Bug Summary

File:projects/compiler-rt/lib/profile/InstrProfilingValue.c
Warning:line 195, column 10
Access to field 'Count' results in a dereference of a null pointer (loaded from variable 'MinCountVNode')

Annotated Source Code

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 "InstrProfiling.h"
11#include "InstrProfilingInternal.h"
12#include "InstrProfilingUtil.h" /* For PS4 getenv shim. */
13#include <limits.h>
14#include <stdio.h>
15#include <stdlib.h>
16#include <string.h>
17#define INSTR_PROF_VALUE_PROF_DATA
18#define INSTR_PROF_COMMON_API_IMPL
19#include "InstrProfData.inc"
20
21static int hasStaticCounters = 1;
22static int OutOfNodesWarnings = 0;
23static int hasNonDefaultValsPerSite = 0;
24#define INSTR_PROF_MAX_VP_WARNS10 10
25#define INSTR_PROF_DEFAULT_NUM_VAL_PER_SITE16 16
26#define INSTR_PROF_VNODE_POOL_SIZE1024 1024
27
28#ifndef _MSC_VER
29/* A shared static pool in addition to the vnodes statically
30 * allocated by the compiler. */
31COMPILER_RT_VISIBILITY__attribute__((visibility("hidden"))) ValueProfNode
32 lprofValueProfNodes[INSTR_PROF_VNODE_POOL_SIZE1024] COMPILER_RT_SECTION(__attribute__((section("" "__llvm_prf_vnds")))
33 COMPILER_RT_SEG INSTR_PROF_VNODES_SECT_NAME_STR)__attribute__((section("" "__llvm_prf_vnds")));
34#endif
35
36COMPILER_RT_VISIBILITY__attribute__((visibility("hidden"))) uint32_t VPMaxNumValsPerSite =
37 INSTR_PROF_DEFAULT_NUM_VAL_PER_SITE16;
38
39COMPILER_RT_VISIBILITY__attribute__((visibility("hidden"))) void lprofSetupValueProfiler() {
40 const char *Str = 0;
41 Str = getenv("LLVM_VP_MAX_NUM_VALS_PER_SITE");
42 if (Str && Str[0]) {
43 VPMaxNumValsPerSite = atoi(Str);
44 hasNonDefaultValsPerSite = 1;
45 }
46 if (VPMaxNumValsPerSite > INSTR_PROF_MAX_NUM_VAL_PER_SITE255)
47 VPMaxNumValsPerSite = INSTR_PROF_MAX_NUM_VAL_PER_SITE255;
48}
49
50COMPILER_RT_VISIBILITY__attribute__((visibility("hidden"))) void lprofSetMaxValsPerSite(uint32_t MaxVals) {
51 VPMaxNumValsPerSite = MaxVals;
52 hasNonDefaultValsPerSite = 1;
53}
54
55/* This method is only used in value profiler mock testing. */
56COMPILER_RT_VISIBILITY__attribute__((visibility("hidden"))) void
57__llvm_profile_set_num_value_sites(__llvm_profile_data *Data,
58 uint32_t ValueKind, uint16_t NumValueSites) {
59 *((uint16_t *)&Data->NumValueSites[ValueKind]) = NumValueSites;
60}
61
62/* This method is only used in value profiler mock testing. */
63COMPILER_RT_VISIBILITY__attribute__((visibility("hidden"))) const __llvm_profile_data *
64__llvm_profile_iterate_data(const __llvm_profile_data *Data) {
65 return Data + 1;
66}
67
68/* This method is only used in value profiler mock testing. */
69COMPILER_RT_VISIBILITY__attribute__((visibility("hidden"))) void *
70__llvm_get_function_addr(const __llvm_profile_data *Data) {
71 return Data->FunctionPointer;
72}
73
74/* Allocate an array that holds the pointers to the linked lists of
75 * value profile counter nodes. The number of element of the array
76 * is the total number of value profile sites instrumented. Returns
77 * 0 if allocation fails.
