1 //===- SSEDomainFix.cpp - Use proper int/float domain for SSE ---*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file contains the SSEDomainFix pass.
12 // Some SSE instructions like mov, and, or, xor are available in different
13 // variants for different operand types. These variant instructions are
14 // equivalent, but on Nehalem and newer cpus there is extra latency
15 // transferring data between integer and floating point domains.
17 // This pass changes the variant instructions to minimize domain crossings.
19 //===----------------------------------------------------------------------===//
21 #define DEBUG_TYPE "sse-domain-fix"
22 #include "X86InstrInfo.h"
23 #include "llvm/CodeGen/MachineFunctionPass.h"
24 #include "llvm/CodeGen/MachineRegisterInfo.h"
25 #include "llvm/ADT/DepthFirstIterator.h"
26 #include "llvm/Support/Allocator.h"
27 #include "llvm/Support/Debug.h"
28 #include "llvm/Support/raw_ostream.h"
31 /// A DomainValue is a bit like LiveIntervals' ValNo, but it also keeps track
32 /// of execution domains.
34 /// An open DomainValue represents a set of instructions that can still switch
35 /// execution domain. Multiple registers may refer to the same open
36 /// DomainValue - they will eventually be collapsed to the same execution
39 /// A collapsed DomainValue represents a single register that has been forced
40 /// into one of more execution domains. There is a separate collapsed
41 /// DomainValue for each register, but it may contain multiple execution
42 /// domains. A register value is initially created in a single execution
43 /// domain, but if we were forced to pay the penalty of a domain crossing, we
44 /// keep track of the fact the the register is now available in multiple
48 // Basic reference counting.
51 // Bitmask of available domains. For an open DomainValue, it is the still
52 // possible domains for collapsing. For a collapsed DomainValue it is the
53 // domains where the register is available for free.
54 unsigned AvailableDomains;
56 // Position of the last defining instruction.
59 // Twiddleable instructions using or defining these registers.
60 SmallVector<MachineInstr*, 8> Instrs;
62 // A collapsed DomainValue has no instructions to twiddle - it simply keeps
63 // track of the domains where the registers are already available.
64 bool isCollapsed() const { return Instrs.empty(); }
66 // Is domain available?
67 bool hasDomain(unsigned domain) const {
68 return AvailableDomains & (1u << domain);
71 // Mark domain as available.
72 void addDomain(unsigned domain) {
73 AvailableDomains |= 1u << domain;
76 // Restrict to a single domain available.
77 void setSingleDomain(unsigned domain) {
78 AvailableDomains = 1u << domain;
81 // Return bitmask of domains that are available and in mask.
82 unsigned getCommonDomains(unsigned mask) const {
83 return AvailableDomains & mask;
86 // First domain available.
87 unsigned getFirstDomain() const {
88 return CountTrailingZeros_32(AvailableDomains);
91 DomainValue() { clear(); }
94 Refs = AvailableDomains = Dist = 0;
100 static const unsigned NumRegs = 16;
103 class SSEDomainFixPass : public MachineFunctionPass {
105 SpecificBumpPtrAllocator<DomainValue> Allocator;
106 SmallVector<DomainValue*,16> Avail;
109 const X86InstrInfo *TII;
110 const TargetRegisterInfo *TRI;
111 MachineBasicBlock *MBB;
112 DomainValue **LiveRegs;
113 typedef DenseMap<MachineBasicBlock*,DomainValue**> LiveOutMap;
118 SSEDomainFixPass() : MachineFunctionPass(ID) {}
120 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
121 AU.setPreservesAll();
122 MachineFunctionPass::getAnalysisUsage(AU);
125 virtual bool runOnMachineFunction(MachineFunction &MF);
127 virtual const char *getPassName() const {
128 return "SSE execution domain fixup";
133 int RegIndex(unsigned Reg);
135 // DomainValue allocation.
136 DomainValue *Alloc(int domain = -1);
137 void Recycle(DomainValue*);
139 // LiveRegs manipulations.
