[avr] gas support for cfi info
Anitha Boyapati
anitha.boyapati@gmail.com
Thu Feb 17 15:35:00 GMT 2011
More information about the Binutils mailing list
Thu Feb 17 15:35:00 GMT 2011
- Previous message (by thread): [avr] gas support for cfi info
- Next message (by thread): [avr] gas support for cfi info
- Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]
On 16 February 2011 23:28, Richard Henderson <rth@redhat.com> wrote: > On 02/15/2011 02:44 PM, Petr Hluzín wrote: >> In avr-tdep.c [1] near avr_dwarf_reg_to_regnum(): >> /* Unfortunately dwarf2 register for SP is 32. */ > > Excellent. We're all on the same page for this. > >> (I can't help you with the value for #define DWARF2_DEFAULT_RETURN_COLUMN 36) >> AFAIK there is no written ABI. Only the calling convention is >> documented (and only the easy cases), the rest is in gdb/gcc/binutils >> sources and people's heads. > > As I recall, GCC defaults to using FIRST_PSEUDO_REGISTER for this, > so as to not overlap any hard registers. I'll continue to so the same. > >> /* Avr-6 call instructions save 3 bytes. */ >> switch (info.bfd_arch_info->mach) > > Thanks. That value is readily available in the assembler as well. > > Anitha pointed out to me via gcc pr17994 that AVR uses post-decrement > for its pushes. I had a brief read over the AVR insn manual, and it's > not crystal clear how multi-byte post-decrement pushes operate. > > I've made an assumption that it happens as-if each byte is pushed > separately. I.e. > > caller: callee: > save rN > save rM > trash <- SP hi(ret) <- CFA > lo(ret) > trash <- SP > > This is the only way I can imagine that call insns interoperate with > byte push/pop insns. > The stack layout is correct. For call/rcall instructions, PC-low is pushed first followed by a PC-high. (I just verified by running/debugging a small app on the device) > All of which means that the return address is at a different offset > from the CFA than I originally thought. This ought to be fixed in > the following. Can you please explain the logic behind the following lines in gcc patch: - offset = -cfa_store.offset; + if (GET_CODE (XEXP (dest, 0)) == POST_DEC) + offset += -cfa_store.offset; + else + offset = -cfa_store.offset; > > Can someone please test these two patches and see if they actually > agree with the hardware? I have tried only compiler patch. Please refer to the attached output for a small testcase. (avr-objdump -WfF). It appeared correct to me. However I have one simple question with regarding the output: The CFI instructions for registers have changed only after the prologue. (For convenience I have attached disassembly too). As far as I understand, DWARF2 spec emits CFI instructions immediately. (Appendix 5 of DWARF2 specification) The other scenario is - how about functions with signals/interrupts? The compiler will give an ICE compiling a function as below: void my_interrupt_handler() __attribute__ (("interrupt")); Likewise, for signal attribute too. I am going to apply assembler patch and test it. Will get back on it shortly. Anitha > > r~ > -------------- next part -------------- call-saved: file format elf32-avr Contents of the .debug_frame section: 00000000 00000010 ffffffff CIE Version: 1 Augmentation: "" Code alignment factor: 1 Data alignment factor: -1 Return address column: 36 DW_CFA_def_cfa: r32 ofs 2 DW_CFA_offset: r36 at cfa-1 DW_CFA_nop DW_CFA_nop 00000014 0000006c 