[llvm-bugs] [Bug 41547] New: wrong cod with "opt -instcombine -deadarghaX0r"

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=41547

            Bug ID: 41547
           Summary: wrong cod with "opt -instcombine -deadarghaX0r"
           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 21805
  --> https://bugs.llvm.org/attachment.cgi?id=21805&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 small1.out && ./small1.out
...checksum after hashing  : 6522DF69
index =

$opt -instcombine -deadarghaX0r small.bc -o small-opt.bc

$clang small-opt.bc -o small2.out && ./small2.out
...checksum after hashing  : 6522DF69
Segmentation fault (core dumped)

------------------------------------
#include<stdio.h>
//--------------
typedef signed char             int8_t;

/* Unsigned.  */
typedef unsigned char           uint8_t;
typedef unsigned int            uint32_t;
typedef unsigned long int       uint64_t;

static uint32_t crc32_tab[256];
static uint32_t crc32_context = 0xFFFFFFFFUL;

static void 
crc32_gentab (void)
{
        uint32_t crc;
        const uint32_t poly = 0xEDB88320UL;
        int i, j;

        for (i = 0; i < 256; i++) {
                crc = i;
                for (j = 8; j > 0; j--) {
                        if (crc & 1) {
                                crc = (crc >> 1) ^ poly;
                        } else {
                                crc >>= 1;
                        }
                }
                crc32_tab[i] = crc;
        }
}

static void 
crc32_byte (uint8_t b) {
        crc32_context = 
                ((crc32_context >> 8) & 0x00FFFFFF) ^ 
                crc32_tab[(crc32_context ^ b) & 0xFF];
}


static void 
crc32_8bytes (uint64_t val)
{
        crc32_byte ((val>>0) & 0xff);
        crc32_byte ((val>>8) & 0xff);
        crc32_byte ((val>>16) & 0xff);
        crc32_byte ((val>>24) & 0xff);
        crc32_byte ((val>>32) & 0xff);
        crc32_byte ((val>>40) & 0xff);
        crc32_byte ((val>>48) & 0xff);
        crc32_byte ((val>>56) & 0xff);
}

static void 
transparent_crc (uint64_t val, char* vname, int flag)
{
        crc32_8bytes(val);
        if (flag) {
                printf("...checksum after hashing %s : %lX\n", vname,
crc32_context ^ 0xFFFFFFFFUL);
        }
}

//----------------------------

uint64_t a;
void main() {
  crc32_gentab();
  int b = 1;
  transparent_crc(a, "", b);
  printf("index = \n");
}

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