78 */
79
80static int allocateValueProfileCounters(__llvm_profile_data *Data) {
81 uint64_t NumVSites = 0;
82 uint32_t VKI;
83
84 /* This function will never be called when value site array is allocated
85 statically at compile time. */
86 hasStaticCounters = 0;
87 /* When dynamic allocation is enabled, allow tracking the max number of
88 * values allowd. */
89 if (!hasNonDefaultValsPerSite)
90 VPMaxNumValsPerSite = INSTR_PROF_MAX_NUM_VAL_PER_SITE255;
91
92 for (VKI = IPVK_First; VKI <= IPVK_Last; ++VKI)
93 NumVSites += Data->NumValueSites[VKI];
94
95 ValueProfNode **Mem =
96 (ValueProfNode **)calloc(NumVSites, sizeof(ValueProfNode *));
97 if (!Mem)
98 return 0;
99 if (!COMPILER_RT_BOOL_CMPXCHG(&Data->Values, 0, Mem)__sync_bool_compare_and_swap(&Data->Values, 0, Mem)) {
100 free(Mem);
101 return 0;
102 }
103 return 1;
104}
105
106static ValueProfNode *allocateOneNode(__llvm_profile_data *Data, uint32_t Index,
107 uint64_t Value) {
108 ValueProfNode *Node;
109
110 if (!hasStaticCounters)
111 return (ValueProfNode *)calloc(1, sizeof(ValueProfNode));
112
113 /* Early check to avoid value wrapping around. */
114 if (CurrentVNode + 1 > EndVNode) {
115 if (OutOfNodesWarnings++ < INSTR_PROF_MAX_VP_WARNS10) {
116 PROF_WARN("Unable to track new values: %s. "fprintf(stderr, "LLVM Profile Warning: " "Unable to track new values: %s. "
" Consider using option -mllvm -vp-counters-per-site=<n> to "
"allocate more" " value profile counters at compile time. \n"
, "Running out of static counters");
117 " Consider using option -mllvm -vp-counters-per-site=<n> to "fprintf(stderr, "LLVM Profile Warning: " "Unable to track new values: %s. "
" Consider using option -mllvm -vp-counters-per-site=<n> to "
"allocate more" " value profile counters at compile time. \n"
, "Running out of static counters");
118 "allocate more"fprintf(stderr, "LLVM Profile Warning: " "Unable to track new values: %s. "
" Consider using option -mllvm -vp-counters-per-site=<n> to "
"allocate more" " value profile counters at compile time. \n"
, "Running out of static counters");
119 " value profile counters at compile time. \n",fprintf(stderr, "LLVM Profile Warning: " "Unable to track new values: %s. "
" Consider using option -mllvm -vp-counters-per-site=<n> to "
"allocate more" " value profile counters at compile time. \n"
, "Running out of static counters");
120 "Running out of static counters")fprintf(stderr, "LLVM Profile Warning: " "Unable to track new values: %s. "
" Consider using option -mllvm -vp-counters-per-site=<n> to "
"allocate more" " value profile counters at compile time. \n"
, "Running out of static counters");
;
121 }
122 return 0;
123 }
124 Node = COMPILER_RT_PTR_FETCH_ADD(ValueProfNode, CurrentVNode, 1)(ValueProfNode *)__sync_fetch_and_add((long *)&CurrentVNode
, sizeof(ValueProfNode) * 1)
;
125 /* Due to section padding, EndVNode point to a byte which is one pass
126 * an incomplete VNode, so we need to skip the last incomplete node. */
127 if (Node + 1 > EndVNode)
128 return 0;
129
130 return Node;
131}
132
133COMPILER_RT_VISIBILITY__attribute__((visibility("hidden"))) void
134__llvm_profile_instrument_target(uint64_t TargetValue, void *Data,
135 uint32_t CounterIndex) {
136 __llvm_profile_data *PData = (__llvm_profile_data *)Data;
137 if (!PData)
4
Assuming 'PData' is non-null
5
Taking false branch
138 return;
139
140 if (!PData->Values) {
6
Assuming the condition is false
7
Taking false branch
141 if (!allocateValueProfileCounters(PData))
142 return;
143 }
144
145 ValueProfNode **ValueCounters = (ValueProfNode **)PData->Values;
146 ValueProfNode *PrevVNode = NULL((void*)0);
147 ValueProfNode *MinCountVNode = NULL((void*)0);
8
'MinCountVNode' initialized to a null pointer value
148 ValueProfNode *CurVNode = ValueCounters[CounterIndex];
149 uint64_t MinCount = UINT64_MAX(18446744073709551615ULL);
150
151 uint8_t VDataCount = 0;
152 while (CurVNode) {
9
Loop condition is false. Execution continues on line 166
153 if (TargetValue == CurVNode->Value) {
154 CurVNode->Count++;
155 return;
156 }
157 if (CurVNode->Count < MinCount) {
158 MinCount = CurVNode->Count;
159 MinCountVNode = CurVNode;
160 }
161 PrevVNode = CurVNode;
162 CurVNode = CurVNode->Next;
163 ++VDataCount;
164 }
165
166 if (VDataCount >= VPMaxNumValsPerSite) {
10
Assuming 'VDataCount' is >= 'VPMaxNumValsPerSite'
11
Taking true branch
167 /* Bump down the min count node's count. If it reaches 0,
168 * evict it. This eviction/replacement policy makes hot
169 * targets more sticky while cold targets less so. In other
170 * words, it makes it less likely for the hot targets to be
171 * prematurally evicted during warmup/establishment period,
172 * when their counts are still low. In a special case when
173 * the number of values tracked is reduced to only one, this
174 * policy will guarantee that the dominating target with >50%
175 * total count will survive in the end. Note that this scheme
176 * allows the runtime to track the min count node in an adaptive
177 * manner. It can correct previous mistakes and eventually
178 * lock on a cold target that is alread in stable state.
