; initialize global_variables_end C=:global_variables_end D=:global_variables 8C=D ; initialize static_memory_end C=:static_memory_end D=x500000 8C=D ; initialize labels_end C=:labels_end D=:labels 8C=D ; open input file J=:input_filename I=d0 syscall x2 J=A ?J<0:input_file_error ; open output file J=:output_filename I=x241 D=x1ed syscall x2 J=A ?J<0:output_file_error :second_pass_starting_point ; write ELF header J=d4 I=:ELF_header D=x78 syscall x1 :read_line ; increment line number D=:line_number C=8D C+=d1 8D=C ; use rbp to store line pointer R=:line :read_line_loop ; read 1 byte into rbp J=d3 I=R D=d1 syscall x0 D=A ?D=0:eof ; check if the character was a newline: C=1R D=xa ?C=D:read_line_loop_end ; check if the character was a tab: D=x9 ; if so, don't increment rbp ?C=D:read_line_loop ; check if the character was a semicolon: D='; ; if so, it's a comment ?C=D:handle_comment R+=d1 !:read_line_loop :handle_comment ; read out rest of line from file J=d3 I=R D=d1 syscall x0 D=A ?D=0:eof C=1R D=xa ; if we didn't reach the end of the line, keep going ?C!D:handle_comment !:read_line_loop_end :read_line_loop_end ; remove whitespace (specifically, ' ' characters) at end of line I=R :remove_terminal_whitespace_loop I-=d1 C=1I D=x20 ?C!D:remove_terminal_whitespace_loop_end ; replace ' ' with a newline D=xa 1I=D !:remove_terminal_whitespace_loop :remove_terminal_whitespace_loop_end ; check if this is a blank line C=:line D=1C C=xa ?C=D:read_line C=': ?C=D:handle_label_definition I=:line J=:"global" C=x20 call :string= D=A ?D!0:handle_global I=:line J=:"local" C=x20 call :string= D=A ?D!0:handle_local ; arguments are treated the same as local variables I=:line J=:"argument" C=x20 call :string= D=A ?D!0:handle_local I=:line J=:"return" C=x20 call :string= D=A ?D!0:handle_return ; set delimiter to newline C=xa I=:line J=:"function" call :string= D=A ?D!0:handle_function !:read_line :eof C=:second_pass D=1C ?D!0:exit_success ; set 2nd pass to 1 1C=d1 ; seek both files back to start J=d3 I=d0 D=d0 syscall x8 J=d4 I=d0 D=d0 syscall x8 !:second_pass_starting_point :exit_success J=d0 syscall x3c align :local_variable_name reserve d8 :handle_local R=I ; emit sub rsp, 8 J=d4 I=:sub_rsp_8 D=d7 syscall x1 I=R ; skip ' ' I+=d1 ; store away pointer to variable name C=:local_variable_name 8C=I ; check if already defined J=:local_variables call :ident_lookup C=A ?C!0:local_redeclaration C=:local_variable_name I=8C J=:local_variables_end J=8J call :ident_copy ; increase stack_end, store it in J C=:stack_end D=4C D+=d8 4C=D 4J=D J+=d4 ; store null terminator 1J=0 ; update :local_variables_end I=:local_variables_end 8I=J ; read the next line !:read_line :sub_rsp_8 x48 x81 xec x08 x00 x00 x00 align :global_start reserve d8 :global_variable_name reserve d8 :handle_global ; ignore if this is the second pass C=:second_pass C=1C ?C!0:read_line ; skip ' ' I+=d1 ; store away pointer to variable name C=:global_variable_name 8C=I ; check if already defined J=:global_variables call :ident_lookup C=A ?C!0:global_redeclaration C=:global_variable_name I=8C J=:global_variables_end J=8J call :ident_copy ; store address D=:static_memory_end C=4D 4J=C J+=d4 ; increase static_memory_end C+=d8 4D=C ; store null terminator 1J=0 ; update :global_variables_end I=:global_variables_end 8I=J ; go read the next line !:read_line :handle_function ; emit prologue J=d4 I=:function_prologue D=d14 syscall x1 ; reset local variable table D=:local_variables 1D=0 C=:local_variables_end 8C=D ; reset stack_end D=:stack_end 4D=0 ; go read the next line !:read_line :function_prologue ; sub rsp, 8 x48 x81 xec x08 x00 x00 x00 ; mov [rsp], rbp x48 x89 x2c x24 ; mov rbp, rsp R=S ; total length: 7 + 4 + 3 = 14 bytes :function_epilogue ; mov rsp, rbp S=R ; mov rbp, [rsp] x48 x8b x2c x24 ; add rsp, 8 x48 x81 xc4 x08 x00 x00 x00 ; ret return ; total length = 15 bytes :handle_label_definition ; ignore if this is the second pass C=:second_pass C=1C ?C!0:read_line ; make sure label only has identifier characters I=:line I+=d1 :label_checking_loop C=1I D=xa ?C=D:label_checking_loop_end I+=d1 B=C call :isident D=A ?D!0:label_checking_loop !:bad_label :label_checking_loop_end I=:line I+=d1 J=:global_variables call :ident_lookup C=A ?C!0:label_redefinition J=:labels_end J=8J I=:line I+=d1 call :ident_copy R=J ; figure out where in the file we are J=d4 I=d0 D=d1 syscall x8 C=A C+=x400000 J=R ; store address 4J=C J+=d4 ; update labels_end C=:labels_end 8C=J ; read the next line !:read_line :handle_return I=:line ; "return " is 7 chars long I+=d7 call :set_rax_to_term J=d4 I=:function_epilogue D=d15 syscall x1 ; go read the next line !:read_line :mov_rsp_rbp S=R :ret return ; copy the newline-terminated identifier from rsi to rdi :ident_copy C=1I B=C call :isident D=A ?D=0:bad_identifier :ident_loop C=1I 1J=C I+=d1 J+=d1 D=xa ?C=D:ident_loop_end B=C call :isident D=A ?D=0:bad_identifier !:ident_loop :ident_loop_end return align :ident_lookup_i reserve d8 ; look up identifier rsi in list rdi ; returns address of whatever's right after the identifier in the list, or 0 if not found :ident_lookup C=:ident_lookup_i 8C=I :ident_lookup_loop ; check if reached the end of the table C=1J ?C=0:return_0 I=:ident_lookup_i I=8I call :ident= C=A ; move past terminator of identifier in table :ident_finish_loop D=1J J+=d1 A=xa ?D!A:ident_finish_loop ; check if this was it ?C!0:return_J ; nope. keep going ; skip over address: J+=d4 !:ident_lookup_loop ; can the character in rbx appear in an identifier? :isident A='0 ?BA:return_1 A='_ ?B=A:return_1 !:return_0 ; set rax to the term in rsi :set_rax_to_term R=I C=1I D='' ?C=D:term_char C=1I D=d58 ?CD:hex_number_loop_end ; one of the digits a-f D=xffffffffffffffa9 !:hex_number_digit :hex_number_0123456789 D=xffffffffffffffd0 :hex_number_digit C+=D ; shift left by 4 R<=d4 ; add digit R+=C I+=d1 !:hex_number_loop :hex_number_loop_end !:term_number_output :term_number_output ; we now have the *unsigned* number in rbp. first, take the sign into consideration C=:number_is_negative D=1C ?D=0:number_not_negative ; R = -R C=R R=d0 R-=C :number_not_negative I=R !:set_rax_to_immediate ; set to the immediate in rsi. :set_rax_to_immediate C=:imm64 8C=I ; write prefix J=d4 D=d2 I=:mov_rax_imm64_prefix syscall x1 ; write immediate J=d4 D=d8 I=:imm64 syscall x1 return align :rax2term_addr reserve d4 :mov_ebx_imm32_prefix xbb :mov_rax_imm64_prefix x48 xb8 align :imm64 reserve d8 :mov_rax_[rbx] x48 x8b x03 ; prefix for mov rax, [rbp+IMM32] :load_rbp_offset_prefix x48 x8b x85 :input_filename str in04b x0 :output_filename str out04b x0 :input_file_error B=:input_file_error_message !:general_error :input_file_error_message str Couldn't open input file. xa x0 :output_file_error B=:output_file_error_message !:general_error :output_file_error_message str Couldn't open output file. xa x0 :bad_identifier B=:bad_identifier_error_message !:program_error :bad_identifier_error_message str Bad identifier. xa x0 :bad_label B=:bad_label_error_message !:program_error :bad_label_error_message str Bad label. xa x0 :bad_term B=:bad_term_error_message !:program_error :bad_term_error_message str Bad term. xa x0 :label_redefinition B=:label_redefinition_error_message !:program_error :label_redefinition_error_message str Label redefinition. xa x0 :global_redeclaration B=:global_redeclaration_error_message !:program_error :global_redeclaration_error_message str Global variable declared twice. xa x0 :local_redeclaration B=:local_redeclaration_error_message !:program_error :local_redeclaration_error_message str Local variable declared twice. xa x0 :general_error call :eputs J=d1 syscall x3c :program_error R=B B=:"Line" call :eputs D=:line_number D=8D B=D call :eputn B=:line_number_separator call :eputs B=R call :eputs J=d1 syscall x3c :"Line" str Line x20 x0 :line_number_separator str : x20 x0 :strlen I=B D=B :strlen_loop C=1I ?C=0:strlen_ret I+=d1 !:strlen_loop :strlen_ret I-=D A=I return ; check if strings in rdi and rsi are equal, up to terminator in rcx :string= D=1I A=1J ?D!A:return_0 ?D=C:return_1 I+=d1 J+=d1 !:string= ; check if strings in rdi and rsi are equal, up to the first non-identifier character :ident= D=1I B=D call :isident ; I ended ?A=0:ident=_I_end D=1J B=D call :isident ; J ended, but I didn't ?A=0:return_0 ; we haven't reached the end of either D=1I A=1J ?D!A:return_0 I+=d1 J+=d1 !:ident= :ident=_I_end D=1J B=D call :isident ; check if J also ended ?A=0:return_1 ; J didn't end !:return_0 :return_0 A=d0 return :return_1 A=d1 return :return_2 A=d2 return :return_3 A=d3 return :return_4 A=d4 return :return_5 A=d5 return :return_6 A=d6 return :return_7 A=d7 return :return_8 A=d8 return :return_J A=J return ; write the character in rbx to the file in rdi. :fputc C=B I=S I-=d1 1I=C D=d1 syscall x1 return ; write the string in rbx to stderr :eputs J=B call :strlen D=A I=J J=d2 syscall x1 return ; write rbx in decimal to stderr :eputn I=B J=S J-=d1 :eputn_loop D=d0 ; divide by 10 B=d10 A=I div ; quotient is new number I=A ; add remainder to string D+='0 1J=D J-=d1 ?I!0:eputn_loop D=S D-=J I=J J=d2 syscall x1 return ; copy rdx bytes from rsi to rdi. ; this copies from the left: if you're doing an overlapped copy, rsi should be greater than rdi :memcpy ?D=0:return_0 A=1I 1J=A I+=d1 J+=d1 D-=d1 !:memcpy ; copy from rdi to rsi, until byte cl is reached :memccpy D=1I 1J=D I+=d1 J+=d1 ?D!C:memccpy return :"global" str global x20 :"argument" str argument x20 :"local" str local x20 :"return" str return x20 :"function" str function xa ; put a 0 byte before the line (this is important for removing whitespace at the end of the line, ; specifically, we don't want this to be a space character) x0 :line reserve d1000 align :global_variables_end reserve d8 :static_memory_end reserve d8 :local_variables_end reserve d8 :stack_end reserve d8 :labels_end reserve d8 :line_number reserve d8 :global_variables reserve d50000 :local_variables reserve d20000 :labels reserve d200000 :second_pass reserve d1 :ELF_header x7f x45 x4c x46 x02 x01 x01 reserve d9 x02 x00 x3e x00 x01 x00 x00 x00 x78 x00 x40 x00 x00 x00 x00 x00 x40 x00 x00 x00 x00 x00 x00 x00 reserve d12 x40 x00 x38 x00 x01 x00 x00 x00 x00 x00 x00 x00 x01 x00 x00 x00 x07 x00 x00 x00 x78 x00 x00 x00 x00 x00 x00 x00 x78 x00 x40 x00 x00 x00 x00 x00 reserve d8 x00 x00 x20 x00 x00 x00 x00 x00 x00 x00 x20 x00 x00 x00 x00 x00 x00 x10 x00 x00 x00 x00 x00 x00 ; NOTE: we shouldn't end the file with a reserve; we don't handle that properly