1//===- SubtargetFeature.cpp - CPU characteristics Implementation ----------===//
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 file implements the SubtargetFeature interface.
11//
12//===----------------------------------------------------------------------===//
13
14#include "llvm/MC/SubtargetFeature.h"
15#include "llvm/Support/Debug.h"
16#include "llvm/Support/Format.h"
17#include "llvm/Support/raw_ostream.h"
18#include <algorithm>
19#include <cassert>
20#include <cctype>
21#include <cstdlib>
22using namespace llvm;
23
24//===----------------------------------------------------------------------===//
25//                          Static Helper Functions
26//===----------------------------------------------------------------------===//
27
28/// hasFlag - Determine if a feature has a flag; '+' or '-'
29///
30static inline bool hasFlag(const StringRef Feature) {
31  assert(!Feature.empty() && "Empty string");
32  // Get first character
33  char Ch = Feature[0];
34  // Check if first character is '+' or '-' flag
35  return Ch == '+' || Ch =='-';
36}
37
38/// StripFlag - Return string stripped of flag.
39///
40static inline std::string StripFlag(const StringRef Feature) {
41  return hasFlag(Feature) ? Feature.substr(1) : Feature;
42}
43
44/// isEnabled - Return true if enable flag; '+'.
45///
46static inline bool isEnabled(const StringRef Feature) {
47  assert(!Feature.empty() && "Empty string");
48  // Get first character
49  char Ch = Feature[0];
50  // Check if first character is '+' for enabled
51  return Ch == '+';
52}
53
54/// PrependFlag - Return a string with a prepended flag; '+' or '-'.
55///
56static inline std::string PrependFlag(const StringRef Feature,
57                                    bool IsEnabled) {
58  assert(!Feature.empty() && "Empty string");
59  if (hasFlag(Feature))
60    return Feature;
61  std::string Prefix = IsEnabled ? "+" : "-";
62  Prefix += Feature;
63  return Prefix;
64}
65
66/// Split - Splits a string of comma separated items in to a vector of strings.
67///
68static void Split(std::vector<std::string> &V, const StringRef S) {
69  if (S.empty())
70    return;
71
72  // Start at beginning of string.
73  size_t Pos = 0;
74  while (true) {
75    // Find the next comma
76    size_t Comma = S.find(',', Pos);
77    // If no comma found then the rest of the string is used
78    if (Comma == std::string::npos) {
79      // Add string to vector
80      V.push_back(S.substr(Pos));
81      break;
82    }
83    // Otherwise add substring to vector
84    V.push_back(S.substr(Pos, Comma - Pos));
85    // Advance to next item
86    Pos = Comma + 1;
87  }
88}
89
90/// Join a vector of strings to a string with a comma separating each element.
91///
92static std::string Join(const std::vector<std::string> &V) {
93  // Start with empty string.
94  std::string Result;
95  // If the vector is not empty
96  if (!V.empty()) {
97    // Start with the first feature
98    Result = V[0];
99    // For each successive feature
100    for (size_t i = 1; i < V.size(); i++) {
101      // Add a comma
102      Result += ",";
103      // Add the feature
104      Result += V[i];
105    }
106  }
107  // Return the features string
108  return Result;
109}
110
111/// Adding features.
112void SubtargetFeatures::AddFeature(const StringRef String,
113                                   bool IsEnabled) {
114  // Don't add empty features
115  if (!String.empty()) {
116    // Convert to lowercase, prepend flag and add to vector
117    Features.push_back(PrependFlag(String.lower(), IsEnabled));
118  }
119}
120
121/// Find KV in array using binary search.
122static const SubtargetFeatureKV *Find(StringRef S, const SubtargetFeatureKV *A,
123                                      size_t L) {
124  // Make the lower bound element we're looking for
125  SubtargetFeatureKV KV;
126  KV.Key = S.data();
127  // Determine the end of the array
128  const SubtargetFeatureKV *Hi = A + L;
129  // Binary search the array
130  const SubtargetFeatureKV *F = std::lower_bound(A, Hi, KV);
131  // If not found then return NULL
132  if (F == Hi || StringRef(F->Key) != S) return NULL;
133  // Return the found array item
134  return F;
135}
136
137/// getLongestEntryLength - Return the length of the longest entry in the table.
138///
139static size_t getLongestEntryLength(const SubtargetFeatureKV *Table,
140                                    size_t Size) {
141  size_t MaxLen = 0;
142  for (size_t i = 0; i < Size; i++)
143    MaxLen = std::max(MaxLen, std::strlen(Table[i].Key));
144  return MaxLen;
145}
146
147/// Display help for feature choices.
