GPU: add memory barriers for vertex and index buffers

This adds memory barriers to use with `GPU_memory_barrier` to ensure that
writes to a vertex or index buffer issued before the barrier are
completed after it, so they can be safely read later by another shader.

`GPU_BARRIER_VERTEX_ATTRIB_ARRAY` should be used for vertex buffers (`GPUVertBuf`),
and `GPU_BARRIER_ELEMENT_ARRAY` should be used for index buffers (`GPUIndexBuf`).

Reviewed By: fclem

Differential Revision: https://developer.blender.org/D13595

source/blender/gpu/GPU_state.h

@@ -40,9 +40,11 @@ typedef enum eGPUBarrier {
   GPU_BARRIER_SHADER_IMAGE_ACCESS = (1 << 0),
   GPU_BARRIER_TEXTURE_FETCH = (1 << 1),
   GPU_BARRIER_SHADER_STORAGE = (1 << 2),
+  GPU_BARRIER_VERTEX_ATTRIB_ARRAY = (1 << 3),
+  GPU_BARRIER_ELEMENT_ARRAY = (1 << 4),
 } eGPUBarrier;
 
-ENUM_OPERATORS(eGPUBarrier, GPU_BARRIER_SHADER_STORAGE)
+ENUM_OPERATORS(eGPUBarrier, GPU_BARRIER_ELEMENT_ARRAY)
 
 /**
  * Defines the fixed pipeline blending equation.

source/blender/gpu/opengl/gl_state.hh

@@ -130,6 +130,12 @@ static inline GLbitfield to_gl(eGPUBarrier barrier_bits)
   if (barrier_bits & GPU_BARRIER_SHADER_STORAGE) {
     barrier |= GL_SHADER_STORAGE_BARRIER_BIT;
   }
+  if (barrier_bits & GPU_BARRIER_VERTEX_ATTRIB_ARRAY) {
+    barrier |= GL_VERTEX_ATTRIB_ARRAY_BARRIER_BIT;
+  }
+  if (barrier_bits & GPU_BARRIER_ELEMENT_ARRAY) {
+    barrier |= GL_ELEMENT_ARRAY_BARRIER_BIT;
+  }
   return barrier;
 }