140 void SetLiveReg(int rx, DomainValue *DV);
142 void Force(int rx, unsigned domain);
143 void Collapse(DomainValue *dv, unsigned domain);
144 bool Merge(DomainValue *A, DomainValue *B);
146 void enterBasicBlock();
147 void visitGenericInstr(MachineInstr*);
148 void visitSoftInstr(MachineInstr*, unsigned mask);
149 void visitHardInstr(MachineInstr*, unsigned domain);
153 char SSEDomainFixPass::ID = 0;
155 /// Translate TRI register number to an index into our smaller tables of
156 /// interesting registers. Return -1 for boring registers.
157 int SSEDomainFixPass::RegIndex(unsigned reg) {
158 assert(X86::XMM15 == X86::XMM0+NumRegs-1 && "Unexpected sort");
160 return reg < NumRegs ? (int) reg : -1;
163 DomainValue *SSEDomainFixPass::Alloc(int domain) {
164 DomainValue *dv = Avail.empty() ?
165 new(Allocator.Allocate()) DomainValue :
166 Avail.pop_back_val();
169 dv->addDomain(domain);
173 void SSEDomainFixPass::Recycle(DomainValue *dv) {
174 assert(dv && "Cannot recycle NULL");
179 /// Set LiveRegs[rx] = dv, updating reference counts.
180 void SSEDomainFixPass::SetLiveReg(int rx, DomainValue *dv) {
181 assert(unsigned(rx) < NumRegs && "Invalid index");
183 LiveRegs = new DomainValue*[NumRegs];
184 std::fill(LiveRegs, LiveRegs+NumRegs, (DomainValue*)0);
187 if (LiveRegs[rx] == dv)
190 assert(LiveRegs[rx]->Refs && "Bad refcount");
191 if (--LiveRegs[rx]->Refs == 0) Recycle(LiveRegs[rx]);
197 // Kill register rx, recycle or collapse any DomainValue.
198 void SSEDomainFixPass::Kill(int rx) {
199 assert(unsigned(rx) < NumRegs && "Invalid index");
200 if (!LiveRegs || !LiveRegs[rx]) return;
202 // Before killing the last reference to an open DomainValue, collapse it to
203 // the first available domain.
204 if (LiveRegs[rx]->Refs == 1 && !LiveRegs[rx]->isCollapsed())
205 Collapse(LiveRegs[rx], LiveRegs[rx]->getFirstDomain());
210 /// Force register rx into domain.
211 void SSEDomainFixPass::Force(int rx, unsigned domain) {
212 assert(unsigned(rx) < NumRegs && "Invalid index");
214 if (LiveRegs && (dv = LiveRegs[rx])) {
215 if (dv->isCollapsed())
216 dv->addDomain(domain);
217 else if (dv->hasDomain(domain))
218 Collapse(dv, domain);
220 // This is an incompatible open DomainValue. Collapse it to whatever and force
221 // the new value into domain. This costs a domain crossing.
222 Collapse(dv, dv->getFirstDomain());
223 assert(LiveRegs[rx] && "Not live after collapse?");
224 LiveRegs[rx]->addDomain(domain);
227 // Set up basic collapsed DomainValue.
228 SetLiveReg(rx, Alloc(domain));
232 /// Collapse open DomainValue into given domain. If there are multiple
233 /// registers using dv, they each get a unique collapsed DomainValue.
234 void SSEDomainFixPass::Collapse(DomainValue *dv, unsigned domain) {
235 assert(dv->hasDomain(domain) && "Cannot collapse");
237 // Collapse all the instructions.
238 while (!dv->Instrs.empty())
239 TII->SetSSEDomain(dv->Instrs.pop_back_val(), domain);
240 dv->setSingleDomain(domain);
242 // If there are multiple users, give them new, unique DomainValues.
243 if (LiveRegs && dv->Refs > 1)
244 for (unsigned rx = 0; rx != NumRegs; ++rx)
245 if (LiveRegs[rx] == dv)
246 SetLiveReg(rx, Alloc(domain));
249 /// Merge - All instructions and registers in B are moved to A, and B is
251 bool SSEDomainFixPass::Merge(DomainValue *A, DomainValue *B) {
252 assert(!A->isCollapsed() && "Cannot merge into collapsed");
253 assert(!B->isCollapsed() && "Cannot merge from collapsed");
256 // Restrict to the domains that A and B have in common.
