[llvm-bugs] [Bug 42804] New: newgvn produces wrong code: Floating point exception

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=42804

            Bug ID: 42804
           Summary: newgvn produces wrong code: Floating point exception
           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 22306
  --> https://bugs.llvm.org/attachment.cgi?id=22306&action=edit
.bc file of the source code

$clang -v
clang version 10.0.0 (trunk 367076)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/jack-zhou/Documents/llvm/llvm_truck/llvm2/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/7.4.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.4.0
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64

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

$opt -inline -sroa -newgvn -rewrite-symbols -instcombine -newgvn -newgvn
small.bc -o small-opt.bc

$clang small-opt.bc -o small.out && ./small.out
Floating point exception (core dumped)


For clang and gcc with the default optimization levels, the program is correct.
--------------------------------------------------
char a, d;
char b[7][2];
int c, g;
char *h;
char *i() {
  char *e = &b[6][1];
  if (c) {
    char *f = &b[2][1];
    return f;
  }
  return e;
}
void j() {
  char *k = &a;
  h = i();
  g = k == h;
  char l = g;
  d = (l == 0) ? 1 : 4 % l;
}
void main() { j(); }

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