[Mlir-commits] [mlir] [mlir][ArmSVE] Add convert_to/from_svbool ops (PR #68586)

[Benjamin Maxwell]

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@@ -481,10 +500,39 @@ class IsScalableVectorOfLengthPred<list<int> allowedLengths> :
                            == }]
                          # allowedlength>)>]>;
 
+// Normalizes an index so it can be bounds checked.
+// Negative values are mapped to their absolute value.
+//  - These are used to index in reverse (i.e. index -1 would be the last element)
+// Positive values are mapped to their value + 1.
+//  - This results the same range of values as the negative indices
+// This allows bounds checking to be: len(list) >= NormalizeIndex<idx>.ret.
+class NormalizeIndex<int value> {
+  int ret = !if(!lt(value, 0), !sub(0, value), !add(value, 1));
+}
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MacDue wrote:

It says it in the comment `"This allows bounds checking to be: len(list) >= NormalizeIndex<idx>.ret"`. Otherwise, you need to do `idx > 0 && idx < len(list) || idx < 0 && -idx <= len(list)` which is not easy to write in tablegen. 

https://github.com/llvm/llvm-project/pull/68586