17aca79d98
The main change here is that we're now able to correctly look up plans for these functions. Previously, due to caching, we could end up with one entry covering most of the address space (because part of the function was at the beginning and one at the end). Now, we can correctly recognise that the part in between does not belong to that function, and we can create a different FuncUnwinders instance for it. It doesn't help the discontinuous function much (its plan will still be garbled), but we can at least properly unwind out of the simple functions in between. Fixing the unwind plans for discontinuous functions requires handling each unwind source specially, and this setup allows us to make the transition incrementally.
257 lines
11 KiB
ArmAsm
257 lines
11 KiB
ArmAsm
# An example of a function which has been split into two parts. Roughly
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# corresponds to this C code.
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# int baz() { return 47; }
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# int bar() { return foo(0); }
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# int foo(int flag) { return flag ? bar() : baz(); }
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# int main() { return foo(1); }
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# The function bar has been placed "in the middle" of foo.
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.text
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.type baz,@function
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baz:
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.cfi_startproc
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movl $47, %eax
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retq
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.cfi_endproc
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.Lbaz_end:
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.size baz, .Lbaz_end-baz
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.type foo,@function
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foo:
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.cfi_startproc
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pushq %rbp
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.cfi_def_cfa_offset 16
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.cfi_offset %rbp, -16
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movq %rsp, %rbp
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.cfi_def_cfa_register %rbp
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subq $16, %rsp
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movl %edi, -8(%rbp)
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cmpl $0, -8(%rbp)
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je foo.__part.2
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jmp foo.__part.1
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.cfi_endproc
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.Lfoo_end:
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.size foo, .Lfoo_end-foo
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foo.__part.1:
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.cfi_startproc
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.cfi_def_cfa %rbp, 16
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.cfi_offset %rbp, -16
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callq bar
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movl %eax, -4(%rbp)
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jmp foo.__part.3
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.Lfoo.__part.1_end:
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.size foo.__part.1, .Lfoo.__part.1_end-foo.__part.1
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.cfi_endproc
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bar:
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.cfi_startproc
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# NB: Decrease the stack pointer to make the unwind info for this function
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# different from the surrounding foo function.
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subq $24, %rsp
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.cfi_def_cfa_offset 32
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xorl %edi, %edi
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callq foo
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addq $24, %rsp
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.cfi_def_cfa %rsp, 8
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retq
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.cfi_endproc
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.Lbar_end:
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.size bar, .Lbar_end-bar
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foo.__part.2:
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.cfi_startproc
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.cfi_def_cfa %rbp, 16
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.cfi_offset %rbp, -16
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callq baz
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movl %eax, -4(%rbp)
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jmp foo.__part.3
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.Lfoo.__part.2_end:
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.size foo.__part.2, .Lfoo.__part.2_end-foo.__part.2
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.cfi_endproc
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foo.__part.3:
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.cfi_startproc
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.cfi_def_cfa %rbp, 16
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.cfi_offset %rbp, -16
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movl -4(%rbp), %eax
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addq $16, %rsp
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popq %rbp
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.cfi_def_cfa %rsp, 8
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retq
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.Lfoo.__part.3_end:
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.size foo.__part.3, .Lfoo.__part.3_end-foo.__part.3
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.cfi_endproc
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.globl main
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.type main,@function
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main:
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.cfi_startproc
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movl $1, %edi
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callq foo
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retq
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.cfi_endproc
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.Lmain_end:
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.size main, .Lmain_end-main
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.section .debug_abbrev,"",@progbits
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.byte 1 # Abbreviation Code
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.byte 17 # DW_TAG_compile_unit
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.byte 1 # DW_CHILDREN_yes
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.byte 37 # DW_AT_producer
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.byte 8 # DW_FORM_string
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.byte 19 # DW_AT_language
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.byte 5 # DW_FORM_data2
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.byte 17 # DW_AT_low_pc
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.byte 1 # DW_FORM_addr
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.byte 85 # DW_AT_ranges
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.byte 35 # DW_FORM_rnglistx
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.byte 116 # DW_AT_rnglists_base
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.byte 23 # DW_FORM_sec_offset
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.byte 0 # EOM(1)
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.byte 0 # EOM(2)
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.byte 2 # Abbreviation Code
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.byte 46 # DW_TAG_subprogram
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.byte 0 # DW_CHILDREN_no
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.byte 17 # DW_AT_low_pc
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.byte 1 # DW_FORM_addr
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.byte 18 # DW_AT_high_pc
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.byte 1 # DW_FORM_addr
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.byte 3 # DW_AT_name
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.byte 8 # DW_FORM_string
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.byte 0 # EOM(1)
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.byte 0 # EOM(2)
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.byte 3 # Abbreviation Code
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.byte 46 # DW_TAG_subprogram
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.byte 1 # DW_CHILDREN_yes
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.byte 85 # DW_AT_ranges
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.byte 35 # DW_FORM_rnglistx
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.byte 64 # DW_AT_frame_base
