[PATCH] D143248: Emit CFI directives in epilogue and enable CFIFixup pass for RISC-V.

[Varun Kumar E via Phabricator via llvm-commits]

varunkumare99 added a comment.

In D143248#4238207 <https://reviews.llvm.org/D143248#4238207>, @shiva0217 wrote:

> In D143248#4177761 <https://reviews.llvm.org/D143248#4177761>, @varunkumare99 wrote:
>
>> In D143248#4131555 <https://reviews.llvm.org/D143248#4131555>, @shiva0217 wrote:
>>
>>> Hi Varun,
>>>
>>> It might be good to have a simple case to illustrate that cfi_remember_state and cfi_restore_state can be generated properly with epilogue CFI.
>>> For examle, could the following case generated with cfi_remember_state and cfi_restore_state as GCC?
>>>
>>>   extern void foo(void);
>>>   void f(int *i) {
>>>     if (*i == 0) {
>>>       *i = 1;
>>>       foo();
>>>       return;
>>>     } else {
>>>       __builtin_printf("Hi");
>>>       *i=0;
>>>     }
>>>   }
>>
>> Hi Shiva, the following is the assembly emitted.
>>
>>   f:
>>   .Lfunc_begin0:
>>   	.loc	0 2 0
>>   	.cfi_startproc
>>   	addi	sp, sp, -16
>>   	.cfi_def_cfa_offset 16
>>   	sd	ra, 8(sp)
>>   	sd	s0, 0(sp)
>>   	.cfi_offset ra, -8
>>   	.cfi_offset s0, -16
>>   	.cfi_remember_state
>>   	mv	s0, a0
>>   .Ltmp0:
>>   	.loc	0 3 6 prologue_end
>>   	lw	a0, 0(a0)
>>   .Ltmp1:
>>   	.loc	0 3 6 is_stmt 0
>>   	beqz	a0, .LBB0_2
>>   .Ltmp2:
>>   	.loc	0 8 3 is_stmt 1
>>   	lui	a0, %hi(.L.str)
>>   	addi	a0, a0, %lo(.L.str)
>>   	call	printf
>>   .Ltmp3:
>>   	.loc	0 9 5
>>   	sw	zero, 0(s0)
>>   .Ltmp4:
>>   	.loc	0 11 1
>>   	ld	ra, 8(sp)
>>   	ld	s0, 0(sp)
>>   .Ltmp5:
>>   	.cfi_restore ra
>>   	.cfi_restore s0
>>   	.loc	0 11 1 epilogue_begin is_stmt 0
>>   	addi	sp, sp, 16
>>   	.cfi_def_cfa_offset 0
>>   	ret
>>   .LBB0_2:
>>   	.cfi_restore_state
>>   .Ltmp6:
>>   	.loc	0 0 1
>>   	li	a0, 1
>>   .Ltmp7:
>>   	.loc	0 4 6 is_stmt 1
>>   	sw	a0, 0(s0)
>>   	.loc	0 5 3
>>   	ld	ra, 8(sp)
>>   	ld	s0, 0(sp)
>>   .Ltmp8:
>>   	.cfi_restore ra
>>   	.cfi_restore s0
>>   	.loc	0 5 3 epilogue_begin is_stmt 0
>>   	addi	sp, sp, 16
>>   	.cfi_def_cfa_offset 0
>>   .Ltmp9:
>>   	tail	foo
>>   .Ltmp10:
>>   .Lfunc_end0:
>>   	.size	f, .Lfunc_end0-f
>>   	.cfi_endproc
>
> Hi Varun,
>
> Could you add the case as a unit test?
> Shouldn't all the epilogue CFI guard by EmitCFI?
>
> The content of epilogue looks good to me.
> Please wait for Maskray and Kito's comments.

Hi Shiva,
I have updated that changes.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D143248/new/

https://reviews.llvm.org/D143248