148///
149static void Help(const SubtargetFeatureKV *CPUTable, size_t CPUTableSize,
150                 const SubtargetFeatureKV *FeatTable, size_t FeatTableSize) {
151  // Determine the length of the longest CPU and Feature entries.
152  unsigned MaxCPULen  = getLongestEntryLength(CPUTable, CPUTableSize);
153  unsigned MaxFeatLen = getLongestEntryLength(FeatTable, FeatTableSize);
154
155  // Print the CPU table.
156  errs() << "Available CPUs for this target:\n\n";
157  for (size_t i = 0; i != CPUTableSize; i++)
158    errs() << format("  %-*s - %s.\n",
159                     MaxCPULen, CPUTable[i].Key, CPUTable[i].Desc);
160  errs() << '\n';
161
162  // Print the Feature table.
163  errs() << "Available features for this target:\n\n";
164  for (size_t i = 0; i != FeatTableSize; i++)
165    errs() << format("  %-*s - %s.\n",
166                     MaxFeatLen, FeatTable[i].Key, FeatTable[i].Desc);
167  errs() << '\n';
168
169  errs() << "Use +feature to enable a feature, or -feature to disable it.\n"
170            "For example, llc -mcpu=mycpu -mattr=+feature1,-feature2\n";
171  std::exit(1);
172}
173
174//===----------------------------------------------------------------------===//
175//                    SubtargetFeatures Implementation
176//===----------------------------------------------------------------------===//
177
178SubtargetFeatures::SubtargetFeatures(const StringRef Initial) {
179  // Break up string into separate features
180  Split(Features, Initial);
181}
182
183
184std::string SubtargetFeatures::getString() const {
185  return Join(Features);
186}
187
188/// SetImpliedBits - For each feature that is (transitively) implied by this
189/// feature, set it.
190///
191static
192void SetImpliedBits(uint64_t &Bits, const SubtargetFeatureKV *FeatureEntry,
193                    const SubtargetFeatureKV *FeatureTable,
194                    size_t FeatureTableSize) {
195  for (size_t i = 0; i < FeatureTableSize; ++i) {
196    const SubtargetFeatureKV &FE = FeatureTable[i];
197
198    if (FeatureEntry->Value == FE.Value) continue;
199
200    if (FeatureEntry->Implies & FE.Value) {
201      Bits |= FE.Value;
202      SetImpliedBits(Bits, &FE, FeatureTable, FeatureTableSize);
203    }
204  }
205}
206
207/// ClearImpliedBits - For each feature that (transitively) implies this
208/// feature, clear it.
209///
210static
211void ClearImpliedBits(uint64_t &Bits, const SubtargetFeatureKV *FeatureEntry,
212                      const SubtargetFeatureKV *FeatureTable,
213                      size_t FeatureTableSize) {
214  for (size_t i = 0; i < FeatureTableSize; ++i) {
215    const SubtargetFeatureKV &FE = FeatureTable[i];
216
217    if (FeatureEntry->Value == FE.Value) continue;
218
219    if (FE.Implies & FeatureEntry->Value) {
220      Bits &= ~FE.Value;
221      ClearImpliedBits(Bits, &FE, FeatureTable, FeatureTableSize);
222    }
223  }
224}
225
226/// ToggleFeature - Toggle a feature and returns the newly updated feature
227/// bits.
228uint64_t
229SubtargetFeatures::ToggleFeature(uint64_t Bits, const StringRef Feature,
230                                 const SubtargetFeatureKV *FeatureTable,
231                                 size_t FeatureTableSize) {
232  // Find feature in table.
233  const SubtargetFeatureKV *FeatureEntry =
234    Find(StripFlag(Feature), FeatureTable, FeatureTableSize);
235  // If there is a match
236  if (FeatureEntry) {
237    if ((Bits & FeatureEntry->Value) == FeatureEntry->Value) {
238      Bits &= ~FeatureEntry->Value;
239
240      // For each feature that implies this, clear it.
241      ClearImpliedBits(Bits, FeatureEntry, FeatureTable, FeatureTableSize);
242    } else {
243      Bits |=  FeatureEntry->Value;
244
245      // For each feature that this implies, set it.
246      SetImpliedBits(Bits, FeatureEntry, FeatureTable, FeatureTableSize);
247    }
248  } else {
249    errs() << "'" << Feature
250           << "' is not a recognized feature for this target"
251           << " (ignoring feature)\n";
252  }
253
254  return Bits;
255}
256
257
258/// getFeatureBits - Get feature bits a CPU.
