1 //===-- NVPTXTargetMachine.cpp - Define TargetMachine for NVPTX -----------===//
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 // Top-level implementation for the NVPTX target.
10 //
11 //===----------------------------------------------------------------------===//
12
13 #include "NVPTXTargetMachine.h"
14 #include "NVPTX.h"
15 #include "NVPTXAliasAnalysis.h"
16 #include "NVPTXAllocaHoisting.h"
17 #include "NVPTXAtomicLower.h"
18 #include "NVPTXCtorDtorLowering.h"
19 #include "NVPTXLowerAggrCopies.h"
20 #include "NVPTXMachineFunctionInfo.h"
21 #include "NVPTXTargetObjectFile.h"
22 #include "NVPTXTargetTransformInfo.h"
23 #include "TargetInfo/NVPTXTargetInfo.h"
24 #include "llvm/ADT/STLExtras.h"
25 #include "llvm/Analysis/TargetTransformInfo.h"
26 #include "llvm/CodeGen/Passes.h"
27 #include "llvm/CodeGen/TargetPassConfig.h"
28 #include "llvm/IR/IntrinsicsNVPTX.h"
29 #include "llvm/MC/TargetRegistry.h"
30 #include "llvm/Pass.h"
31 #include "llvm/Passes/PassBuilder.h"
32 #include "llvm/Support/CommandLine.h"
33 #include "llvm/Target/TargetMachine.h"
34 #include "llvm/Target/TargetOptions.h"
35 #include "llvm/TargetParser/Triple.h"
36 #include "llvm/Transforms/IPO/ExpandVariadics.h"
37 #include "llvm/Transforms/Scalar.h"
38 #include "llvm/Transforms/Scalar/GVN.h"
39 #include "llvm/Transforms/Vectorize/LoadStoreVectorizer.h"
40 #include <cassert>
41 #include <optional>
42 #include <string>
43
44 using namespace llvm;
45
46 // LSV is still relatively new; this switch lets us turn it off in case we
47 // encounter (or suspect) a bug.
48 static cl::opt<bool>
49 DisableLoadStoreVectorizer("disable-nvptx-load-store-vectorizer",
50 cl::desc("Disable load/store vectorizer"),
51 cl::init(false), cl::Hidden);
52
53 // TODO: Remove this flag when we are confident with no regressions.
54 static cl::opt<bool> DisableRequireStructuredCFG(
55 "disable-nvptx-require-structured-cfg",
56 cl::desc("Transitional flag to turn off NVPTX's requirement on preserving "
57 "structured CFG. The requirement should be disabled only when "
58 "unexpected regressions happen."),
59 cl::init(false), cl::Hidden);
60
61 static cl::opt<bool> UseShortPointersOpt(
62 "nvptx-short-ptr",
63 cl::desc(
64 "Use 32-bit pointers for accessing const/local/shared address spaces."),
65 cl::init(false), cl::Hidden);
66
67 namespace llvm {
68
69 void initializeGenericToNVVMLegacyPassPass(PassRegistry &);
70 void initializeNVPTXAllocaHoistingPass(PassRegistry &);
71 void initializeNVPTXAssignValidGlobalNamesPass(PassRegistry &);
72 void initializeNVPTXAtomicLowerPass(PassRegistry &);
73 void initializeNVPTXCtorDtorLoweringLegacyPass(PassRegistry &);
74 void initializeNVPTXLowerAggrCopiesPass(PassRegistry &);
75 void initializeNVPTXLowerAllocaPass(PassRegistry &);
76 void initializeNVPTXLowerUnreachablePass(PassRegistry &);
77 void initializeNVPTXCtorDtorLoweringLegacyPass(PassRegistry &);
78 void initializeNVPTXLowerArgsPass(PassRegistry &);
79 void initializeNVPTXProxyRegErasurePass(PassRegistry &);
80 void initializeNVVMIntrRangePass(PassRegistry &);
81 void initializeNVVMReflectPass(PassRegistry &);
82 void initializeNVPTXAAWrapperPassPass(PassRegistry &);
83 void initializeNVPTXExternalAAWrapperPass(PassRegistry &);
84
85 } // end namespace llvm
86
LLVMInitializeNVPTXTarget()87 extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeNVPTXTarget() {
88 // Register the target.
