[llvm-bugs] [Bug 143215] [RISCV] missed optimization: use sh or sw when can infer the offset from alignment

[LLVM Bugs via llvm-bugs]

Issue	143215
Summary	[RISCV] missed optimization: use sh or sw when can infer the offset from alignment
Labels	new issue
Assignees
Reporter	BaoshanPang

    https://godbolt.org/z/YP9WP9rET

For the C code:
```
typedef struct {
    char a;
    char b;
    char c;
    int len;
    char e;
    int len2;
} __attribute__((packed)) str_t;

void foo(str_t *p __attribute__((aligned(4)))) {
    p->len = 0;
    p->len2 = 0;
}
```

The asm generated is:

```
foo:
        sb      zero, 3(a0)
        sb      zero, 4(a0)
        sb      zero, 5(a0)
        sb zero, 6(a0)
        sb      zero, 8(a0)
        sb      zero, 9(a0)
 sb      zero, 10(a0)
        sb      zero, 11(a0)
 ret
```

For 'len', the middle two 'sb' can be converted to one 'sh'; for 'len2', the four sb can be converted to one 'sw'.

_______________________________________________
llvm-bugs mailing list
llvm-bugs@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-bugs