| Issue |
75595
|
| 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 C20624F 1411B9B7 C20624F C20624F C20624F C20624F
file2.c C20624F 1411B9B7 C20624F C20624F 1411B9B7 C20624F
```
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_a0[2];
static uint64_t g_b0[2];
static uint64_t g_9 = 1UL;
static int32_t g_11 = 0x6B471DFDL;
static int8_t g_19 = 0x49L;
static void func_1(void);
static void func_1(void) {
int32_t l_14 = 0x0E864896L;
int i;
int ii_0;
// fusion
for (i = 0, ii_0 = 0; i < 1; i++, ii_0++) {
g_a0[ii_0] = g_19 * l_14 + g_11;
}
int jj_0;
for (jj_0 = 0; jj_0 < 2; jj_0++) {
g_b0[jj_0] = g_19 * g_a0[jj_0] + g_9;
}
}
int main(void) {
int i;
int print_hash_value = 0;
platform_main_begin();
crc32_gentab();
func_1();
transparent_crc(g_9, "g_9", print_hash_value);
transparent_crc(g_11, "g_11", print_hash_value);
transparent_crc(g_19, "g_19", print_hash_value);
for (i = 0; i < 2; i++) {
transparent_crc(g_a0[i], "g_a0[i]", print_hash_value);
}
for (i = 0; i < 2; i++) {
transparent_crc(g_b0[i], "g_b0[i]", print_hash_value);
}
platform_main_end(crc32_context ^ 0xFFFFFFFFUL, print_hash_value);
return 0;
}
```
**file2.c**
```
#include "csmith.h"
static int32_t g_a0[2];
static uint64_t g_b0[2];
static uint64_t g_9 = 1UL;
static int32_t g_11 = 0x6B471DFDL;
static int8_t g_19 = 0x49L;
static void func_1(void);
static void func_1(void) {
int32_t l_14 = 0x0E864896L;
int i;
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 <= 1 && i < 1) {
g_a0[ii_0] = g_19 * l_14 + g_11;
i++;
ii_0++;
}
if (ij_0 <= 2 && jj_0 < 2) {
g_b0[jj_0] = g_19 * g_a0[jj_0] + g_9;
jj_0++;
}
}
}
int i;
int main(void) {
int print_hash_value = 0;
platform_main_begin();
crc32_gentab();
func_1();
transparent_crc(g_9, "g_9", print_hash_value);
transparent_crc(g_11, "g_11", print_hash_value);
transparent_crc(g_19, "g_19", print_hash_value);
for (i = 0; i < 2; i++) {
transparent_crc(g_a0[i], "g_a0[i]", print_hash_value);
}
for (i = 0; i < 2; i++) {
transparent_crc(g_b0[i], "g_b0[i]", print_hash_value);
}
platform_main_end(crc32_context ^ 0xFFFFFFFFUL, print_hash_value);
return 0;
}
```
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