[llvm-bugs] [Bug 41637] New: wrong code (Uncertain results) with "opt -inline -gvn -jump-threading -reg2mem -inferattrs -structurizecfg -gvn"

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=41637

            Bug ID: 41637
           Summary: wrong code (Uncertain results) with "opt -inline -gvn
                    -jump-threading -reg2mem -inferattrs -structurizecfg
                    -gvn"
           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 21837
  --> https://bugs.llvm.org/attachment.cgi?id=21837&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 -o small.bc

$clang small.bc -o small.out && ./small.out
0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 
---------------
0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 
65535 0 0 0 0 0 0 0 0

In this step, without optimization, the results are identical after running
many times.

$opt -inline -gvn -jump-threading -reg2mem -inferattrs -structurizecfg -gvn   
small.bc -o small-opt.bc

$clang small-opt.bc -o small1.out && ./small1.out
0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 
---------------
0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 
27135 0 0 0 0 0 0 0 0

$ clang small-opt.bc -o small1.out && ./small1.out
0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 
---------------
0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 
25599 0 0 0 0 0 0 0 0

In this step, the results of optimized code are different after running many
times.

--------------------------------------------
#include<stdio.h>
//------------------------
typedef signed char             int8_t;
typedef int                     int32_t;
/* Unsigned.  */
typedef unsigned char           uint8_t;
typedef unsigned short int      uint16_t;
typedef unsigned int            uint32_t;

uint32_t a, e;
uint16_t b[5][9];
int8_t c[10];
uint16_t *d = &b[4][0];
int32_t *f(uint16_t h, uint16_t k);
uint8_t g() {
  f(0, 0);
  return 0;
}
int32_t *f(uint16_t h, uint16_t k) {
l:

  if (k < *d)
    for (; e;) {
      int8_t *m = &c[2];
      *m = e;
      if (a)
        goto l;
    }
  --*d;
  return 0;
}
void main() {
  int i, j, n = 0;
  for (i = 0; i < 5; i++){
    for (j = 0; j < 9; j++){
      printf("%d ", b[i][j]);

    }
    printf("\n");
  }
  printf("---------------\n");

  g();

  for (i = 0; i < 5; i++){
    for (j = 0; j < 9; j++){
      printf("%d ", b[i][j]);

    }
    printf("\n");
  }

}

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