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[libFuzzer] simplify the value profiling callback further: don't use (idx MOD prime) on the hot path where it is useless anyway 

llvm-svn: 293239
This commit is contained in:
Kostya Serebryany 2017-01-27 00:39:12 +00:00
parent 86fc8305ec
commit 70182deaae
3 changed files with 11 additions and 10 deletions
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2
llvm/lib/Fuzzer/FuzzerTracePC.cpp
View File

@ -73,7 +73,7 @@ void TracePC::HandleCallerCallee(uintptr_t Caller, uintptr_t Callee) {
const uintptr_t kBits = 12;
const uintptr_t kMask = (1 << kBits) - 1;
uintptr_t Idx = (Caller & kMask) | ((Callee & kMask) << kBits);
ValueProfileMap.AddValue(Idx);
ValueProfileMap.AddValueModPrime(Idx);
}
void TracePC::InitializePrintNewPCs() {

4
llvm/lib/Fuzzer/FuzzerTracePC.h
View File

@ -47,7 +47,6 @@ struct TableOfRecentCompares {
class TracePC {
public:
static const size_t kFeatureSetSize = ValueBitMap::kNumberOfItems;
void HandleTrace(uint32_t *guard, uintptr_t PC);
void HandleInit(uint32_t *start, uint32_t *stop);
@ -58,9 +57,6 @@ class TracePC {
void SetUseValueProfile(bool VP) { UseValueProfile = VP; }
void SetPrintNewPCs(bool P) { DoPrintNewPCs = P; }
template <class Callback> size_t CollectFeatures(Callback CB);
bool UpdateValueProfileMap(ValueBitMap *MaxValueProfileMap) {
return UseValueProfile && MaxValueProfileMap->MergeFrom(ValueProfileMap);
}
void ResetMaps() {
ValueProfileMap.Reset();

15
llvm/lib/Fuzzer/FuzzerValueBitMap.h
View File

@ -18,12 +18,12 @@ namespace fuzzer {
// A bit map containing kMapSizeInWords bits.
struct ValueBitMap {
static const size_t kMapSizeInBits = 65371; // Prime.
static const size_t kMapSizeInBitsAligned = 1 << 16; // 2^16
static const size_t kMapSizeInBits = 1 << 16;
static const size_t kMapPrimeMod = 65371; // Largest Prime < kMapSizeInBits;
static const size_t kBitsInWord = (sizeof(uintptr_t) * 8);
static const size_t kMapSizeInWords = kMapSizeInBitsAligned / kBitsInWord;
static const size_t kMapSizeInWords = kMapSizeInBits / kBitsInWord;
public:
static const size_t kNumberOfItems = kMapSizeInBits;
// Clears all bits.
void Reset() { memset(Map, 0, sizeof(Map)); }
@ -31,7 +31,7 @@ struct ValueBitMap {
// Returns true if the bit was changed from 0 to 1.
ATTRIBUTE_NO_SANITIZE_ALL
inline bool AddValue(uintptr_t Value) {
uintptr_t Idx = Value < kMapSizeInBits ? Value : Value % kMapSizeInBits;
uintptr_t Idx = Value % kMapSizeInBits;
uintptr_t WordIdx = Idx / kBitsInWord;
uintptr_t BitIdx = Idx % kBitsInWord;
uintptr_t Old = Map[WordIdx];
@ -40,6 +40,11 @@ struct ValueBitMap {
return New != Old;
}
ATTRIBUTE_NO_SANITIZE_ALL
inline bool AddValueModPrime(uintptr_t Value) {
return AddValue(Value % kMapPrimeMod);
}
inline bool Get(uintptr_t Idx) {
assert(Idx < kMapSizeInBits);
uintptr_t WordIdx = Idx / kBitsInWord;