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Remove redundant call to SetFree for objects bigger than 4GB #119930

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Remove redundant call to SetFree for objects bigger than 4GB #119930

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Remove redundant call to SetFree for objects bigger than 4GB
Alikhalesi Sep 20, 2025
a0c07d2
Fix indentions
Alikhalesi Sep 23, 2025
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76 changes: 33 additions & 43 deletions src/coreclr/gc/gc.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -36272,40 +36272,35 @@ void gc_heap::make_unused_array (uint8_t* x, size_t size, BOOL clearp, BOOL rese
reset_memory (x, size);
}
}
#ifndef HOST_64BIT
((CObjectHeader*)x)->SetFree(size);

#ifdef HOST_64BIT
#else

#if BIGENDIAN
#error "This won't work on big endian platforms"
#endif

size_t size_as_object = (uint32_t)(size - free_object_base_size) + free_object_base_size;
//
// If the size is more than 4GB, we need to create multiple objects because of
// the Array::m_NumComponents is uint32_t and the high 32 bits of unused array
// size is ignored in regular object size computation.
//
uint8_t * tmp = x;
size_t remaining_size = size;

if (size_as_object < size)
while (remaining_size > UINT32_MAX)
{
//
// If the size is more than 4GB, we need to create multiple objects because of
// the Array::m_NumComponents is uint32_t and the high 32 bits of unused array
// size is ignored in regular object size computation.
//
uint8_t * tmp = x + size_as_object;
size_t remaining_size = size - size_as_object;

while (remaining_size > UINT32_MAX)
{
// Make sure that there will be at least Align(min_obj_size) left
size_t current_size = UINT32_MAX - get_alignment_constant (FALSE)
- Align (min_obj_size, get_alignment_constant (FALSE));
// Make sure that there will be at least Align(min_obj_size) left
size_t current_size = UINT32_MAX - get_alignment_constant (FALSE)
- Align (min_obj_size, get_alignment_constant (FALSE));

((CObjectHeader*)tmp)->SetFree(current_size);
((CObjectHeader*)tmp)->SetFree(current_size);

remaining_size -= current_size;
tmp += current_size;
}

((CObjectHeader*)tmp)->SetFree(remaining_size);
remaining_size -= current_size;
tmp += current_size;
}

((CObjectHeader*)tmp)->SetFree(remaining_size);
#endif

if (clearp)
Expand All @@ -36315,41 +36310,36 @@ void gc_heap::make_unused_array (uint8_t* x, size_t size, BOOL clearp, BOOL rese
// Clear memory set by make_unused_array.
void gc_heap::clear_unused_array (uint8_t* x, size_t size)
{
#ifndef HOST_64BIT
UNREFERENCED_PARAMETER(size);
// Also clear the sync block
*(((PTR_PTR)x)-1) = 0;

((CObjectHeader*)x)->UnsetFree();

#ifdef HOST_64BIT
#else

#if BIGENDIAN
#error "This won't work on big endian platforms"
#endif

// The memory could have been cleared in the meantime. We have to mirror the algorithm
// from make_unused_array since we cannot depend on the object sizes in memory.
size_t size_as_object = (uint32_t)(size - free_object_base_size) + free_object_base_size;
uint8_t * tmp = x;
size_t remaining_size = size;

if (size_as_object < size)
while (remaining_size > UINT32_MAX)
{
uint8_t * tmp = x + size_as_object;
size_t remaining_size = size - size_as_object;

while (remaining_size > UINT32_MAX)
{
size_t current_size = UINT32_MAX - get_alignment_constant (FALSE)
- Align (min_obj_size, get_alignment_constant (FALSE));

((CObjectHeader*)tmp)->UnsetFree();

remaining_size -= current_size;
tmp += current_size;
}
size_t current_size = UINT32_MAX - get_alignment_constant (FALSE)
- Align (min_obj_size, get_alignment_constant (FALSE));

*(((PTR_PTR)tmp)-1) = 0;
((CObjectHeader*)tmp)->UnsetFree();

remaining_size -= current_size;
tmp += current_size;
}
#else
UNREFERENCED_PARAMETER(size);

*(((PTR_PTR)tmp)-1) = 0;
((CObjectHeader*)tmp)->UnsetFree();
#endif
}

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