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 /// \file Implements the SubtargetFeature interface.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/MC/SubtargetFeature.h"
15 #include "llvm/ADT/ArrayRef.h"
16 #include "llvm/ADT/SmallVector.h"
17 #include "llvm/ADT/StringExtras.h"
18 #include "llvm/ADT/StringRef.h"
19 #include "llvm/ADT/Triple.h"
20 #include "llvm/Config/llvm-config.h"
21 #include "llvm/Support/Compiler.h"
22 #include "llvm/Support/Debug.h"
23 #include "llvm/Support/Format.h"
24 #include "llvm/Support/raw_ostream.h"
25 #include <algorithm>
26 #include <cassert>
27 #include <cstddef>
28 #include <cstring>
29 #include <iterator>
30 #include <string>
31 #include <vector>
32 
33 using namespace llvm;
34 
35 /// Determine if a feature has a flag; '+' or '-'
36 static inline bool hasFlag(StringRef Feature) {
37   assert(!Feature.empty() && "Empty string");
38   // Get first character
39   char Ch = Feature[0];
40   // Check if first character is '+' or '-' flag
41   return Ch == '+' || Ch =='-';
42 }
43 
44 /// Return string stripped of flag.
45 static inline std::string StripFlag(StringRef Feature) {
46   return hasFlag(Feature) ? Feature.substr(1) : Feature;
47 }
48 
49 /// Return true if enable flag; '+'.
50 static inline bool isEnabled(StringRef Feature) {
51   assert(!Feature.empty() && "Empty string");
52   // Get first character
53   char Ch = Feature[0];
54   // Check if first character is '+' for enabled
55   return Ch == '+';
56 }
57 
58 /// Splits a string of comma separated items in to a vector of strings.
59 static void Split(std::vector<std::string> &V, StringRef S) {
60   SmallVector<StringRef, 3> Tmp;
61   S.split(Tmp, ',', -1, false /* KeepEmpty */);
62   V.assign(Tmp.begin(), Tmp.end());
63 }
64 
65 void 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.
74 static 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 /// Return the length of the longest entry in the table.
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 static void Help(ArrayRef<SubtargetFeatureKV> CPUTable,
94                  ArrayRef<SubtargetFeatureKV> FeatTable) {
95   // Determine the length of the longest CPU and Feature entries.
96   unsigned MaxCPULen  = getLongestEntryLength(CPUTable);
97   unsigned MaxFeatLen = getLongestEntryLength(FeatTable);
98 
99   // Print the CPU table.
100   errs() << "Available CPUs for this target:\n\n";
101   for (auto &CPU : CPUTable)
102     errs() << format("  %-*s - %s.\n", MaxCPULen, CPU.Key, CPU.Desc);
103   errs() << '\n';
104 
105   // Print the Feature table.
106   errs() << "Available features for this target:\n\n";
107   for (auto &Feature : FeatTable)
108     errs() << format("  %-*s - %s.\n", MaxFeatLen, Feature.Key, Feature.Desc);
109   errs() << '\n';
110 
111   errs() << "Use +feature to enable a feature, or -feature to disable it.\n"
112             "For example, llc -mcpu=mycpu -mattr=+feature1,-feature2\n";
113 }
114 
115 SubtargetFeatures::SubtargetFeatures(StringRef Initial) {
116   // Break up string into separate features
117   Split(Features, Initial);
118 }
119 
120 std::string SubtargetFeatures::getString() const {
121   return join(Features.begin(), Features.end(), ",");
122 }
123 
124 /// For each feature that is (transitively) implied by this feature, set it.
125 static
126 void SetImpliedBits(FeatureBitset &Bits, const SubtargetFeatureKV &FeatureEntry,
127                     ArrayRef<SubtargetFeatureKV> FeatureTable) {
128   for (const SubtargetFeatureKV &FE : FeatureTable) {
129     if (FeatureEntry.Value == FE.Value) continue;
130 
131     if ((FeatureEntry.Implies & FE.Value).any()) {
132       Bits |= FE.Value;
133       SetImpliedBits(Bits, FE, FeatureTable);
134     }
135   }
136 }
137 
138 /// For each feature that (transitively) implies this feature, clear it.
139 static
140 void ClearImpliedBits(FeatureBitset &Bits,
141                       const SubtargetFeatureKV &FeatureEntry,
142                       ArrayRef<SubtargetFeatureKV> FeatureTable) {
143   for (const SubtargetFeatureKV &FE : FeatureTable) {
144     if (FeatureEntry.Value == FE.Value) continue;
145 
146     if ((FE.Implies & FeatureEntry.Value).any()) {
147       Bits &= ~FE.Value;
148       ClearImpliedBits(Bits, FE, FeatureTable);
149     }
150   }
151 }
152 
153 void
154 SubtargetFeatures::ToggleFeature(FeatureBitset &Bits, StringRef Feature,
155                                  ArrayRef<SubtargetFeatureKV> FeatureTable) {
156   // Find feature in table.
