Extra xor when icmp eq 0 compared to GCC

[Godbolt for Clang f8467698d8cdbac6e02cdc1aab643d1ac733ec19](https://godbolt.org/z/Pad7M5WMK)

Flags for GCC and Clang is -O3:

```
extern void fdecl_0 (int, long);

void fdef_9 (int a) {
if (a == 0) {
fdecl_0 (0, 0);
// __builtin_unreachable ();
}
return;
}
```

generates this x86 assembly:

```
fdef_9:
test edi, edi
je .LBB0_2
ret
.LBB0_2:
xor edi, edi
xor esi, esi
jmp fdecl_0@PLT
```

GCC x86 generated assembly:

```
"fdef_9":
test edi, edi
je .L4
ret
.L4:
xor esi, esi
jmp "fdecl_0"
```

GCC removes that extra xor edi, edi instruction.

LLVM assembly:
```
define dso_local void @fdef_9(i32 noundef %a) local_unnamed_addr {
entry:
%cmp = icmp eq i32 %a, 0
br i1 %cmp, label %if.then, label %if.end

if.then:
tail call void @fdecl_0(i32 noundef 0, i64 noundef 0) #2
br label %if.end

if.end:
ret void
}

declare void @fdecl_0(i32 noundef, i64 noundef) local_unnamed_addr #1
```