89 RegisterTargetMachine<NVPTXTargetMachine32> X(getTheNVPTXTarget32());
90 RegisterTargetMachine<NVPTXTargetMachine64> Y(getTheNVPTXTarget64());
91
92 PassRegistry &PR = *PassRegistry::getPassRegistry();
93 // FIXME: This pass is really intended to be invoked during IR optimization,
94 // but it's very NVPTX-specific.
95 initializeNVVMReflectPass(PR);
96 initializeNVVMIntrRangePass(PR);
97 initializeGenericToNVVMLegacyPassPass(PR);
98 initializeNVPTXAllocaHoistingPass(PR);
99 initializeNVPTXAssignValidGlobalNamesPass(PR);
100 initializeNVPTXAtomicLowerPass(PR);
101 initializeNVPTXLowerArgsPass(PR);
102 initializeNVPTXLowerAllocaPass(PR);
103 initializeNVPTXLowerUnreachablePass(PR);
104 initializeNVPTXCtorDtorLoweringLegacyPass(PR);
105 initializeNVPTXLowerAggrCopiesPass(PR);
106 initializeNVPTXProxyRegErasurePass(PR);
107 initializeNVPTXDAGToDAGISelLegacyPass(PR);
108 initializeNVPTXAAWrapperPassPass(PR);
109 initializeNVPTXExternalAAWrapperPass(PR);
110 }
111
computeDataLayout(bool is64Bit,bool UseShortPointers)112 static std::string computeDataLayout(bool is64Bit, bool UseShortPointers) {
113 std::string Ret = "e";
114
115 if (!is64Bit)
116 Ret += "-p:32:32";
117 else if (UseShortPointers)
118 Ret += "-p3:32:32-p4:32:32-p5:32:32";
119
120 Ret += "-i64:64-i128:128-v16:16-v32:32-n16:32:64";
121
122 return Ret;
123 }
124
NVPTXTargetMachine(const Target & T,const Triple & TT,StringRef CPU,StringRef FS,const TargetOptions & Options,std::optional<Reloc::Model> RM,std::optional<CodeModel::Model> CM,CodeGenOptLevel OL,bool is64bit)125 NVPTXTargetMachine::NVPTXTargetMachine(const Target &T, const Triple &TT,
126 StringRef CPU, StringRef FS,
127 const TargetOptions &Options,
128 std::optional<Reloc::Model> RM,
129 std::optional<CodeModel::Model> CM,
130 CodeGenOptLevel OL, bool is64bit)
131 // The pic relocation model is used regardless of what the client has
132 // specified, as it is the only relocation model currently supported.
