Re: [PATCH v3 0/5] LoongArch tls le model linker relaxation support.

[Xi Ruoyao <xry111@xry111.site>]

On Fri, 2023-12-15 at 18:06 +0800, changjiachen wrote:
> First, after a test, the R_LARCH_TLS_LE_ADD_R can be generated using ".reloc.,R_LARCH_TLS_LE_ADD_R,sym", 
> or "%le_add_r(sym)". However,".reloc" generates R_LARCH_TLS_LE_ADD_R relocation directly, and it is not 
> easy to add "R_LARCH_RELAX" relocation. "%le_add_r(sym)" Adds the R_LARCH_TLS_LE_ADD_R and R_LARCH_RELAX 
> relocation commands, which is easier to implement.
>
> Of course, there is another way to generate ".reloc.,R_LARCH_TLS_LE_ADD_R,sym" and 
> ".reloc.,R_LARCH_RELAX,sym" directly in gcc. However, this implementation causes the 
> -mrelax/-mno-relax option to be set in both gcc and gas, which can be confusing.

GCC 14 already have -mrelax/-mno-relax options.  This is not confusing
at all.

> One problem with this is that add.d $r12,$r12,$r2 and add.d $r12,$r12,$r2, 
> %le_add_r(sym) are too similar, so I have to add comments in loongarch_fix_opcodes[]. 
> The goal is to make it as clear as possible to developers.

No, normal developers (not Binutils developers) should not be mandated
to read Binutils code to understand something.  OTOH they should read
the documentation of GAS.  So make it clear somewhere in the doc.

And I've told you if you must go with an additional operand in add.d,
you should reject things like:

add.d $a0,$a0,$a0,8

but now:

$ cat t.s
add.d $a0,$a0,$a0,8
$ gas/as-new t.s
$ binutils/objdump -d a.out

a.out:     file format elf64-loongarch


Disassembly of section .text:

0000000000000000 <.text>:
   0:	0010b084 	add.d       	$a0, $a0, $t0

Now is it clear that this behavior is unacceptable?

Is it too difficult or unreasonable to make it an error with message
"the fourth operand of the add.d instruction must be %le_add_r"?!  Or
didn't I make it clear?

-- 
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University