257 unsigned common = A->getCommonDomains(B->AvailableDomains);
260 A->AvailableDomains = common;
261 A->Dist = std::max(A->Dist, B->Dist);
262 A->Instrs.append(B->Instrs.begin(), B->Instrs.end());
263 for (unsigned rx = 0; rx != NumRegs; ++rx)
264 if (LiveRegs[rx] == B)
269 void SSEDomainFixPass::enterBasicBlock() {
270 // Try to coalesce live-out registers from predecessors.
271 for (MachineBasicBlock::livein_iterator i = MBB->livein_begin(),
272 e = MBB->livein_end(); i != e; ++i) {
273 int rx = RegIndex(*i);
274 if (rx < 0) continue;
275 for (MachineBasicBlock::const_pred_iterator pi = MBB->pred_begin(),
276 pe = MBB->pred_end(); pi != pe; ++pi) {
277 LiveOutMap::const_iterator fi = LiveOuts.find(*pi);
278 if (fi == LiveOuts.end()) continue;
279 DomainValue *pdv = fi->second[rx];
281 if (!LiveRegs || !LiveRegs[rx]) {
286 // We have a live DomainValue from more than one predecessor.
287 if (LiveRegs[rx]->isCollapsed()) {
288 // We are already collapsed, but predecessor is not. Force him.
289 unsigned domain = LiveRegs[rx]->getFirstDomain();
290 if (!pdv->isCollapsed() && pdv->hasDomain(domain))
291 Collapse(pdv, domain);
295 // Currently open, merge in predecessor.
296 if (!pdv->isCollapsed())
297 Merge(LiveRegs[rx], pdv);
299 Force(rx, pdv->getFirstDomain());
304 // A hard instruction only works in one domain. All input registers will be
305 // forced into that domain.
306 void SSEDomainFixPass::visitHardInstr(MachineInstr *mi, unsigned domain) {
307 // Collapse all uses.
308 for (unsigned i = mi->getDesc().getNumDefs(),
309 e = mi->getDesc().getNumOperands(); i != e; ++i) {
310 MachineOperand &mo = mi->getOperand(i);
311 if (!mo.isReg()) continue;
312 int rx = RegIndex(mo.getReg());
313 if (rx < 0) continue;
317 // Kill all defs and force them.
318 for (unsigned i = 0, e = mi->getDesc().getNumDefs(); i != e; ++i) {
319 MachineOperand &mo = mi->getOperand(i);
320 if (!mo.isReg()) continue;
321 int rx = RegIndex(mo.getReg());
322 if (rx < 0) continue;
328 // A soft instruction can be changed to work in other domains given by mask.
329 void SSEDomainFixPass::visitSoftInstr(MachineInstr *mi, unsigned mask) {
330 // Bitmask of available domains for this instruction after taking collapsed
331 // operands into account.
332 unsigned available = mask;
334 // Scan the explicit use operands for incoming domains.
335 SmallVector<int, 4> used;
337 for (unsigned i = mi->getDesc().getNumDefs(),
338 e = mi->getDesc().getNumOperands(); i != e; ++i) {
339 MachineOperand &mo = mi->getOperand(i);
340 if (!mo.isReg()) continue;
341 int rx = RegIndex(mo.getReg());
342 if (rx < 0) continue;
343 if (DomainValue *dv = LiveRegs[rx]) {
344 // Bitmask of domains that dv and available have in common.
345 unsigned common = dv->getCommonDomains(available);
346 // Is it possible to use this collapsed register for free?
347 if (dv->isCollapsed()) {
348 // Restrict available domains to the ones in common with the operand.
349 // If there are no common domains, we must pay the cross-domain
350 // penalty for this operand.
351 if (common) available = common;
353 // Open DomainValue is compatible, save it for merging.
356 // Open DomainValue is not compatible with instruction. It is useless
362 // If the collapsed operands force a single domain, propagate the collapse.
363 if (isPowerOf2_32(available)) {
364 unsigned domain = CountTrailingZeros_32(available);
365 TII->SetSSEDomain(mi, domain);
366 visitHardInstr(mi, domain);
370 // Kill off any remaining uses that don't match available, and build a list of
371 // incoming DomainValues that we want to merge.
