[llvm-bugs] [Bug 50969] New: ICE on valid code with -O1: fatal error: error in backend: Instruction Combining seems stuck in an infinite loop after 100 iterations.

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=50969

            Bug ID: 50969
           Summary: ICE on valid code with -O1: fatal error: error in
                    backend: Instruction Combining seems stuck in an
                    infinite loop after 100 iterations.
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: C
          Assignee: unassignedclangbugs at nondot.org
          Reporter: cnsun at uwaterloo.ca
                CC: blitzrakete at gmail.com, dgregor at apple.com,
                    erik.pilkington at gmail.com, llvm-bugs at lists.llvm.org,
                    richard-llvm at metafoo.co.uk

$ clang-trunk -v
clang version 13.0.0 (https://github.com/llvm/llvm-project.git
65eb4028ad0322115ff5420499806db79a27289e)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/cnsun/usr/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/10
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/9
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/10
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64

$ cat mutant.c
mul_double ()
{
int j, *prod;
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (j = 0; j < 4; j++)
for (; j < 4; j++)
*prod = 0;
}

$ clang-trunk -O1 -w mutant.c
fatal error: error in backend: Instruction Combining seems stuck in an infinite
loop after 100 iterations.
clang-13: error: clang frontend command failed with exit code 70 (use -v to see
invocation)
clang version 13.0.0 (https://github.com/llvm/llvm-project.git
65eb4028ad0322115ff5420499806db79a27289e)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/cnsun/usr/bin
clang-13: note: diagnostic msg:
********************

PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
clang-13: note: diagnostic msg: /tmp/mutant-000f7c.c
clang-13: note: diagnostic msg: /tmp/mutant-000f7c.sh
clang-13: note: diagnostic msg:

********************

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