[llvm] [SCEV] Prove no-self-wrap from negative power of two step (PR #101416)

[Nikita Popov via llvm-commits]

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@@ -455,15 +455,16 @@ define void @vscale_countdown_ne(ptr nocapture %A, i32 %n) mustprogress vscale_r
 ; CHECK-NEXT:    %start = sub i32 %n, %vscale
 ; CHECK-NEXT:    --> ((-1 * vscale)<nsw> + %n) U: full-set S: full-set
 ; CHECK-NEXT:    %iv = phi i32 [ %sub, %for.body ], [ %start, %entry ]
-; CHECK-NEXT:    --> {((-1 * vscale)<nsw> + %n),+,(-1 * vscale)<nsw>}<%for.body> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %for.body: Computable }
+; CHECK-NEXT:    --> {((-1 * vscale)<nsw> + %n),+,(-1 * vscale)<nsw>}<%for.body> U: full-set S: full-set Exits: ((vscale * (-1 + (-1 * (((-2 * vscale)<nsw> + %n) /u vscale))<nsw>)<nsw>) + %n) LoopDispositions: { %for.body: Computable }
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nikic wrote:

Drop the TODO above.

https://github.com/llvm/llvm-project/pull/101416