[PATCH] D113577: [SCEV] Support rewriting ZExt expressions with loop guard info.

Mon Nov 15 10:03:59 PST 2021

fhahn added a comment.

In D113577#3132006 <https://reviews.llvm.org/D113577#3132006>, @nikic wrote:

> In D113577#3131976 <https://reviews.llvm.org/D113577#3131976>, @fhahn wrote:
>
>> rebased.
>>
>> @nikic it looks like there's a crash on the llvm-compile-time-tracker with the latest version (applying rewrites), but I was unable to reproduce this locally with various combinations of flags. What compiler/flags is used by the tracker to build the compiler used?
>>
>> The log to the failure is http://llvm-compile-time-tracker.com/show_error.php?commit=d628e5e177b9a9dd4f279ce7c301fd312be0cfa7 in case you have any ideas.
>
> Here's the (unreduced) IR, crashes for me under `opt -O1`: https://gist.github.com/nikic/bd117601aedea5f03b5750571d07624e
>
> I just ran the `/root/llvm-compile-time-tracker/llvm-project-build/bin/clang -DNDEBUG  -fno-experimental-new-pass-manager -O3 -fomit-frame-pointer -flto -DNDEBUG -g   -w -Werror=date-time -MD -MT tools/CMakeFiles/fpcmp-target.dir/fpcmp.c.o -MF tools/CMakeFiles/fpcmp-target.dir/fpcmp.c.o.d -o tools/CMakeFiles/fpcmp-target.dir/fpcmp.c.o   -c /root/llvm-compile-time-tracker/llvm-test-suite/tools/fpcmp.c` command after adjusting to local paths, but sometimes these things depend on external deps like the used libc.

Thanks! I think I figured out the issue: `RewriteMap[Expr] = Rewriter.visit(RewriteTo);`  may add an entry to `RewriteMap` before evaluating `RewriteTo` depending on the compiler used.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D113577/new/

https://reviews.llvm.org/D113577