[llvm] [VPlan] Use wide IV if scalar lanes > 0 are used with scalable vectors. (PR #169796)

[Florian Hahn via llvm-commits]

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@@ -15,25 +15,22 @@ define void @test_invar_gep(ptr %dst) #0 {
 ; CHECK-NEXT:    [[TMP3:%.*]] = mul nuw i64 [[TMP2]], 4
 ; CHECK-NEXT:    [[N_MOD_VF:%.*]] = urem i64 100, [[TMP3]]
 ; CHECK-NEXT:    [[N_VEC:%.*]] = sub i64 100, [[N_MOD_VF]]
+; CHECK-NEXT:    [[TMP5:%.*]] = call <vscale x 4 x i64> @llvm.stepvector.nxv4i64()
+; CHECK-NEXT:    [[TMP4:%.*]] = mul nsw <vscale x 4 x i64> [[TMP5]], splat (i64 1)
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fhahn wrote:

Yes, there are cases where we currently may not be able to sink I think. The tests cover (the only?) code path where we extract the last lane of an IV in the loop for scalable vectors.

https://github.com/llvm/llvm-project/pull/169796