[PATCH] D85036: [llvm-cov] reset executation count to 0 after wrapped segment

[Zequan Wu via Phabricator via llvm-commits]

zequanwu added a comment.

In D85036#2222873 <https://reviews.llvm.org/D85036#2222873>, @vsk wrote:

> Hi @zequanwu, we've started seeing a regression due to this change in swift (https://ci.swift.org/view/swift-master-next/job/oss-swift-incremental-RA-osx-master-next/7818/consoleText, see the bit about 'coverage_smoke.swift'). Here's the failure we see:
>
>              165:  165| 2| throw CustomError.Err // CHECK-COV: {{ *}}[[@LINE]]|{{ *}}2
>   check:167'0            X~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ error: no match found
>   check:167'1                                                                          with "@LINE" equal to "167"
>   check:167'2                                                                   ?      possible intended match
>              166:  166| 2| } catch {
>   check:167'0     ~~~~~~~~~~~~~~~~~~
>              167:  167| 1| if b { // CHECK-COV: {{ *}}[[@LINE]]|{{ *}}2
>   check:167'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>              168:  168| 1| return 1 // CHECK-COV: {{ *}}[[@LINE]]|{{ *}}1
>   check:167'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>              169:  169| 1| }
>
> The issue is that line 167 ("if b {") has an execution count of 1, even though it's actually reached twice. Before this change, the wrapped count from the catch block starting on line 166 would apply on line 167, all the way through the IfStmt condition (giving an execution count of 2). But with this change, seeing as the IfStmt condition doesn't get its own region, the line execution count gets picked up from the "Then" side of the IfStmt.
>
> I'm concerned that this nested statements generated in clang as well as swift. Do you have some idea about how to address this?
>
> I wonder whether we can make use of gap regions to fix the clang bugs you were looking at. I noticed that this fixed an issue in instrprof-comdat.h, but it's possible that that was caused by a bug in clang that has since been fixed (per the note).

Hi, I don't know how swift generate the regions. Shouldn't IfStmt gets its own regions covering from `if` keyword to thenStmt? Is that intended not to do so in swift?
My original thought about this is for one line if there is any new line segment which is start of region, we should ignore the wrapped line segment, and the new line segment count should be the accurate one. Do you have dumping result of segments (`-debug-only=coverage-mapping`) so we can take a deeper look?


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