| Issue |
75586
|
| Summary |
unexpected output results in fusion using -Os
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
Elowen-jjw
|
For the following two c files, I performed the equivalent transformation of loop from **file1.c** to **file2.c**. I ran these two files respectively using different optimization levels including **-O0**, **-O1**, **-O2**, **-O3**, **-Os**, **-Ofast**. The exact output results(i.e. checksum values) are:
```
-O0 -O1 -O2 -O3 -Os -Ofast
file1.c F2F952A1 F2F952A1 AAF00380 AAF00380 AAF00380 AAF00380
file2.c F2F952A1 F2F952A1 AAF00380 AAF00380 F2F952A1 AAF00380
```
Please help me to explain why these two files produced different output results when using the same optimization level(i.e. -Os), thank you.
command line:
```
clang <filename.c> <optimization level> -lm -I $CSMITH_HOME/include && ./a.out
```
version: clang+llvm 14.0.0
os: ubuntu 22.04
**file1.c**
```
#include "csmith.h"
static int32_t g_a4[2];
static int64_t g_b4[2];
struct S0 {
volatile int64_t f0;
int8_t f1;
uint8_t f2;
volatile int16_t f3;
};
union U1 {
int64_t f0;
uint8_t f1;
uint8_t f2;
const int64_t f3;
volatile struct S0 f4;
};
static int32_t g_3 = 0xA73D2D67L;
static int32_t *g_5 = (void *)0;
static uint16_t g_16[2] = {0x8D20L, 0x8D20L};
static int32_t **volatile g_18 = &g_5;
static volatile union U1 g_25 = {0xDF34FFDEABFD090DLL};
static int32_t func_1(void);
static int32_t *func_7(void);
static int32_t func_1(void) {
(*g_18) = func_7();
return g_16[1];
}
static int32_t *func_7() {
int32_t *l_17[2][1];
int i, j;
int ii_0;
// fusion
for (i = 0, ii_0 = 0; i < 2; i++, ii_0++) {
for (j = 0; j < 1; j++) {
l_17[i][j] = &g_3;
g_a4[ii_0] = g_16[0] * g_3 - g_25.f2;
}
}
int jj_0;
for (jj_0 = 0; jj_0 < 1; jj_0++) {
g_b4[jj_0] = g_25.f3 * g_a4[jj_0] - g_25.f2;
}
return l_17[0][0];
}
int main(void) {
int i, j, k;
int print_hash_value = 0;
platform_main_begin();
crc32_gentab();
func_1();
transparent_crc(g_3, "g_3", print_hash_value);
for (i = 0; i < 2; i++) {
transparent_crc(g_16[i], "g_16[i]", print_hash_value);
}
transparent_crc(g_25.f0, "g_25.f0", print_hash_value);
for (i = 0; i < 2; i++) {
transparent_crc(g_a4[i], "g_a4[i]", print_hash_value);
}
for (i = 0; i < 2; i++) {
transparent_crc(g_b4[i], "g_b4[i]", print_hash_value);
}
platform_main_end(crc32_context ^ 0xFFFFFFFFUL, print_hash_value);
return 0;
}
```
**file2.c**
```
#include "csmith.h"
static int32_t g_a4[2];
static int64_t g_b4[2];
struct S0 {
volatile int64_t f0;
int8_t f1;
uint8_t f2;
volatile int16_t f3;
};
union U1 {
int64_t f0;
uint8_t f1;
uint8_t f2;
const int64_t f3;
volatile struct S0 f4;
};
static int32_t g_3 = 0xA73D2D67L;
static int32_t *g_5 = (void *)0;
static uint16_t g_16[2] = {0x8D20L, 0x8D20L};
static int32_t **volatile g_18 = &g_5;
static volatile union U1 g_25 = {0xDF34FFDEABFD090DLL};
static int32_t func_1(void);
static int32_t *func_7(void);
static int32_t func_1(void) {
(*g_18) = func_7();
return g_16[1];
}
static int32_t *func_7() {
int32_t *l_17[2][1];
int i, j;
int ii_0;
int jj_0;
int ij_0;
// fusion
for (i = 0, ii_0 = 0, jj_0 = 0, ij_0 = 0; ij_0 <= 2; ij_0++) {
if (ij_0 <= 2 && i < 2) {
for (j = 0; j < 1; j++) {
l_17[i][j] = &g_3;
g_a4[ii_0] = g_16[0] * g_3 - g_25.f2;
}
i++;
ii_0++;
}
if (ij_0 <= 1 && jj_0 < 1) {
g_b4[jj_0] = g_25.f3 * g_a4[jj_0] - g_25.f2;
jj_0++;
}
}
return l_17[0][0];
}
int main(void) {
int i, j, k;
int print_hash_value = 0;
platform_main_begin();
crc32_gentab();
func_1();
transparent_crc(g_3, "g_3", print_hash_value);
for (i = 0; i < 2; i++) {
transparent_crc(g_16[i], "g_16[i]", print_hash_value);
}
transparent_crc(g_25.f0, "g_25.f0", print_hash_value);
for (i = 0; i < 2; i++) {
transparent_crc(g_a4[i], "g_a4[i]", print_hash_value);
}
for (i = 0; i < 2; i++) {
transparent_crc(g_b4[i], "g_b4[i]", print_hash_value);
}
platform_main_end(crc32_context ^ 0xFFFFFFFFUL, print_hash_value);
return 0;
}
```
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