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

[Shiva Chen via Phabricator via llvm-commits]

shiva0217 added a comment.

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.


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  https://reviews.llvm.org/D143248/new/

https://reviews.llvm.org/D143248