8ec4db5e17
**Context** Follow-up to [#147460](https://github.com/llvm/llvm-project/pull/147460), which added the ability to surface register-resident variable locations. This PR moves the annotation logic out of `Instruction::Dump()` and into `Disassembler::PrintInstructions()`, and adds lightweight state tracking so we only print changes at range starts and when variables go out of scope. --- ## What this does While iterating the instructions for a function, we maintain a “live variable map” keyed by `lldb::user_id_t` (the `Variable`’s ID) to remember each variable’s last emitted location string. For each instruction: - **New (or newly visible) variable** → print `name = <location>` once at the start of its DWARF location range, cache it. - **Location changed** (e.g., DWARF range switched to a different register/const) → print the updated mapping. - **Out of scope** (was tracked previously but not found for the current PC) → print `name = <undef>` and drop it. This produces **concise, stateful annotations** that highlight variable lifetime transitions without spamming every line. --- ## Why in `PrintInstructions()`? - Keeps `Instruction` stateless and avoids changing the `Instruction::Dump()` virtual API. - Makes it straightforward to diff state across instructions (`prev → current`) inside the single driver loop. --- ## How it works (high-level) 1. For the current PC, get in-scope variables via `StackFrame::GetInScopeVariableList(/*get_parent=*/true)`. 2. For each `Variable`, query `DWARFExpressionList::GetExpressionEntryAtAddress(func_load_addr, current_pc)` (added in #144238). 3. If the entry exists, call `DumpLocation(..., eDescriptionLevelBrief, abi)` to get a short, ABI-aware location string (e.g., `DW_OP_reg3 RBX → RBX`). 4. Compare against the last emitted location in the live map: - If not present → emit `name = <location>` and record it. - If different → emit updated mapping and record it. 5. After processing current in-scope variables, compute the set difference vs. the previous map and emit `name = <undef>` for any that disappeared. Internally: - We respect file↔load address translation already provided by `DWARFExpressionList`. - We reuse the ABI to map LLVM register numbers to arch register names. --- ## Example output (x86_64, simplified) ``` -> 0x55c6f5f6a140 <+0>: cmpl $0x2, %edi ; argc = RDI, argv = RSI 0x55c6f5f6a143 <+3>: jl 0x55c6f5f6a176 ; <+54> at d_original_example.c:6:3 0x55c6f5f6a145 <+5>: pushq %r15 0x55c6f5f6a147 <+7>: pushq %r14 0x55c6f5f6a149 <+9>: pushq %rbx 0x55c6f5f6a14a <+10>: movq %rsi, %rbx 0x55c6f5f6a14d <+13>: movl %edi, %r14d 0x55c6f5f6a150 <+16>: movl $0x1, %r15d ; argc = R14 0x55c6f5f6a156 <+22>: nopw %cs:(%rax,%rax) ; i = R15, argv = RBX 0x55c6f5f6a160 <+32>: movq (%rbx,%r15,8), %rdi 0x55c6f5f6a164 <+36>: callq 0x55c6f5f6a030 ; symbol stub for: puts 0x55c6f5f6a169 <+41>: incq %r15 0x55c6f5f6a16c <+44>: cmpq %r15, %r14 0x55c6f5f6a16f <+47>: jne 0x55c6f5f6a160 ; <+32> at d_original_example.c:5:10 0x55c6f5f6a171 <+49>: popq %rbx ; i = <undef> 0x55c6f5f6a172 <+50>: popq %r14 ; argv = RSI 0x55c6f5f6a174 <+52>: popq %r15 ; argc = RDI 0x55c6f5f6a176 <+54>: xorl %eax, %eax 0x55c6f5f6a178 <+56>: retq ``` Only transitions are shown: the start of a location, changes, and end-of-lifetime. --- ## Scope & limitations (by design) - Handles **simple locations** first (registers, const-in-register cases surfaced by `DumpLocation`). - **Memory/composite locations** are out of scope for this PR. - Annotations appear **only at range boundaries** (start/change/end) to minimize noise. - Output is **target-independent**; register names come from the target ABI. ## Implementation notes - All annotation printing now happens in `Disassembler::PrintInstructions()`. - Uses `std::unordered_map<lldb::user_id_t, std::string>` as the live map. - No persistent state across calls; the map is rebuilt while walking instruction by instruction. - **No changes** to the `Instruction` interface. --- ## Requested feedback - Placement and wording of the `<undef>` marker. - Whether we should optionally gate this behind a setting (currently always on when disassembling with an `ExecutionContext`). - Preference for immediate inclusion of tests vs. follow-up patch. --- Thanks for reviewing! Happy to adjust behavior/format based on feedback. --------- Co-authored-by: Jonas Devlieghere <jonas@devlieghere.com> Co-authored-by: Adrian Prantl <adrian.prantl@gmail.com>
290 lines
14 KiB
ArmAsm
290 lines
14 KiB
ArmAsm
/* Original C (for context):
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* __attribute__((noinline))
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* int main(int argc, char **argv) {
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* int i = argc; // i in a reg (DW_OP_regN)
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* asm volatile("" :: "r"(i)); // keep i live here
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* i = 0; // i becomes const 0 (DW_OP_constu 0, stack_value)
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* asm volatile("" :: "r"(i)); // keep the const range materialized
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* return 0; // i ends -> <undef> after its range
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* }
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*/
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.file "seed_reg_const_undef.c"
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.text
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.globl main # -- Begin function main
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.p2align 4
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.type main,@function
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main: # @main
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.Lfunc_begin0:
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.file 0 "." "seed_reg_const_undef.c" md5 0x5e8dbf089d1bd72d395da802210b3138
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.loc 0 3 0 # seed_reg_const_undef.c:3:0
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.cfi_startproc
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# %bb.0: # %entry
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#DEBUG_VALUE: main:argc <- $edi
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#DEBUG_VALUE: main:argv <- $rsi
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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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.Ltmp0:
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#DEBUG_VALUE: main:i <- $edi
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.loc 0 5 3 prologue_end # seed_reg_const_undef.c:5:3
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#APP
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#NO_APP
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.Ltmp1:
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#DEBUG_VALUE: main:i <- 0
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.loc 0 7 3 # seed_reg_const_undef.c:7:3
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xorl %eax, %eax
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#APP
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#NO_APP
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.loc 0 8 3 # seed_reg_const_undef.c:8:3
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xorl %eax, %eax
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.loc 0 8 3 epilogue_begin is_stmt 0 # seed_reg_const_undef.c:8:3
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popq %rbp
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.cfi_def_cfa %rsp, 8
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retq
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.Ltmp2:
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.Lfunc_end0:
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.size main, .Lfunc_end0-main
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.cfi_endproc
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# -- End function
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.section .debug_loclists,"",@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 1 # Offset entry count
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.Lloclists_table_base0:
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.long .Ldebug_loc0-.Lloclists_table_base0
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.Ldebug_loc0:
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.byte 4 # DW_LLE_offset_pair
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.uleb128 .Ltmp0-.Lfunc_begin0 # starting offset
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.uleb128 .Ltmp1-.Lfunc_begin0 # ending offset
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.byte 1 # Loc expr size
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.byte 85 # super-register DW_OP_reg5
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.byte 4 # DW_LLE_offset_pair
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.uleb128 .Ltmp1-.Lfunc_begin0 # starting offset
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.uleb128 .Lfunc_end0-.Lfunc_begin0 # ending offset
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.byte 3 # Loc expr size
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.byte 17 # DW_OP_consts
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.byte 0 # 0
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.byte 159 # DW_OP_stack_value
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.byte 0 # DW_LLE_end_of_list
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.Ldebug_list_header_end0:
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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 37 # DW_FORM_strx1
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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 37 # DW_FORM_strx1
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.byte 114 # DW_AT_str_offsets_base
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.byte 23 # DW_FORM_sec_offset
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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 37 # DW_FORM_strx1
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.byte 17 # DW_AT_low_pc
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.byte 27 # DW_FORM_addrx
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.byte 18 # DW_AT_high_pc
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.byte 6 # DW_FORM_data4
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.byte 115 # DW_AT_addr_base
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.byte 23 # DW_FORM_sec_offset
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.ascii "\214\001" # DW_AT_loclists_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 1 # DW_CHILDREN_yes
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.byte 17 # DW_AT_low_pc
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.byte 27 # DW_FORM_addrx
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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 122 # DW_AT_call_all_calls
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.byte 25 # DW_FORM_flag_present
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.byte 3 # DW_AT_name
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.byte 37 # DW_FORM_strx1
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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 37 # DW_FORM_strx1
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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 52 # DW_TAG_variable
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.byte 0 # DW_CHILDREN_no
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.byte 2 # DW_AT_location
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.byte 34 # DW_FORM_loclistx
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.byte 3 # DW_AT_name
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.byte 37 # DW_FORM_strx1
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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 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 37 # DW_FORM_strx1
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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 6 # 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 .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] 0xc:0x5b DW_TAG_compile_unit
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.byte 0 # DW_AT_producer
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.short 29 # DW_AT_language
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.byte 1 # DW_AT_name
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.long .Lstr_offsets_base0 # DW_AT_str_offsets_base
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.long .Lline_table_start0 # DW_AT_stmt_list
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.byte 2 # DW_AT_comp_dir
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.byte 0 # DW_AT_low_pc
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.long .Lfunc_end0-.Lfunc_begin0 # DW_AT_high_pc
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.long .Laddr_table_base0 # DW_AT_addr_base
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.long .Lloclists_table_base0 # DW_AT_loclists_base
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.byte 2 # Abbrev [2] 0x27:0x2d DW_TAG_subprogram
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.byte 0 # DW_AT_low_pc
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.long .Lfunc_end0-.Lfunc_begin0 # DW_AT_high_pc
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.byte 1 # DW_AT_frame_base
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.byte 86