179 *
180 * In very rare cases, this replacement scheme may still lead
181 * to target loss. For instance, out of \c N value slots, \c N-1
182 * slots are occupied by luke warm targets during the warmup
183 * period and the remaining one slot is competed by two or more
184 * very hot targets. If those hot targets occur in an interleaved
185 * way, none of them will survive (gain enough weight to throw out
186 * other established entries) due to the ping-pong effect.
187 * To handle this situation, user can choose to increase the max
188 * number of tracked values per value site. Alternatively, a more
189 * expensive eviction mechanism can be implemented. It requires
190 * the runtime to track the total number of evictions per-site.
191 * When the total number of evictions reaches certain threshold,
192 * the runtime can wipe out more than one lowest count entries
193 * to give space for hot targets.
194 */
195 if (!MinCountVNode->Count || !(--MinCountVNode->Count)) {
12
Access to field 'Count' results in a dereference of a null pointer (loaded from variable 'MinCountVNode')
196 CurVNode = MinCountVNode;
197 CurVNode->Value = TargetValue;
198 CurVNode->Count++;
199 }
200 return;
201 }
202
203 CurVNode = allocateOneNode(PData, CounterIndex, TargetValue);
204 if (!CurVNode)
205 return;
206 CurVNode->Value = TargetValue;
207 CurVNode->Count++;
208
209 uint32_t Success = 0;
210 if (!ValueCounters[CounterIndex])
211 Success =
212 COMPILER_RT_BOOL_CMPXCHG(&ValueCounters[CounterIndex], 0, CurVNode)__sync_bool_compare_and_swap(&ValueCounters[CounterIndex]
, 0, CurVNode)
;
213 else if (PrevVNode && !PrevVNode->Next)
214 Success = COMPILER_RT_BOOL_CMPXCHG(&(PrevVNode->Next), 0, CurVNode)__sync_bool_compare_and_swap(&(PrevVNode->Next), 0, CurVNode
)
;
215
216 if (!Success && !hasStaticCounters) {
217 free(CurVNode);
218 return;
219 }
220}
221
222/*
223 * The target values are partitioned into multiple regions/ranges. There is one
224 * contiguous region which is precise -- every value in the range is tracked
225 * individually. A value outside the precise region will be collapsed into one
226 * value depending on the region it falls in.
227 *
228 * There are three regions:
229 * 1. (-inf, PreciseRangeStart) and (PreciseRangeLast, LargeRangeValue) belong
230 * to one region -- all values here should be mapped to one value of
231 * "PreciseRangeLast + 1".
232 * 2. [PreciseRangeStart, PreciseRangeLast]
233 * 3. Large values: [LargeValue, +inf) maps to one value of LargeValue.
234 *
235 * The range for large values is optional. The default value of INT64_MIN
236 * indicates it is not specified.
237 */
238COMPILER_RT_VISIBILITY__attribute__((visibility("hidden"))) void __llvm_profile_instrument_range(
239 uint64_t TargetValue, void *Data, uint32_t CounterIndex,
240 int64_t PreciseRangeStart, int64_t PreciseRangeLast, int64_t LargeValue) {
241
242 if (LargeValue != INT64_MIN(-9223372036854775807LL -1) && (int64_t)TargetValue >= LargeValue)
1
Assuming the condition is false
243 TargetValue = LargeValue;
244 else if ((int64_t)TargetValue < PreciseRangeStart ||
2
Taking false branch
245 (int64_t)TargetValue > PreciseRangeLast)
246 TargetValue = PreciseRangeLast + 1;
247
248 __llvm_profile_instrument_target(TargetValue, Data, CounterIndex);
3
Calling '__llvm_profile_instrument_target'
249}
250
251/*
252 * A wrapper struct that represents value profile runtime data.
253 * Like InstrProfRecord class which is used by profiling host tools,
254 * ValueProfRuntimeRecord also implements the abstract intefaces defined in
255 * ValueProfRecordClosure so that the runtime data can be serialized using
256 * shared C implementation.
