[llvm-bugs] [Bug 41320] New: FunctionAttrs pass failed to deduce and/or propagate function attributes

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=41320

            Bug ID: 41320
           Summary: FunctionAttrs pass failed to deduce and/or propagate
                    function attributes
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: cszide at 163.com
                CC: llvm-bugs at lists.llvm.org

Created attachment 21710
  --> https://bugs.llvm.org/attachment.cgi?id=21710&action=edit
.bc file of the source code

$clang -v
clang version 9.0.0 (trunk 355281)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/jack-zhou/Documents/llvm/llvm_truck/llvm/build4/bin
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.3.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.3.0
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64

$clang -O3 -c -emit-llvm  -mllvm -disable-llvm-optzns small.c

$opt -slp-vectorizer -sroa -loop-rotate -jump-threading  small.bc -o
small-opt.bc

$opt -functionattrs small-opt.bc
In this step, opt will run a long time and cannot terminate.
I check it using godbolt, the problem also occurs for llvm 7/trunk. The
following is the output.

/compiler-explorer/c-preload/compiler-wrapper: line 21: 24515 Killed           
      "$@"

Compiler returned: 137

--------------------------------------------
a[];
b;
c() {
  int d;
  int *e = &d;
  int *f[][6] = {a, a};
  for (;;)
    for (d = 9; d > 13;) {
      int **g = &f[0][1];
      *g = f[0][0];
      h(**g);
      e[b];
    }
}

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