Support `constref` parameters passing. (#3249)

* Support `constref` parameters passing.

* Fix.

* Fix.

* Add test and diagnostic on mix use of __constref and no_diff.

* check for [constref] on differentiable member method.

---------

Co-authored-by: Yong He <yhe@nvidia.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/source/slang/slang-ast-modifier.h b/source/slang/slang-ast-modifier.h
index af5823db4..68824b931 100644
--- a/source/slang/slang-ast-modifier.h
+++ b/source/slang/slang-ast-modifier.h
@@ -161,6 +161,11 @@ class RefModifier : public Modifier
     SLANG_AST_CLASS(RefModifier)
 };
 
+// `__ref` modifier for by-reference parameter passing
+class ConstRefModifier : public Modifier
+{
+    SLANG_AST_CLASS(ConstRefModifier)
+};
 
 // This is a special sentinel modifier that gets added
 // to the list when we have multiple variable declarations
@@ -919,6 +924,14 @@ class NonmutatingAttribute : public Attribute
     SLANG_AST_CLASS(NonmutatingAttribute)
 };
 
+// A `[constref]` attribute, which indicates that the `this` parameter of
+// a member function should be passed by reference.
+//
+class ConstRefAttribute : public Attribute
+{
+    SLANG_AST_CLASS(ConstRefAttribute)
+};
+
 
 // A `[__readNone]` attribute, which indicates that a function
 // computes its results strictly based on argument values, without