntrinsicInst *, 4> &PTrues) {
if (PTrues.size() <= 1)
return false;
// Find the ptrue with the most lanes.
auto *MostEncompassingPTrue = *std::max_element(
PTrues.begin(), PTrues.end(), [](auto *PTrue1, auto *PTrue2) {
auto *PTrue1VTy = cast<ScalableVectorType>(PTrue1->getType());
auto *PTrue2VTy = cast<ScalableVectorType>(PTrue2->getType());
return PTrue1VTy->getElementCount().getKnownMinValue() <
PTrue2VTy->getElementCount().getKnownMinValue();
});
// Remove the most encompassing ptrue, as well as any promoted ptrues, leaving
// behind only the ptrues to be coalesced.
PTrues.remove(MostEncompassingPTrue);
PTrues.remove_if(isPTruePromoted);
// Hoist MostEncompassingPTrue to the start of the basic block. It is always
// safe to do this, since ptrue intrinsic calls are guaranteed to have no
// predecessors.
MostEncompassingPTrue->moveBefore(BB, BB.getFirstInsertionPt());
LLVMContext &Ctx = BB.getContext();
IRBuilder<> Builder(Ctx);
Builder.SetInsertPoint(&BB, ++MostEncompassingPTrue->getIterator());
auto *MostEncompassingPTrueVTy =
cast<VectorType>(MostEncompassingPTrue->getType());
auto *ConvertToSVBool = Builder.CreateIntrinsic(
Intrinsic::aarch64_sve_convert_to_svbool, {MostEncompassingPTrueVTy},
{MostEncompassingPTrue});
bool ConvertFromCreated = false;
for (auto *PTrue : PTrues) {
auto *PTrueVTy = cast<VectorType>(PTrue->getType());
// Only create the converts if the types are not already the same, otherwise
// just use the most encompassing ptrue.
if (MostEncompassingPTrueVTy != PTrueVTy) {
ConvertFromCreated = true;
Builder.SetInsertPoint(&BB, ++ConvertToSVBool->getIterator());
auto *ConvertFromSVBool =
Builder.CreateIntrinsic(Intrinsic::aarch64_sve_convert_from_svbool,
{PTrueVTy}, {ConvertToSVBool});
PTrue->replaceAllUsesWith(ConvertFromSVBool);
} else
PTrue->replaceAllUsesWith(MostEncompassingPTrue);
PTrue->eraseFromParent();
}
// We never used the ConvertTo so remove it
if (!ConvertFromCreated)
ConvertToSVBool->eraseFromParent();
return true;
}
/// The goal of this function is to remove redundant calls to the SVE ptrue
/// intrinsic in each basic block within the given functions.
///
/// SVE ptrues have two representations in LLVM IR:
/// - a logical representation -- an arbitrary-width scalable vector of i1s,
/// i.e. <vscale x N x i1>.
/// - a physical representation (svbool, <vscale x 16 x i1>) -- a 16-element
/// scalable vector of i1s, i.e. <vscale x 16 x i1>.
///
/// The SVE ptrue intrinsic is used to create a logical representation of an SVE
/// predicate. Suppose that we have two SVE ptrue intrinsic calls: P1 and P2. If
/// P1 creates a logical SVE predicate that is at least as wide as the logical
/// SVE predicate created by P2, then all of the bits that are true in the
/// physical representation of P2 are necessarily also true in the physical
/// representation of P1. P1 'encompasses' P2, therefore, the intrinsic call to
/// P2 is redundant and can be replaced by an SVE reinterpret of P1 via
/// convert.{to,from}.svbool.
///
/// Currently, this pass only coalesces calls to SVE ptrue intrinsics
/// if they match the following conditions:
///
/// - the call to the intrinsic uses either the SV_ALL or SV_POW2 patterns.
/// SV_ALL indicates that all bits of the predicate vector are to be set to
/// true. SV_POW2 indicates that all bits of the predicate vector up to the
/// largest power-of-two are to be set to true.
/// - the result of the call to the intrinsic is not promoted to a wider
/// predicate. In this case, keeping the extra ptrue leads to better codegen
/// -- coalescing here would create an irreducible chain of SVE reinterprets
/// via convert.{to,from}.svbool.
