[SLP] Increase UsesLimit to 64 (llvm#99467)

Since commit 82b800e addressed the
issue llvm#99327 , we see some performance regression (13%) on some
verilator generated C++ code. This is because the UsesLimit is set to 8,
which is too small for the verilator generated code. I have analyzed the
need for the UsesLimit from [1] and found that the UsesLimit should be
at least 64 to cover most of these cases. Thus, This patch increases the
UsesLimit to 64.

Link:
llvm#99327 (comment)
[1]

Signed-off-by: Yangyu Chen <[email protected]>

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -209,7 +209,7 @@ static const unsigned AliasedCheckLimit = 10;
 
 // Limit of the number of uses for potentially transformed instructions/values,
 // used in checks to avoid compile-time explode.
-static constexpr int UsesLimit = 8;
+static constexpr int UsesLimit = 64;
 
 // Another limit for the alias checks: The maximum distance between load/store
 // instructions where alias checks are done.