1 /*===- InstrProfilingValue.c - Support library for PGO instrumentation ----===*\
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 #include <limits.h>
11 #include <stdio.h>
12 #include <stdlib.h>
13 #include <string.h>
14 
15 #include "InstrProfiling.h"
16 #include "InstrProfilingInternal.h"
17 #include "InstrProfilingUtil.h"
18 
19 #define INSTR_PROF_VALUE_PROF_DATA
20 #define INSTR_PROF_COMMON_API_IMPL
21 #include "InstrProfData.inc"
22 
23 static int hasStaticCounters = 1;
24 static int OutOfNodesWarnings = 0;
25 static int hasNonDefaultValsPerSite = 0;
26 #define INSTR_PROF_MAX_VP_WARNS 10
27 #define INSTR_PROF_DEFAULT_NUM_VAL_PER_SITE 16
28 #define INSTR_PROF_VNODE_POOL_SIZE 1024
29 
30 #ifndef _MSC_VER
31 /* A shared static pool in addition to the vnodes statically
32  * allocated by the compiler.  */
33 COMPILER_RT_VISIBILITY ValueProfNode
34     lprofValueProfNodes[INSTR_PROF_VNODE_POOL_SIZE] COMPILER_RT_SECTION(
35        COMPILER_RT_SEG INSTR_PROF_VNODES_SECT_NAME_STR);
36 #endif
37 
38 COMPILER_RT_VISIBILITY uint32_t VPMaxNumValsPerSite =
39     INSTR_PROF_DEFAULT_NUM_VAL_PER_SITE;
40 
41 COMPILER_RT_VISIBILITY void lprofSetupValueProfiler() {
42   const char *Str = 0;
43   Str = getenv("LLVM_VP_MAX_NUM_VALS_PER_SITE");
44   if (Str && Str[0]) {
45     VPMaxNumValsPerSite = atoi(Str);
46     hasNonDefaultValsPerSite = 1;
47   }
48   if (VPMaxNumValsPerSite > INSTR_PROF_MAX_NUM_VAL_PER_SITE)
49     VPMaxNumValsPerSite = INSTR_PROF_MAX_NUM_VAL_PER_SITE;
50 }
51 
52 COMPILER_RT_VISIBILITY void lprofSetMaxValsPerSite(uint32_t MaxVals) {
53   VPMaxNumValsPerSite = MaxVals;
54   hasNonDefaultValsPerSite = 1;
55 }
56 
57 /* This method is only used in value profiler mock testing.  */
58 COMPILER_RT_VISIBILITY void
59 __llvm_profile_set_num_value_sites(__llvm_profile_data *Data,
60                                    uint32_t ValueKind, uint16_t NumValueSites) {
61   *((uint16_t *)&Data->NumValueSites[ValueKind]) = NumValueSites;
62 }
63 
64 /* This method is only used in value profiler mock testing.  */
65 COMPILER_RT_VISIBILITY const __llvm_profile_data *
66 __llvm_profile_iterate_data(const __llvm_profile_data *Data) {
67   return Data + 1;
68 }
69 
70 /* This method is only used in value profiler mock testing.  */
71 COMPILER_RT_VISIBILITY void *
72 __llvm_get_function_addr(const __llvm_profile_data *Data) {
73   return Data->FunctionPointer;
74 }
75 
76 /* Allocate an array that holds the pointers to the linked lists of
77  * value profile counter nodes. The number of element of the array
78  * is the total number of value profile sites instrumented. Returns
79  * 0 if allocation fails.
