| Issue |
114185
|
| Summary |
Incorrect assembly code generated with -Os
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
mushenoy
|
For the below sample source file - the assembly code generated is incorrect.
Sample.c:
```
struct sample {
struct sample *next;
char a;
};
char function (char);
void test(void);
void* test_function (const struct sample *c)
{
char type;
if (c) {
type = c->a;
test();
}
function(type);
return (void *)0;
}
```
Compilation command:
```
clang --target=aarch64-linux-gnu -save-temps -c sample.c -o sample.o -Os
```
In the assembly:
- No conditional branch is generated to check if `c` is non-null.
- test function call is done unconditionally
Assembly code:
```
test_function:
stp x29, x30, [sp, #-32]!
str x19, [sp, #16]
mov x29, sp
ldrb w19, [x0, #8]
bl test
mov w0, w19
bl function
mov x0, xzr
ldr x19, [sp, #16]
ldp x29, x30, [sp], #32
ret
```
x86_64:
```
test_function:
push rbx
movsx ebx, byte ptr [rdi + 8]
call test@PLT
mov edi, ebx
call function@PLT
xor eax, eax
pop rbx
ret
```
Observations:
- The issue is observed when -Os is used
- Code gets generated correctly when `type` variable is initialized with some value.
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