259///
260uint64_t SubtargetFeatures::getFeatureBits(const StringRef CPU,
261                                         const SubtargetFeatureKV *CPUTable,
262                                         size_t CPUTableSize,
263                                         const SubtargetFeatureKV *FeatureTable,
264                                         size_t FeatureTableSize) {
265  if (!FeatureTableSize || !CPUTableSize)
266    return 0;
267
268#ifndef NDEBUG
269  for (size_t i = 1; i < CPUTableSize; i++) {
270    assert(strcmp(CPUTable[i - 1].Key, CPUTable[i].Key) < 0 &&
271           "CPU table is not sorted");
272  }
273  for (size_t i = 1; i < FeatureTableSize; i++) {
274    assert(strcmp(FeatureTable[i - 1].Key, FeatureTable[i].Key) < 0 &&
275          "CPU features table is not sorted");
276  }
277#endif
278  uint64_t Bits = 0;                    // Resulting bits
279
280  // Check if help is needed
281  if (CPU == "help")
282    Help(CPUTable, CPUTableSize, FeatureTable, FeatureTableSize);
283
284  // Find CPU entry if CPU name is specified.
285  if (!CPU.empty()) {
286    const SubtargetFeatureKV *CPUEntry = Find(CPU, CPUTable, CPUTableSize);
287    // If there is a match
288    if (CPUEntry) {
289      // Set base feature bits
290      Bits = CPUEntry->Value;
291
292      // Set the feature implied by this CPU feature, if any.
293      for (size_t i = 0; i < FeatureTableSize; ++i) {
294        const SubtargetFeatureKV &FE = FeatureTable[i];
295        if (CPUEntry->Value & FE.Value)
296          SetImpliedBits(Bits, &FE, FeatureTable, FeatureTableSize);
297      }
298    } else {
299      errs() << "'" << CPU
300             << "' is not a recognized processor for this target"
301             << " (ignoring processor)\n";
302    }
303  }
304
305  // Iterate through each feature
306  for (size_t i = 0, E = Features.size(); i < E; i++) {
307    const StringRef Feature = Features[i];
308
309    // Check for help
310    if (Feature == "+help")
311      Help(CPUTable, CPUTableSize, FeatureTable, FeatureTableSize);
312
313    // Find feature in table.
314    const SubtargetFeatureKV *FeatureEntry =
315                       Find(StripFlag(Feature), FeatureTable, FeatureTableSize);
316    // If there is a match
317    if (FeatureEntry) {
318      // Enable/disable feature in bits
319      if (isEnabled(Feature)) {
320        Bits |=  FeatureEntry->Value;
321
322        // For each feature that this implies, set it.
323        SetImpliedBits(Bits, FeatureEntry, FeatureTable, FeatureTableSize);
324      } else {
325        Bits &= ~FeatureEntry->Value;
326
327        // For each feature that implies this, clear it.
328        ClearImpliedBits(Bits, FeatureEntry, FeatureTable, FeatureTableSize);
329      }
330    } else {
331      errs() << "'" << Feature
332             << "' is not a recognized feature for this target"
333             << " (ignoring feature)\n";
334    }
335  }
336
337  return Bits;
338}
339
340/// print - Print feature string.
341///
342void SubtargetFeatures::print(raw_ostream &OS) const {
343  for (size_t i = 0, e = Features.size(); i != e; ++i)
344    OS << Features[i] << "  ";
345  OS << "\n";
346}
347
348#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
349/// dump - Dump feature info.
350///
351void SubtargetFeatures::dump() const {
352  print(dbgs());
353}
354#endif
355
356/// getDefaultSubtargetFeatures - Return a string listing the features
357/// associated with the target triple.
358///
359/// FIXME: This is an inelegant way of specifying the features of a
360/// subtarget. It would be better if we could encode this information
361/// into the IR. See <rdar://5972456>.
362///
363void SubtargetFeatures::getDefaultSubtargetFeatures(const Triple& Triple) {
364  if (Triple.getVendor() == Triple::Apple) {
365    if (Triple.getArch() == Triple::ppc) {
366      // powerpc-apple-*
367      AddFeature("altivec");
368    } else if (Triple.getArch() == Triple::ppc64) {
369      // powerpc64-apple-*
370      AddFeature("64bit");
371      AddFeature("altivec");
372    }
373  }
374}
375