80  */
81 
82 static int allocateValueProfileCounters(__llvm_profile_data *Data) {
83   uint64_t NumVSites = 0;
84   uint32_t VKI;
85 
86   /* This function will never be called when value site array is allocated
87      statically at compile time.  */
88   hasStaticCounters = 0;
89   /* When dynamic allocation is enabled, allow tracking the max number of
90    * values allowd.  */
91   if (!hasNonDefaultValsPerSite)
92     VPMaxNumValsPerSite = INSTR_PROF_MAX_NUM_VAL_PER_SITE;
93 
94   for (VKI = IPVK_First; VKI <= IPVK_Last; ++VKI)
95     NumVSites += Data->NumValueSites[VKI];
96 
97   ValueProfNode **Mem =
98       (ValueProfNode **)calloc(NumVSites, sizeof(ValueProfNode *));
99   if (!Mem)
100     return 0;
101   if (!COMPILER_RT_BOOL_CMPXCHG(&Data->Values, 0, Mem)) {
102     free(Mem);
103     return 0;
104   }
105   return 1;
106 }
107 
108 static ValueProfNode *allocateOneNode(__llvm_profile_data *Data, uint32_t Index,
109                                       uint64_t Value) {
110   ValueProfNode *Node;
111 
112   if (!hasStaticCounters)
113     return (ValueProfNode *)calloc(1, sizeof(ValueProfNode));
114 
115   /* Early check to avoid value wrapping around.  */
116   if (CurrentVNode + 1 > EndVNode) {
117     if (OutOfNodesWarnings++ < INSTR_PROF_MAX_VP_WARNS) {
118       PROF_WARN("Unable to track new values: %s. "
119                 " Consider using option -mllvm -vp-counters-per-site=<n> to "
120                 "allocate more"
121                 " value profile counters at compile time. \n",
122                 "Running out of static counters");
123     }
124     return 0;
125   }
126   Node = COMPILER_RT_PTR_FETCH_ADD(ValueProfNode, CurrentVNode, 1);
127   /* Due to section padding, EndVNode point to a byte which is one pass
128    * an incomplete VNode, so we need to skip the last incomplete node. */
129   if (Node + 1 > EndVNode)
130     return 0;
131 
132   return Node;
133 }
134 
135 COMPILER_RT_VISIBILITY void
136 __llvm_profile_instrument_target(uint64_t TargetValue, void *Data,
137                                  uint32_t CounterIndex) {
138   __llvm_profile_data *PData = (__llvm_profile_data *)Data;
139   if (!PData)
140     return;
141 
142   if (!PData->Values) {
143     if (!allocateValueProfileCounters(PData))
144       return;
145   }
146 
147   ValueProfNode **ValueCounters = (ValueProfNode **)PData->Values;
148   ValueProfNode *PrevVNode = NULL;
149   ValueProfNode *MinCountVNode = NULL;
150   ValueProfNode *CurVNode = ValueCounters[CounterIndex];
151   uint64_t MinCount = UINT64_MAX;
152 
153   uint8_t VDataCount = 0;
154   while (CurVNode) {
155     if (TargetValue == CurVNode->Value) {
156       CurVNode->Count++;
157       return;
158     }
159     if (CurVNode->Count < MinCount) {
160       MinCount = CurVNode->Count;
161       MinCountVNode = CurVNode;
162     }
163     PrevVNode = CurVNode;
164     CurVNode = CurVNode->Next;
165     ++VDataCount;
166   }
167 
168   if (VDataCount >= VPMaxNumValsPerSite) {
169     /* Bump down the min count node's count. If it reaches 0,
170      * evict it. This eviction/replacement policy makes hot
171      * targets more sticky while cold targets less so. In other
172      * words, it makes it less likely for the hot targets to be
173      * prematurally evicted during warmup/establishment period,
174      * when their counts are still low. In a special case when
175      * the number of values tracked is reduced to only one, this
176      * policy will guarantee that the dominating target with >50%
177      * total count will survive in the end. Note that this scheme
178      * allows the runtime to track the min count node in an adaptive
179      * manner. It can correct previous mistakes and eventually
180      * lock on a cold target that is alread in stable state.
