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SkRegion: Use less memory for SkRegion::Oper

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Also add fuzzer.

BUG=chromium:797940
Change-Id: Id6d483120f3325c3b1085a90277d56a4f7a0e989
Reviewed-on: https://skia-review.googlesource.com/118623
Commit-Queue: Hal Canary <halcanary@google.com>
Reviewed-by: Cary Clark <caryclark@skia.org>
This commit is contained in:
Hal Canary 2018-04-04 10:52:00 -04:00 committed by Skia Commit-Bot
parent 5ba24a1125
commit c5a1c1f92f
1 changed files with 94 additions and 71 deletions
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165
src/core/SkRegion.cpp
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@ -26,6 +26,44 @@ SkDEBUGCODE(int32_t gRgnAllocCounter;)
/////////////////////////////////////////////////////////////////////////////////////////////////
constexpr int kRunArrayStackCount = 256;
// This is a simple data structure which is like a SkSTArray<N,T,true>, except that:
// - It does not initialize memory.
// - It does not distinguish between reserved space and initialized space.
// - resizeToAtLeast() instead of resize()
// - Uses sk_realloc_throw()
// - Can never be made smaller.
// Measurement: for the `region_union_16` benchmark, this is 6% faster.
class RunArray {
public:
RunArray() { fPtr = fStack; }
#ifdef SK_DEBUG
int count() const { return fCount; }
#endif
SkRegion::RunType& operator[](int i) {
SkASSERT((unsigned)i < (unsigned)fCount);
return fPtr[i];
}
/** Resize the array to a size greater-than-or-equal-to count. */
void resizeToAtLeast(int count) {
if (count > fCount) {
// leave at least 50% extra space for future growth.
count += count >> 1;
fMalloc.realloc(count);
if (fPtr == fStack) {
memcpy(fMalloc.get(), fStack, fCount * sizeof(SkRegion::RunType));
}
fPtr = fMalloc.get();
fCount = count;
}
}
private:
SkRegion::RunType fStack[kRunArrayStackCount];
SkAutoTMalloc<SkRegion::RunType> fMalloc;
int fCount = kRunArrayStackCount;
SkRegion::RunType* fPtr; // non-owning pointer
};
/* Pass in the beginning with the intervals.
* We back up 1 to read the interval-count.
* Return the beginning of the next scanline (i.e. the next Y-value)
@ -711,10 +749,21 @@ struct spanRec {
}
};
static SkRegion::RunType* operate_on_span(const SkRegion::RunType a_runs[],
const SkRegion::RunType b_runs[],
SkRegion::RunType dst[],
int min, int max) {
static int distance_to_sentinel(const SkRegion::RunType* runs) {
const SkRegion::RunType* ptr = runs;
while (*ptr != SkRegion::kRunTypeSentinel) { ptr += 2; }
return ptr - runs;
}
static int operate_on_span(const SkRegion::RunType a_runs[],
const SkRegion::RunType b_runs[],
RunArray* array, int dstOffset,
int min, int max) {
// This is a worst-case for this span plus two for TWO terminating sentinels.
array->resizeToAtLeast(
dstOffset + distance_to_sentinel(a_runs) + distance_to_sentinel(b_runs) + 2);
SkRegion::RunType* dst = &(*array)[dstOffset]; // get pointer AFTER resizing.
spanRec rec;
bool firstInterval = true;
@ -729,19 +778,19 @@ static SkRegion::RunType* operate_on_span(const SkRegion::RunType a_runs[],
// add left,rite to our dst buffer (checking for coincidence
if ((unsigned)(rec.fInside - min) <= (unsigned)(max - min) &&
left < rite) { // skip if equal
if (firstInterval || dst[-1] < left) {
if (firstInterval || *(dst - 1) < left) {
*dst++ = (SkRegion::RunType)(left);
*dst++ = (SkRegion::RunType)(rite);
firstInterval = false;
} else {
// update the right edge
dst[-1] = (SkRegion::RunType)(rite);
*(dst - 1) = (SkRegion::RunType)(rite);
}
}
}
SkASSERT(dst < &(*array)[array->count() - 1]);
*dst++ = SkRegion::kRunTypeSentinel;
return dst;
return dst - &(*array)[0];
}
#if defined _WIN32
@ -757,47 +806,45 @@ static const struct {
{ 1, 3 }, // Union
{ 1, 2 } // XOR
};
// need to ensure that the op enum lines up with our minmax array
static_assert(0 == SkRegion::kDifference_Op, "");
static_assert(1 == SkRegion::kIntersect_Op, "");
static_assert(2 == SkRegion::kUnion_Op, "");
static_assert(3 == SkRegion::kXOR_Op, "");
class RgnOper {
public:
RgnOper(int top, SkRegion::RunType dst[], SkRegion::Op op) {
// need to ensure that the op enum lines up with our minmax array
SkASSERT(SkRegion::kDifference_Op == 0);
SkASSERT(SkRegion::kIntersect_Op == 1);
SkASSERT(SkRegion::kUnion_Op == 2);
SkASSERT(SkRegion::kXOR_Op == 3);
SkASSERT((unsigned)op <= 3);
fStartDst = dst;
fPrevDst = dst + 1;
fPrevLen = 0; // will never match a length from operate_on_span
fTop = (SkRegion::RunType)(top); // just a first guess, we might update this
fMin = gOpMinMax[op].fMin;
fMax = gOpMinMax[op].fMax;
}
RgnOper(int top, RunArray* array, SkRegion::Op op)
: fMin(gOpMinMax[op].fMin)
, fMax(gOpMinMax[op].fMax)
, fArray(array)
, fTop((SkRegion::RunType)top) // just a first guess, we might update this
{ SkASSERT((unsigned)op <= 3); }
void addSpan(int bottom, const SkRegion::RunType a_runs[],
const SkRegion::RunType b_runs[]) {
// skip X values and slots for the next Y+intervalCount
SkRegion::RunType* start = fPrevDst + fPrevLen + 2;
int start = fPrevDst + fPrevLen + 2;
// start points to beginning of dst interval
SkRegion::RunType* stop = operate_on_span(a_runs, b_runs, start, fMin, fMax);
size_t len = stop - start;
int stop = operate_on_span(a_runs, b_runs, fArray, start, fMin, fMax);
size_t len = SkToSizeT(stop - start);
SkASSERT(len >= 1 && (len & 1) == 1);
SkASSERT(SkRegion::kRunTypeSentinel == stop[-1]);
SkASSERT(SkRegion::kRunTypeSentinel == (*fArray)[stop - 1]);
// Assert memcmp won't exceed fArray->count().
