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  // Determine the end of the array
125  const SubtargetFeatureKV *Hi = A + L;
126  // Binary search the array
127  const SubtargetFeatureKV *F = std::lower_bound(A, Hi, S);
128  // If not found then return NULL
129  if (F == Hi || StringRef(F->Key) != S) return NULL;
130  // Return the found array item
131  return F;
132}
133
134/// getLongestEntryLength - Return the length of the longest entry in the table.
135///
136static size_t getLongestEntryLength(const SubtargetFeatureKV *Table,
137                                    size_t Size) {
138  size_t MaxLen = 0;
139  for (size_t i = 0; i < Size; i++)
140    MaxLen = std::max(MaxLen, std::strlen(Table[i].Key));
141  return MaxLen;
142}
143
144/// Display help for feature choices.
145///
146static void Help(const SubtargetFeatureKV *CPUTable, size_t CPUTableSize,
147                 const SubtargetFeatureKV *FeatTable, size_t FeatTableSize) {
148  // Determine the length of the longest CPU and Feature entries.
149  unsigned MaxCPULen  = getLongestEntryLength(CPUTable, CPUTableSize);
150  unsigned MaxFeatLen = getLongestEntryLength(FeatTable, FeatTableSize);
151
152  // Print the CPU table.
153  errs() << "Available CPUs for this target:\n\n";
154  for (size_t i = 0; i != CPUTableSize; i++)
155    errs() << format("  %-*s - %s.\n",
156                     MaxCPULen, CPUTable[i].Key, CPUTable[i].Desc);
157  errs() << '\n';
158
159  // Print the Feature table.
160  errs() << "Available features for this target:\n\n";
161  for (size_t i = 0; i != FeatTableSize; i++)
162    errs() << format("  %-*s - %s.\n",
163                     MaxFeatLen, FeatTable[i].Key, FeatTable[i].Desc);
164  errs() << '\n';
165
166  errs() << "Use +feature to enable a feature, or -feature to disable it.\n"
167            "For example, llc -mcpu=mycpu -mattr=+feature1,-feature2\n";
168  std::exit(1);
169}
170
171//===----------------------------------------------------------------------===//
172//                    SubtargetFeatures Implementation
173//===----------------------------------------------------------------------===//
174
175SubtargetFeatures::SubtargetFeatures(const StringRef Initial) {
176  // Break up string into separate features
177  Split(Features, Initial);
178}
179
180
181std::string SubtargetFeatures::getString() const {
182  return Join(Features);
183}
184
185/// SetImpliedBits - For each feature that is (transitively) implied by this
186/// feature, set it.
187///
188static
189void SetImpliedBits(uint64_t &Bits, const SubtargetFeatureKV *FeatureEntry,
190                    const SubtargetFeatureKV *FeatureTable,
191                    size_t FeatureTableSize) {
192  for (size_t i = 0; i < FeatureTableSize; ++i) {
193    const SubtargetFeatureKV &FE = FeatureTable[i];
194
195    if (FeatureEntry->Value == FE.Value) continue;
196
197    if (FeatureEntry->Implies & FE.Value) {
198      Bits |= FE.Value;
199      SetImpliedBits(Bits, &FE, FeatureTable, FeatureTableSize);
200    }
201  }
202}
203
204/// ClearImpliedBits - For each feature that (transitively) implies this
205/// feature, clear it.
206///
207static
208void ClearImpliedBits(uint64_t &Bits, const SubtargetFeatureKV *FeatureEntry,
209                      const SubtargetFeatureKV *FeatureTable,
210                      size_t FeatureTableSize) {
211  for (size_t i = 0; i < FeatureTableSize; ++i) {
212    const SubtargetFeatureKV &FE = FeatureTable[i];
213
214    if (FeatureEntry->Value == FE.Value) continue;
215
216    if (FE.Implies & FeatureEntry->Value) {
217      Bits &= ~FE.Value;
218      ClearImpliedBits(Bits, &FE, FeatureTable, FeatureTableSize);
219    }
220  }
221}
222
223/// ToggleFeature - Toggle a feature and returns the newly updated feature
224/// bits.
225uint64_t
226SubtargetFeatures::ToggleFeature(uint64_t Bits, const StringRef Feature,
227                                 const SubtargetFeatureKV *FeatureTable,
228                                 size_t FeatureTableSize) {
229  // Find feature in table.
230  const SubtargetFeatureKV *FeatureEntry =
231    Find(StripFlag(Feature), FeatureTable, FeatureTableSize);
232  // If there is a match
233  if (FeatureEntry) {
234    if ((Bits & FeatureEntry->Value) == FeatureEntry->Value) {
235      Bits &= ~FeatureEntry->Value;
236
237      // For each feature that implies this, clear it.