181      *
182      * In very rare cases,  this replacement scheme may still lead
183      * to target loss. For instance, out of \c N value slots, \c N-1
184      * slots are occupied by luke warm targets during the warmup
185      * period and the remaining one slot is competed by two or more
186      * very hot targets. If those hot targets occur in an interleaved
187      * way, none of them will survive (gain enough weight to throw out
188      * other established entries) due to the ping-pong effect.
189      * To handle this situation, user can choose to increase the max
190      * number of tracked values per value site. Alternatively, a more
191      * expensive eviction mechanism can be implemented. It requires
192      * the runtime to track the total number of evictions per-site.
193      * When the total number of evictions reaches certain threshold,
194      * the runtime can wipe out more than one lowest count entries
195      * to give space for hot targets.
196      */
197     if (!MinCountVNode->Count || !(--MinCountVNode->Count)) {
198       CurVNode = MinCountVNode;
199       CurVNode->Value = TargetValue;
200       CurVNode->Count++;
201     }
202     return;
203   }
204 
205   CurVNode = allocateOneNode(PData, CounterIndex, TargetValue);
206   if (!CurVNode)
207     return;
208   CurVNode->Value = TargetValue;
209   CurVNode->Count++;
210 
211   uint32_t Success = 0;
212   if (!ValueCounters[CounterIndex])
213     Success =
214         COMPILER_RT_BOOL_CMPXCHG(&ValueCounters[CounterIndex], 0, CurVNode);
215   else if (PrevVNode && !PrevVNode->Next)
216     Success = COMPILER_RT_BOOL_CMPXCHG(&(PrevVNode->Next), 0, CurVNode);
217 
218   if (!Success && !hasStaticCounters) {
219     free(CurVNode);
220     return;
221   }
222 }
223 
224 /*
225  * The target values are partitioned into multiple regions/ranges. There is one
226  * contiguous region which is precise -- every value in the range is tracked
227  * individually. A value outside the precise region will be collapsed into one
228  * value depending on the region it falls in.
229  *
230  * There are three regions:
231  * 1. (-inf, PreciseRangeStart) and (PreciseRangeLast, LargeRangeValue) belong
232  * to one region -- all values here should be mapped to one value of
233  * "PreciseRangeLast + 1".
234  * 2. [PreciseRangeStart, PreciseRangeLast]
235  * 3. Large values: [LargeValue, +inf) maps to one value of LargeValue.
236  *
237  * The range for large values is optional. The default value of INT64_MIN
238  * indicates it is not specified.
239  */
240 COMPILER_RT_VISIBILITY void __llvm_profile_instrument_range(
241     uint64_t TargetValue, void *Data, uint32_t CounterIndex,
242     int64_t PreciseRangeStart, int64_t PreciseRangeLast, int64_t LargeValue) {
243 
244   if (LargeValue != INT64_MIN && (int64_t)TargetValue >= LargeValue)
245     TargetValue = LargeValue;
246   else if ((int64_t)TargetValue < PreciseRangeStart ||
247            (int64_t)TargetValue > PreciseRangeLast)
248     TargetValue = PreciseRangeLast + 1;
249 
250   __llvm_profile_instrument_target(TargetValue, Data, CounterIndex);
251 }
252 
253 /*
254  * A wrapper struct that represents value profile runtime data.
255  * Like InstrProfRecord class which is used by profiling host tools,
256  * ValueProfRuntimeRecord also implements the abstract intefaces defined in
257  * ValueProfRecordClosure so that the runtime data can be serialized using
258  * shared C implementation.
