================
@@ -755,6 +769,43 @@ bool llvm::validateDelinearizationResult(ScalarEvolution
&SE,
if (!isKnownLessThan(&SE, Subscript, Size))
return false;
}
+
+ // The offset computation is as follows:
+ //
+ // Offset = I_n +
+ // S_n * I_{n-1} +
+ // ... +
+ // (S_2 * ... * S_n) * I_1
+ //
+ // Regarding this as a function from (I_1, I_2, ..., I_n) to integers, it
+ // must be injective. To guarantee it, the above calculation must not
+ // overflow. Since we have already checked that 0 <= I_k < S_k for k = 2..n,
+ // the minimum and maximum values occur in the following cases:
+ //
+ // Min = [I_1][0]...[0] = S_2 * ... * S_n * I_1
----------------
kasuga-fj wrote:
Because DA appears to allow the outermost subscript to be negative, e.g.,
https://github.com/llvm/llvm-project/blob/318236da1feb7e6a5030252e02853e6ed54b39ac/llvm/test/Analysis/DependenceAnalysis/Propagating.ll#L310-L314.
That said, I don't know if this is important or not.
https://github.com/llvm/llvm-project/pull/169902
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