MVKPipeline: shorten vertex attribute format's length when stride < size
Metal currently does not support overlapping attribute loads and asserts on
them. Prevent it by shortening format's vector length to fit within the stride,
but print a cautionary message.
An example of affected program is Kingdom Come: Deliverance, which sets
attribute format to RGBA32 in IA and binding stride to 12, while the shader
input is just a float3.
diff --git a/MoltenVK/MoltenVK/GPUObjects/MVKPipeline.mm b/MoltenVK/MoltenVK/GPUObjects/MVKPipeline.mm
index d6b710d..b2f9930 100644
--- a/MoltenVK/MoltenVK/GPUObjects/MVKPipeline.mm
+++ b/MoltenVK/MoltenVK/GPUObjects/MVKPipeline.mm
@@ -688,6 +688,33 @@
return VK_FORMAT_UNDEFINED;
}
+// Returns a format of the same base type with vector length adjusted to fit size.
+static MTLVertexFormat mvkAdjustFormatVectorToSize(MTLVertexFormat format, uint32_t size) {
+#define MVK_ADJUST_FORMAT_CASE(size_1, type, suffix) \
+ case MTLVertexFormat##type##4##suffix: if (size >= 4 * (size_1)) { return MTLVertexFormat##type##4##suffix; } \
+ case MTLVertexFormat##type##3##suffix: if (size >= 3 * (size_1)) { return MTLVertexFormat##type##3##suffix; } \
+ case MTLVertexFormat##type##2##suffix: if (size >= 2 * (size_1)) { return MTLVertexFormat##type##2##suffix; } \
+ case MTLVertexFormat##type##suffix: if (size >= 1 * (size_1)) { return MTLVertexFormat##type##suffix; } \
+ return MTLVertexFormatInvalid;
+
+ switch (format) {
+ MVK_ADJUST_FORMAT_CASE(1, UChar, )
+ MVK_ADJUST_FORMAT_CASE(1, Char, )
+ MVK_ADJUST_FORMAT_CASE(1, UChar, Normalized)
+ MVK_ADJUST_FORMAT_CASE(1, Char, Normalized)
+ MVK_ADJUST_FORMAT_CASE(2, UShort, )
+ MVK_ADJUST_FORMAT_CASE(2, Short, )
+ MVK_ADJUST_FORMAT_CASE(2, UShort, Normalized)
+ MVK_ADJUST_FORMAT_CASE(2, Short, Normalized)
+ MVK_ADJUST_FORMAT_CASE(2, Half, )
+ MVK_ADJUST_FORMAT_CASE(4, Float, )
+ MVK_ADJUST_FORMAT_CASE(4, UInt, )
+ MVK_ADJUST_FORMAT_CASE(4, Int, )
+ default: return format;
+ }
+#undef MVK_ADJUST_FORMAT_CASE
+}
+
// Returns a retained MTLComputePipelineDescriptor for the tess. control stage of a tessellated draw constructed from this instance, or nil if an error occurs.
// It is the responsibility of the caller to release the returned descriptor.
MTLComputePipelineDescriptor* MVKGraphicsPipeline::newMTLTessControlStageDescriptor(const VkGraphicsPipelineCreateInfo* pCreateInfo,
@@ -1177,9 +1204,10 @@
// If this is the case, fetch a translated artificial buffer binding, using the same MTLBuffer,
// but that is translated so that the reduced VA offset fits into the binding stride.
const VkVertexInputBindingDescription* pVKVB = pVI->pVertexBindingDescriptions;
+ uint32_t attrSize = 0;
for (uint32_t j = 0; j < vbCnt; j++, pVKVB++) {
if (pVKVB->binding == pVKVA->binding) {
- uint32_t attrSize = getPixelFormats()->getBytesPerBlock(pVKVA->format);
+ attrSize = getPixelFormats()->getBytesPerBlock(pVKVA->format);
if (pVKVB->stride == 0) {
// The step is set to constant, but we need to change stride to be non-zero for metal.
// Look for the maximum offset + size to set as the stride.
@@ -1187,7 +1215,7 @@
auto vbDesc = inputDesc.layouts[vbIdx];
uint32_t strideLowBound = vaOffset + attrSize;
if (vbDesc.stride < strideLowBound) vbDesc.stride = strideLowBound;
- } else if (vaOffset + attrSize > pVKVB->stride) {
+ } else if (vaOffset && vaOffset + attrSize > pVKVB->stride) {
// Move vertex attribute offset into the stride. This vertex attribute may be
// combined with other vertex attributes into the same translated buffer binding.
// But if the reduced offset combined with the vertex attribute size still won't
@@ -1208,7 +1236,16 @@
}
auto vaDesc = inputDesc.attributes[pVKVA->location];
- vaDesc.format = (decltype(vaDesc.format))getPixelFormats()->getMTLVertexFormat(pVKVA->format);
+ auto mtlFormat = (decltype(vaDesc.format))getPixelFormats()->getMTLVertexFormat(pVKVA->format);
+ if (pVKVB->stride && attrSize > pVKVB->stride) {
+ /* Metal does not support overlapping loads. Truncate format vector length to prevent an assertion
+ * and hope it's not used by the shader. */
+ MTLVertexFormat newFormat = mvkAdjustFormatVectorToSize((MTLVertexFormat)mtlFormat, pVKVB->stride);
+ reportError(VK_SUCCESS, "Found attribute with size (%u) larger than it's binding's stride (%u). Changing descriptor format from %s to %s.",
+ attrSize, pVKVB->stride, getPixelFormats()->getName((MTLVertexFormat)mtlFormat), getPixelFormats()->getName(newFormat));
+ mtlFormat = (decltype(vaDesc.format))newFormat;
+ }
+ vaDesc.format = mtlFormat;
vaDesc.bufferIndex = (decltype(vaDesc.bufferIndex))getMetalBufferIndexForVertexAttributeBinding(vaBinding);
vaDesc.offset = vaOffset;
}
