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