5d088ba304
[lldb] Track CFA pointer metadata in StackID
In this commit:
9c8e71644227 [lldb] Make StackID call Fix{Code,Data} pointers (#152796)
We made StackID keep track of the CFA without any pointer metadata in
it. This is necessary when comparing two StackIDs to determine which one
is "younger".
However, the CFA inside StackIDs is also used in other contexts through
the method StackID::GetCallFrameAddress. One notable case is
DWARFExpression: the computation of `DW_OP_call_frame_address` is done
using StackID. This feeds into many other places, e.g. expression
evaluation may require the address of a variable that is computed from
the CFA; to access the variable without faulting, we may need to
preserve the pointer metadata. As such, StackID must be able to provide
both versions of the CFA.
In the spirit of allowing consumers of pointers to decide what to do
with pointer metadata, this patch changes StackID to store both versions
of the cfa pointer. Two getter methods are provided, and all call sites
except DWARFExpression preserve their existing behavior (stripped
pointer). Other alternatives were considered:
* Just store the raw pointer. This would require changing the
comparisong operator `<` to also receive a Process, as the comparison
requires stripped pointers. It wasn't clear if all call-sites had a
non-null process, whereas we know we have a process when creating a
StackID.
* Store a weak pointer to the process inside the class, and then strip
metadata as needed. This would require a `weak_ptr::lock` in many
operations of LLDB, and it felt wasteful. It also prevents stripping
of the pointer if the process has gone away.
This patch also changes RegisterContextUnwind::ReadFrameAddress, which
is the method computing the CFA fed into StackID, to also preserve the
signature pointers.
227 lines
10 KiB
ArmAsm
227 lines
10 KiB
ArmAsm
; The assembly below corresponds to this program:
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; __attribute__((nodebug))
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; int foo() {
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; return 10;
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; }
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; int main(int argc, char **argv) {
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; foo();
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; return 0;
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; }
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;
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; The assembly was edited in two places (search for "EDIT"):
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; 1. A "orr x29, x29, #0x1000000000000000" instruction was added in foo. This
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; effectively changes the CFA value of the frame above foo (i.e. main).
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; 2. In main, the DWARF location of `argv` was changed to DW_AT_call_frame_cfa.
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;
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; This allows us to stop in foo, go to frame 1 (main) and do `v &argv`,
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; obtaining the result of evaluating DW_AT_call_frame_cfa.
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.section __TEXT,__text,regular,pure_instructions
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.globl _foo ; -- Begin function foo
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.p2align 2
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_foo: ; @foo
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Lfunc_begin0:
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.cfi_startproc
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orr x29, x29, #0x1000000000000000 ; EDIT: Set top byte of fp.
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stp x29, x30, [sp, #-16]! ; 16-byte Folded Spill
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mov x29, sp
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.cfi_def_cfa w29, 16
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.cfi_offset w30, -8
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.cfi_offset w29, -16
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mov w0, #10 ; =0xa
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ldp x29, x30, [sp], #16 ; 16-byte Folded Reload
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ret
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Lfunc_end0:
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.cfi_endproc
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; -- End function
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.globl _main ; -- Begin function main
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.p2align 2
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_main: ; @main
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Lfunc_begin1:
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.file 1 "/test" "test.c"
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.loc 1 6 0 ; test.c:6:0
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.cfi_startproc
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sub sp, sp, #48
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stp x29, x30, [sp, #32] ; 16-byte Folded Spill
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add x29, sp, #32
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.cfi_def_cfa w29, 16
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.cfi_offset w30, -8
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.cfi_offset w29, -16
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mov w8, #0 ; =0x0
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str w8, [sp, #12] ; 4-byte Folded Spill
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stur wzr, [x29, #-4]
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stur w0, [x29, #-8]
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str x1, [sp, #16]
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Ltmp0:
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bl _foo
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ldr w0, [sp, #12] ; 4-byte Folded Reload
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ldp x29, x30, [sp, #32] ; 16-byte Folded Reload
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add sp, sp, #48
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ret
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Ltmp1:
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Lfunc_end1:
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.cfi_endproc
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; -- End function
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.section __DWARF,__debug_abbrev,regular,debug
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Lsection_abbrev:
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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 14 ; DW_FORM_strp
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.byte 19 ; DW_AT_language
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.byte 5 ; DW_FORM_data2
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.byte 3 ; DW_AT_name
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.byte 14 ; DW_FORM_strp
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.ascii "\202|" ; DW_AT_LLVM_sysroot
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.byte 14 ; DW_FORM_strp
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.ascii "\357\177" ; DW_AT_APPLE_sdk
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.byte 14 ; DW_FORM_strp
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.byte 16 ; DW_AT_stmt_list
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.byte 23 ; DW_FORM_sec_offset
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.byte 27 ; DW_AT_comp_dir
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.byte 14 ; DW_FORM_strp
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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 6 ; DW_FORM_data4
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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 1 ; DW_CHILDREN_yes
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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 6 ; DW_FORM_data4
