Fix pointers and C-like layout in varying parameters (#8425)

Closes #8409, but ended up being more about fixing another bug. While
the issue itself seems to only be a simple typo fix (see second commit
in this PR), I found out during writing a test that pointers never got
correct locations regardless of layout. Their locations were always
assigned to zero due to lacking a resource usage entry in `TypeLayout`.
They were also missing the `Flat` decoration, so I went ahead and added
that too.

I can split this up into two separate PRs if that's preferred; both
aspects just share a test right now and fix a similar-looking issue in
the resulting SPIR-V.

1 files changed, 15 insertions, 1 deletions

diff --git a/source/slang/slang-type-layout.cpp b/source/slang/slang-type-layout.cpp
index fb40382c5..519b3ab06 100644
--- a/source/slang/slang-type-layout.cpp
+++ b/source/slang/slang-type-layout.cpp
@@ -1387,7 +1387,7 @@ LayoutRulesImpl kCPushConstantRulesImpl_ = {
 
 LayoutRulesImpl kCVaryingInputLayoutRulesImpl_ = {
     &kCLayoutRulesFamilyImpl,
-    &kGLSLVaryingOutputLayoutRulesImpl,
+    &kGLSLVaryingInputLayoutRulesImpl,
     &kGLSLObjectLayoutRulesImpl,
 };
 
@@ -5680,6 +5680,20 @@ RefPtr<TypeLayout> getSimpleVaryingParameterTypeLayout(
 
         return typeLayout;
     }
+    else if (as<PtrType>(type))
+    {
+        RefPtr<TypeLayout> typeLayout = new PointerTypeLayout();
+        typeLayout->type = type;
+        typeLayout->rules = rules;
+
+        for (int rr = 0; rr < varyingRulesCount; ++rr)
+        {
+            auto info = varyingRules[rr]->GetPointerLayout();
+            typeLayout->addResourceUsage(info.kind, info.size);
+        }
+
+        return typeLayout;
+    }
     else if (auto vecType = as<VectorExpressionType>(type))
     {
         auto elementType = vecType->getElementType();