From c94ca1692e101df87215232e87fa7edadc1a7b05 Mon Sep 17 00:00:00 2001
From: Ellie Hermaszewska <ellieh@nvidia.com>
Date: Tue, 1 Jul 2025 23:36:02 +0800
Subject: Allow Link time constant array length sizing, warn on unsupported
 functionality (#7067)

* Add link time array layout test

* Add link time constant array size compilation test

* Link time constant array size test

* Allow getting link time array size

Closes https://github.com/shader-slang/slang/issues/6753

* format

* Switch to SIMPLE test and check output

* Implement without binary api changes

* diagnose on link time constant sized array

* fix test

---------

Co-authored-by: Yong He <yonghe@outlook.com>
---
 source/slang/slang-check-decl.cpp     |  5 +++++
 source/slang/slang-diagnostic-defs.h  |  8 ++++++++
 source/slang/slang-reflection-api.cpp | 36 +++++++++++++++++++++++++++++++----
 3 files changed, 45 insertions(+), 4 deletions(-)

(limited to 'source')

diff --git a/source/slang/slang-check-decl.cpp b/source/slang/slang-check-decl.cpp
index 0dd859bb2..9e4d5a6d3 100644
--- a/source/slang/slang-check-decl.cpp
+++ b/source/slang/slang-check-decl.cpp
@@ -10468,6 +10468,11 @@ void SemanticsVisitor::validateArraySizeForVariable(VarDeclBase* varDecl)
         getSink()->diagnose(varDecl, Diagnostics::invalidArraySize);
         return;
     }
+
+    if (elementCount->isLinkTimeVal())
+    {
+        getSink()->diagnose(varDecl, Diagnostics::linkTimeConstantArraySize);
+    }
 }
 
 bool getExtensionTargetDeclList(
diff --git a/source/slang/slang-diagnostic-defs.h b/source/slang/slang-diagnostic-defs.h
index 384a81f9b..8efdf1d91 100644
--- a/source/slang/slang-diagnostic-defs.h
+++ b/source/slang/slang-diagnostic-defs.h
@@ -1587,6 +1587,14 @@ DIAGNOSTIC(
     switchDuplicateCases,
     "duplicate cases not allowed within a 'switch' statement")
 
+// 310xx: link time specializaion
+DIAGNOSTIC(
+    31000,
+    Warning,
+    linkTimeConstantArraySize,
+    "Link-time constant sized arrays are a work in progress feature, some aspects of the "
+    "reflection API may not work")
+
 // TODO: need to assign numbers to all these extra diagnostics...
 DIAGNOSTIC(39999, Fatal, cyclicReference, "cyclic reference '$0'.")
 DIAGNOSTIC(
diff --git a/source/slang/slang-reflection-api.cpp b/source/slang/slang-reflection-api.cpp
index b0d88e954..56a82e17e 100644
--- a/source/slang/slang-reflection-api.cpp
+++ b/source/slang/slang-reflection-api.cpp
@@ -4,6 +4,7 @@
 #include "slang-check-impl.h"
 #include "slang-check.h"
 #include "slang-compiler.h"
+#include "slang-deprecated.h"
 #include "slang-syntax.h"
 #include "slang-type-layout.h"
 #include "slang.h"
@@ -567,21 +568,46 @@ SLANG_API SlangReflectionVariable* spReflectionType_GetFieldByIndex(
 }
 
 SLANG_API size_t spReflectionType_GetElementCount(SlangReflectionType* inType)
+{
+    return spReflectionType_GetSpecializedElementCount(inType, nullptr);
+}
+
+SLANG_API size_t spReflectionType_GetSpecializedElementCount(
+    SlangReflectionType* inType,
+    SlangReflection* reflection)
 {
     auto type = convert(inType);
     if (!type)
         return 0;
 
+    IntVal* elementCount;
+    bool isUnsized;
     if (auto arrayType = as<ArrayExpressionType>(type))
     {
-        return !arrayType->isUnsized() ? (size_t)getIntVal(arrayType->getElementCount()) : 0;
+        elementCount = arrayType->getElementCount();
+        isUnsized = arrayType->isUnsized();
     }
     else if (auto vectorType = as<VectorExpressionType>(type))
     {
-        return (size_t)getIntVal(vectorType->getElementCount());
+        elementCount = vectorType->getElementCount();
+        isUnsized = false;
+    }
+    else
+    {
+        return 0;
     }
 
-    return 0;
+    if (const auto program = convert(reflection))
+    {
+        if (const auto componentType = program->getProgram())
+        {
+            if (const auto c = componentType->tryFoldIntVal(elementCount))
+                return c->getValue();
+        }
+    }
+
+    const auto isWithoutSize = isUnsized || elementCount->isLinkTimeVal();
+    return isWithoutSize ? 0 : (size_t)getIntVal(elementCount);
 }
 
 SLANG_API SlangReflectionType* spReflectionType_GetElementType(SlangReflectionType* inType)
@@ -1945,7 +1971,9 @@ struct ExtendedTypeLayoutContext
             LayoutSize elementCount = LayoutSize::infinite();
             if (auto arrayType = as<ArrayExpressionType>(arrayTypeLayout->type))
             {
-                if (!arrayType->isUnsized())
+                const auto isWithoutSize =
+                    arrayType->isUnsized() || arrayType->getElementCount()->isLinkTimeVal();
+                if (!isWithoutSize)
                 {
                     elementCount = LayoutSize::RawValue(getIntVal(arrayType->getElementCount()));
                 }
-- 
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