133 : LLVMTargetMachine(T, computeDataLayout(is64bit, UseShortPointersOpt), TT,
134 CPU, FS, Options, Reloc::PIC_,
135 getEffectiveCodeModel(CM, CodeModel::Small), OL),
136 is64bit(is64bit), TLOF(std::make_unique<NVPTXTargetObjectFile>()),
137 Subtarget(TT, std::string(CPU), std::string(FS), *this),
138 StrPool(StrAlloc) {
139 if (TT.getOS() == Triple::NVCL)
140 drvInterface = NVPTX::NVCL;
141 else
142 drvInterface = NVPTX::CUDA;
143 if (!DisableRequireStructuredCFG)
144 setRequiresStructuredCFG(true);
145 initAsmInfo();
146 }
147
148 NVPTXTargetMachine::~NVPTXTargetMachine() = default;
149
anchor()150 void NVPTXTargetMachine32::anchor() {}
151
NVPTXTargetMachine32(const Target & T,const Triple & TT,StringRef CPU,StringRef FS,const TargetOptions & Options,std::optional<Reloc::Model> RM,std::optional<CodeModel::Model> CM,CodeGenOptLevel OL,bool JIT)152 NVPTXTargetMachine32::NVPTXTargetMachine32(const Target &T, const Triple &TT,
153 StringRef CPU, StringRef FS,
154 const TargetOptions &Options,
155 std::optional<Reloc::Model> RM,
156 std::optional<CodeModel::Model> CM,
157 CodeGenOptLevel OL, bool JIT)
158 : NVPTXTargetMachine(T, TT, CPU, FS, Options, RM, CM, OL, false) {}
159
anchor()160 void NVPTXTargetMachine64::anchor() {}
161
NVPTXTargetMachine64(const Target & T,const Triple & TT,StringRef CPU,StringRef FS,const TargetOptions & Options,std::optional<Reloc::Model> RM,std::optional<CodeModel::Model> CM,CodeGenOptLevel OL,bool JIT)162 NVPTXTargetMachine64::NVPTXTargetMachine64(const Target &T, const Triple &TT,
163 StringRef CPU, StringRef FS,
164 const TargetOptions &Options,
165 std::optional<Reloc::Model> RM,
166 std::optional<CodeModel::Model> CM,
167 CodeGenOptLevel OL, bool JIT)
168 : NVPTXTargetMachine(T, TT, CPU, FS, Options, RM, CM, OL, true) {}
169
170 namespace {
171
172 class NVPTXPassConfig : public TargetPassConfig {
173 public:
NVPTXPassConfig(NVPTXTargetMachine & TM,PassManagerBase & PM)174 NVPTXPassConfig(NVPTXTargetMachine &TM, PassManagerBase &PM)
175 : TargetPassConfig(TM, PM) {}
176
getNVPTXTargetMachine() const177 NVPTXTargetMachine &getNVPTXTargetMachine() const {
178 return getTM<NVPTXTargetMachine>();
179 }
180
181 void addIRPasses() override;
182 bool addInstSelector() override;
183 void addPreRegAlloc() override;
184 void addPostRegAlloc() override;
185 void addMachineSSAOptimization() override;
186
187 FunctionPass *createTargetRegisterAllocator(bool) override;
188 void addFastRegAlloc() override;
189 void addOptimizedRegAlloc() override;
190
addRegAssignAndRewriteFast()191 bool addRegAssignAndRewriteFast() override {
192 llvm_unreachable("should not be used");
193 }
194
addRegAssignAndRewriteOptimized()195 bool addRegAssignAndRewriteOptimized() override {
196 llvm_unreachable("should not be used");
197 }
198
199 private:
200 // If the opt level is aggressive, add GVN; otherwise, add EarlyCSE. This
201 // function is only called in opt mode.
202 void addEarlyCSEOrGVNPass();
203
204 // Add passes that propagate special memory spaces.
205 void addAddressSpaceInferencePasses();
206
207 // Add passes that perform straight-line scalar optimizations.
208 void addStraightLineScalarOptimizationPasses();
209 };
210
211 } // end anonymous namespace
212
createPassConfig(PassManagerBase & PM)213 TargetPassConfig *NVPTXTargetMachine::createPassConfig(PassManagerBase &PM) {
214 return new NVPTXPassConfig(*this, PM);
215 }
216
createMachineFunctionInfo(BumpPtrAllocator & Allocator,const Function & F,const TargetSubtargetInfo * STI) const217 MachineFunctionInfo *NVPTXTargetMachine::createMachineFunctionInfo(
218 BumpPtrAllocator &Allocator, const Function &F,
219 const TargetSubtargetInfo *STI) const {
220 return NVPTXMachineFunctionInfo::create<NVPTXMachineFunctionInfo>(Allocator,
221 F, STI);
222 }
223
registerDefaultAliasAnalyses(AAManager & AAM)224 void NVPTXTargetMachine::registerDefaultAliasAnalyses(AAManager &AAM) {
225 AAM.registerFunctionAnalysis<NVPTXAA>();
226 }
227
registerPassBuilderCallbacks(PassBuilder & PB)228 void NVPTXTargetMachine::registerPassBuilderCallbacks(PassBuilder &PB) {
229 #define GET_PASS_REGISTRY "NVPTXPassRegistry.def"
230 #include "llvm/Passes/TargetPassRegistry.inc"
231
232 PB.registerPipelineStartEPCallback(
233 [this](ModulePassManager &PM, OptimizationLevel Level) {
234 FunctionPassManager FPM;
235 FPM.addPass(NVVMReflectPass(Subtarget.getSmVersion()));
236 // Note: NVVMIntrRangePass was causing numerical discrepancies at one
237 // point, if issues crop up, consider disabling.
