[llvm] [LoopVectorizer] Prune VFs based on plan register pressure (PR #132190)

[Sam Tebbs via llvm-commits]

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@@ -12,28 +12,28 @@ define i32 @mla_i32(ptr noalias nocapture readonly %A, ptr noalias nocapture rea
 ; CHECK:       for.body.preheader:
 ; CHECK-NEXT:    br i1 false, label [[SCALAR_PH:%.*]], label [[VECTOR_PH:%.*]]
 ; CHECK:       vector.ph:
-; CHECK-NEXT:    [[N_RND_UP:%.*]] = add i32 [[N]], 15
-; CHECK-NEXT:    [[N_MOD_VF:%.*]] = urem i32 [[N_RND_UP]], 16
+; CHECK-NEXT:    [[N_RND_UP:%.*]] = add i32 [[N]], 7
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SamTebbs33 wrote:

Thanks Dave, that patch does indeed help and the only change after cherry picking over Elvis's changes is that the first `sext` is moved next to the second one. Once that PR is merged I'll rebase on top of it to get rid of this regression here.

https://github.com/llvm/llvm-project/pull/132190