///
/// EXAMPLE:
///
/// %1 = <vscale x 8 x i1> ptrue(i32 SV_ALL)
/// ; Logical: <1, 1, 1, 1, 1, 1, 1, 1>
/// ; Physical: <1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0>
/// ...
///
/// %2 = <vscale x 4 x i1> ptrue(i32 SV_ALL)
/// ; Logical: <1, 1, 1, 1>
/// ; Physical: <1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0>
/// ...
///
/// Here, %2 can be replaced by an SVE reinterpret of %1, giving, for instance:
///
/// %1 = <vscale x 8 x i1> ptrue(i32 i31)
/// %2 = <vscale x 16 x i1> convert.to.svbool(<vscale x 8 x i1> %1)
/// %3 = <vscale x 4 x i1> convert.from.svbool(<vscale x 16 x i1> %2)
///
bool SVEIntrinsicOpts::optimizePTrueIntrinsicCalls(
SmallSetVector<Function *, 4> &Functions) {
bool Changed = false;
for (auto *F : Functions) {
for (auto &BB : *F) {
SmallSetVector<IntrinsicInst *, 4> SVAllPTrues;
SmallSetVector<IntrinsicInst *, 4> SVPow2PTrues;
// For each basic block, collect the used ptrues and try to coalesce them.
for (Instruction &I : BB) {
if (I.use_empty())
continue;
auto *IntrI = dyn_cast<IntrinsicInst>(&I);
if (!IntrI || IntrI->getIntrinsicID() != Intrinsic::aarch64_sve_ptrue)
continue;
const auto PTruePattern =
cast<ConstantInt>(IntrI->getOperand(0))->getZExtValue();
if (PTruePattern == AArch64SVEPredPattern::all)
SVAllPTrues.insert(IntrI);
if (PTruePattern == AArch64SVEPredPattern::pow2)
SVPow2PTrues.insert(IntrI);
}
Changed |= coalescePTrueIntrinsicCalls(BB, SVAllPTrues);
Changed |= coalescePTrueIntrinsicCalls(BB, SVPow2PTrues);
}
}
return Changed;
}
// This is done in SVEIntrinsicOpts rather than InstCombine so that we introduce
// scalable stores as late as possible
bool SVEIntrinsicOpts::optimizePredicateStore(Instruction *I) {
auto *F = I->getFunction();
auto Attr = F->getFnAttribute(Attribute::VScaleRange);
if (!Attr.isValid())
return false;
unsigned MinVScale = Attr.getVScaleRangeMin();
Optional<unsigned> MaxVScale = Attr.getVScaleRangeMax();
// The transform needs to know the exact runtime length of scalable vectors
if (!MaxVScale || MinVScale != MaxVScale)
return false;
auto *PredType =
ScalableVectorType::get(Type::getInt1Ty(I->getContext()), 16);
auto *FixedPredType =
FixedVectorType::get(Type::getInt8Ty(I->getContext()), MinVScale * 2);
// If we have a store..
auto *Store = dyn_cast<StoreInst>(I);
if (!Store || !Store->isSimple())
return false;
// ..that is storing a predicate vector sized worth of bits..
if (Store->getOperand(0)->getType() != FixedPredType)
return false;
// ..where the value stored comes from a vector extract..
auto *IntrI = dyn_cast<IntrinsicInst>(Store->getOperand(0));
if (!IntrI ||
IntrI->getIntrinsicID() != Intrinsic::experimental_vector_extract)
return false;
// ..that is extracting from index 0..
if (!cast<ConstantInt>(IntrI->getOperand(1))->isZero())
return false;
// ..where the value being extract from comes from a bitcast
auto *BitCast = dyn_cast<BitCastInst>(IntrI->getOperand(0));
if (!BitCast)
return false;
// ..and the bitcast is casting from predicate type
if (BitCast->getOperand(0)->getType() != PredType)
return false;
IRBuilder<> Builder(I->getContext());
Builder.SetInsertPoint(I);
auto *PtrBitCast = Builder.CreateBitCast(
Store->getPointerOperand(),
PredType->getPointerTo(Store->getPointerAddressSpace()));
Builder.CreateStore(BitCast->getOperand(0), PtrBitCast);
Store->eraseFromParent();
if (IntrI->getNumUses() == 0)
IntrI->eraseFromParent();
if (BitCast->getNumUses() == 0)
BitCast->eraseFromParent();
return true;
}
// This is done in SVEIntrinsicOpts rather than InstCombine so that we introduce
// scalable loads as late as possible
bool SVEIntrinsicOpts::optimizePredicateLoad(Instruction *I) {
auto *F = I->getFunction();
auto Attr = F->getFnAttribute(Attribute::VScaleRange);
if (!Attr.isValid())
return false;
unsigned MinVScale = Attr.getVScaleRangeMin();
Optional<unsigned> MaxVScale = Attr.getVScaleRangeMax();
// The transform needs to know the exact runtime length of scalable vectors
if (!MaxVScale || MinVScale != MaxVScale)
return false;
auto *PredType =
ScalableVectorType::get(Type::getInt1Ty(I->getContext()), 16);
auto *FixedPredType =
FixedVectorType::get(Type::getInt8Ty(I->getContext()), MinVScale * 2);
// If we have a bitcast..