SkASSERT(fArray->count() >= SkToInt(start + len - 1));
if (fPrevLen == len &&
(1 == len || !memcmp(fPrevDst, start,
(1 == len || !memcmp(&(*fArray)[fPrevDst],
&(*fArray)[start],
(len - 1) * sizeof(SkRegion::RunType)))) {
// update Y value
fPrevDst[-2] = (SkRegion::RunType)(bottom);
(*fArray)[fPrevDst - 2] = (SkRegion::RunType)bottom;
} else { // accept the new span
if (len == 1 && fPrevLen == 0) {
fTop = (SkRegion::RunType)(bottom); // just update our bottom
fTop = (SkRegion::RunType)bottom; // just update our bottom
} else {
start[-2] = (SkRegion::RunType)(bottom);
start[-1] = SkToS32(len >> 1);
(*fArray)[start - 2] = (SkRegion::RunType)bottom;
(*fArray)[start - 1] = SkToS32(len >> 1);
fPrevDst = start;
fPrevLen = len;
}
@ -805,8 +852,10 @@ public:
}
int flush() {
fStartDst[0] = fTop;
fPrevDst[fPrevLen] = SkRegion::kRunTypeSentinel;
(*fArray)[fStartDst] = fTop;
// Previously reserved enough for TWO sentinals.
SkASSERT(fArray->count() > SkToInt(fPrevDst + fPrevLen));
(*fArray)[fPrevDst + fPrevLen] = SkRegion::kRunTypeSentinel;
return (int)(fPrevDst - fStartDst + fPrevLen + 1);
}
@ -815,10 +864,11 @@ public:
uint8_t fMin, fMax;
private:
SkRegion::RunType* fStartDst;
SkRegion::RunType* fPrevDst;
size_t fPrevLen;
SkRegion::RunType fTop;
RunArray* fArray;
int fStartDst = 0;
int fPrevDst = 1;
size_t fPrevLen = 0; // will never match a length from operate_on_span
SkRegion::RunType fTop;
};
// want a unique value to signal that we exited due to quickExit
@ -826,7 +876,7 @@ private:
static int operate(const SkRegion::RunType a_runs[],
const SkRegion::RunType b_runs[],
SkRegion::RunType dst[],
RunArray* dst,
SkRegion::Op op,
bool quickExit) {
const SkRegion::RunType gEmptyScanline[] = {
@ -951,26 +1001,6 @@ static int count_to_intervals(int count) {
}
#endif
/* Given a number of intervals, what is the worst case representation of that
many intervals?
Worst case (from a storage perspective), is a vertical stack of single
intervals: TOP + N * (BOTTOM INTERVALCOUNT LEFT RIGHT SENTINEL) + SENTINEL
*/
static int intervals_to_count(int intervals) {
return 1 + intervals * 5 + 1;
}
/* Given the intervalCounts of RunTypes in two regions, return the worst-case number
of RunTypes need to store the result after a region-op.
*/
static int compute_worst_case_count(int a_intervals, int b_intervals) {
// Our heuristic worst case is ai * (bi + 1) + bi * (ai + 1)
int intervals = 2 * a_intervals * b_intervals + a_intervals + b_intervals;
// convert back to number of RunType values
return intervals_to_count(intervals);
}
static bool setEmptyCheck(SkRegion* result) {
return result ? result->setEmpty() : false;
}
@ -1073,20 +1103,13 @@ bool SkRegion::Oper(const SkRegion& rgnaOrig, const SkRegion& rgnbOrig, Op op,
const RunType* a_runs = rgna->getRuns(tmpA, &a_intervals);
const RunType* b_runs = rgnb->getRuns(tmpB, &b_intervals);
int dstCount = compute_worst_case_count(a_intervals, b_intervals);
SkAutoSTMalloc<256, RunType> array(dstCount);
#ifdef SK_DEBUG
// Sometimes helpful to seed everything with a known value when debugging
// sk_memset32((uint32_t*)array.get(), 0x7FFFFFFF, dstCount);
#endif
int count = operate(a_runs, b_runs, array.get(), op, nullptr == result);
SkASSERT(count <= dstCount);
RunArray array;
int count = operate(a_runs, b_runs, &array, op, nullptr == result);
SkASSERT(count <= array.count());
if (result) {
SkASSERT(count >= 0);
return result->setRuns(array.get(), count);
return result->setRuns(&array[0], count);
} else {
return (QUICK_EXIT_TRUE_COUNT == count) || !isRunCountEmpty(count);
}