expose value of constant integers in module reflection (#6367)

* Expose value of constant integers in module reflection

This commit adds `VariableReflection::getDefaultValueInt` to get the value of a variable if it is a compile-time constant integer.
TODO: currently it works only if the initializer expression is an integer literal, references to other constant values are not handled.

* Update VarDecl folded constant value during DeclBodyVisitor

Constant folding for integer values is already done internally by _validateCircularVarDefinition, this just reuses the result.

* Address review comments & formatting

* Formatting

---------

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

2 files changed, 26 insertions, 1 deletions

diff --git a/examples/reflection-api/compute-simple.slang b/examples/reflection-api/compute-simple.slang
index 3d8872180..00d45d857 100644
--- a/examples/reflection-api/compute-simple.slang
+++ b/examples/reflection-api/compute-simple.slang
@@ -1,5 +1,8 @@
 // compute-simple.slang
 
+static const uint THREADGROUP_SIZE_X = 8;
+static const uint THREADGROUP_SIZE_Y = THREADGROUP_SIZE_X;
+
 struct ImageProcessingOptions
 {
     float3 tintColor;
@@ -10,7 +13,7 @@ struct ImageProcessingOptions
 }
 
 [shader("compute")]
-[numthreads(8, 8)]
+[numthreads(THREADGROUP_SIZE_X, THREADGROUP_SIZE_Y)]
 void processImage(
     uint3 threadID : SV_DispatchThreadID,
     uniform Texture2D inputImage,
diff --git a/examples/reflection-api/main.cpp b/examples/reflection-api/main.cpp
index c072c641b..2ff4475bf 100644
--- a/examples/reflection-api/main.cpp
+++ b/examples/reflection-api/main.cpp
@@ -114,6 +114,21 @@ struct ReflectingPrinting
 
         List<ComPtr<slang::IComponentType>> componentsToLink;
 
+        // ### Variable decls
+        //
+        key("global constants");
+        WITH_ARRAY()
+        for (auto decl : module->getModuleReflection()->getChildren())
+        {
+            if (auto varDecl = decl->asVariable(); varDecl &&
+                                                   varDecl->findModifier(slang::Modifier::Const) &&
+                                                   varDecl->findModifier(slang::Modifier::Static))
+            {
+                element();
+                printVariable(varDecl);
+            }
+        }
+
         // ### Finding Entry Points
         //
 
@@ -213,6 +228,13 @@ struct ReflectingPrinting
         printQuotedString(name);
         key("type");
         printType(type);
+
+        int64_t value;
+        if (SLANG_SUCCEEDED(variable->getDefaultValueInt(&value)))
+        {
+            key("value");
+            printf("%" PRId64, value);
+        }
     }
 
     // ### Types