00000000 FDE cie=00000000 pc=00000000..000000ce DW_CFA_advance_loc: 2 to 00000002 DW_CFA_def_cfa_offset: 3 DW_CFA_advance_loc: 2 to 00000004 DW_CFA_def_cfa_offset: 4 DW_CFA_advance_loc: 2 to 00000006 DW_CFA_def_cfa_offset: 5 DW_CFA_advance_loc: 2 to 00000008 DW_CFA_def_cfa_offset: 6 DW_CFA_advance_loc: 2 to 0000000a DW_CFA_def_cfa_offset: 7 DW_CFA_advance_loc: 2 to 0000000c DW_CFA_def_cfa_offset: 8 DW_CFA_advance_loc: 2 to 0000000e DW_CFA_def_cfa_offset: 9 DW_CFA_advance_loc: 2 to 00000010 DW_CFA_def_cfa_offset: 10 DW_CFA_advance_loc: 2 to 00000012 DW_CFA_def_cfa_offset: 11 DW_CFA_advance_loc: 2 to 00000014 DW_CFA_def_cfa_offset: 12 DW_CFA_advance_loc: 2 to 00000016 DW_CFA_def_cfa_offset: 13 DW_CFA_advance_loc: 2 to 00000018 DW_CFA_def_cfa_offset: 14 DW_CFA_advance_loc: 2 to 0000001a DW_CFA_def_cfa_offset: 15 DW_CFA_advance_loc: 2 to 0000001c DW_CFA_def_cfa_offset: 16 DW_CFA_advance_loc: 2 to 0000001e DW_CFA_def_cfa_offset: 17 DW_CFA_advance_loc: 2 to 00000020 DW_CFA_def_cfa_offset: 18 DW_CFA_advance_loc: 4 to 00000024 DW_CFA_def_cfa_offset: 20 DW_CFA_offset: r28 at cfa-18 DW_CFA_offset: r17 at cfa-17 DW_CFA_offset: r16 at cfa-16 DW_CFA_offset: r15 at cfa-15 DW_CFA_offset: r14 at cfa-14 DW_CFA_offset: r13 at cfa-13 DW_CFA_offset: r12 at cfa-12 DW_CFA_offset: r11 at cfa-11 DW_CFA_offset: r10 at cfa-10 DW_CFA_offset: r9 at cfa-9 DW_CFA_offset: r8 at cfa-8 DW_CFA_offset: r7 at cfa-7 DW_CFA_offset: r6 at cfa-6 DW_CFA_offset: r5 at cfa-5 DW_CFA_offset: r4 at cfa-4 DW_CFA_offset: r3 at cfa-3 DW_CFA_offset: r2 at cfa-2 DW_CFA_advance_loc: 4 to 00000028 DW_CFA_def_cfa_register: r28 DW_CFA_advance_loc: 2 to 0000002a DW_CFA_def_cfa_offset: 36 DW_CFA_advance_loc: 10 to 00000034 DW_CFA_def_cfa_register: r32 DW_CFA_nop DW_CFA_nop 00000084 00000014 00000000 FDE cie=00000000 pc=000000ce..000000de DW_CFA_advance_loc: 4 to 000000d2 DW_CFA_def_cfa_offset: 4 DW_CFA_offset: r28 at cfa-2 DW_CFA_advance_loc: 4 to 000000d6 DW_CFA_def_cfa_register: r28 call-saved: file format elf32-avr Contents of the .debug_frame section: 00000000 00000010 ffffffff CIE "" cf=1 df=-1 ra=36 LOC CFA ra 00000000 r32+2 c-1 00000014 0000006c 00000000 FDE cie=00000000 pc=00000000..000000ce LOC CFA r2 r3 r4 r5 r6 r7 r8 r9 r10 r11 r12 r13 r14 r15 r16 r17 r28 ra 00000000 r32+2 u u u u u u u u u u u u u u u u u c-1 00000002 r32+3 u u u u u u u u u u u u u u u u u c-1 00000004 r32+4 u u u u u u u u u u u u u u u u u c-1 00000006 r32+5 u u u u u u u u u u u u u u u u u c-1 00000008 r32+6 u u u u u u u u u u u u u u u u u c-1 0000000a r32+7 u u u u u u u u u u u u u u u u u c-1 0000000c r32+8 u u u u u u u u u u u u u u u u u c-1 0000000e r32+9 u u u u u u u u u u u u u u u u u c-1 00000010 r32+10 u u u u u u u u u u u u u u u u u c-1 00000012 r32+11 u u u u u u u u u u u u u u u u u c-1 00000014 r32+12 u u u u u u u u u u u u u u u u u c-1 00000016 r32+13 u u u u u u u u u u u u u u u u u c-1 00000018 r32+14 u u u u u u u u u u u u u u u u u c-1 0000001a r32+15 u u u u u u u u u u u u u u u u u c-1 0000001c r32+16 u u u u u u u u u u u u u u u u u c-1 0000001e r32+17 u u u u u u u u u u u u u u u u u c-1 00000020 r32+18 u u u u u u u u u u u u u u u u u c-1 00000024 r32+20 c-2 c-3 c-4 c-5 c-6 c-7 c-8 c-9 c-10 c-11 c-12 c-13 c-14 c-15 c-16 c-17 c-18 c-1 00000028 r28+20 c-2 c-3 c-4 c-5 c-6 c-7 c-8 c-9 c-10 c-11 c-12 c-13 c-14 c-15 c-16 c-17 c-18 c-1 0000002a r28+36 c-2 c-3 c-4 c-5 c-6 c-7 c-8 c-9 c-10 