[PATCH] D44886: [RISCV] Support linker relax function call from auipc and jalr to jal

[Shiva Chen via Phabricator via llvm-commits]

shiva0217 added a comment.

In https://reviews.llvm.org/D44886#1065531, @asb wrote:

> Given that Simon's https://reviews.llvm.org/D45181 will be dependent on this (as it should really query whether linker relaxation is enabled), it probably makes sense to get this merged sooner rather than later.


Hi Alex.

> I think the options are:
> 
> 1. Merge as is

If we merge as is will leave the relocation difference between assembly code and object file as you described.

> 2. Modify this patch so it adds RISCV_RELAX to pcrel_hi and pcrel_lo relocations when linker relaxation is enabled, then have a follow-up patch that emits CALL.
> 
>   The psabi doc doesn't discuss attaching RISCV_RELAX to relocations other than RISCV_CALL or RISCV_CALL_PLT, but presumably binutils ld will use it for other pairs?

The psabi doc didn't mention add RISCV_RELAX to pcrel_hi and pcrel_lo relocations and I have done some experiments. It seems that attaching RISCV_RELAX to pcrel_hi and pcrel_lo relocations can't relax aupic and jalr to jal by Binutils ld. So we have to use R_RISCV_CALL and R_RISCV_RELAX for function call relaxation.

I have updated the patch to generate call pseudoinstruction as your comments in https://reviews.llvm.org/D44886?id=140176#inline-398646.


Repository:
  rL LLVM

https://reviews.llvm.org/D44886