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.byte 24 # DW_FORM_exprloc
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.byte 3 # DW_AT_name
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.byte 8 # DW_FORM_string
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.byte 0 # EOM(1)
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.byte 0 # EOM(2)
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.byte 4 # Abbreviation Code
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.byte 5 # DW_TAG_formal_parameter
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.byte 0 # DW_CHILDREN_no
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.byte 2 # DW_AT_location
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.byte 24 # DW_FORM_exprloc
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.byte 3 # DW_AT_name
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.byte 8 # DW_FORM_string
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.byte 73 # DW_AT_type
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.byte 19 # DW_FORM_ref4
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.byte 0 # EOM(1)
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.byte 0 # EOM(2)
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.byte 5 # Abbreviation Code
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.byte 36 # DW_TAG_base_type
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.byte 0 # DW_CHILDREN_no
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.byte 3 # DW_AT_name
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.byte 8 # DW_FORM_string
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.byte 62 # DW_AT_encoding
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.byte 11 # DW_FORM_data1
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.byte 11 # DW_AT_byte_size
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.byte 11 # DW_FORM_data1
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.byte 0 # EOM(1)
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.byte 0 # EOM(2)
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.byte 0 # EOM(3)
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.section .debug_info,"",@progbits
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.Lcu_begin0:
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.long .Ldebug_info_end0-.Ldebug_info_start0 # Length of Unit
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.Ldebug_info_start0:
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.short 5 # DWARF version number
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.byte 1 # DWARF Unit Type
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.byte 8 # Address Size (in bytes)
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.long .debug_abbrev # Offset Into Abbrev. Section
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.byte 1 # Abbrev [1] DW_TAG_compile_unit
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.asciz "Hand-written DWARF" # DW_AT_producer
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.short 29 # DW_AT_language
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.quad 0 # DW_AT_low_pc
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.byte 1 # DW_AT_ranges
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.long .Lrnglists_table_base0 # DW_AT_rnglists_base
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.byte 2 # Abbrev [2] DW_TAG_subprogram
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.quad baz # DW_AT_low_pc
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.quad .Lbaz_end # DW_AT_high_pc
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.asciz "baz" # DW_AT_name
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.byte 2 # Abbrev [2] DW_TAG_subprogram
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.quad bar # DW_AT_low_pc
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.quad .Lbar_end # DW_AT_high_pc
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.asciz "bar" # DW_AT_name
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.byte 3 # Abbrev [3] DW_TAG_subprogram
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.byte 0 # DW_AT_ranges
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.byte 1 # DW_AT_frame_base
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.byte 86
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.asciz "foo" # DW_AT_name
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.byte 4 # Abbrev [4] DW_TAG_formal_parameter
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.byte 2 # DW_AT_location
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.byte 145
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.byte 120
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.asciz "flag" # DW_AT_name
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.long .Lint-.Lcu_begin0 # DW_AT_type
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.byte 0 # End Of Children Mark
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.byte 2 # Abbrev [2] DW_TAG_subprogram
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.quad main # DW_AT_low_pc
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.quad .Lmain_end # DW_AT_high_pc
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.asciz "main" # DW_AT_name
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.Lint:
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.byte 5 # Abbrev [5] DW_TAG_base_type
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.asciz "int" # DW_AT_name
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.byte 5 # DW_AT_encoding
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.byte 4 # DW_AT_byte_size
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.byte 0 # End Of Children Mark
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.Ldebug_info_end0:
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.section .debug_rnglists,"",@progbits
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.long .Ldebug_list_header_end0-.Ldebug_list_header_start0 # Length
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.Ldebug_list_header_start0:
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.short 5 # Version
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.byte 8 # Address size
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.byte 0 # Segment selector size
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.long 2 # Offset entry count
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.Lrnglists_table_base0:
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.long .Ldebug_ranges0-.Lrnglists_table_base0
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.long .Ldebug_ranges1-.Lrnglists_table_base0
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.Ldebug_ranges0:
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.byte 6 # DW_RLE_start_end
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.quad foo
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.quad .Lfoo_end
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.byte 6 # DW_RLE_start_end
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.quad foo.__part.1
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.quad .Lfoo.__part.1_end
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.byte 6 # DW_RLE_start_end
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.quad foo.__part.2
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.quad .Lfoo.__part.2_end
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.byte 6 # DW_RLE_start_end
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.quad foo.__part.3
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.quad .Lfoo.__part.3_end
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.byte 0 # DW_RLE_end_of_list
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.Ldebug_ranges1:
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.byte 6 # DW_RLE_start_end
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.quad baz
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.quad .Lbaz_end
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.byte 6 # DW_RLE_start_end
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.quad bar
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.quad .Lbar_end
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.byte 6 # DW_RLE_start_end
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.quad foo.__part.1
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.quad .Lfoo.__part.1_end
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.byte 6 # DW_RLE_start_end
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.quad foo.__part.2
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.quad .Lfoo.__part.2_end
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.byte 6 # DW_RLE_start_end
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.quad foo.__part.3
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.quad .Lfoo.__part.3_end
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.byte 6 # DW_RLE_start_end
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.quad foo
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.quad .Lfoo_end
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.byte 6 # DW_RLE_start_end
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.quad main
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.quad .Lmain_end
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.byte 0 # DW_RLE_end_of_list
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.Ldebug_list_header_end0:
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.section ".note.GNU-stack","",@progbits
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