issue: unexpected results in optimizations

[Jingwen Wu <elowen.jjw@gmail.com>]

[-- Attachment #1.1: Type: text/plain, Size: 768 bytes --]

Hello, I'm sorry to bother you. And I have some gcc compiler optimization
questions to ask you.
First of all, I used csmith tools to generate c files randomly. Meanwhile,
the final running result was the checksum for global variables in a c file.
For the two c files in the attachment, I performed the equivalent
transformation of loop from *initial.**c* to *transformed.c*. And the two
files produced different results (i.e. different checksum values) when
using *-Os* optimization level, while the results of both were the same
when using other levels of optimization such as *-O0*, -O1, -O2, -O3,
*-Ofast*.
Please help me to explain why this is, thank you.

command line: *gcc file.c -Os -lm -I $CSMITH_HOME/include && ./a.out*
version: gcc 12.2.0
os: ubuntu 22.04

[-- Attachment #2: initial.c --]
[-- Type: application/octet-stream, Size: 2322 bytes --]


#include "csmith.h"

static int32_t g_a83[69];
static int32_t g_b83[69];

static volatile uint16_t g_2[3][2][1] = {{{0x439BL}, {8UL}}, {{8UL}, {0x439BL}}, {{8UL}, {8UL}}};
static int32_t g_3 = 0xB4E1265AL;
static uint8_t g_13 = 0x83L;
static int16_t g_15[1] = {0x4F23L};
static int32_t *g_20 = &g_3;
static int32_t *const *g_53 = &g_20;
static int32_t *const **g_52 = &g_53;
static int32_t *g_92 = &g_3;
static volatile uint8_t g_167 = 8UL;
static int32_t g_258 = 0xDB41F928L;
static volatile uint8_t *volatile g_261 = &g_167;
static volatile int32_t g_267 = 0x9B2E194DL;
static int32_t **volatile g_389 = &g_92;

static void func_1(void);

static void func_1(void) {
  int32_t l_14 = 0xDD013D0BL;

  if (g_2[1][1][0]) {
    uint32_t l_36[1][3];
    uint8_t *l_37 = &g_13;
    int i, j;
    for (i = 0; i < 1; i++) {
      for (j = 0; j < 3; j++) {
        l_36[i][j] = 0xB839BF5BL;
      }
    }
    if ((~(((***g_52) = l_36[0][1]) ^ (safe_div_func_int64_t_s_s((l_14 || 0x12L), g_15[0]))))) {
      int ii_4;
      // fusion in max execTimes
      for (g_13 = 8, ii_4 = 0; (g_13 <= 44); g_13 = safe_add_func_uint64_t_u_u(g_13, 1), ii_4++) {
        g_a83[ii_4] = g_258 * g_13 + (*g_261);
      }
      int jj_4;
      for (jj_4 = 0; jj_4 < 69; jj_4++) {
        g_b83[jj_4] = (**g_389) * g_a83[jj_4] - g_267;
      }
    } else {
    	uint8_t **l_81 = &l_37;
      uint8_t ***l_80 = &l_81;
    }
  }
}

int main(void) {
  int i, j, k;
  int print_hash_value = 0;
  platform_main_begin();
  crc32_gentab();
  func_1();
  for (i = 0; i < 3; i++) {
    for (j = 0; j < 2; j++) {
      for (k = 0; k < 1; k++) {
        transparent_crc(g_2[i][j][k], "g_2[i][j][k]", print_hash_value);
      }
    }
  }
  transparent_crc(g_3, "g_3", print_hash_value);
  transparent_crc(g_13, "g_13", print_hash_value);
  for (i = 0; i < 1; i++) {
    transparent_crc(g_15[i], "g_15[i]", print_hash_value);
  }
  transparent_crc(g_167, "g_167", print_hash_value);
  transparent_crc(g_258, "g_258", print_hash_value);
  transparent_crc(g_267, "g_267", print_hash_value);
  for (i = 0; i < 69; i++) {
    transparent_crc(g_a83[i], "g_a83[i]", print_hash_value);
  }
  for (i = 0; i < 69; i++) {
    transparent_crc(g_b83[i], "g_b83[i]", print_hash_value);
  }
  platform_main_end(crc32_context ^ 0xFFFFFFFFUL, print_hash_value);
  return 0;
}