238 FPM.addPass(NVVMIntrRangePass());
239 PM.addPass(createModuleToFunctionPassAdaptor(std::move(FPM)));
240 });
241 }
242
243 TargetTransformInfo
getTargetTransformInfo(const Function & F) const244 NVPTXTargetMachine::getTargetTransformInfo(const Function &F) const {
245 return TargetTransformInfo(NVPTXTTIImpl(this, F));
246 }
247
248 std::pair<const Value *, unsigned>
getPredicatedAddrSpace(const Value * V) const249 NVPTXTargetMachine::getPredicatedAddrSpace(const Value *V) const {
250 if (auto *II = dyn_cast<IntrinsicInst>(V)) {
251 switch (II->getIntrinsicID()) {
252 case Intrinsic::nvvm_isspacep_const:
253 return std::make_pair(II->getArgOperand(0), llvm::ADDRESS_SPACE_CONST);
254 case Intrinsic::nvvm_isspacep_global:
255 return std::make_pair(II->getArgOperand(0), llvm::ADDRESS_SPACE_GLOBAL);
256 case Intrinsic::nvvm_isspacep_local:
257 return std::make_pair(II->getArgOperand(0), llvm::ADDRESS_SPACE_LOCAL);
258 case Intrinsic::nvvm_isspacep_shared:
259 case Intrinsic::nvvm_isspacep_shared_cluster:
260 return std::make_pair(II->getArgOperand(0), llvm::ADDRESS_SPACE_SHARED);
261 default:
262 break;
263 }
264 }
265 return std::make_pair(nullptr, -1);
266 }
267
addEarlyCSEOrGVNPass()268 void NVPTXPassConfig::addEarlyCSEOrGVNPass() {
269 if (getOptLevel() == CodeGenOptLevel::Aggressive)
270 addPass(createGVNPass());
271 else
272 addPass(createEarlyCSEPass());
273 }
274
addAddressSpaceInferencePasses()275 void NVPTXPassConfig::addAddressSpaceInferencePasses() {
276 // NVPTXLowerArgs emits alloca for byval parameters which can often
277 // be eliminated by SROA.
278 addPass(createSROAPass());
279 addPass(createNVPTXLowerAllocaPass());
280 addPass(createInferAddressSpacesPass());
281 addPass(createNVPTXAtomicLowerPass());
282 }
283
addStraightLineScalarOptimizationPasses()284 void NVPTXPassConfig::addStraightLineScalarOptimizationPasses() {
285 addPass(createSeparateConstOffsetFromGEPPass());
286 addPass(createSpeculativeExecutionPass());
287 // ReassociateGEPs exposes more opportunites for SLSR. See
288 // the example in reassociate-geps-and-slsr.ll.
289 addPass(createStraightLineStrengthReducePass());
290 // SeparateConstOffsetFromGEP and SLSR creates common expressions which GVN or
291 // EarlyCSE can reuse. GVN generates significantly better code than EarlyCSE
292 // for some of our benchmarks.
293 addEarlyCSEOrGVNPass();
294 // Run NaryReassociate after EarlyCSE/GVN to be more effective.
