[llvm] [LV] Separate runtime check cost from total overhead in profitability check (PR #176754)

[Luke Lau via llvm-commits]

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@@ -257,7 +257,7 @@ define ptr @std_find_caller(ptr noundef %first, ptr noundef %last) {
 ; CHECK-NEXT:    [[TMP1:%.*]] = sub i64 [[TMP0]], [[FIRST3]]
 ; CHECK-NEXT:    [[TMP2:%.*]] = lshr exact i64 [[TMP1]], 1
 ; CHECK-NEXT:    [[TMP3:%.*]] = add nuw i64 [[TMP2]], 1
-; CHECK-NEXT:    [[MIN_ITERS_CHECK:%.*]] = icmp ult i64 [[TMP1]], 126
+; CHECK-NEXT:    [[MIN_ITERS_CHECK:%.*]] = icmp ult i64 [[TMP1]], 14
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lukel97 wrote:

Looks like cttz.elts in the earlyexit block costs 4 on AArch64, so we were overcosting the checks in MinTC2 by at least 40. Makes sense that the min TC would drop significantly then

https://github.com/llvm/llvm-project/pull/176754