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Re: [PATCH] i386: Update -mfunction-return= for return with pop
> On Mon, Feb 26, 2018 at 2:05 AM, Martin Liška <mliska@suse.cz> wrote:
> > On 02/25/2018 02:37 AM, H.J. Lu wrote:
> >> PR target/r84530
> >
> > Just a nit I've noticed:
> >
> > s/r84530/84530
>
> Fixed.
>
> --
> H.J.
> From f08b8721ed038cefcee5a0bb1329b90a2d322269 Mon Sep 17 00:00:00 2001
> From: "H.J. Lu" <hjl.tools@gmail.com>
> Date: Sat, 24 Feb 2018 05:05:49 -0800
> Subject: [PATCH] i386: Update -mfunction-return= for return with pop
>
> When -mfunction-return= is used, simple_return_pop_internal should pop
> return address into ECX register, adjust stack by bytes to pop from stack
> and jump to the return thunk via ECX register.
>
> Tested on i686 and x86-64.
>
> PR target/84530
> * config/i386/i386-protos.h (ix86_output_indirect_jmp): Remove
> the bool argument.
> (ix86_output_indirect_function_return): New prototype.
> (ix86_split_simple_return_pop_internal): Likewise.
> * config/i386/i386.c (indirect_return_via_cx): New.
> (indirect_return_via_cx_bnd): Likewise.
> (indirect_thunk_name): Handle return va CX_REG.
> (output_indirect_thunk_function): Create alias for
> __x86_return_thunk_[re]cx and __x86_return_thunk_[re]cx_bnd.
> (ix86_output_indirect_jmp): Remove the bool argument.
> (ix86_output_indirect_function_return): New function.
> (ix86_split_simple_return_pop_internal): Likewise.
> * config/i386/i386.md (*indirect_jump): Don't pass false
> to ix86_output_indirect_jmp.
> (*tablejump_1): Likewise.
> (simple_return_pop_internal): Change it to define_insn_and_split.
> Call ix86_split_simple_return_pop_internal to split it for
> -mfunction-return=.
> (simple_return_indirect_internal): Call
> ix86_output_indirect_function_return instead of
> ix86_output_indirect_jmp.
It seems to make sense. Since LLVM has picked up our thunk names now,
I wonder if they have same bug or someohow already assigned a name
to this thunk. In the second case we probably ought to match it. Do
you know what LLVM uses?
Honza