[llvm-bugs] [Bug 40393] New: Clang crashes while building Linux kernel due to [llvm] r351626 - Reapply "[CGP] Check for existing inttotpr before creating new one"

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=40393

            Bug ID: 40393
           Summary: Clang crashes while building Linux kernel due to
                    [llvm] r351626 - Reapply "[CGP] Check for existing
                    inttotpr before creating new one"
           Product: clang
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: LLVM Codegen
          Assignee: unassignedclangbugs at nondot.org
          Reporter: maxim.kuvyrkov at gmail.com
                CC: llvm-bugs at lists.llvm.org, neeilans at live.com,
                    richard-llvm at metafoo.co.uk

Hi,

Linaro's TCWG LLVM+Kernel tracking bisected kernel build regression down to
this commit.

Successfully identified regression in CI configuration
llvm-master-aarch64-lts-defconfig for llvm between bad_rev
be88539b85204041f727ec6499315884b3d886b0 and baseline_rev
4a22fb18c7935c6c1bae1af0b2e4a4c9e256ee04 .

Culprit:
<cut>
commit 85a0467a11bc748a242a858dfb950fce2956fa79
Author: Roman Tereshin <rtereshin at apple.com>
Date:   Fri Jan 18 20:13:42 2019 +0000

   [CGP] Check for existing inttotpr before creating new one

   Make sure CodeGenPrepare doesn't emit multiple inttoptr instructions of
   the same integer value while sinking address computations, but rather
   CSEs them on the fly: excessive inttoptr's confuse SCEV into thinking
   that related pointers have nothing to do with each other.

   This problem blocks LoadStoreVectorizer from vectorizing some of the
   loads / stores in a downstream target.

   Reviewed By: hfinkel

   Differential Revision: https://reviews.llvm.org/D56838

   llvm-svn: 351582
</cut>

Results regressed from (for last_good ==
d4023bd2cb2606db1a734966b14f865a52c68285)

<cut>
reset_artifacts:
-10
build_llvm:
-1
linux_n_obj:
all
</cut>

to (for first_bad == 85a0467a11bc748a242a858dfb950fce2956fa79)

<cut>
reset_artifacts:
-10
build_llvm:
-1
linux_n_obj:
5131
</cut>

Artifacts of last_good build:
https://ci.linaro.org/job/tcwg_kernel-bisect-llvm-master-aarch64-lts-defconfig/4/artifact/artifacts/build-d4023bd2cb2606db1a734966b14f865a52c68285/
Artifacts of first_bad build:
https://ci.linaro.org/job/tcwg_kernel-bisect-llvm-master-aarch64-lts-defconfig/4/artifact/artifacts/build-85a0467a11bc748a242a858dfb950fce2956fa79/

Reproduce builds:
<cut>
mkdir investigate-llvm-85a0467a11bc748a242a858dfb950fce2956fa79
cd investigate-llvm-85a0467a11bc748a242a858dfb950fce2956fa79
git clone https://git.linaro.org/toolchain/jenkins-scripts
wget
https://ci.linaro.org/job/tcwg_kernel-bisect-llvm-master-aarch64-lts-defconfig/4/artifact/artifacts/manifests/build-baseline.sh
./jenkins-scripts/tcwg_kernel-build.sh @@ build-baseline.sh
wget
https://ci.linaro.org/job/tcwg_kernel-bisect-llvm-master-aarch64-lts-defconfig/4/artifact/artifacts/test.sh
chmod +x test.sh
cd llvm
# Reproduce first_bad build
git checkout --detach 85a0467a11bc748a242a858dfb950fce2956fa79
../test.sh
# Reproduce last_good build
git checkout --detach d4023bd2cb2606db1a734966b14f865a52c68285
../test.sh
cd ..
</cut>

History of pending regressions and results:
https://git.linaro.org/toolchain/ci/base-artifacts.git/log/?h=linaro-local/ci/tcwg_kernel/llvm-master-aarch64-lts-defconfig

Bisect log:
https://ci.linaro.org/job/tcwg_kernel-bisect-llvm-master-aarch64-lts-defconfig/4/artifact/artifacts/bisect.log/*view*/
Artifacts:
https://ci.linaro.org/job/tcwg_kernel-bisect-llvm-master-aarch64-lts-defconfig/4/artifact/artifacts/
Build URL:
https://ci.linaro.org/job/tcwg_kernel-bisect-llvm-master-aarch64-lts-defconfig/4/
Build log:
https://ci.linaro.org/job/tcwg_kernel-bisect-llvm-master-aarch64-lts-defconfig/4/consoleText

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