[llvm] [VPlan] Update final IV exit value via VPlan. (PR #112147)

[via llvm-commits]

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@@ -545,11 +546,13 @@ define i64 @diff_exit_block_pre_inc_use2() {
 ; CHECK-NEXT:    [[TMP6:%.*]] = xor <4 x i1> [[TMP5]], splat (i1 true)
 ; CHECK-NEXT:    [[TMP7:%.*]] = call i1 @llvm.vector.reduce.or.v4i1(<4 x i1> [[TMP6]])
 ; CHECK-NEXT:    [[TMP8:%.*]] = icmp eq i64 [[INDEX_NEXT3]], 64
+; CHECK-NEXT:    [[VEC_IND_NEXT]] = add <4 x i64> [[VEC_IND]], splat (i64 4)
 ; CHECK-NEXT:    [[TMP9:%.*]] = or i1 [[TMP7]], [[TMP8]]
 ; CHECK-NEXT:    br i1 [[TMP9]], label [[MIDDLE_SPLIT:%.*]], label [[LOOP]], !llvm.loop [[LOOP0:![0-9]+]]
 ; CHECK:       middle.split:
 ; CHECK-NEXT:    br i1 [[TMP7]], label [[LOOP_EARLY_EXIT:%.*]], label [[MIDDLE_BLOCK:%.*]]
 ; CHECK:       middle.block:
+; CHECK-NEXT:    [[TMP10:%.*]] = extractelement <4 x i64> [[VEC_IND]], i32 3
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ayalz wrote:

Good to note at commit message that some opportunities may be lost, and leave some TODO to regain them?

https://github.com/llvm/llvm-project/pull/112147