From 84148b80b167f5102e5f4813671b97bc1faeb5f0 Mon Sep 17 00:00:00 2001
From: Yong He <yonghe@outlook.com>
Date: Fri, 13 Jun 2025 17:06:05 -0700
Subject: Fix a bug in empty array legalization. (#7444)

---
 source/slang/slang-ir-legalize-empty-array.cpp |  8 ++++--
 tests/language-feature/0-array-2.slang         | 40 ++++++++++++++++++++++++++
 2 files changed, 45 insertions(+), 3 deletions(-)
 create mode 100644 tests/language-feature/0-array-2.slang

diff --git a/source/slang/slang-ir-legalize-empty-array.cpp b/source/slang/slang-ir-legalize-empty-array.cpp
index 561327565..1f7d59783 100644
--- a/source/slang/slang-ir-legalize-empty-array.cpp
+++ b/source/slang/slang-ir-legalize-empty-array.cpp
@@ -71,15 +71,17 @@ struct EmptyArrayLoweringContext
             [&](IRGetElementPtr* gep)
             {
                 const auto base = gep->getBase();
-                return hasEmptyArrayPtrType(base) || base->getOp() == kIROp_undefined
+                return hasEmptyArrayPtrType(gep) || hasEmptyArrayPtrType(base) ||
+                               base->getOp() == kIROp_undefined
                            ? builder.emitUndefined(gep->getDataType())
                            : nullptr;
             },
             [&](IRFieldAddress* gep)
             {
                 const auto base = gep->getBase();
-                return base->getOp() == kIROp_undefined ? builder.emitUndefined(gep->getDataType())
-                                                        : nullptr;
+                return hasEmptyArrayPtrType(gep) || base->getOp() == kIROp_undefined
+                           ? builder.emitUndefined(gep->getDataType())
+                           : nullptr;
             },
             [&](IRLoad* load)
             {
diff --git a/tests/language-feature/0-array-2.slang b/tests/language-feature/0-array-2.slang
new file mode 100644
index 000000000..37d576d89
--- /dev/null
+++ b/tests/language-feature/0-array-2.slang
@@ -0,0 +1,40 @@
+//TEST(compute):COMPARE_COMPUTE(filecheck-buffer=CHECK):
+//TEST(compute):COMPARE_COMPUTE(filecheck-buffer=CHECK): -vk
+
+public struct ContextND<let N: int>
+{
+    public uint3 thread_id;
+    public int[N] call_id;
+
+    public ContextND<0> map(int)
+    {
+        return { thread_id };
+    }
+
+    public ContextND<M> map<let M : int>(int[M] mapping)
+    {
+        ContextND<M> result;
+        result.thread_id = thread_id;
+        for (int i = 0; i < M; ++i)
+            result.call_id[i] = call_id[mapping[i]];
+        return result;
+    }
+}
+
+typealias Context = ContextND<0>;
+
+//TEST_INPUT: set value = out ubuffer(data=[0 0 0 0], stride=4)
+RWStructuredBuffer<int> value;
+
+void store(Context context, in int v) { value[0] = v; }
+
+[shader("compute")]
+[numthreads(1, 1, 1)]
+void computeMain(uint3 dispatchThreadID: SV_DispatchThreadID)
+{
+    Context context = {dispatchThreadID};
+    int c = 1;
+    int m_c = 0;
+    // CHECK: 1
+    store(context.map(m_c), c);
+}
\ No newline at end of file
-- 
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