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/ADT/ArrayRef.h"
16#include "llvm/ADT/StringExtras.h"
17#include "llvm/Support/Debug.h"
18#include "llvm/Support/Format.h"
19#include "llvm/Support/raw_ostream.h"
20#include <algorithm>
21#include <cassert>
22#include <cctype>
23#include <cstdlib>
24using namespace llvm;
25
26//===----------------------------------------------------------------------===//
27//                          Static Helper Functions
28//===----------------------------------------------------------------------===//
29
30/// hasFlag - Determine if a feature has a flag; '+' or '-'
31///
32static inline bool hasFlag(StringRef Feature) {
33  assert(!Feature.empty() && "Empty string");
34  // Get first character
35  char Ch = Feature[0];
36  // Check if first character is '+' or '-' flag
37  return Ch == '+' || Ch =='-';
38}
39
40/// StripFlag - Return string stripped of flag.
41///
42static inline std::string StripFlag(StringRef Feature) {
43  return hasFlag(Feature) ? Feature.substr(1) : Feature;
44}
45
46/// isEnabled - Return true if enable flag; '+'.
47///
48static inline bool isEnabled(StringRef Feature) {
49  assert(!Feature.empty() && "Empty string");
50  // Get first character
51  char Ch = Feature[0];
52  // Check if first character is '+' for enabled
53  return Ch == '+';
54}
55
56/// Split - Splits a string of comma separated items in to a vector of strings.
57///
58static void Split(std::vector<std::string> &V, StringRef S) {
59  SmallVector<StringRef, 3> Tmp;
60  S.split(Tmp, ',', -1, false /* KeepEmpty */);
61  V.assign(Tmp.begin(), Tmp.end());
62}
63
64/// Adding features.
65void SubtargetFeatures::AddFeature(StringRef String, bool Enable) {
66  // Don't add empty features.
67  if (!String.empty())
68    // Convert to lowercase, prepend flag if we don't already have a flag.
69    Features.push_back(hasFlag(String) ? String.lower()
70                                       : (Enable ? "+" : "-") + String.lower());
71}
72
73/// Find KV in array using binary search.
74static const SubtargetFeatureKV *Find(StringRef S,
75                                      ArrayRef<SubtargetFeatureKV> A) {
76  // Binary search the array
77  auto F = std::lower_bound(A.begin(), A.end(), S);
78  // If not found then return NULL
79  if (F == A.end() || StringRef(F->Key) != S) return nullptr;
80  // Return the found array item
81  return F;
82}
83
84/// getLongestEntryLength - Return the length of the longest entry in the table.
85///
86static size_t getLongestEntryLength(ArrayRef<SubtargetFeatureKV> Table) {
87  size_t MaxLen = 0;
88  for (auto &I : Table)
89    MaxLen = std::max(MaxLen, std::strlen(I.Key));
90  return MaxLen;
91}
92
93/// Display help for feature choices.
94///
95static void Help(ArrayRef<SubtargetFeatureKV> CPUTable,
96                 ArrayRef<SubtargetFeatureKV> FeatTable) {
97  // Determine the length of the longest CPU and Feature entries.
98  unsigned MaxCPULen  = getLongestEntryLength(CPUTable);
99  unsigned MaxFeatLen = getLongestEntryLength(FeatTable);
100
101  // Print the CPU table.
102  errs() << "Available CPUs for this target:\n\n";
103  for (auto &CPU : CPUTable)
104    errs() << format("  %-*s - %s.\n", MaxCPULen, CPU.Key, CPU.Desc);
105  errs() << '\n';
106
107  // Print the Feature table.
108  errs() << "Available features for this target:\n\n";
109  for (auto &Feature : FeatTable)
110    errs() << format("  %-*s - %s.\n", MaxFeatLen, Feature.Key, Feature.Desc);
111  errs() << '\n';
112
113  errs() << "Use +feature to enable a feature, or -feature to disable it.\n"
114            "For example, llc -mcpu=mycpu -mattr=+feature1,-feature2\n";
115}
116
117//===----------------------------------------------------------------------===//
118//                    SubtargetFeatures Implementation
119//===----------------------------------------------------------------------===//
120
121SubtargetFeatures::SubtargetFeatures(StringRef Initial) {
122  // Break up string into separate features
123  Split(Features, Initial);
124}
125
126
127std::string SubtargetFeatures::getString() const {
128  return join(Features.begin(), Features.end(), ",");
129}
130
131/// SetImpliedBits - For each feature that is (transitively) implied by this
132/// feature, set it.
133///
134static
135void SetImpliedBits(FeatureBitset &Bits, const SubtargetFeatureKV *FeatureEntry,
136                    ArrayRef<SubtargetFeatureKV> FeatureTable) {
137  for (auto &FE : FeatureTable) {
138    if (FeatureEntry->Value == FE.Value) continue;
139
140    if ((FeatureEntry->Implies & FE.Value).any()) {
141      Bits |= FE.Value;
142      SetImpliedBits(Bits, &FE, FeatureTable);
143    }
144  }
145}
146
147/// ClearImpliedBits - For each feature that (transitively) implies this
148/// feature, clear it.