auto *BitCast = dyn_cast<BitCastInst>(I);
if (!BitCast || BitCast->getType() != PredType)
return false;
// ..whose operand is a vector_insert..
auto *IntrI = dyn_cast<IntrinsicInst>(BitCast->getOperand(0));
if (!IntrI ||
IntrI->getIntrinsicID() != Intrinsic::experimental_vector_insert)
return false;
// ..that is inserting into index zero of an undef vector..
if (!isa<UndefValue>(IntrI->getOperand(0)) ||
!cast<ConstantInt>(IntrI->getOperand(2))->isZero())
return false;
// ..where the value inserted comes from a load..
auto *Load = dyn_cast<LoadInst>(IntrI->getOperand(1));
if (!Load || !Load->isSimple())
return false;
// ..that is loading a predicate vector sized worth of bits..
if (Load->getType() != FixedPredType)
return false;
IRBuilder<> Builder(I->getContext());
Builder.SetInsertPoint(Load);
auto *PtrBitCast = Builder.CreateBitCast(
Load->getPointerOperand(),
PredType->getPointerTo(Load->getPointerAddressSpace()));
auto *LoadPred = Builder.CreateLoad(PredType, PtrBitCast);
BitCast->replaceAllUsesWith(LoadPred);
BitCast->eraseFromParent();
if (IntrI->getNumUses() == 0)
IntrI->eraseFromParent();
if (Load->getNumUses() == 0)
Load->eraseFromParent();
return true;
}
bool SVEIntrinsicOpts::optimizeInstructions(
SmallSetVector<Function *, 4> &Functions) {
bool Changed = false;
for (auto *F : Functions) {
DominatorTree *DT = &getAnalysis<DominatorTreeWrapperPass>(*F).getDomTree();
// Traverse the DT with an rpo walk so we see defs before uses, allowing
// simplification to be done incrementally.
BasicBlock *Root = DT->getRoot();
ReversePostOrderTraversal<BasicBlock *> RPOT(Root);
for (auto *BB : RPOT) {
for (Instruction &I : make_early_inc_range(*BB)) {
switch (I.getOpcode()) {
case Instruction::Store:
Changed |= optimizePredicateStore(&I);
break;
case Instruction::BitCast:
Changed |= optimizePredicateLoad(&I);
break;
}
}
}
}
return Changed;
}
bool SVEIntrinsicOpts::optimizeFunctions(
SmallSetVector<Function *, 4> &Functions) {
bool Changed = false;
Changed |= optimizePTrueIntrinsicCalls(Functions);
Changed |= optimizeInstructions(Functions);
return Changed;
}
bool SVEIntrinsicOpts::runOnModule(Module &M) {
bool Changed = false;
SmallSetVector<Function *, 4> Functions;
// Check for SVE intrinsic declarations first so that we only iterate over
// relevant functions. Where an appropriate declaration is found, store the
// function(s) where it is used so we can target these only.
for (auto &F : M.getFunctionList()) {
if (!F.isDeclaration())
continue;
switch (F.getIntrinsicID()) {
case Intrinsic::experimental_vector_extract:
case Intrinsic::experimental_vector_insert:
case Intrinsic::aarch64_sve_ptrue:
for (User *U : F.users())
Functions.insert(cast<Instruction>(U)->getFunction());
break;
default:
break;
}
}
if (!Functions.empty())
Changed |= optimizeFunctions(Functions);
return Changed;
}
|