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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 14 ; DW_FORM_strp
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.byte 58 ; DW_AT_decl_file
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.byte 11 ; DW_FORM_data1
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.byte 59 ; DW_AT_decl_line
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.byte 11 ; DW_FORM_data1
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.byte 39 ; DW_AT_prototyped
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.byte 25 ; DW_FORM_flag_present
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.byte 73 ; DW_AT_type
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.byte 19 ; DW_FORM_ref4
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.byte 63 ; DW_AT_external
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.byte 25 ; DW_FORM_flag_present
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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 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 14 ; DW_FORM_strp
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.byte 58 ; DW_AT_decl_file
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.byte 11 ; DW_FORM_data1
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.byte 59 ; DW_AT_decl_line
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.byte 11 ; DW_FORM_data1
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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 4 ; 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 14 ; DW_FORM_strp
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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 5 ; Abbreviation Code
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.byte 15 ; DW_TAG_pointer_type
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.byte 0 ; DW_CHILDREN_no
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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 0 ; EOM(3)
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.section __DWARF,__debug_info,regular,debug
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Lsection_info:
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Lcu_begin0:
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.set Lset0, Ldebug_info_end0-Ldebug_info_start0 ; Length of Unit
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.long Lset0
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Ldebug_info_start0:
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.short 4 ; DWARF version number
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.set Lset1, Lsection_abbrev-Lsection_abbrev ; Offset Into Abbrev. Section
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.long Lset1
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.byte 8 ; Address Size (in bytes)
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.byte 1 ; Abbrev [1] 0xb:0x76 DW_TAG_compile_unit
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.long 0 ; DW_AT_producer
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.short 12 ; DW_AT_language
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.long 47 ; DW_AT_name
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.long 54 ; DW_AT_LLVM_sysroot
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.long 165 ; DW_AT_APPLE_sdk
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.set Lset2, Lline_table_start0-Lsection_line ; DW_AT_stmt_list
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.long Lset2
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.long 180 ; DW_AT_comp_dir
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.quad Lfunc_begin1 ; DW_AT_low_pc
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.set Lset3, Lfunc_end1-Lfunc_begin1 ; DW_AT_high_pc
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.long Lset3
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.byte 2 ; Abbrev [2] 0x32:0x36 DW_TAG_subprogram
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.quad Lfunc_begin1 ; DW_AT_low_pc
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.set Lset4, Lfunc_end1-Lfunc_begin1 ; DW_AT_high_pc
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.long Lset4
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.byte 1 ; DW_AT_frame_base
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.byte 109
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.long 247 ; DW_AT_name
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.byte 1 ; DW_AT_decl_file
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.byte 6 ; DW_AT_decl_line
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; DW_AT_prototyped
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.long 107 ; DW_AT_type
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; DW_AT_external
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.byte 3 ; Abbrev [3] 0x4b:0xe 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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.long 256 ; DW_AT_name
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.byte 1 ; DW_AT_decl_file
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.byte 6 ; DW_AT_decl_line
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.long 103 ; DW_AT_type
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.byte 3 ; Abbrev [3] 0x59:0xe DW_TAG_formal_parameter
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.byte 1 ; DW_AT_location
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.byte 0x9c ; EDIT: DW_AT_call_frame_cfa
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.long 261 ; DW_AT_name
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.byte 1 ; DW_AT_decl_file
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.byte 6 ; DW_AT_decl_line
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.long 110 ; DW_AT_type
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.byte 0 ; End Of Children Mark
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.byte 4 ; Abbrev [4] 0x68:0x7 DW_TAG_base_type
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.long 252 ; 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 5 ; Abbrev [5] 0x6f:0x5 DW_TAG_pointer_type
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.long 115 ; DW_AT_type
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.byte 5 ; Abbrev [5] 0x74:0x5 DW_TAG_pointer_type
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.long 120 ; DW_AT_type
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.byte 4 ; Abbrev [4] 0x79:0x7 DW_TAG_base_type
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.long 266 ; DW_AT_name
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.byte 6 ; DW_AT_encoding
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.byte 1 ; 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 __DWARF,__debug_str,regular,debug
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Linfo_string:
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.asciz "Apple clang " ; string offset=0
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.asciz "test.c" ; string offset=47
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.asciz "/Applications/Xcode..........................................................................................." ; string offset=54
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.asciz ".............." ; string offset=165
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.asciz "......................................................../llvm_src1" ; string offset=180
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.asciz "main" ; string offset=247
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.asciz "int" ; string offset=252
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.asciz "argc" ; string offset=256
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.asciz "argv" ; string offset=261
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.asciz "char" ; string offset=266
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.subsections_via_symbols
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.section __DWARF,__debug_line,regular,debug
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Lsection_line:
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Lline_table_start0:
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