3 files changed, 72 insertions, 0 deletions
diff --git a/source/slang/slang-emit-c-like.cpp b/source/slang/slang-emit-c-like.cpp
index 009ca17f9..d21e16186 100644
--- a/source/slang/slang-emit-c-like.cpp
+++ b/source/slang/slang-emit-c-like.cpp
@@ -894,6 +894,12 @@ bool CLikeSourceEmitter::shouldFoldInstIntoUseSites(IRInst* inst)
     case kIROp_Alloca:
         return false;
 
+    // Never fold these, because their result cannot be computed
+    // as a sub-expression (they must be emitted as a declaration
+    // or statement).
+    case kIROp_DefaultConstruct:
+        return false;
+
     // Always fold these in, because they are trivial
     //
     case kIROp_IntLit:
diff --git a/tests/pipeline/ray-tracing/ray-query-subroutine.slang b/tests/pipeline/ray-tracing/ray-query-subroutine.slang
new file mode 100644
index 000000000..501071717
--- /dev/null
+++ b/tests/pipeline/ray-tracing/ray-query-subroutine.slang
@@ -0,0 +1,40 @@
+// ray-query-subroutine.slang
+
+// Regression test for passing a `RayQuery` value into a subroutine.
+
+//TEST:CROSS_COMPILE: -profile sm_6_5 -stage compute -entry computeMain -target dxil-assembly
+
+RWStructuredBuffer<int> gOutput;
+RaytracingAccelerationStructure gScene;
+
+int helper<let N : int>(RayQuery<N> q)
+{
+    RayDesc ray;
+    ray.Origin = 0;
+    ray.Direction = 0;
+    ray.TMin = 0;
+    ray.TMax = 1000.0;
+    q.TraceRayInline(
+        /* accellerationStructure: */   gScene,
+        /* rayFlags: */                 N,
+        /* instanceInclusionmask: */    0xFFFFFFFF,
+        /* ray: */                      ray );
+
+    return 1;
+}
+
+[shader("compute")]
+void computeMain(uint tid : SV_DispatchThreadID)
+{
+    // Note: The original issue was due to "folding" of an instruction
+    // into use sites as part of emitting high-level-language code.
+    //
+    // In this case, the initial value of `rayQuery` has only a single
+    // use (in the call to `helper()`) and as a result was subject to
+    // "folding" during emit, because it had no side-effects.
+
+    RayQuery<0> rayQuery;
+    let result = helper(rayQuery);
+
+    gOutput[tid.x] = result;
+}
diff --git a/tests/pipeline/ray-tracing/ray-query-subroutine.slang.hlsl b/tests/pipeline/ray-tracing/ray-query-subroutine.slang.hlsl
new file mode 100644
index 000000000..5906823e5
--- /dev/null
+++ b/tests/pipeline/ray-tracing/ray-query-subroutine.slang.hlsl
@@ -0,0 +1,26 @@
+//TEST_IGNORE_FILE:
+
+RaytracingAccelerationStructure gScene_0 : register(t0);
+
+int helper_0(RayQuery<int(0) > q_0)
+{
+    RayDesc ray_0;
+    ray_0.Origin = (vector<float,3>) int(0);
+    ray_0.Direction = (vector<float,3>) int(0);
+    ray_0.TMin = (float) int(0);
+    ray_0.TMax = 1000.00000000000000000000;
+    q_0.TraceRayInline(gScene_0, (uint) int(0), (uint) int(-1), ray_0);
+    return int(1);
+}
+
+RWStructuredBuffer<int > gOutput_0 : register(u0);
+
+[shader("compute")][numthreads(1, 1, 1)]
+void computeMain(uint tid_0 : SV_DISPATCHTHREADID)
+{
+    RayQuery<int(0) > rayQuery_0;
+    int _S1 = helper_0(rayQuery_0);
+
+    gOutput_0[tid_0.x] = _S1;
+    return;
+}