Avoid calling `unroll_place()` in a common case.

[nnethercote]

This reduces the execution time for ucd-check by 25%.

r? @nikomatsakis

[arielb1]

Borrows that start from 2 separate locals can never overlap (and of course legal programs can never have borrow overlap).

Why isn't it possible to perform binning by place (by changing each_borrow_involving_path to do an "intersection query")?

[nikomatsakis]

@arielb1 that is what I was proposing in #53159 -- it takes some refactoring though to achieve.

[nikomatsakis]

Hmm. For the case of ucd-check in particular, I was hoping to just eliminate the borrows (that's what was proposed in #53643) and -- more generally -- to eventually refactor to a hashing-like scheme (as described in #53328 and #53643).

But, this is a super simple fix of course that seems worth landing regardless. I wouldn't mind putting off particularly the latter two refactorings if we can, as I might rather just try to do it as part of a move to a polonius based system. (Which will still want to solve similar problems, of course)

[nikomatsakis]

Also true: this was also a motivator for the refactoring happening in #53247 -- it would allow us to do this check for a broader range of places (since we can access the base place in O(1) time)

[nikomatsakis]

@bors r+

Anyway, as I said, seems worth landing this quick hack for now, why not?

[bors]

📌 Commit 130e556 has been approved by nikomatsakis

[bors]

⌛ Testing commit 130e556 with merge 7d32905...

[bors]

💔 Test failed - status-travis

[rust-highfive]

The job dist-i686-apple of your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

[00:05:10]       Memory: 8 GB
[00:05:10]       Boot ROM Version: VMW71.00V.0.B64.1704110547
[00:05:10]       Apple ROM Info: [MS_VM_CERT/SHA1/27d66596a61c48dd3dc7216fd715126e33f59ae7]Welcome to the Virtual Machine
[00:05:10]       SMC Version (system): 2.8f0
[00:05:10]       Serial Number (system): VMl7OBTl7RfY
[00:05:10] 
[00:05:10] hw.ncpu: 4
[00:05:10] hw.byteorder: 1234
[00:05:10] hw.memsize: 8589934592
---
[01:13:59] thread 'main' panicked at 'failed to download openssl source: exit code: 6', bootstrap/native.rs:611:17
[01:13:59] note: Run with `RUST_BACKTRACE=1` for a backtrace.
[01:13:59] failed to run: /Users/travis/build/rust-lang/rust/build/bootstrap/debug/bootstrap build
[01:13:59] Build completed unsuccessfully in 1:07:18
[01:13:59] make: *** [all] Error 1

The command "stamp sh -x -c "$RUN_SCRIPT"" exited with 2.
travis_time:start:00a93c74
$ date && (curl -fs --head https://google.com | grep ^Date: | sed 's/Date: //g' || true)
---
travis_fold:start:after_failure.2
travis_time:start:070f5b28
$ ls -lat $HOME/Library/Logs/DiagnosticReports/
total 0
drwx------+ 15 travis  staff  510 Jan 25  2018 ..
drwx------   2 travis  staff   68 Dec  6  2017 .
travis_fold:end:after_failure.2
travis_fold:start:after_failure.3
travis_time:start:157ad010
$ find $HOME/Library/Logs/DiagnosticReports -type f -name '*.crash' -not -name '*.stage2-*.crash' -not -name 'com.apple.CoreSimulator.CoreSimulatorService-*.crash' -exec printf travis_fold":start:crashlog\n\033[31;1m%s\033[0m\n" {} \; -exec head -750 {} \; -exec echo travis_fold":"end:crashlog \; || true
$ find $HOME/Library/Logs/DiagnosticReports -type f -name '*.crash' -not -name '*.stage2-*.crash' -not -name 'com.apple.CoreSimulator.CoreSimulatorService-*.crash' -exec printf travis_fold":start:crashlog\n\033[31;1m%s\033[0m\n" {} \; -exec head -750 {} \; -exec echo travis_fold":"end:crashlog \; || true
travis_time:end:157ad010:start=1535563661128347000,finish=1535563661164061000,duration=35714000
travis_fold:end:after_failure.3
travis_fold:start:after_failure.4
travis_time:start:015a1c9a
$ ln -s . checkout && for CORE in obj/cores/core.*; do EXE=$(echo $CORE | sed 's|obj/cores/core\.[0-9]*\.!checkout!\(.*\)|\1|;y|!|/|'); if [ -f "$EXE" ]; then printf travis_fold":start:crashlog\n\033[31;1m%s\033[0m\n" "$CORE"; gdb -q -c "$CORE" "$EXE" -iex 'set auto-load off' -iex 'dir src/' -iex 'set sysroot .' -ex bt -ex q; echo travis_fold":"end:crashlog; fi; done || true
travis_fold:end:after_failure.4
travis_fold:start:after_failure.5
travis_time:start:11034564
travis_time:start:11034564
$ cat ./obj/build/x86_64-unknown-linux-gnu/native/asan/build/lib/asan/clang_rt.asan-dynamic-i386.vers || true
cat: ./obj/build/x86_64-unknown-linux-gnu/native/asan/build/lib/asan/clang_rt.asan-dynamic-i386.vers: No such file or directory
travis_fold:end:after_failure.5
travis_fold:start:after_failure.6
travis_time:start:1f8f916f
$ dmesg | grep -i kill
$ dmesg | grep -i kill
Unable to obtain kernel buffer: Operation not permitted
usage: sudo dmesg
travis_fold:end:after_failure.6

Done. Your build exited with 1.

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

[nnethercote]

@bors retry

[bors]

⌛ Testing commit 130e556 with merge c096519...

[bors]

💔 Test failed - status-travis

[rust-highfive]

The job dist-i686-freebsd of your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

travis_time:end:0f0609e9:start=1535612258616811800,finish=1535612258624815133,duration=8003333
travis_fold:end:after_failure.3
travis_fold:start:after_failure.4
travis_time:start:1adf8184
$ ln -s . checkout && for CORE in obj/cores/core.*; do EXE=$(echo $CORE | sed 's|obj/cores/core\.[0-9]*\.!checkout!\(.*\)|\1|;y|!|/|'); if [ -f "$EXE" ]; then printf travis_fold":start:crashlog\n\033[31;1m%s\033[0m\n" "$CORE"; gdb -q -c "$CORE" "$EXE" -iex 'set auto-load off' -iex 'dir src/' -iex 'set sysroot .' -ex bt -ex q; echo travis_fold":"end:crashlog; fi; done || true
travis_fold:end:after_failure.4
travis_fold:start:after_failure.5
travis_time:start:191a7834
travis_time:start:191a7834
$ cat ./obj/build/x86_64-unknown-linux-gnu/native/asan/build/lib/asan/clang_rt.asan-dynamic-i386.vers || true
cat: ./obj/build/x86_64-unknown-linux-gnu/native/asan/build/lib/asan/clang_rt.asan-dynamic-i386.vers: No such file or directory
travis_fold:end:after_failure.5
travis_fold:start:after_failure.6
travis_time:start:25869231
$ dmesg | grep -i kill

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

[nnethercote]

@bors retry

[bors]

⌛ Testing commit 130e556 with merge 03fe4c7...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: nikomatsakis
Pushing 03fe4c7 to master...