[PATCH] D111519: [WIP] [RISCV] Emit cfi directives for function epilogue

[Shivam Gupta via Phabricator via llvm-commits]

xgupta added a comment.

In D111519#3115534 <https://reviews.llvm.org/D111519#3115534>, @jrtc27 wrote:

> In D111519#3115513 <https://reviews.llvm.org/D111519#3115513>, @xgupta wrote:
>
>> Hello @luismarques,
>>
>> can you please tell me how you have generated this assembly mentioned in the commit summary(.c file)?
>>
>>   define void @branch_and_tail_call(i1 %a) {
>>   ; RV32-LABEL: branch_and_tail_call:
>>   ; RV32:       # %bb.0:
>>   ; RV32-NEXT:    addi sp, sp, -16
>>   ; RV32-NEXT:    .cfi_def_cfa_offset 16
>>   ; RV32-NEXT:    sw ra, 12(sp)
>>   ; RV32-NEXT:    .cfi_offset ra, -4
>>   ; RV32-NEXT:    andi a0, a0, 1
>>   ; RV32-NEXT:    beqz a0, .LBB2_2
>>   ; RV32-NEXT:  # %bb.1: # %blue_pill
>>   ; RV32-NEXT:    lw ra, 12(sp)
>>   ; RV32-NEXT:    .cfi_restore ra
>>   ; RV32-NEXT:    addi sp, sp, 16
>>   ; RV32-NEXT:    .cfi_def_cfa_offset 0
>>   ; RV32-NEXT:    tail foo
>>   ; RV32-NEXT:  .LBB2_2: # %red_pill
>>   ; RV32-NEXT:    call bar
>>   ; RV32-NEXT:    lw ra, 12(sp)
>>   ; RV32-NEXT:    .cfi_restore ra
>>   ; RV32-NEXT:    addi sp, sp, 16
>>   ; RV32-NEXT:    .cfi_def_cfa_offset 0
>>   ; RV32-NEXT:    ret
>>   }
>
> This is clearly the branch_and_tail_call test case in frame-info.ll that had the `; FIXME: fix use of .cfi_restore with wrong CFAs`.

I am still looking for .c file so that I can test/diff it (clang riscv assembly) with gcc riscv generated assembly. Side question if someone knows why clang riscv emits .cfi_restore in epilogue (for frame-info.ll after applying this patch) while clang x86 does not. What is the use of .cf_restore in riscv that is not needed in x86? I have read .cfi_restore directive in https://sourceware.org/binutils/docs/as/CFI-directives.html but definition didn't give the answer.


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