[-- Attachment #3: transformed.c --]
[-- Type: application/octet-stream, Size: 2457 bytes --]


#include "csmith.h"

static int32_t g_a83[69];
static int32_t g_b83[69];

static volatile uint16_t g_2[3][2][1] = {{{0x439BL}, {8UL}}, {{8UL}, {0x439BL}}, {{8UL}, {8UL}}};
static int32_t g_3 = 0xB4E1265AL;
static uint8_t g_13 = 0x83L;
static int16_t g_15[1] = {0x4F23L};
static int32_t *g_20 = &g_3;
static int32_t *const *g_53 = &g_20;
static int32_t *const **g_52 = &g_53;
static int32_t *g_92 = &g_3;
static volatile uint8_t g_167 = 8UL;
static int32_t g_258 = 0xDB41F928L;
static volatile uint8_t *volatile g_261 = &g_167;
static volatile int32_t g_267 = 0x9B2E194DL;
static int32_t **volatile g_389 = &g_92;

static void func_1(void);

static void func_1(void) {
  int32_t l_14 = 0xDD013D0BL;

  if (g_2[1][1][0]) {
    uint32_t l_36[1][3];
    uint8_t *l_37 = &g_13;
    int i, j;
    for (i = 0; i < 1; i++) {
      for (j = 0; j < 3; j++) {
        l_36[i][j] = 0xB839BF5BL;
      }
    }
    if ((~(((***g_52) = l_36[0][1]) ^ (safe_div_func_int64_t_s_s((l_14 || 0x12L), g_15[0]))))) {
      int ii_4;
      int jj_4;
      int ij_4;
      // fusion in max execTimes
      for (g_13 = 8, ii_4 = 0, jj_4 = 0, ij_4 = 0; ij_4 <= 69; ij_4++) {
        if (ij_4 <= 37 && (g_13 <= 44)) {
          g_a83[ii_4] = g_258 * g_13 + (*g_261);
          g_13 = safe_add_func_uint64_t_u_u(g_13, 1);
          ii_4++;
        }
        if (ij_4 <= 69 && jj_4 < 69) {
          g_b83[jj_4] = (**g_389) * g_a83[jj_4] - g_267;
          jj_4++;
        }
      }
    } else {
    	uint8_t **l_81 = &l_37;
      uint8_t ***l_80 = &l_81;
    }
  }
}

int main(void) {
  int i, j, k;
  int print_hash_value = 0;
  platform_main_begin();
  crc32_gentab();
  func_1();
  for (i = 0; i < 3; i++) {
    for (j = 0; j < 2; j++) {
      for (k = 0; k < 1; k++) {
        transparent_crc(g_2[i][j][k], "g_2[i][j][k]", print_hash_value);
      }
    }
  }
  transparent_crc(g_3, "g_3", print_hash_value);
  transparent_crc(g_13, "g_13", print_hash_value);
  for (i = 0; i < 1; i++) {
    transparent_crc(g_15[i], "g_15[i]", print_hash_value);
  }
  transparent_crc(g_167, "g_167", print_hash_value);
  transparent_crc(g_258, "g_258", print_hash_value);
  transparent_crc(g_267, "g_267", print_hash_value);
  for (i = 0; i < 69; i++) {
    transparent_crc(g_a83[i], "g_a83[i]", print_hash_value);
  }
  for (i = 0; i < 69; i++) {
    transparent_crc(g_b83[i], "g_b83[i]", print_hash_value);
  }
  platform_main_end(crc32_context ^ 0xFFFFFFFFUL, print_hash_value);
  return 0;
}