157   const SubtargetFeatureKV *FeatureEntry =
158       Find(StripFlag(Feature), FeatureTable);
159   // If there is a match
160   if (FeatureEntry) {
161     if ((Bits & FeatureEntry->Value) == FeatureEntry->Value) {
162       Bits &= ~FeatureEntry->Value;
163       // For each feature that implies this, clear it.
164       ClearImpliedBits(Bits, *FeatureEntry, FeatureTable);
165     } else {
166       Bits |=  FeatureEntry->Value;
167 
168       // For each feature that this implies, set it.
169       SetImpliedBits(Bits, *FeatureEntry, FeatureTable);
170     }
171   } else {
172     errs() << "'" << Feature << "' is not a recognized feature for this target"
173            << " (ignoring feature)\n";
174   }
175 }
176 
177 void SubtargetFeatures::ApplyFeatureFlag(FeatureBitset &Bits, StringRef Feature,
178                                     ArrayRef<SubtargetFeatureKV> FeatureTable) {
179   assert(hasFlag(Feature));
180 
181   // Find feature in table.
182   const SubtargetFeatureKV *FeatureEntry =
183       Find(StripFlag(Feature), FeatureTable);
184   // If there is a match
185   if (FeatureEntry) {
186     // Enable/disable feature in bits
187     if (isEnabled(Feature)) {
188       Bits |= FeatureEntry->Value;
189 
190       // For each feature that this implies, set it.
191       SetImpliedBits(Bits, *FeatureEntry, FeatureTable);
192     } else {
193       Bits &= ~FeatureEntry->Value;
194 
195       // For each feature that implies this, clear it.
196       ClearImpliedBits(Bits, *FeatureEntry, FeatureTable);
197     }
198   } else {
199     errs() << "'" << Feature << "' is not a recognized feature for this target"
200            << " (ignoring feature)\n";
201   }
202 }
203 
204 FeatureBitset
205 SubtargetFeatures::getFeatureBits(StringRef CPU,
206                                   ArrayRef<SubtargetFeatureKV> CPUTable,
207                                   ArrayRef<SubtargetFeatureKV> FeatureTable) {
208   if (CPUTable.empty() || FeatureTable.empty())
209     return FeatureBitset();
210 
211   assert(std::is_sorted(std::begin(CPUTable), std::end(CPUTable)) &&
212          "CPU table is not sorted");
213   assert(std::is_sorted(std::begin(FeatureTable), std::end(FeatureTable)) &&
214          "CPU features table is not sorted");
215   // Resulting bits
216   FeatureBitset Bits;
217 
218   // Check if help is needed
219   if (CPU == "help")
220     Help(CPUTable, FeatureTable);
221 
222   // Find CPU entry if CPU name is specified.
223   else if (!CPU.empty()) {
224     const SubtargetFeatureKV *CPUEntry = Find(CPU, CPUTable);
225 
226     // If there is a match
227     if (CPUEntry) {
228       // Set base feature bits
229       Bits = CPUEntry->Value;
230 
231       // Set the feature implied by this CPU feature, if any.
232       for (auto &FE : FeatureTable) {
233         if ((CPUEntry->Value & FE.Value).any())
234           SetImpliedBits(Bits, FE, FeatureTable);
235       }
236     } else {
237       errs() << "'" << CPU << "' is not a recognized processor for this target"
238              << " (ignoring processor)\n";
239     }
240   }
241 
242   // Iterate through each feature
243   for (const std::string &Feature : Features) {
244     // Check for help
245     if (Feature == "+help")
246       Help(CPUTable, FeatureTable);
247 
248     ApplyFeatureFlag(Bits, Feature, FeatureTable);
249   }
250 
251   return Bits;
252 }
253 
254 void SubtargetFeatures::print(raw_ostream &OS) const {
255   for (auto &F : Features)
256     OS << F << " ";
257   OS << "\n";
258 }
259 
260 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
261 LLVM_DUMP_METHOD void SubtargetFeatures::dump() const {
262   print(dbgs());
263 }
264 #endif
265 
266 void SubtargetFeatures::getDefaultSubtargetFeatures(const Triple& Triple) {
267   // FIXME: This is an inelegant way of specifying the features of a
268   // subtarget. It would be better if we could encode this information
269   // into the IR. See <rdar://5972456>.
270   if (Triple.getVendor() == Triple::Apple) {
271     if (Triple.getArch() == Triple::ppc) {
272       // powerpc-apple-*
273       AddFeature("altivec");
274     } else if (Triple.getArch() == Triple::ppc64) {
275       // powerpc64-apple-*
276       AddFeature("64bit");
277       AddFeature("altivec");
278     }
279   }
280 }
281