295 addPass(createNaryReassociatePass());
296 // NaryReassociate on GEPs creates redundant common expressions, so run
297 // EarlyCSE after it.
298 addPass(createEarlyCSEPass());
299 }
300
addIRPasses()301 void NVPTXPassConfig::addIRPasses() {
302 // The following passes are known to not play well with virtual regs hanging
303 // around after register allocation (which in our case, is *all* registers).
304 // We explicitly disable them here. We do, however, need some functionality
305 // of the PrologEpilogCodeInserter pass, so we emulate that behavior in the
306 // NVPTXPrologEpilog pass (see NVPTXPrologEpilogPass.cpp).
307 disablePass(&PrologEpilogCodeInserterID);
308 disablePass(&MachineLateInstrsCleanupID);
309 disablePass(&MachineCopyPropagationID);
310 disablePass(&TailDuplicateID);
311 disablePass(&StackMapLivenessID);
312 disablePass(&LiveDebugValuesID);
313 disablePass(&PostRAMachineSinkingID);
314 disablePass(&PostRASchedulerID);
315 disablePass(&FuncletLayoutID);
316 disablePass(&PatchableFunctionID);
317 disablePass(&ShrinkWrapID);
318
319 addPass(createNVPTXAAWrapperPass());
320 addPass(createExternalAAWrapperPass([](Pass &P, Function &, AAResults &AAR) {
321 if (auto *WrapperPass = P.getAnalysisIfAvailable<NVPTXAAWrapperPass>())
322 AAR.addAAResult(WrapperPass->getResult());
323 }));
324
325 // NVVMReflectPass is added in addEarlyAsPossiblePasses, so hopefully running
326 // it here does nothing. But since we need it for correctness when lowering
327 // to NVPTX, run it here too, in case whoever built our pass pipeline didn't
328 // call addEarlyAsPossiblePasses.
329 const NVPTXSubtarget &ST = *getTM<NVPTXTargetMachine>().getSubtargetImpl();
330 addPass(createNVVMReflectPass(ST.getSmVersion()));
331
332 if (getOptLevel() != CodeGenOptLevel::None)
333 addPass(createNVPTXImageOptimizerPass());
334 addPass(createNVPTXAssignValidGlobalNamesPass());
335 addPass(createGenericToNVVMLegacyPass());
336
337 // NVPTXLowerArgs is required for correctness and should be run right
338 // before the address space inference passes.
339 addPass(createNVPTXLowerArgsPass());
340 if (getOptLevel() != CodeGenOptLevel::None) {
341 addAddressSpaceInferencePasses();
342 addStraightLineScalarOptimizationPasses();
343 }
344
345 addPass(createAtomicExpandLegacyPass());
346 addPass(createExpandVariadicsPass(ExpandVariadicsMode::Lowering));
347 addPass(createNVPTXCtorDtorLoweringLegacyPass());
348
349 // === LSR and other generic IR passes ===
350 TargetPassConfig::addIRPasses();
351 // EarlyCSE is not always strong enough to clean up what LSR produces. For
352 // example, GVN can combine
353 //
354 // %0 = add %a, %b
355 // %1 = add %b, %a
356 //
357 // and
358 //
359 // %0 = shl nsw %a, 2
360 // %1 = shl %a, 2
361 //
362 // but EarlyCSE can do neither of them.
363 if (getOptLevel() != CodeGenOptLevel::None) {
364 addEarlyCSEOrGVNPass();
365 if (!DisableLoadStoreVectorizer)
366 addPass(createLoadStoreVectorizerPass());
367 addPass(createSROAPass());
368 }
369
370 const auto &Options = getNVPTXTargetMachine().Options;
371 addPass(createNVPTXLowerUnreachablePass(Options.TrapUnreachable,
372 Options.NoTrapAfterNoreturn));
373 }
374
addInstSelector()375 bool NVPTXPassConfig::addInstSelector() {
376 const NVPTXSubtarget &ST = *getTM<NVPTXTargetMachine>().getSubtargetImpl();
377
378 addPass(createLowerAggrCopies());
379 addPass(createAllocaHoisting());
380 addPass(createNVPTXISelDag(getNVPTXTargetMachine(), getOptLevel()));
381
382 if (!ST.hasImageHandles())
383 addPass(createNVPTXReplaceImageHandlesPass());
384
385 return false;
386 }
387
addPreRegAlloc()388 void NVPTXPassConfig::addPreRegAlloc() {
389 // Remove Proxy Register pseudo instructions used to keep `callseq_end` alive.
