From fdf061e278720ec066a1fac8f1f35a22e817bf2d Mon Sep 17 00:00:00 2001
From: Yong He <yonghe@outlook.com>
Date: Thu, 21 Nov 2024 14:07:23 -0800
Subject: Add datalayout for constant buffers. (#5608)

* Add datalayout for constant buffers.

* Fixes.

* Fix test.

* Fix glsl codegen.

* Update spirv-specific doc.

* Fix test.

* Fix binding in the presense of specialization constants.

* address comments.

* Add a test for constant buffer layout.
---
 source/slang/slang-check-decl.cpp | 43 ++++++++++++++++++++++++++++-----------
 1 file changed, 31 insertions(+), 12 deletions(-)

(limited to 'source/slang/slang-check-decl.cpp')

diff --git a/source/slang/slang-check-decl.cpp b/source/slang/slang-check-decl.cpp
index 07d5dd1fa..251ce6a69 100644
--- a/source/slang/slang-check-decl.cpp
+++ b/source/slang/slang-check-decl.cpp
@@ -110,6 +110,7 @@ struct SemanticsDeclHeaderVisitor : public SemanticsDeclVisitorBase,
     void checkMeshOutputDecl(VarDeclBase* varDecl);
     void maybeApplyLayoutModifier(VarDeclBase* varDecl);
     void checkVarDeclCommon(VarDeclBase* varDecl);
+    void checkPushConstantBufferType(VarDeclBase* varDecl);
 
     void visitVarDecl(VarDecl* varDecl) { checkVarDeclCommon(varDecl); }
 
@@ -1707,6 +1708,10 @@ void SemanticsDeclHeaderVisitor::maybeApplyLayoutModifier(VarDeclBase* varDecl)
             addModifier(varDecl, formatAttrib);
         }
     }
+    else
+    {
+        checkPushConstantBufferType(varDecl);
+    }
 }
 
 bool isSpecializationConstant(VarDeclBase* varDecl)
@@ -1721,6 +1726,32 @@ bool isSpecializationConstant(VarDeclBase* varDecl)
     return false;
 }
 
+void SemanticsDeclHeaderVisitor::checkPushConstantBufferType(VarDeclBase* varDecl)
+{
+    if (varDecl->findModifier<PushConstantAttribute>())
+    {
+        // If we see a ConstantBuffer<T, DefaultLayout> parameter marked as "push_constant", we need
+        // to set its type to ConstantBuffer<T, Std430>.
+        if (auto cbufferType = as<ConstantBufferType>(varDecl->type))
+        {
+            if (cbufferType->getLayoutType() == m_astBuilder->getDefaultLayoutType())
+            {
+                varDecl->type.type = getConstantBufferType(
+                    cbufferType->getElementType(),
+                    m_astBuilder->getStd430LayoutType());
+            }
+        }
+        else if (isGlobalShaderParameter(varDecl))
+        {
+            // If this is a global variable with [vk::push_constant] attribute,
+            // we need to make sure to wrap it in a `ConstantBuffer`.
+            //
+            varDecl->type.type =
+                getConstantBufferType(varDecl->type, m_astBuilder->getStd430LayoutType());
+        }
+    }
+}
+
 void SemanticsDeclHeaderVisitor::checkVarDeclCommon(VarDeclBase* varDecl)
 {
     // A variable that didn't have an explicit type written must
@@ -1935,20 +1966,8 @@ void SemanticsDeclHeaderVisitor::checkVarDeclCommon(VarDeclBase* varDecl)
         }
     }
 
-
     if (as<NamespaceDeclBase>(varDecl->parentDecl))
     {
-        // If this is a global variable with [vk::push_constant] attribute,
-        // we need to make sure to wrap it in a `ConstantBuffer`.
-
-        if (!as<ConstantBufferType>(varDecl->type))
-        {
-            if (varDecl->findModifier<PushConstantAttribute>())
-            {
-                varDecl->type.type = m_astBuilder->getConstantBufferType(varDecl->type);
-            }
-        }
-
         if (getModuleDecl(varDecl)->hasModifier<GLSLModuleModifier>())
         {
             // If we are in GLSL compatiblity mode, we want to treat all global variables
-- 
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