OK.
On Tue, Sep 4, 2018 at 11:13 AM, H.J. Lu <hjl.to...@gmail.com> wrote: > On Mon, Sep 3, 2018 at 10:01 AM, H.J. Lu <hjl.to...@gmail.com> wrote: >> On Mon, Sep 3, 2018 at 9:44 AM, Michael Matz <m...@suse.de> wrote: >>> Hi, >>> >>> On Mon, 3 Sep 2018, H.J. Lu wrote: >>> >>>> > So, what's the testcase testing then? Before the patch it doesn't ICE, >>>> > after the patch it doesn't ICE. What should I look out for so I can see >>>> > that what the testcase is producing without the patch is wrong? >>>> >>>> Before the patch, debug info is wrong since it uses hard frame pointer >>>> which isn't set up for the function. You can do "readelf -w" on .o file to >>>> verify the debug info. >>> >>> Yeah, that's what I thought as well, but it's correct: >>> >>> % ./gcc/cc1plus -quiet -O2 -g -fno-omit-frame-pointer -fvar-tracking x.cc >>> % gcc -c x.s >>> % readelf -wfi x.o >>> ... >>> <1><8a>: Abbrev Number: 9 (DW_TAG_subprogram) >>> <8b> DW_AT_specification: <0x3a> >>> <8f> DW_AT_decl_line : 6 >>> <90> DW_AT_decl_column : 5 >>> <91> DW_AT_object_pointer: <0xa7> >>> <95> DW_AT_low_pc : 0x0 >>> <9d> DW_AT_high_pc : 0x3 >>> <a5> DW_AT_frame_base : 1 byte block: 9c >>> (DW_OP_call_frame_cfa) >>> <a7> DW_AT_GNU_all_call_sites: 1 >>> ... >>> <2><fe>: Abbrev Number: 11 (DW_TAG_formal_parameter) >>> <ff> DW_AT_name : d >>> <101> DW_AT_decl_file : 1 >>> <102> DW_AT_decl_line : 6 >>> <103> DW_AT_decl_column : 63 >>> <104> DW_AT_type : <0x78> >>> <108> DW_AT_location : 2 byte block: 91 8 (DW_OP_fbreg: 8) >>> ... >>> DW_CFA_def_cfa: r7 (rsp) ofs 8 >>> DW_CFA_offset: r16 (rip) at cfa-8 >>> DW_CFA_nop >>> DW_CFA_nop >>> ... >>> >>> So, argument 'd' is supposed to be at DW_AT_frame_base + 8, which is >>> %rsp+8+8, aka %rsp+16, which is correct given that it's the eigth argument >>> (including the implicit this parameter). >> >> Can we use DW_AT_frame_base when the frame pointer isn't available? >> If yes, >> >> gcc_assert ((SUPPORTS_STACK_ALIGNMENT >> && (elim == hard_frame_pointer_rtx >> || elim == stack_pointer_rtx)) >> || elim == (frame_pointer_needed >> ? hard_frame_pointer_rtx >> : stack_pointer_rtx)); >> >> should be changed to >> >> gcc_assert (elim == hard_frame_pointer_rtx >> || elim == stack_pointer_rtx); >> >> This will also fix: >> >> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86593 >> > > Since hard frame pointer is encoded with DW_OP_fbreg which uses the > DW_AT_frame_base attribute, not hard frame pointer directly, we should > allow hard frame pointer when generating DWARF info even if frame pointer > isn't used. > > OK for trunk? > > -- > H.J.
