From 34f8b5e722aede018e275324c43055cad9a9ca5a Mon Sep 17 00:00:00 2001
From: jsmall-nvidia <jsmall@nvidia.com>
Date: Thu, 21 Apr 2022 10:06:55 -0400
Subject: Example for compiler crash with recursive function calling (#2196)

* #include an absolute path didn't work - because paths were taken to always be relative.

* Add crash when lowering a recursive function.

* Add simplified recursive crash example.

* Fix typos/tabs.
---
 tests/current-bugs/mul-crash.slang            | 27 ++++++++++++++++++++++++++
 tests/current-bugs/recursive-call-crash.slang | 28 +++++++++++++++++++++++++++
 2 files changed, 55 insertions(+)
 create mode 100644 tests/current-bugs/mul-crash.slang
 create mode 100644 tests/current-bugs/recursive-call-crash.slang

(limited to 'tests')

diff --git a/tests/current-bugs/mul-crash.slang b/tests/current-bugs/mul-crash.slang
new file mode 100644
index 000000000..a5ee7e62c
--- /dev/null
+++ b/tests/current-bugs/mul-crash.slang
@@ -0,0 +1,27 @@
+//DISABLE_TEST:SIMPLE: -target hlsl -entry computeMain -stage compute
+
+// This test crashes when enabled, with a stack overrun. The crash happens when lowering into IR.
+// NOTE! That the code has a bug in that the mul function calls itself - so would exhaust the stack *when run*.
+// This exhausts the stack when compiling which shouldn't happen.
+
+RWStructuredBuffer<float> outputBuffer;
+
+struct SomeType
+{
+    float2x2 v;
+};
+
+float mul(SomeType a, float2 v) { return mul(a, v).x; }
+
+[numthreads(4, 1, 1)]
+void computeMain(uint3 dispatchThreadID : SV_DispatchThreadID)
+{
+    uint tid = dispatchThreadID.x;
+
+    float inVal = float(tid);
+
+    float2 v = float2(inVal, inVal + 2);
+    SomeType t = { inVal + 1, 0, 1, 0 };
+    
+    outputBuffer[tid] = mul(t, v).x;
+} 
\ No newline at end of file
diff --git a/tests/current-bugs/recursive-call-crash.slang b/tests/current-bugs/recursive-call-crash.slang
new file mode 100644
index 000000000..4641827a5
--- /dev/null
+++ b/tests/current-bugs/recursive-call-crash.slang
@@ -0,0 +1,28 @@
+//DISABLE_TEST:SIMPLE: -target hlsl -entry computeMain -stage compute
+
+// This is a simplified version of the mul-crash.slang test, that shows the underlying issue is recursion.
+// This test crashes when enabled, with a stack overrun. The crash happens when lowering into IR.
+//
+// It appears recursion in GLSL/HLSL is not allowed (at least with earlier shader models), but the compiler 
+// shouldn't crash. Moreover the Slang language can support recursion today on non GPU targets.
+
+RWStructuredBuffer<int> outputBuffer;
+
+int doRecursive(int a)
+{
+    if (a > 0)
+    {
+        return doRecursive(a - 1) + 2;
+    }
+    return 10;
+}
+
+[numthreads(4, 1, 1)]
+void computeMain(uint3 dispatchThreadID : SV_DispatchThreadID)
+{
+    uint tid = dispatchThreadID.x;
+
+    let val = doRecursive(tid);
+
+    outputBuffer[tid] = val;
+} 
\ No newline at end of file
-- 
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