[llvm] [LoopFlatten] Add option to version loops instead of widening IVs (PR #166156)

[Ehsan Amiri via llvm-commits]

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@@ -102,6 +102,10 @@ static cl::opt<bool>
     VersionLoops("loop-flatten-version-loops", cl::Hidden, cl::init(true),
                  cl::desc("Version loops if flattened loop could overflow"));
 
+static cl::opt<bool> VersionLoopsOverWiden(
+    "loop-flatten-version-over-widen", cl::Hidden, cl::init(false),
+    cl::desc("Version loops and generate runtime checks over widening the IV"));
+
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amehsan wrote:

Can't we avoid introducing a new option and instead make the existing options achieve what is needed here?Basically when `loop-flatten-widen-iv` is set to `false`, given that the default value of `loop-flatten-version-loops` is `true` we should see the behavior that is expected from the newly introduced option.  The advantage is that there are fewer options and they work closer to what you expect from them.

I think most of your changes will remain still the same or very close to what you already have. You just don't need a new option for this.

Extracting `versionLoop` code in a static function is a good idea anyways. 




https://github.com/llvm/llvm-project/pull/166156