[llvm] [VPlan] Add initial CFG simplification, removing BranchOnCond true. (PR #106748)

[David Sherwood via llvm-commits]

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@@ -54,14 +54,11 @@ define void @test_widen_exp_v2(ptr noalias %p2, ptr noalias %p, i64 %n) #5 {
 ;
 ; TFCOMMON-LABEL: @test_widen_exp_v2(
 ; TFCOMMON-NEXT:  entry:
-; TFCOMMON-NEXT:    [[TMP0:%.*]] = add i64 [[N:%.*]], 1
-; TFCOMMON-NEXT:    [[N_RND_UP:%.*]] = add i64 [[TMP0]], 1
-; TFCOMMON-NEXT:    [[N_MOD_VF:%.*]] = urem i64 [[N_RND_UP]], 2
-; TFCOMMON-NEXT:    [[N_VEC:%.*]] = sub i64 [[N_RND_UP]], [[N_MOD_VF]]
-; TFCOMMON-NEXT:    [[TMP1:%.*]] = sub i64 [[TMP0]], 2
-; TFCOMMON-NEXT:    [[TMP2:%.*]] = icmp ugt i64 [[TMP0]], 2
+; TFCOMMON-NEXT:    [[N_RND_UP:%.*]] = add i64 [[TMP0:%.*]], 1
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david-arm wrote:

At first I found this pretty confusing - it seemed to change the preheader code without any branch simplifications in the middle block. Then I realised we also run `instsimplify` afterwards, which makes it hard to understand what's going on.

https://github.com/llvm/llvm-project/pull/106748