Fix an issue with double-counting uniform data for CUDA/CPU (#1545)

The `SimpleScopeLayoutBuilder` helper that is used to build up binding information for entry-point parameter lists has logic to try to support both explicit and implicit binding of parameters. This logic was added as part of supporting dual-source color blending on Vulkan. The basic approach is similar to that used for the global scope, where parameters with explicit binding first "carve out" the ranges they claim via a `UsedRangeSet`, and then parameters without explicit binding allocate space from what is left.

The logic is (seemingly by accident) also applied to uniform/ordinary data, which creates a problem because the `ScopeLayoutBuilder` base type is also responsible for computing a layout for uniform/ordinary data that is 100% implicit (while dealing with all the relevant alignment restrictions). That logic goes on to add the computed uniform/ordinary resource usage to the computed type layout, but because such a layout has already been computed (albeit without taking alignment into account), the result is that the uniform/ordinary usage is reported at approximately double what it should be.

The fix here is to skip uniform/ordinary resource usage when doing the explicit/implicit dance in `SimpleScopeLayoutBuilder`. This approach means that explicit bindings on entry-point `uniform` parameters will only apply to resources (which matches our rules for the global scope, where we don't allow for explicit binding on uniform/ordinary parameters). This is appropriate since the only reason we are supported explicit layout at all is for dual-source color blending (in general, we only support explicit `register` and `[[vk::binding(...)]]` modifiers on global parameters; users are stuck with our computed layouts in all other cases.

Co-authored-by: Yong He <yonghe@outlook.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/source/slang/slang-parameter-binding.cpp b/source/slang/slang-parameter-binding.cpp
index 7676c89b0..90b5d9824 100644
--- a/source/slang/slang-parameter-binding.cpp
+++ b/source/slang/slang-parameter-binding.cpp
@@ -2315,6 +2315,7 @@ struct SimpleScopeLayoutBuilder : ScopeLayoutBuilder
             for (auto paramTypeResInfo : paramTypeLayout->resourceInfos)
             {
                 auto kind = paramTypeResInfo.kind;
+                if (kind == LayoutResourceKind::Uniform) continue;
 
                 // We will look for an explicit/existing binding in
                 // the parameter var layout, which would represent
@@ -2344,6 +2345,7 @@ struct SimpleScopeLayoutBuilder : ScopeLayoutBuilder
             for (auto paramTypeResInfo : paramTypeLayout->resourceInfos)
             {
                 auto kind = paramTypeResInfo.kind;
+                if (kind == LayoutResourceKind::Uniform) continue;
 
                 // We only care about parameters that are not already
                 // explicitly bound, so we will skip those that already
@@ -2368,6 +2370,7 @@ struct SimpleScopeLayoutBuilder : ScopeLayoutBuilder
             for (auto paramTypeResInfo : paramTypeLayout->resourceInfos)
             {
                 auto kind = paramTypeResInfo.kind;
+                if (kind == LayoutResourceKind::Uniform) continue;
 
                 auto paramResInfo = paramVarLayout->FindResourceInfo(kind);
                 SLANG_ASSERT(paramResInfo);