238      ClearImpliedBits(Bits, FeatureEntry, FeatureTable, FeatureTableSize);
239    } else {
240      Bits |=  FeatureEntry->Value;
241
242      // For each feature that this implies, set it.
243      SetImpliedBits(Bits, FeatureEntry, FeatureTable, FeatureTableSize);
244    }
245  } else {
246    errs() << "'" << Feature
247           << "' is not a recognized feature for this target"
248           << " (ignoring feature)\n";
249  }
250
251  return Bits;
252}
253
254
255/// getFeatureBits - Get feature bits a CPU.
256///
257uint64_t SubtargetFeatures::getFeatureBits(const StringRef CPU,
258                                         const SubtargetFeatureKV *CPUTable,
259                                         size_t CPUTableSize,
260                                         const SubtargetFeatureKV *FeatureTable,
261                                         size_t FeatureTableSize) {
262  if (!FeatureTableSize || !CPUTableSize)
263    return 0;
264
265#ifndef NDEBUG
266  for (size_t i = 1; i < CPUTableSize; i++) {
267    assert(strcmp(CPUTable[i - 1].Key, CPUTable[i].Key) < 0 &&
268           "CPU table is not sorted");
269  }
270  for (size_t i = 1; i < FeatureTableSize; i++) {
271    assert(strcmp(FeatureTable[i - 1].Key, FeatureTable[i].Key) < 0 &&
272          "CPU features table is not sorted");
273  }
274#endif
275  uint64_t Bits = 0;                    // Resulting bits
276
277  // Check if help is needed
278  if (CPU == "help")
279    Help(CPUTable, CPUTableSize, FeatureTable, FeatureTableSize);
280
281  // Find CPU entry if CPU name is specified.
282  if (!CPU.empty()) {
283    const SubtargetFeatureKV *CPUEntry = Find(CPU, CPUTable, CPUTableSize);
284    // If there is a match
285    if (CPUEntry) {
286      // Set base feature bits
287      Bits = CPUEntry->Value;
288
289      // Set the feature implied by this CPU feature, if any.
290      for (size_t i = 0; i < FeatureTableSize; ++i) {
291        const SubtargetFeatureKV &FE = FeatureTable[i];
292        if (CPUEntry->Value & FE.Value)
293          SetImpliedBits(Bits, &FE, FeatureTable, FeatureTableSize);
294      }
295    } else {
296      errs() << "'" << CPU
297             << "' is not a recognized processor for this target"
298             << " (ignoring processor)\n";
299    }
300  }
301
302  // Iterate through each feature
303  for (size_t i = 0, E = Features.size(); i < E; i++) {
304    const StringRef Feature = Features[i];
305
306    // Check for help
307    if (Feature == "+help")
308      Help(CPUTable, CPUTableSize, FeatureTable, FeatureTableSize);
309
310    // Find feature in table.
311    const SubtargetFeatureKV *FeatureEntry =
312                       Find(StripFlag(Feature), FeatureTable, FeatureTableSize);
313    // If there is a match
314    if (FeatureEntry) {
315      // Enable/disable feature in bits
316      if (isEnabled(Feature)) {
317        Bits |=  FeatureEntry->Value;
318
319        // For each feature that this implies, set it.
320        SetImpliedBits(Bits, FeatureEntry, FeatureTable, FeatureTableSize);
321      } else {
322        Bits &= ~FeatureEntry->Value;
323
324        // For each feature that implies this, clear it.
325        ClearImpliedBits(Bits, FeatureEntry, FeatureTable, FeatureTableSize);
326      }
327    } else {
328      errs() << "'" << Feature
329             << "' is not a recognized feature for this target"
330             << " (ignoring feature)\n";
331    }
332  }
333
334  return Bits;
335}
336
337/// print - Print feature string.
338///
339void SubtargetFeatures::print(raw_ostream &OS) const {
340  for (size_t i = 0, e = Features.size(); i != e; ++i)
341    OS << Features[i] << "  ";
342  OS << "\n";
343}
344
345#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
346/// dump - Dump feature info.
347///
348void SubtargetFeatures::dump() const {
349  print(dbgs());
350}
351#endif
352
353/// Adds the default features for the specified target triple.
354///
355/// FIXME: This is an inelegant way of specifying the features of a
356/// subtarget. It would be better if we could encode this information
357/// into the IR. See <rdar://5972456>.
358///
359void SubtargetFeatures::getDefaultSubtargetFeatures(const Triple& Triple) {
360  if (Triple.getVendor() == Triple::Apple) {
361    if (Triple.getArch() == Triple::ppc) {
362      // powerpc-apple-*
363      AddFeature("altivec");
364    } else if (Triple.getArch() == Triple::ppc64) {
365      // powerpc64-apple-*
366      AddFeature("64bit");
367      AddFeature("altivec");
368    }
369  }
370}
371