Fix IR lowering bug of do-while loops. (#3941)

1 files changed, 26 insertions, 0 deletions

diff --git a/tests/bugs/gh-3930.slang b/tests/bugs/gh-3930.slang
new file mode 100644
index 000000000..6ba860ef3
--- /dev/null
+++ b/tests/bugs/gh-3930.slang
@@ -0,0 +1,26 @@
+// A regression: the do-while loop ir lowering logic is making incorrect assumptions and is
+// broken after short circuiting expr change, leading to invalid IR being generated from lowering
+// (a block has two terminator insts).
+
+//TEST:SIMPLE(filecheck=CHECK): -target spirv -emit-spirv-directly
+
+// CHECK: OpEntryPoint
+
+struct Constants {
+  uint *buffer;
+}
+[[vk::push_constant]] Constants push_constants;
+
+[shader("compute")] [numthreads(1, 1, 1)] void compute(void) {
+  uint index = push_constants.buffer[0];
+
+  [[unroll]] for (uint i = 0; i < 2; i++) {
+    GroupMemoryBarrierWithWaveSync();
+
+    if (index > 0 && i < push_constants.buffer[index - 1]) {
+      do {
+        index--;
+      } while (index > 0 && i < push_constants.buffer[index - 1]);
+    }
+  }
+}