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Avoid unnecessary work for identical locations in Buffer.BlockCopy #36

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Feb 4, 2015
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Avoid unnecessary work for identical locations in Buffer.BlockCopy #36

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7 changes: 5 additions & 2 deletions src/vm/comutilnative.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1443,9 +1443,12 @@ FCIMPL5(VOID, Buffer::BlockCopy, ArrayBase *src, int srcOffset, ArrayBase *dst,
if (srcLen < (SIZE_T)srcOffset + (SIZE_T)count || dstLen < (SIZE_T)dstOffset + (SIZE_T)count) {
FCThrowArgumentVoid(NULL, W("Argument_InvalidOffLen"));
}

PTR_BYTE srcPtr = src->GetDataPtr() + srcOffset;
PTR_BYTE dstPtr = dst->GetDataPtr() + dstOffset;

if (count > 0) {
memmove(dst->GetDataPtr() + dstOffset, src->GetDataPtr() + srcOffset, count);
if ((srcPtr != dstPtr) && (count > 0)) {
memmove(dstPtr, srcPtr, count);
}

FC_GC_POLL();
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Should FC_GC_POLL() also be moved inside the if test, i.e. only run when work is done?

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FC_GC_POLL should be done all the time even when no work is done. Otherwise, there is a risk of GC starvation - the suspension for GC would take hang if there is a thread that calls BlockCopy in a tight loop.

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