From 138efb9c25aadd319db6e6300a263574d90e3391 Mon Sep 17 00:00:00 2001
From: Jay Kwak <82421531+jkwak-work@users.noreply.github.com>
Date: Thu, 24 Jul 2025 16:47:21 -0700
Subject: Avoid early specialization for witness tables in SimplifyIR (#7636)

* Avoid early specialization for witness tables in SimplifyIR

Prevents SimplifyIR from prematurely specializing witness tables before
the main specialization pass. Witness tables are hoistable immutable
objects that must maintain consistent signatures to avoid incorrect
deduplication. SimplifyIR was incorrectly transforming expressions like
"witness_table_t(%IFoo)(specialize(%7, %GenericValue4))" into
"witness_table_t(%IFoo)(%Foo)" even when %GenericValue4 was unused.

Fixes #7233

* Add a missing test file
---
 .../generic-value-parameter-via-interface.slang    | 44 ++++++++++++++++++++++
 1 file changed, 44 insertions(+)
 create mode 100644 tests/language-feature/interfaces/generic-value-parameter-via-interface.slang

(limited to 'tests/language-feature/interfaces')

diff --git a/tests/language-feature/interfaces/generic-value-parameter-via-interface.slang b/tests/language-feature/interfaces/generic-value-parameter-via-interface.slang
new file mode 100644
index 000000000..abc1131e8
--- /dev/null
+++ b/tests/language-feature/interfaces/generic-value-parameter-via-interface.slang
@@ -0,0 +1,44 @@
+//TEST:INTERPRET(filecheck=CHECK):
+
+interface IFoo
+{
+    void test();
+};
+
+struct Foo<let GenericValue : uint> : IFoo
+{
+    void test()
+    {
+        printf("GenericValue=%d, value=%d\n", GenericValue, value);
+    }
+
+    uint value;
+};
+
+void testInterfaceAsParameter(IFoo foo)
+{
+    foo.test();
+}
+
+void testInterfaceAsGeneric<T:IFoo>(T foo)
+{
+    foo.test();
+}
+
+void main()
+{
+    // CHECK-COUNT-2:GenericValue=0, value=0
+    Foo<0> foo0 = {0};
+    testInterfaceAsParameter(foo0);
+    testInterfaceAsGeneric(foo0);
+
+    // CHECK-COUNT-2:GenericValue=1, value=1
+    Foo<1> foo1 = {1};
+    testInterfaceAsParameter(foo1);
+    testInterfaceAsGeneric(foo1);
+
+    // CHECK-COUNT-2:GenericValue=2, value=2
+    Foo<2> foo2 = {2};
+    testInterfaceAsParameter(foo2);
+    testInterfaceAsGeneric(foo2);
+}
-- 
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