On Mon, Sep 18, 2017 at 09:50:45AM +0200, Eric Botcazou wrote: > .set L$set$24,LEFDE3-LASFDE3 > .long L$set$24 # FDE Length > LASFDE3: > .long LASFDE3-EH_frame1 # FDE CIE offset > .quad LCOLDB1-. # FDE initial location > .set L$set$25,LCOLDE1-LCOLDB1 > .quad L$set$25 # FDE address range > .byte 0x8 # uleb128 0x8; Augmentation size > .quad LLSDAC5-. # Language Specific Data Area > .byte 0x1 # DW_CFA_set_loc > .quad LCFI1-. > .byte 0xe # DW_CFA_def_cfa_offset > .byte 0x10 # uleb128 0x10 > .byte 0x83 # DW_CFA_offset, column 0x3 > .byte 0x2 # uleb128 0x2 > > Note the DW_CFA_set_loc operation: it's the only case where the compiler > emits > it (DW_CFA_advance_loc4 is usually emitted) and is the source of the problem, > since it appears that the PC-relative relocation is not applied to the > operand > of the DW_CFA_set_loc (unlike to the 2 other cases in the FDE).
That sounds like a Darwin bug in handling of DW_CFA_set_loc in .eh_frame section, the encoding/size of the DW_CFA_set_loc operand is an encoded pointer, always absolute address in .debug_frame section, and whatever the CIE augmentation says should be used otherwise, i.e. the same as e.g. FDE initial location pointer. As that is LCOLDB1-. in the same FDE, it means LCFI1-. is right. That said, there is indeed no reason to emit DW_CFA_set_loc when we have a label, so your patch is ok for trunk. That doesn't mean Darwin shouldn't be fixed. libgcc unwind-dw2.c for DW_CFA_set_loc uses read_encoded_value and so I believe should DTRT. > This DW_CFA_set_loc instruction is emitted by add_cfis_to_fde for the second > FDE generated for the cold part of a function but doesn't seem necessary any > more, since there is a label (LCOLDB1) to be used now (this can also be seen > on Linux with the -fno-dwarf2-cfi-asm option). > > Bootstrapped/regtested on x86-64/Linux by me and various versions of Darwin > by > Iain, Dominique and myself. OK for the mainline? > > > 2017-09-18 Eric Botcazou <ebotca...@adacore.com> > > PR target/81361 > * dwarf2cfi.c (add_cfis_to_fde): Do not generate DW_CFA_set_loc > after switching to a new text section. Jakub