diff --git a/mlir/lib/IR/BuiltinAttributes.cpp b/mlir/lib/IR/BuiltinAttributes.cpp
--- a/mlir/lib/IR/BuiltinAttributes.cpp
+++ b/mlir/lib/IR/BuiltinAttributes.cpp
@@ -1466,7 +1466,12 @@
   auto processElt = [&](decltype(*attr.begin()) value, size_t index) {
     auto newInt = mapping(value);
     assert(newInt.getBitWidth() == bitWidth);
-    writeBits(data.data(), index * storageBitWidth, newInt);
+    if (attr.isSplat() && bitWidth == 1) {
+      // Handle the special encoding of splat of bool.
+      data[0] = newInt.isZero() ? 0 : -1;
+    } else {
+      writeBits(data.data(), index * storageBitWidth, newInt);
+    }
   };
 
   // Check for the splat case.