* PING^2: [PATCH] i386: Add TARGET_INDIRECT_BRANCH_REGISTER
@ 2018-02-14 4:16 H.J. Lu
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From: H.J. Lu @ 2018-02-14 4:16 UTC (permalink / raw)
To: GCC Patches; +Cc: Jan Hubicka
On Thu, Feb 8, 2018 at 10:05 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Sun, Jan 28, 2018 at 11:56 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>> On Sat, Jan 27, 2018 at 2:12 PM, H.J. Lu <hongjiu.lu@intel.com> wrote:
>>> For
>>>
>>> ---
>>> struct C {
>>> virtual ~C();
>>> virtual void f();
>>> };
>>>
>>> void
>>> f (C *p)
>>> {
>>> p->f();
>>> p->f();
>>> }
>>> ---
>>>
>>> -mindirect-branch=thunk-extern -O2 on x86-64 GNU/Linux generates:
>>>
>>> _Z1fP1C:
>>> .LFB0:
>>> .cfi_startproc
>>> pushq %rbx
>>> .cfi_def_cfa_offset 16
>>> .cfi_offset 3, -16
>>> movq (%rdi), %rax
>>> movq %rdi, %rbx
>>> jmp .LIND1
>>> .LIND0:
>>> pushq 16(%rax)
>>> jmp __x86_indirect_thunk
>>> .LIND1:
>>> call .LIND0
>>> movq (%rbx), %rax
>>> movq %rbx, %rdi
>>> popq %rbx
>>> .cfi_def_cfa_offset 8
>>> movq 16(%rax), %rax
>>> jmp __x86_indirect_thunk_rax
>>> .cfi_endproc
>>>
>>> x86-64 is supposed to have asynchronous unwind tables by default, but
>>> there is nothing that reflects the change in the (relative) frame
>>> address after .LIND0. That region really has to be moved outside of
>>> the .cfi_startproc/.cfi_endproc bracket.
>>>
>>> This patch adds TARGET_INDIRECT_BRANCH_REGISTER to force indirect
>>> branch via register when -mindirect-branch=thunk-extern is used. Now,
>>> -mindirect-branch=thunk-extern -O2 on x86-64 GNU/Linux generates:
>>>
>>> _Z1fP1C:
>>> .LFB0:
>>> .cfi_startproc
>>> pushq %rbx
>>> .cfi_def_cfa_offset 16
>>> .cfi_offset 3, -16
>>> movq (%rdi), %rax
>>> movq %rdi, %rbx
>>> movq 16(%rax), %rax
>>> call __x86_indirect_thunk_rax
>>> movq (%rbx), %rax
>>> movq %rbx, %rdi
>>> popq %rbx
>>> .cfi_def_cfa_offset 8
>>> movq 16(%rax), %rax
>>> jmp __x86_indirect_thunk_rax
>>> .cfi_endproc
>>>
>>> Now "-mindirect-branch=thunk-extern" is equivalent to
>>> "-mindirect-branch=thunk-extern -mindirect-branch-register", which is
>>> used by Linux kernel.
>>>
>>> Tested on i686 and x86-64. OK for trunk?
>>>
>>> Thanks.
>>>
>>> H.J.
>>> ----
>>> gcc/
>>>
>>> PR target/84039
>>> * config/i386/constraints.md (Bs): Replace
>>> ix86_indirect_branch_register with
>>> TARGET_INDIRECT_BRANCH_REGISTER.
>>> (Bw): Likewise.
>>> * config/i386/i386.md (indirect_jump): Likewise.
>>> (tablejump): Likewise.
>>> (*sibcall_memory): Likewise.
>>> (*sibcall_value_memory): Likewise.
>>> Peepholes of indirect call and jump via memory: Likewise.
>>> * config/i386/i386.opt: Likewise.
>>> * config/i386/predicates.md (indirect_branch_operand): Likewise.
>>> (GOT_memory_operand): Likewise.
>>> (call_insn_operand): Likewise.
>>> (sibcall_insn_operand): Likewise.
>>> (GOT32_symbol_operand): Likewise.
>>> * config/i386/i386.h (TARGET_INDIRECT_BRANCH_REGISTER): New.
>>>
>>
>> Here is the updated patch to disallow *sibcall_GOT_32 and *sibcall_value_GOT_32
>> for TARGET_INDIRECT_BRANCH_REGISTER.
>>
>> Tested on i686 and x86-64. OK for trunk?
>>
>
> Hi Jan,
>
> https://gcc.gnu.org/ml/gcc-patches/2018-01/msg02233.html
>
> Is OK for trunk?
>
Hi Jan,
Can you take a look? I have more retpoline patches which
depend on this one.
Thanks.
--
H.J.
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