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fix(device): add preferred mask + required-only fallback to GetMemoryType (#59)

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GetMemoryType was a bare first-superset match that threw whenever no
memory type satisfied the requested property flags. Callers combining a
mandatory flag with a perf-only one (HOST_VISIBLE | DEVICE_LOCAL for the
descriptor heaps) would then fail allocation on any device without a
host-visible device-local heap (no resizable BAR).

It now takes a `preferred` mask distinct from `required`: a type
satisfying both is chosen first, falling back to a required-only match
when the preference is unavailable, and throwing only when even
`required` cannot be met. VulkanBuffer::Create/Resize gain an optional
trailing `preferredPropertyFlags`, and the descriptor heaps now treat
DEVICE_LOCAL as a preference on top of mandatory HOST_VISIBLE.

This does not touch any flush/barrier behaviour — coherency is not
assumed anywhere here.

Adds tests/MemoryTypeFallback, a pure-CPU test that installs synthetic
memory layouts and exercises selection, preference, fallback, and the
unsatisfiable-required throw.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
catbot 2026-06-16 16:03:50 +00:00
commit 294c1378b5
6 changed files with 218 additions and 13 deletions
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27
implementations/Crafter.Graphics-Device.cpp
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@ -811,17 +811,32 @@ void Device::Initialize() {
}
}
std::uint32_t Device::GetMemoryType(uint32_t typeBits, VkMemoryPropertyFlags properties) {
for (uint32_t i = 0; i < memoryProperties.memoryTypeCount; i++)
std::uint32_t Device::GetMemoryType(uint32_t typeBits, VkMemoryPropertyFlags required, VkMemoryPropertyFlags preferred) {
// First pass: honour the preferred bits on top of the required ones.
// Second pass (when nothing matched, or no preferences were given): drop
// the preferences and match the required bits alone. Vulkan orders the
// memory types so first-superset-match is generally optimal, so a plain
// linear scan suffices for each pass. We only throw when even `required`
// cannot be satisfied — i.e. no valid memory exists for the allocation.
for (VkMemoryPropertyFlags wanted : {required | preferred, required})
{
if ((typeBits & 1) == 1)
uint32_t bits = typeBits;
for (uint32_t i = 0; i < memoryProperties.memoryTypeCount; i++)
{
if ((memoryProperties.memoryTypes[i].propertyFlags & properties) == properties)
if ((bits & 1) == 1)
{
return i;
if ((memoryProperties.memoryTypes[i].propertyFlags & wanted) == wanted)
{
return i;
}
}
bits >>= 1;
}
// No preferences to fall back from — the second pass would be identical.
if (preferred == 0) {
break;
}
typeBits >>= 1;
}
throw std::runtime_error("Could not find a matching memory type");