[llvm-bugs] [Bug 42750] New: jump-threading produces wrong code with "opt -loop-rotate -gvn -licm -partial-inliner -jump-threading"

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=42750

            Bug ID: 42750
           Summary: jump-threading produces wrong code with "opt
                    -loop-rotate -gvn -licm -partial-inliner
                    -jump-threading"
           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 22284
  --> https://bugs.llvm.org/attachment.cgi?id=22284&action=edit
.bc file of the source code

$clang -v
clang version 9.0.0 (https://github.com/llvm/llvm-project.git
1e393064fa2732e721524f95a12348b0fd981167)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/jack-zhou/Documents/llvm/llvm_truck/llvm-project/build/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

$gcc small.c -o small.out && ./small.out
checksum = 0

$opt -loop-rotate -gvn -licm -partial-inliner -jump-threading small.bc -o
small-opt.bc

$clang small-opt.bc -o small1.out && ./small1.out
checksum = 401040

-----------------------------------------------------------
#include<stdio.h>
int a, c = 2;
unsigned b=1;
void d() {
  for (; a >= 0; a--) {
    --b;
    if (c)
      continue;
    for (;;)
      ;
  }
}
void main() {
  d();
  printf("checksum = %X\n", b);
}

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