Add `[ForwardDerivativeOf]` attribute. (#2501)

* Add [ForwardDerivativeOf] attribute.

* Fix handling around phi nodes.

* Fixes.

* Remove IR opcode for ForwardDerivativeOfDecoration.

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

1 files changed, 20 insertions, 0 deletions

diff --git a/source/slang/slang-ast-support-types.cpp b/source/slang/slang-ast-support-types.cpp
index 7133f2a65..1f30e0238 100644
--- a/source/slang/slang-ast-support-types.cpp
+++ b/source/slang/slang-ast-support-types.cpp
@@ -14,4 +14,24 @@ QualType::QualType(Type* type)
     }
 }
 
+void removeModifier(ModifiableSyntaxNode* syntax, Modifier* toRemove)
+{
+    Modifier* prev = nullptr;
+    for (auto modifier = syntax->modifiers.first; modifier; modifier = modifier->next)
+    {
+        if (modifier == toRemove)
+        {
+            if (prev)
+            {
+                prev->next = modifier->next;
+            }
+            else
+            {
+                syntax->modifiers.first = syntax->modifiers.first->next;
+            }
+            break;
+        }
+        prev = modifier;
+    }
+}
 }