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# DW_AT_call_all_calls
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.byte 3 # DW_AT_name
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.byte 0 # DW_AT_decl_file
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.byte 3 # DW_AT_decl_line
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# DW_AT_prototyped
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.long 84 # DW_AT_type
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# DW_AT_external
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.byte 3 # Abbrev [3] 0x36:0xa DW_TAG_formal_parameter
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.byte 1 # DW_AT_location
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.byte 85
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.byte 5 # DW_AT_name
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.byte 0 # DW_AT_decl_file
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.byte 3 # DW_AT_decl_line
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.long 84 # DW_AT_type
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.byte 3 # Abbrev [3] 0x40:0xa DW_TAG_formal_parameter
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.byte 1 # DW_AT_location
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.byte 84
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.byte 6 # DW_AT_name
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.byte 0 # DW_AT_decl_file
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.byte 3 # DW_AT_decl_line
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.long 88 # DW_AT_type
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.byte 4 # Abbrev [4] 0x4a:0x9 DW_TAG_variable
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.byte 0 # DW_AT_location
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.byte 8 # DW_AT_name
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.byte 0 # DW_AT_decl_file
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.byte 4 # DW_AT_decl_line
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.long 84 # DW_AT_type
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.byte 0 # End Of Children Mark
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.byte 5 # Abbrev [5] 0x54:0x4 DW_TAG_base_type
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.byte 4 # 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 6 # Abbrev [6] 0x58:0x5 DW_TAG_pointer_type
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.long 93 # DW_AT_type
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.byte 6 # Abbrev [6] 0x5d:0x5 DW_TAG_pointer_type
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.long 98 # DW_AT_type
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.byte 5 # Abbrev [5] 0x62:0x4 DW_TAG_base_type
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.byte 7 # 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 .debug_str_offsets,"",@progbits
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.long 40 # Length of String Offsets Set
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.short 5
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.short 0
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.Lstr_offsets_base0:
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.section .debug_str,"MS",@progbits,1
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.Linfo_string0:
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.asciz "clang version 22.0.0git (https://github.com/UltimateForce21/llvm-project.git 79c0a9e1e7da0f727c41d27c9c6ff8a28bb7d06f)" # string offset=0
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.Linfo_string1:
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.asciz "seed_reg_const_undef.c" # string offset=119
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.Linfo_string2:
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.asciz "." # string offset=142
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.Linfo_string3:
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.asciz "main" # string offset=144
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.Linfo_string4:
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.asciz "int" # string offset=149
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.Linfo_string5:
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.asciz "argc" # string offset=153
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.Linfo_string6:
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.asciz "argv" # string offset=158
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.Linfo_string7:
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.asciz "char" # string offset=163
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.Linfo_string8:
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.asciz "i" # string offset=168
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.section .debug_str_offsets,"",@progbits
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.long .Linfo_string0
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.long .Linfo_string1
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.long .Linfo_string2
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.long .Linfo_string3
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.long .Linfo_string4
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.long .Linfo_string5
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.long .Linfo_string6
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.long .Linfo_string7
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.long .Linfo_string8
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.section .debug_addr,"",@progbits
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.long .Ldebug_addr_end0-.Ldebug_addr_start0 # Length of contribution
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.Ldebug_addr_start0:
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.short 5 # DWARF version number
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.byte 8 # Address size
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.byte 0 # Segment selector size
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.Laddr_table_base0:
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.quad .Lfunc_begin0
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.Ldebug_addr_end0:
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.ident "clang version 22.0.0git (https://github.com/UltimateForce21/llvm-project.git 79c0a9e1e7da0f727c41d27c9c6ff8a28bb7d06f)"
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.section ".note.GNU-stack","",@progbits
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.addrsig
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.section .debug_line,"",@progbits
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.Lline_table_start0:
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