c-11 c-12 c-13 c-14 c-15 c-16 c-17 c-18 c-1 00000034 r32+36 c-2 c-3 c-4 c-5 c-6 c-7 c-8 c-9 c-10 c-11 c-12 c-13 c-14 c-15 c-16 c-17 c-18 c-1 00000084 00000014 00000000 FDE cie=00000000 pc=000000ce..000000de LOC CFA r28 ra 000000ce r32+2 u c-1 000000d2 r32+4 c-2 c-1 000000d6 r28+4 c-2 c-1 -------------- next part -------------- A non-text attachment was scrubbed... Name: call-saved.c Type: text/x-csrc Size: 281 bytes Desc: not available URL: <https://sourceware.org/pipermail/binutils/attachments/20110217/0a343bb8/attachment.bin> -------------- next part -------------- call-saved: file format elf32-avr Disassembly of section .text: 00000000 <foo>: 0: 2f 92 push r2 2: 3f 92 push r3 4: 4f 92 push r4 6: 5f 92 push r5 8: 6f 92 push r6 a: 7f 92 push r7 c: 8f 92 push r8 e: 9f 92 push r9 10: af 92 push r10 12: bf 92 push r11 14: cf 92 push r12 16: df 92 push r13 18: ef 92 push r14 1a: ff 92 push r15 1c: 0f 93 push r16 1e: 1f 93 push r17 20: df 93 push r29 22: cf 93 push r28 24: cd b7 in r28, 0x3d ; 61 26: de b7 in r29, 0x3e ; 62 28: 60 97 sbiw r28, 0x10 ; 16 2a: 0f b6 in r0, 0x3f ; 63 2c: f8 94 cli 2e: de bf out 0x3e, r29 ; 62 30: 0f be out 0x3f, r0 ; 63 32: cd bf out 0x3d, r28 ; 61 34: 8e 2d mov r24, r14 36: 9f 2d mov r25, r15 38: 80 0f add r24, r16 3a: 91 1f adc r25, r17 3c: 29 81 ldd r18, Y+1 ; 0x01 3e: 3a 81 ldd r19, Y+2 ; 0x02 40: 82 0f add r24, r18 42: 93 1f adc r25, r19 44: 2b 81 ldd r18, Y+3 ; 0x03 46: 3c 81 ldd r19, Y+4 ; 0x04 48: 82 0f add r24, r18 4a: 93 1f adc r25, r19 4c: 2d 81 ldd r18, Y+5 ; 0x05 4e: 3e 81 ldd r19, Y+6 ; 0x06 50: 82 0f add r24, r18 52: 93 1f adc r25, r19 54: 2f 81 ldd r18, Y+7 ; 0x07 56: 38 85 ldd r19, Y+8 ; 0x08 58: 82 0f add r24, r18 5a: 93 1f adc r25, r19 5c: 29 85 ldd r18, Y+9 ; 0x09 5e: 3a 85 ldd r19, Y+10 ; 0x0a 60: 82 0f add r24, r18 62: 93 1f adc r25, r19 64: eb 84 ldd r14, Y+11 ; 0x0b 66: fc 84 ldd r15, Y+12 ; 0x0c 68: e8 0e add r14, r24 6a: f9 1e adc r15, r25 6c: 8d 85 ldd r24, Y+13 ; 0x0d 6e: 9e 85 ldd r25, Y+14 ; 0x0e 70: 2f 85 ldd r18, Y+15 ; 0x0f 72: 38 89 ldd r19, Y+16 ; 0x10 74: 82 0f add r24, r18 76: 93 1f adc r25, r19 78: 82 0d add r24, r2 7a: 93 1d adc r25, r3 7c: 84 0d add r24, r4 7e: 95 1d adc r25, r5 80: 86 0d add r24, r6 82: 97 1d adc r25, r7 84: 88 0d add r24, r8 86: 99 1d adc r25, r9 88: 8a 0d add r24, r10 8a: 9b 1d adc r25, r11 8c: 08 2f mov r16, r24 8e: 19 2f mov r17, r25 90: 0c 0d add r16, r12 92: 1d 1d adc r17, r13 94: 0e 0d add r16, r14 96: 1f 1d adc r17, r15 98: 80 2f mov r24, r16 9a: 91 2f mov r25, r17 9c: 60 96 adiw r28, 0x10 ; 16 9e: 0f b6 in r0, 0x3f ; 63 a0: f8 94 cli a2: de bf out 0x3e, r29 ; 62 a4: 0f be out 0x3f, r0 ; 63 a6: cd bf out 0x3d, r28 ; 61 a8: cf 91 pop r28 aa: df 91 pop r29 ac: 1f 91 pop r17 ae: 0f 91 pop r16 b0: ff 90 pop r15 b2: ef 90 pop r14 b4: df 90 pop r13 b6: cf 90 pop r12 b8: bf 90 pop r11 ba: af 90 pop r10 bc: 9f 90 pop r9 be: 8f 90 pop r8 c0: 7f 90 pop r7 c2: 6f 90 pop r6 c4: 5f 90 pop r5 c6: 4f 90 pop r4 c8: 3f 90 pop r3 ca: 2f 90 pop r2 cc: 08 95 ret 000000ce <main>: ce: df 93 push r29 d0: cf 93 push r28 d2: cd b7 in r28, 0x3d ; 61 d4: de b7 in r29, 0x3e ; 62 d6: 94 df rcall .-216 ; 0x0 <foo> d8: cf 91 pop r28 da: df 91 pop r29 dc: 08 95 ret
- Previous message (by thread): [avr] gas support for cfi info
- Next message (by thread): [avr] gas support for cfi info
- Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]
More information about the Binutils mailing list