Fix single iteration loop detection logic. (#3287)

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

2 files changed, 16 insertions, 2 deletions

diff --git a/source/slang/slang-ir-simplify-cfg.cpp b/source/slang/slang-ir-simplify-cfg.cpp
index 0fe752c8f..127a515ce 100644
--- a/source/slang/slang-ir-simplify-cfg.cpp
+++ b/source/slang/slang-ir-simplify-cfg.cpp
@@ -97,8 +97,8 @@ static bool isTrivialSingleIterationLoop(
         {
             if (!context.domTree->dominates(loop->getParent(), branchTarget))
                 return false;
-            if (targetBlock != loop->getBreakBlock())
-                return false;
+            if (branchTarget != loop->getBreakBlock())
+                continue;
             if (findBreakableRegionHeaderInst(context.domTree, block) != loop)
             {
                 // If the break is initiated from a nested region, this is not trivial.
diff --git a/tests/ir/loop-unroll-simplify.slang b/tests/ir/loop-unroll-simplify.slang
new file mode 100644
index 000000000..f935b8b1e
--- /dev/null
+++ b/tests/ir/loop-unroll-simplify.slang
@@ -0,0 +1,14 @@
+//TEST:SIMPLE(filecheck=CHECK): -entry main -target hlsl -profile cs_6_3
+
+RWStructuredBuffer<int> output;
+
+void main()
+{
+    // Test that the unrolled code does not have trivial single iteration loops.
+    // CHECK-NOT: break
+    [ForceUnroll]
+    for (int i = 0; i < 2; i++)
+    {
+        output[i] = i;
+    }
+}