259  */
260 typedef struct ValueProfRuntimeRecord {
261   const __llvm_profile_data *Data;
262   ValueProfNode **NodesKind[IPVK_Last + 1];
263   uint8_t **SiteCountArray;
264 } ValueProfRuntimeRecord;
265 
266 /* ValueProfRecordClosure Interface implementation. */
267 
268 static uint32_t getNumValueSitesRT(const void *R, uint32_t VK) {
269   return ((const ValueProfRuntimeRecord *)R)->Data->NumValueSites[VK];
270 }
271 
272 static uint32_t getNumValueDataRT(const void *R, uint32_t VK) {
273   uint32_t S = 0, I;
274   const ValueProfRuntimeRecord *Record = (const ValueProfRuntimeRecord *)R;
275   if (Record->SiteCountArray[VK] == INSTR_PROF_NULLPTR)
276     return 0;
277   for (I = 0; I < Record->Data->NumValueSites[VK]; I++)
278     S += Record->SiteCountArray[VK][I];
279   return S;
280 }
281 
282 static uint32_t getNumValueDataForSiteRT(const void *R, uint32_t VK,
283                                          uint32_t S) {
284   const ValueProfRuntimeRecord *Record = (const ValueProfRuntimeRecord *)R;
285   return Record->SiteCountArray[VK][S];
286 }
287 
288 static ValueProfRuntimeRecord RTRecord;
289 static ValueProfRecordClosure RTRecordClosure = {
290     &RTRecord,          INSTR_PROF_NULLPTR, /* GetNumValueKinds */
291     getNumValueSitesRT, getNumValueDataRT,  getNumValueDataForSiteRT,
292     INSTR_PROF_NULLPTR, /* RemapValueData */
293     INSTR_PROF_NULLPTR, /* GetValueForSite, */
294     INSTR_PROF_NULLPTR  /* AllocValueProfData */
295 };
296 
297 static uint32_t
298 initializeValueProfRuntimeRecord(const __llvm_profile_data *Data,
299                                  uint8_t *SiteCountArray[]) {
300   unsigned I, J, S = 0, NumValueKinds = 0;
301   ValueProfNode **Nodes = (ValueProfNode **)Data->Values;
302   RTRecord.Data = Data;
303   RTRecord.SiteCountArray = SiteCountArray;
304   for (I = 0; I <= IPVK_Last; I++) {
305     uint16_t N = Data->NumValueSites[I];
306     if (!N)
307       continue;
308 
309     NumValueKinds++;
310 
311     RTRecord.NodesKind[I] = Nodes ? &Nodes[S] : INSTR_PROF_NULLPTR;
312     for (J = 0; J < N; J++) {
313       /* Compute value count for each site. */
314       uint32_t C = 0;
315       ValueProfNode *Site =
316           Nodes ? RTRecord.NodesKind[I][J] : INSTR_PROF_NULLPTR;
317       while (Site) {
318         C++;
319         Site = Site->Next;
320       }
321       if (C > UCHAR_MAX)
322         C = UCHAR_MAX;
323       RTRecord.SiteCountArray[I][J] = C;
324     }
325     S += N;
326   }
327   return NumValueKinds;
328 }
329 
330 static ValueProfNode *getNextNValueData(uint32_t VK, uint32_t Site,
331                                         InstrProfValueData *Dst,
332                                         ValueProfNode *StartNode, uint32_t N) {
333   unsigned I;
334   ValueProfNode *VNode = StartNode ? StartNode : RTRecord.NodesKind[VK][Site];
335   for (I = 0; I < N; I++) {
336     Dst[I].Value = VNode->Value;
337     Dst[I].Count = VNode->Count;
338     VNode = VNode->Next;
339   }
340   return VNode;
341 }
342 
343 static uint32_t getValueProfDataSizeWrapper(void) {
344   return getValueProfDataSize(&RTRecordClosure);
345 }
346 
347 static uint32_t getNumValueDataForSiteWrapper(uint32_t VK, uint32_t S) {
348   return getNumValueDataForSiteRT(&RTRecord, VK, S);
349 }
350 
351 static VPDataReaderType TheVPDataReader = {
352     initializeValueProfRuntimeRecord, getValueProfRecordHeaderSize,
353     getFirstValueProfRecord,          getNumValueDataForSiteWrapper,
354     getValueProfDataSizeWrapper,      getNextNValueData};
355 
356 COMPILER_RT_VISIBILITY VPDataReaderType *lprofGetVPDataReader() {
357   return &TheVPDataReader;
358 }
359