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Fix two out-of-bounds cache accesses causing device loss under dense caches (#4, #5) #6

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Fix two out-of-bounds cache accesses causing device loss under dense caches (#4, #5) #6

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2b38930
SharcUpdateHit/SharcUpdateMiss: skip HASH_GRID_INVALID_CACHE_INDEX be…
halukoral Jul 28, 2026
247520e
SharcResolveEntry: clamp the recovery linear probe to the table capacity
halukoral Jul 28, 2026
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16 changes: 14 additions & 2 deletions include/SharcCommon.h
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Original file line number Diff line number Diff line change
Expand Up @@ -564,6 +564,12 @@ void SharcUpdateMiss(in SharcParameters sharcParameters, in SharcState sharcStat
for (int i = 0; i < sharcState.pathLength; ++i)
{
HashGridIndex hashGridIndex = sharcState.cacheIndices[i];
// A full bucket makes HashGridInsertEntry return HASH_GRID_INVALID_CACHE_INDEX and SharcUpdateHit stores
// that sentinel into cacheIndices verbatim. It must be skipped before the responsive offset/mask block:
// masking it unconditionally rewrites it to SHARC_CACHE_INDEX_BIT_MASK, which is no longer INVALID, so
// SharcAddVoxelData's guard passes and the atomics land far past the end of the accumulation buffer
if (hashGridIndex == HASH_GRID_INVALID_CACHE_INDEX)
continue;
bool isNewSample = false;
#if SHARC_ENABLE_RESPONSIVE_LIGHTING
if (isResponsiveLighting)
Expand Down Expand Up @@ -659,6 +665,9 @@ bool SharcUpdateHit(in SharcParameters sharcParameters, inout SharcState sharcSt
for (i = 0; i < sharcState.pathLength; ++i)
{
HashGridIndex tempHashGridIndex = sharcState.cacheIndices[i];
// Skip full-bucket sentinels before the responsive offset/mask block — same reasoning as SharcUpdateMiss
if (tempHashGridIndex == HASH_GRID_INVALID_CACHE_INDEX)
continue;
bool isNewSample = false;
#if SHARC_ENABLE_RESPONSIVE_LIGHTING
if (responsiveCacheIndex != HASH_GRID_INVALID_CACHE_INDEX)
Expand Down Expand Up @@ -892,10 +901,13 @@ void SharcResolveEntry(uint entryIndex, SharcParameters sharcParameters, SharcRe

// Performs hash map lookup to find existing entries in case previous insertions
// encountered collisions and a different slot was assigned.
// Uses a fixed-size linear probe window
// Uses a fixed-size linear probe window, clamped to the table capacity: an application is allowed to
// allocate exactly `capacity` entries, so entries in the last window cannot blindly look forward —
// doing so reads past the end of the hash-entry and resolved buffers once those slots become occupied
if (sampleNumPrev == 0)
{
for (uint i = entryIndex + 1; i < entryIndex + 1 + SHARC_LINEAR_PROBE_WINDOW_SIZE; ++i)
uint probeEnd = min(entryIndex + 1 + SHARC_LINEAR_PROBE_WINDOW_SIZE, sharcParameters.hashGridData.capacity);
for (uint i = entryIndex + 1; i < probeEnd; ++i)
{
HashGridKey hashKeyOld = BUFFER_AT_OFFSET(sharcParameters.hashGridData.hashEntriesBuffer, i);
if (hashKeyOld == hashGridKey)
Expand Down