390 addPass(createNVPTXProxyRegErasurePass());
391 }
392
addPostRegAlloc()393 void NVPTXPassConfig::addPostRegAlloc() {
394 addPass(createNVPTXPrologEpilogPass());
395 if (getOptLevel() != CodeGenOptLevel::None) {
396 // NVPTXPrologEpilogPass calculates frame object offset and replace frame
397 // index with VRFrame register. NVPTXPeephole need to be run after that and
398 // will replace VRFrame with VRFrameLocal when possible.
399 addPass(createNVPTXPeephole());
400 }
401 }
402
createTargetRegisterAllocator(bool)403 FunctionPass *NVPTXPassConfig::createTargetRegisterAllocator(bool) {
404 return nullptr; // No reg alloc
405 }
406
addFastRegAlloc()407 void NVPTXPassConfig::addFastRegAlloc() {
408 addPass(&PHIEliminationID);
409 addPass(&TwoAddressInstructionPassID);
410 }
411
addOptimizedRegAlloc()412 void NVPTXPassConfig::addOptimizedRegAlloc() {
413 addPass(&ProcessImplicitDefsID);
414 addPass(&LiveVariablesID);
415 addPass(&MachineLoopInfoID);
416 addPass(&PHIEliminationID);
417
418 addPass(&TwoAddressInstructionPassID);
419 addPass(&RegisterCoalescerID);
420
421 // PreRA instruction scheduling.
422 if (addPass(&MachineSchedulerID))
423 printAndVerify("After Machine Scheduling");
424
425 addPass(&StackSlotColoringID);
426
427 // FIXME: Needs physical registers
428 // addPass(&MachineLICMID);
429
430 printAndVerify("After StackSlotColoring");
431 }
432
addMachineSSAOptimization()433 void NVPTXPassConfig::addMachineSSAOptimization() {
434 // Pre-ra tail duplication.
435 if (addPass(&EarlyTailDuplicateID))
436 printAndVerify("After Pre-RegAlloc TailDuplicate");
437
438 // Optimize PHIs before DCE: removing dead PHI cycles may make more
439 // instructions dead.
440 addPass(&OptimizePHIsID);
441
442 // This pass merges large allocas. StackSlotColoring is a different pass
443 // which merges spill slots.
444 addPass(&StackColoringID);
445
446 // If the target requests it, assign local variables to stack slots relative
447 // to one another and simplify frame index references where possible.
448 addPass(&LocalStackSlotAllocationID);
449
450 // With optimization, dead code should already be eliminated. However
451 // there is one known exception: lowered code for arguments that are only
452 // used by tail calls, where the tail calls reuse the incoming stack
453 // arguments directly (see t11 in test/CodeGen/X86/sibcall.ll).
454 addPass(&DeadMachineInstructionElimID);
455 printAndVerify("After codegen DCE pass");
456
457 // Allow targets to insert passes that improve instruction level parallelism,
458 // like if-conversion. Such passes will typically need dominator trees and
459 // loop info, just like LICM and CSE below.
460 if (addILPOpts())
461 printAndVerify("After ILP optimizations");
462
463 addPass(&EarlyMachineLICMID);
464 addPass(&MachineCSEID);
465
466 addPass(&MachineSinkingID);
467 printAndVerify("After Machine LICM, CSE and Sinking passes");
468
469 addPass(&PeepholeOptimizerID);
470 printAndVerify("After codegen peephole optimization pass");
471 }
472