[mlir][spirv] Emit error when block to be unlinked has uses after structurization

[IgWod-IMG]

This fixes the bug where deserializer would fail, with as assert, during the control flow structurization when a block to be removed still had uses. This indicates that the block that was sunk still is being referenced outside the region as the control flow is not structured.

closes #163099

[llvmbot]

@llvm/pr-subscribers-mlir-spirv

@llvm/pr-subscribers-mlir

Author: Igor Wodiany (IgWod-IMG)

Changes

This fixes the bug where deserializer would fail, with as assert, during the control flow structurization when a block to be removed still had uses. This indicates that the block that was sunk still is being referenced outside the region as the control flow is not structured.

closes #163099

---

Full diff: https://github.com/llvm/llvm-project/pull/163942.diff

1 Files Affected:

• (modified) mlir/lib/Target/SPIRV/Deserialization/Deserializer.cpp (+5)

diff --git a/mlir/lib/Target/SPIRV/Deserialization/Deserializer.cpp b/mlir/lib/Target/SPIRV/Deserialization/Deserializer.cpp
index 0c3e87a8dc1ef..d9ad8fb144b61 100644
--- a/mlir/lib/Target/SPIRV/Deserialization/Deserializer.cpp
+++ b/mlir/lib/Target/SPIRV/Deserialization/Deserializer.cpp
@@ -2619,6 +2619,11 @@ LogicalResult ControlFlowStructurizer::structurize() {
   // region. We cannot handle such cases given that once a value is sinked into
   // the SelectionOp/LoopOp's region, there is no escape for it.
   for (auto *block : constructBlocks) {
+    if (!block->use_empty())
+      return emitError(block->getParent()->getLoc(),
+                       "failed control flow structurization: "
+                       "block has uses outside of the "
+                       "enclosing selection/loop construct");
     for (Operation &op : *block)
       if (!op.use_empty())
         return op.emitOpError("failed control flow structurization: value has "

[IgWod-IMG]

I tired to add a test similar to selection.spv but unfortunetely you cannot have expected-error {{...}} in this setting.

Also, any idea why libcxx tests failed? It looks like CI just gave up, but this change should have no impact on it. I guess I can just ignore it?