[Mlir-commits] [mlir] 3ebb3ef - [mlir][bytecode] Fix crash when reading DenseIntOrFPElementsAttr with unsupported element type (#184773)

[llvmlistbot at llvm.org]

Author: Mehdi Amini
Date: 2026-03-05T12:17:46Z
New Revision: 3ebb3ef542aa51307b12b748ad62567cbc0722cb

URL: https://github.com/llvm/llvm-project/commit/3ebb3ef542aa51307b12b748ad62567cbc0722cb
DIFF: https://github.com/llvm/llvm-project/commit/3ebb3ef542aa51307b12b748ad62567cbc0722cb.diff

LOG: [mlir][bytecode] Fix crash when reading DenseIntOrFPElementsAttr with unsupported element type (#184773)

When a bytecode type callback substitutes a type that does not implement
DenseElementTypeInterface (e.g., \!test.i32 replacing i32), the bytecode
reader attempted to reconstruct a DenseIntOrFPElementsAttr with that
type. This unconditionally called getDenseElementBitWidth() which hit an
llvm_unreachable on unsupported types.

Fix this by validating the element type implements
DenseElementTypeInterface in readDenseIntOrFPElementsAttr before
proceeding. If the check fails, a proper diagnostic is emitted and
reading fails gracefully instead of crashing.

Fixes #128317

Added: 
    mlir/test/Bytecode/invalid/invalid-dense-elem-type-interface.mlir

Modified: 
    mlir/lib/IR/BuiltinDialectBytecode.cpp

Removed: 
    


################################################################################
diff  --git a/mlir/lib/IR/BuiltinDialectBytecode.cpp b/mlir/lib/IR/BuiltinDialectBytecode.cpp
index 8cf25391ba11a..73ec3eec69615 100644
--- a/mlir/lib/IR/BuiltinDialectBytecode.cpp
+++ b/mlir/lib/IR/BuiltinDialectBytecode.cpp
@@ -151,6 +151,17 @@ static void writeFileLineColRangeLocs(DialectBytecodeWriter &writer,
 static LogicalResult
 readDenseIntOrFPElementsAttr(DialectBytecodeReader &reader, ShapedType type,
                              SmallVectorImpl<char> &rawData) {
+  // Validate that the element type implements DenseElementTypeInterface.
+  // Without this check, downstream code unconditionally calls
+  // getDenseElementBitWidth() which asserts on unsupported types.
+  if (!llvm::isa<DenseElementType>(type.getElementType())) {
+    reader.emitError()
+        << "DenseIntOrFPElementsAttr element type must implement "
+           "DenseElementTypeInterface, but got: "
+        << type.getElementType();
+    return failure();
+  }
+
   ArrayRef<char> blob;
   if (failed(reader.readBlob(blob)))
     return failure();

diff  --git a/mlir/test/Bytecode/invalid/invalid-dense-elem-type-interface.mlir b/mlir/test/Bytecode/invalid/invalid-dense-elem-type-interface.mlir
new file mode 100644
index 0000000000000..2a03dd8ef4b23
--- /dev/null
+++ b/mlir/test/Bytecode/invalid/invalid-dense-elem-type-interface.mlir
@@ -0,0 +1,15 @@
+// RUN: not mlir-opt %s --test-bytecode-roundtrip="test-kind=2" 2>&1 | FileCheck %s
+
+// Regression test: test-kind=2 replaces i32 with !test.i32 (a type that does
+// not implement DenseElementTypeInterface). This should produce a proper error
+// instead of an assertion failure when deserializing DenseIntOrFPElementsAttr.
+
+// CHECK: DenseIntOrFPElementsAttr element type must implement DenseElementTypeInterface, but got: '!test.i32'
+// CHECK: failed to read bytecode
+
+module {
+  func.func @test() -> tensor<10xi32> {
+    %0 = arith.constant dense<42> : tensor<10xi32>
+    return %0 : tensor<10xi32>
+  }
+}