257 */
258typedef struct ValueProfRuntimeRecord {
259 const __llvm_profile_data *Data;
260 ValueProfNode **NodesKind[IPVK_Last + 1];
261 uint8_t **SiteCountArray;
262} ValueProfRuntimeRecord;
263
264/* ValueProfRecordClosure Interface implementation. */
265
266static uint32_t getNumValueSitesRT(const void *R, uint32_t VK) {
267 return ((const ValueProfRuntimeRecord *)R)->Data->NumValueSites[VK];
268}
269
270static uint32_t getNumValueDataRT(const void *R, uint32_t VK) {
271 uint32_t S = 0, I;
272 const ValueProfRuntimeRecord *Record = (const ValueProfRuntimeRecord *)R;
273 if (Record->SiteCountArray[VK] == INSTR_PROF_NULLPTR((void*)0))
274 return 0;
275 for (I = 0; I < Record->Data->NumValueSites[VK]; I++)
276 S += Record->SiteCountArray[VK][I];
277 return S;
278}
279
280static uint32_t getNumValueDataForSiteRT(const void *R, uint32_t VK,
281 uint32_t S) {
282 const ValueProfRuntimeRecord *Record = (const ValueProfRuntimeRecord *)R;
283 return Record->SiteCountArray[VK][S];
284}
285
286static ValueProfRuntimeRecord RTRecord;
287static ValueProfRecordClosure RTRecordClosure = {
288 &RTRecord, INSTR_PROF_NULLPTR((void*)0), /* GetNumValueKinds */
289 getNumValueSitesRT, getNumValueDataRT, getNumValueDataForSiteRT,
290 INSTR_PROF_NULLPTR((void*)0), /* RemapValueData */
291 INSTR_PROF_NULLPTR((void*)0), /* GetValueForSite, */
292 INSTR_PROF_NULLPTR((void*)0) /* AllocValueProfData */
293};
294
295static uint32_t
296initializeValueProfRuntimeRecord(const __llvm_profile_data *Data,
297 uint8_t *SiteCountArray[]) {
298 unsigned I, J, S = 0, NumValueKinds = 0;
299 ValueProfNode **Nodes = (ValueProfNode **)Data->Values;
300 RTRecord.Data = Data;
301 RTRecord.SiteCountArray = SiteCountArray;
302 for (I = 0; I <= IPVK_Last; I++) {
303 uint16_t N = Data->NumValueSites[I];
304 if (!N)
305 continue;
306
307 NumValueKinds++;
308
309 RTRecord.NodesKind[I] = Nodes ? &Nodes[S] : INSTR_PROF_NULLPTR((void*)0);
310 for (J = 0; J < N; J++) {
311 /* Compute value count for each site. */
312 uint32_t C = 0;
313 ValueProfNode *Site =
314 Nodes ? RTRecord.NodesKind[I][J] : INSTR_PROF_NULLPTR((void*)0);
315 while (Site) {
316 C++;
317 Site = Site->Next;
318 }
319 if (C > UCHAR_MAX(127*2 +1))
320 C = UCHAR_MAX(127*2 +1);
321 RTRecord.SiteCountArray[I][J] = C;
322 }
323 S += N;
324 }
325 return NumValueKinds;
326}
327
328static ValueProfNode *getNextNValueData(uint32_t VK, uint32_t Site,
329 InstrProfValueData *Dst,
330 ValueProfNode *StartNode, uint32_t N) {
331 unsigned I;
332 ValueProfNode *VNode = StartNode ? StartNode : RTRecord.NodesKind[VK][Site];
333 for (I = 0; I < N; I++) {
334 Dst[I].Value = VNode->Value;
335 Dst[I].Count = VNode->Count;
336 VNode = VNode->Next;
337 }
338 return VNode;
339}
340
341static uint32_t getValueProfDataSizeWrapper(void) {
342 return getValueProfDataSize(&RTRecordClosure);
343}
344
345static uint32_t getNumValueDataForSiteWrapper(uint32_t VK, uint32_t S) {
346 return getNumValueDataForSiteRT(&RTRecord, VK, S);
347}
348
349static VPDataReaderType TheVPDataReader = {
350 initializeValueProfRuntimeRecord, getValueProfRecordHeaderSize,
351 getFirstValueProfRecord, getNumValueDataForSiteWrapper,
352 getValueProfDataSizeWrapper, getNextNValueData};
353
354COMPILER_RT_VISIBILITY__attribute__((visibility("hidden"))) VPDataReaderType *lprofGetVPDataReader() {
355 return &TheVPDataReader;
356}