Interpreting an assembler listing
The -l flag of the as command produces a listing of an assembler language file.
The -l flag of the as command produces a listing of an assembler language file.
Assume that a programmer wants to display the words "hello, world."
The C program would appear as follows:
main ( )
{
printf ("hello, world\n");
}
Assembling the hello.s file with the following command:
as -l hello.s
produces an output file named hello.lst. The complete assembler
listing for hello.lst is as follows:
hello.s V4.0 01/25/1994
File# Line# Mode Name Loc Ctr Object Code Source
0 1 | #############################
0 2 | # C source code
0 3 | #############################
0 4 | # hello()
0 5 | # {
0 6 | # printf("hello,world\n");
0 7 | # }
0 8 | #############################
0 9 | # Compile as follows:
0 10 | # cc -o helloworld hello.s
0 11 | #
0 12 | #############################
0 13 | .file "hello.s"
0 14 | #Static data entry in
0 15 | #T(able)O(f)C(ontents)
0 16 | .toc
0 17 | COM data 00000000 00000040 T.data: .tc data[tc],data[rw]
0 18 | .globl main[ds]
0 19 | #main[ds] contains definitions for
0 20 | #runtime linkage of function main
0 21 | .csect main[ds]
0 22 | COM main 00000000 00000000 .long .main[PR]
0 23 | COM main 00000004 00000050 .long TOC[tc0]
0 24 | COM main 00000008 00000000 .long 0
0 25 | #Function entry in
0 26 | #T(able)O(f)C(ontents)
0 27 | .toc
0 28 | COM .main 00000000 00000034 T.hello: .tc .main[tc],main[ds]
0 29 | .globl .main[PR]
0 30 |
0 31 | #Set routine stack variables
0 32 | #Values are specific to
0 33 | #the current routine and can
0 34 | #vary from routine to routine
0 35 | 00000020 .set argarea, 32
0 36 | 00000018 .set linkarea, 24
0 37 | 00000000 .set locstckarea, 0
0 38 | 00000001 .set ngprs, 1
0 39 | 00000000 .set nfprs, 0
0 40 | 0000003c .set szdsa, 8*nfprs+4*ngprs+linkarea+
argarea+locstckarea
0 41 |
0 42 | #Main routine
0 43 | .csect .main[PR]
0 44 |
0 45 |
0 46 | #PROLOG: Called Routines
0 47 | # Responsibilities
0 48 | #Get link reg.
0 49 | COM .main 00000000 7c0802a6 mflr 0
0 50 | #Not required to Get/Save CR
0 51 | #because current routine does
0 52 | #not alter it.
0 53 |
0 54 | #Not required to Save FPR's
0 55 | #14-31 because current routine
0 56 | #does not alter them.
0 57 |
0 58 | #Save GPR 31.
0 59 | COM .main 00000004 bfe1fffc stm 31, -8*nfprs-4*ngprs(1)
0 60 | #Save LR if non-leaf routine.
0 61 | COM .main 00000008 90010008 st 0, 8(1)
0 62 | #Decrement stack ptr and save
0 63 | #back chain.
0 64 | COM .main 0000000c 9421ffc4 stu 1, -szdsa(1)
0 65 |
0 66 |
0 67 | #Program body
0 68 | #Load static data address
0 69 | COM .main 00000010 81c20000 l 14,T.data(2)
0 70 | #Line 3, file hello.c
0 71 | #Load address of data string
0 72 | #from data addr.
0 73 | #This is a parameter to printf()
0 74 | COM .main 00000014 386e0000 cal 3,_helloworld(14)
0 75 | #Call printf function
0 76 | COM .main 00000018 4bffffe9 bl .printf[PR]
0 77 | COM .main 0000001c 4def7b82 cror 15, 15, 15
0 78 |
0 79 |
0 80 | #EPILOG: Return Sequence
0 81 | #Get saved LR.
0 82 | COM .main 00000020 80010044 l 0, szdsa+8(1)
0 83 |
0 84 | #Routine did not save CR.
0 85 | #Restore of CR not necessary.
0 86 |
0 87 | #Restore stack ptr
0 88 | COM .main 00000024 3021003c ai 1, 1, szdsa
0 89 | #Restore GPR 31.