149///
150static
151void ClearImpliedBits(FeatureBitset &Bits,
152                      const SubtargetFeatureKV *FeatureEntry,
153                      ArrayRef<SubtargetFeatureKV> FeatureTable) {
154  for (auto &FE : FeatureTable) {
155    if (FeatureEntry->Value == FE.Value) continue;
156
157    if ((FE.Implies & FeatureEntry->Value).any()) {
158      Bits &= ~FE.Value;
159      ClearImpliedBits(Bits, &FE, FeatureTable);
160    }
161  }
162}
163
164/// ToggleFeature - Toggle a feature and update the feature bits.
165void
166SubtargetFeatures::ToggleFeature(FeatureBitset &Bits, StringRef Feature,
167                                 ArrayRef<SubtargetFeatureKV> FeatureTable) {
168
169  // Find feature in table.
170  const SubtargetFeatureKV *FeatureEntry =
171      Find(StripFlag(Feature), FeatureTable);
172  // If there is a match
173  if (FeatureEntry) {
174    if ((Bits & FeatureEntry->Value) == FeatureEntry->Value) {
175      Bits &= ~FeatureEntry->Value;
176      // For each feature that implies this, clear it.
177      ClearImpliedBits(Bits, FeatureEntry, FeatureTable);
178    } else {
179      Bits |=  FeatureEntry->Value;
180
181      // For each feature that this implies, set it.
182      SetImpliedBits(Bits, FeatureEntry, FeatureTable);
183    }
184  } else {
185    errs() << "'" << Feature
186           << "' is not a recognized feature for this target"
187           << " (ignoring feature)\n";
188  }
189}
190
191void SubtargetFeatures::ApplyFeatureFlag(FeatureBitset &Bits, StringRef Feature,
192                                    ArrayRef<SubtargetFeatureKV> FeatureTable) {
193
194  assert(hasFlag(Feature));
195
196  // Find feature in table.
197  const SubtargetFeatureKV *FeatureEntry =
198      Find(StripFlag(Feature), FeatureTable);
199  // If there is a match
200  if (FeatureEntry) {
201    // Enable/disable feature in bits
202    if (isEnabled(Feature)) {
203      Bits |= FeatureEntry->Value;
204
205      // For each feature that this implies, set it.
206      SetImpliedBits(Bits, FeatureEntry, FeatureTable);
207    } else {
208      Bits &= ~FeatureEntry->Value;
209
210      // For each feature that implies this, clear it.
211      ClearImpliedBits(Bits, FeatureEntry, FeatureTable);
212    }
213  } else {
214    errs() << "'" << Feature
215           << "' is not a recognized feature for this target"
216           << " (ignoring feature)\n";
217  }
218}
219
220
221/// getFeatureBits - Get feature bits a CPU.
222///
223FeatureBitset
224SubtargetFeatures::getFeatureBits(StringRef CPU,
225                                  ArrayRef<SubtargetFeatureKV> CPUTable,
226                                  ArrayRef<SubtargetFeatureKV> FeatureTable) {
227
228  if (CPUTable.empty() || FeatureTable.empty())
229    return FeatureBitset();
230
231#ifndef NDEBUG
232  assert(std::is_sorted(std::begin(CPUTable), std::end(CPUTable)) &&
233         "CPU table is not sorted");
234  assert(std::is_sorted(std::begin(FeatureTable), std::end(FeatureTable)) &&
235         "CPU features table is not sorted");
236#endif
237  // Resulting bits
238  FeatureBitset Bits;
239
240  // Check if help is needed
241  if (CPU == "help")
242    Help(CPUTable, FeatureTable);
243
244  // Find CPU entry if CPU name is specified.
245  else if (!CPU.empty()) {
246    const SubtargetFeatureKV *CPUEntry = Find(CPU, CPUTable);
247
248    // If there is a match
249    if (CPUEntry) {
250      // Set base feature bits
251      Bits = CPUEntry->Value;
252
253      // Set the feature implied by this CPU feature, if any.
254      for (auto &FE : FeatureTable) {
255        if ((CPUEntry->Value & FE.Value).any())
256          SetImpliedBits(Bits, &FE, FeatureTable);
257      }
258    } else {
259      errs() << "'" << CPU
260             << "' is not a recognized processor for this target"
261             << " (ignoring processor)\n";
262    }
263  }
264
265  // Iterate through each feature
266  for (auto &Feature : Features) {
267    // Check for help
268    if (Feature == "+help")
269      Help(CPUTable, FeatureTable);
270
271    ApplyFeatureFlag(Bits, Feature, FeatureTable);
272  }
273
274  return Bits;
275}
276
277/// print - Print feature string.
278///
279void SubtargetFeatures::print(raw_ostream &OS) const {
280  for (auto &F : Features)
281    OS << F << " ";
282  OS << "\n";
283}
284
285#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
286/// dump - Dump feature info.
287///
288LLVM_DUMP_METHOD void SubtargetFeatures::dump() const {
289  print(dbgs());
290}
291#endif
292
293/// Adds the default features for the specified target triple.
294///
295/// FIXME: This is an inelegant way of specifying the features of a
296/// subtarget. It would be better if we could encode this information
297/// into the IR. See <rdar://5972456>.
298///
299void SubtargetFeatures::getDefaultSubtargetFeatures(const Triple& Triple) {
300  if (Triple.getVendor() == Triple::Apple) {
301    if (Triple.getArch() == Triple::ppc) {
302      // powerpc-apple-*
303      AddFeature("altivec");
304    } else if (Triple.getArch() == Triple::ppc64) {
305      // powerpc64-apple-*
306      AddFeature("64bit");
307      AddFeature("altivec");
308    }
309  }
310}
311