372 SmallVector<DomainValue*,4> doms;
373 for (SmallVector<int, 4>::iterator i=used.begin(), e=used.end(); i!=e; ++i) {
375 DomainValue *dv = LiveRegs[rx];
376 // This useless DomainValue could have been missed above.
377 if (!dv->getCommonDomains(available)) {
381 // sorted, uniqued insert.
382 bool inserted = false;
383 for (SmallVector<DomainValue*,4>::iterator i = doms.begin(), e = doms.end();
384 i != e && !inserted; ++i) {
387 else if (dv->Dist < (*i)->Dist) {
396 // doms are now sorted in order of appearance. Try to merge them all, giving
397 // priority to the latest ones.
399 while (!doms.empty()) {
401 dv = doms.pop_back_val();
405 DomainValue *latest = doms.pop_back_val();
406 if (Merge(dv, latest)) continue;
408 // If latest didn't merge, it is useless now. Kill all registers using it.
409 for (SmallVector<int,4>::iterator i=used.begin(), e=used.end(); i != e; ++i)
410 if (LiveRegs[*i] == latest)
414 // dv is the DomainValue we are going to use for this instruction.
418 dv->AvailableDomains = available;
419 dv->Instrs.push_back(mi);
421 // Finally set all defs and non-collapsed uses to dv.
422 for (unsigned i = 0, e = mi->getDesc().getNumOperands(); i != e; ++i) {
423 MachineOperand &mo = mi->getOperand(i);
424 if (!mo.isReg()) continue;
425 int rx = RegIndex(mo.getReg());
426 if (rx < 0) continue;
427 if (!LiveRegs || !LiveRegs[rx] || (mo.isDef() && LiveRegs[rx]!=dv)) {
434 void SSEDomainFixPass::visitGenericInstr(MachineInstr *mi) {
435 // Process explicit defs, kill any XMM registers redefined.
436 for (unsigned i = 0, e = mi->getDesc().getNumDefs(); i != e; ++i) {
437 MachineOperand &mo = mi->getOperand(i);
438 if (!mo.isReg()) continue;
439 int rx = RegIndex(mo.getReg());
440 if (rx < 0) continue;
445 bool SSEDomainFixPass::runOnMachineFunction(MachineFunction &mf) {
447 TII = static_cast<const X86InstrInfo*>(MF->getTarget().getInstrInfo());
448 TRI = MF->getTarget().getRegisterInfo();
452 assert(NumRegs == X86::VR128RegClass.getNumRegs() && "Bad regclass");
454 // If no XMM registers are used in the function, we can skip it completely.
455 bool anyregs = false;
456 for (TargetRegisterClass::const_iterator I = X86::VR128RegClass.begin(),
457 E = X86::VR128RegClass.end(); I != E; ++I)
458 if (MF->getRegInfo().isPhysRegUsed(*I)) {
462 if (!anyregs) return false;
464 MachineBasicBlock *Entry = MF->begin();
465 SmallPtrSet<MachineBasicBlock*, 16> Visited;
466 for (df_ext_iterator<MachineBasicBlock*, SmallPtrSet<MachineBasicBlock*, 16> >
467 DFI = df_ext_begin(Entry, Visited), DFE = df_ext_end(Entry, Visited);
471 for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); I != E;
473 MachineInstr *mi = I;
474 if (mi->isDebugValue()) continue;
476 std::pair<uint16_t, uint16_t> domp = TII->GetSSEDomain(mi);
479 visitSoftInstr(mi, domp.second);
481 visitHardInstr(mi, domp.first);
483 visitGenericInstr(mi);
486 // Save live registers at end of MBB - used by enterBasicBlock().
488 LiveOuts.insert(std::make_pair(MBB, LiveRegs));
492 // Clear the LiveOuts vectors. Should we also collapse any remaining
494 for (LiveOutMap::const_iterator i = LiveOuts.begin(), e = LiveOuts.end();
499 Allocator.DestroyAll();
504 FunctionPass *llvm::createSSEDomainFixPass() {
505 return new SSEDomainFixPass();