Promote member decorations to descriptor binding decorations

[panos-lunarg]

This is basically a follow-up on #141.
Decorations like readonly or writeonly are being parsed but they are only applied to descriptor block variables.
This patch scans each descriptor's member decorations and those that are common to all members are promoted to the descriptor as well.

[CLAassistant]

All committers have signed the CLA.

[chaoticbob]

Was curious why this starts at 1 intead of 0?

[panos-lunarg]

Member decoration at 0 is read in the line above. Then the rest are logical &ed (edit: well this is the bitwise operator but the variables are booleans) one at a time. Result is if a decoration is true for all members, in the end it will remain true. These will be promoted to the whole descriptor. If there is only one decoration (at 0) then its decorations will be promoted to the whole descriptor.

[panos-lunarg]

With the intention of adding a test for this change I attempt to reuse the non_writtable_image.spv shader.
Because decorations were not being tested for descriptor bindings I had to touch all .yaml files. Hope it is the right way

[spencer-lunarg]

looks good to me, the tests (that aren't NONE) make sense to me looking at it

[spencer-lunarg]

After taking a second look at this, I am not sure if this is the correct move, if you have a shader like

layout(set=0, binding=0) buffer storage_buffer {
    float a; // non-readable
    float b; // non-writable
} foo;

               OpCapability Shader
               OpMemoryModel Logical GLSL450
               OpEntryPoint GLCompute %main "main"
               OpExecutionMode %main LocalSize 1 1 1
               OpMemberDecorate %storage_buffer 0 Offset 0
               OpMemberDecorate %storage_buffer 1 Offset 4
               OpMemberDecorate %storage_buffer 0 NonReadable
               OpMemberDecorate %storage_buffer 1 NonWritable
               OpDecorate %storage_buffer BufferBlock
               OpDecorate %foo DescriptorSet 0
               OpDecorate %foo Binding 0
       %void = OpTypeVoid
          %3 = OpTypeFunction %void
      %float = OpTypeFloat 32
%storage_buffer = OpTypeStruct %float %float
%_ptr_Uniform_storage_buffer = OpTypePointer Uniform %storage_buffer
        %foo = OpVariable %_ptr_Uniform_storage_buffer Uniform
       %main = OpFunction %void None %3
          %5 = OpLabel
               OpReturn
               OpFunctionEnd

I don't think the desired result for spirv-reflect is to have the whole descriptor marked as both NonReadable and NonWriteable

[panos-lunarg]

I assume you mean the following example:

layout(set=0, binding=0) buffer storage_buffer {
    writeonly float a; // non-readable
    readonly float b; // non-writable
} foo;

In the above example since none of the decorations are common between all member, none will be promoted to the whole descriptor.
In order to get both readonly and writeonly promoted to the whole descriptor all member must have the decorations. Something like this:

layout(set=0, binding=0) buffer storage_buffer {
    readonly writeonly float a; // both non-readable and non-writable
    readonly writeonly float b; // both non-readable and non-writable
} foo;

This indeed will mark storage_buffer as both readonly and writeonly but if glslang allows you to mark a member with both then I don't see the problem in promoting both to the descriptor

[spencer-lunarg]

In order to get both readonly and writeonly promoted to the whole descriptor all member must have the decorations.

Awww, I see, yes, you are doing &= on these

Could you quick add my example as a test case (show casing this code works like we intend it to) then I think I'm convinced this is ready to go

[spencer-lunarg]

looks good, as expected!