[clang] Fix cir vec cmp fold (PR #202502)

[Andy Kaylor via cfe-commits]

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@@ -3509,7 +3535,9 @@ OpFoldResult cir::VecCmpOp::fold(FoldAdaptor adaptor) {
     }
     }
 
-    elements[i] = cir::IntAttr::get(getType().getElementType(), cmpResult);
+    // Vector comparison results are 0 (false) or -1 / all-ones (true).
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andykaylor wrote:

This isn't quite right. A VecCmpOp can also be created that returns a vector of signed i1. Technically, I guess the true case there is -1 as an i1, but it's used differently in that case.

https://github.com/llvm/llvm-project/pull/202502