On 17/09/18 12:19, Eric Botcazou wrote:
> Hi,
>
> this is a regression present on mainline, 8 and 7 branches. The new, RTL
> implementation of arm32_output_mi_thunk breaks during the libstdc++ build if
> you configure the compiler with -mlong-calls by default:
>
> 0xdb57eb gen_reg_rtx(machine_mode)
> /home/eric/svn/gcc/gcc/emit-rtl.c:1155
> 0xde9ae7 force_reg(machine_mode, rtx_def*)
> /home/eric/svn/gcc/gcc/explow.c:654
> 0x1bf73bf gen_sibcall(rtx_def*, rtx_def*, rtx_def*)
> /home/eric/svn/gcc/gcc/config/arm/arm.md:8272
> 0x187d3b1 arm32_output_mi_thunk
> /home/eric/svn/gcc/gcc/config/arm/arm.c:26762
> 0x187d4af arm_output_mi_thunk
> /home/eric/svn/gcc/gcc/config/arm/arm.c:26783
> 0xcb9c94 cgraph_node::expand_thunk(bool, bool)
> /home/eric/svn/gcc/gcc/cgraphunit.c:1783
>
> because the code is wired for a short call. Moreover, in PIC mode you need
> to
> work harder and fix up the minipool too with -mlong-calls.
>
> Tested on ARM/Linux, OK for mainline, 8 and 7 branches?
>
>
> 2018-09-17 Eric Botcazou <ebotca...@adacore.com>
>
> * config/arm/arm.c (arm_reorg): Skip Thumb reorg pass for thunks.
this seems to contradict your statement above about having to work
harder to fix up minipools. why is it correct to skip this entirely?
> (arm32_output_mi_thunk): Deal with long calls.
>
>
> 2018-09-17 Eric Botcazou <ebotca...@adacore.com>
>
> * g++.dg/other/thunk2a.C: New test.
> * g++.dg/other/thunk2b.C: Likewise.
>
>
> p.diff
>
>
> Index: config/arm/arm.c
> ===================================================================
> --- config/arm/arm.c (revision 264342)
> +++ config/arm/arm.c (working copy)
> @@ -17647,7 +17647,9 @@ arm_reorg (void)
>
> if (use_cmse)
> cmse_nonsecure_call_clear_caller_saved ();
> - if (TARGET_THUMB1)
> + if (cfun->is_thunk)
> + ;
> + else if (TARGET_THUMB1)
> thumb1_reorg ();
> else if (TARGET_THUMB2)
> thumb2_reorg ();
> @@ -26721,6 +26723,8 @@ static void
> arm32_output_mi_thunk (FILE *file, tree, HOST_WIDE_INT delta,
> HOST_WIDE_INT vcall_offset, tree function)
> {
> + const bool long_call_p = arm_is_long_call_p (function);
> +
> /* On ARM, this_regno is R0 or R1 depending on
> whether the function returns an aggregate or not.
> */
> @@ -26758,9 +26762,22 @@ arm32_output_mi_thunk (FILE *file, tree,
> TREE_USED (function) = 1;
> }
> rtx funexp = XEXP (DECL_RTL (function), 0);
> + if (long_call_p)
> + {
> + emit_move_insn (temp, funexp);
> + funexp = temp;
> + }
> funexp = gen_rtx_MEM (FUNCTION_MODE, funexp);
> - rtx_insn * insn = emit_call_insn (gen_sibcall (funexp, const0_rtx,
> NULL_RTX));
> + rtx_insn *insn = emit_call_insn (gen_sibcall (funexp, const0_rtx,
> NULL_RTX));
> SIBLING_CALL_P (insn) = 1;
> + emit_barrier ();
Why do we need a barrier here unconditionally (ie in the non-longcall case)?
R.
> +
> + /* Indirect calls require a bit of fixup in PIC mode. */
> + if (long_call_p)
> + {
> + split_all_insns_noflow ();
> + arm_reorg ();
> + }
>
> insn = get_insns ();
> shorten_branches (insn);
>
>
> thunk2a.C
>
>
> // { dg-do compile { target arm*-*-* } }
> // { dg-options "-mlong-calls -ffunction-sections }
>
> class a {
> public:
> virtual ~a();
> };
>
> class b : virtual a {};
>
> class c : b {
> ~c();
> };
>
> c::~c() {}
>
>
> thunk2b.C
>
>
> // { dg-do compile { target arm*-*-* && fpic } }
> // { dg-options "-mlong-calls -ffunction-sections -fPIC }
>
> class a {
> public:
> virtual ~a();
> };
>
> class b : virtual a {};
>
> class c : b {
> ~c();
> };
>
> c::~c() {}
>