0 90 | COM .main 00000028 bbe1fffc lm 31, -8*nfprs-4*ngprs(1)
0 91 |
0 92 | #Routine did not save FPR's.
0 93 | #Restore of FPR's not necessary.
0 94 |
0 95 | #Move return address
0 96 | #to Link Register.
0 97 | COM .main 0000002c 7c0803a6 mtlr0
0 98 | #Return to address
0 99 | #held in Link Register.
0 100 | COM .main 00000030 4e800021 brl
0 101 |
0 102 |
0 103 | #External variables
0 104 | .extern.printf[PR]
0 105 |
0 106 | ##############################
0 107 | #Data
0 108 | ##############################
0 109 | #String data placed in
0 110 | #static csect data[rw]
0 111 | .csect data[rw]
0 112 | .align2
0 113 | _helloworld:
0 114 | COM data 00000000 68656c6c .byte 0x68,0x65,0x6c,0x6c
0 115 | COM data 00000004 6f2c776f .byte 0x6f,0x2c,0x77,0x6f
0 116 | COM data 00000008 726c640a .byte 0x72,0x6c,0x64,0xa,0x0
| COM data 0000000c 00
The first line of the assembler listing gives two pieces of information:
- Name of the source file (in this case, hello.s)
- Date the listing file was created
The assembler listing contains several columns. The column headings are:
| Item | Description |
|---|---|
| File# | Lists the source file number. Files included with the M4 macro processor (-l option) are displayed by the number of the file in which the statement was found. |
| Line# | Refers to the line number of the assembler source code. |
| Mode | Indicates the current assembly mode for this instruction. |
| Name | Lists the name of the csect where this line of source code originates. |
| Loc Ctr | Lists the value contained in the assembler's location counter. The listing shows a location counter value only for assembler language instructions that generate object code. |
| Object Code | Shows the hexadecimal representation of the object code generated
by each line of the assembler program. Since each instruction is 32
bits, each line in the assembler listing shows a maximum of 4 bytes.
Any remaining bytes in a line of assembler source code are shown on
the following line or lines. Note: If pass two failed, the assembler
listing will not contain object code.
|
| Source | Lists the assembler source code for the program. A limit of 100 ASCII characters will be displayed per line. |
If the -s option flag is used on the command line, the assembler listing contains mnemonic cross-reference information.
If the assembly mode is in the PowerPC® category (com, ppc, or 601), one column heading is PowerPC®. This column contains the PowerPC® mnemonic for each instance where the POWER® family mnemonic is used in the source program. The any assembly mode does not belong to any category, but is treated as though in the PowerPC® category.
If the assembly mode is in the POWER® family category (pwr or pwr2), one column heading is POWER® family. This column contains the POWER® family mnemonic for each instance where the PowerPC® mnemonic is used in the source program.
The following assembler listing uses the com assembly mode.
The source program uses POWER® family mnemonics. The assembler listing
has a PowerPC® mnemonic cross-reference.
L_dfmt_1.s V4.0 01/26/1994
File# Line# Mode Name Loc Ctr Object Code PowerPC Source
0 1 |
0 2 | #%% -L
0 3 | machine "com"
0 4 | csect dfmt[PR]
0 5 | using data,5
0 6 | COM dfmt 00000000 8025000c lwz l1,d1 # 8025000c
0 7 | COM dfmt 00000004 b8c50018 lmw lm 6,d0 # b8650018
0 8 | COM dfmt 00000008 b0e50040 sth 7,d8 # b0e50040
0 9 | COM dfmt 0000000c 80230020 lwz l 1,0x20(3) # 80230020
0 10 | COM dfmt 00000010 30220003 addic ai 1,2,3 # 30220003
0 11 | COM dfmt 00000014 0cd78300 twi ti 6,23,-32000 # 0cd78300
0 12 | COM dfmt 00000018 2c070af0 cmpi 0,7,2800 # 2c070af0
0 13 | COM dfmt 0000001c 2c070af0 cmpi 0,0,7,2800 # 2c070af0
0 14 | COM dfmt 00000020 30220003 subic si 1,2,-3 # 30220003
0 15 | COM dfmt 00000024 34220003 subic. si. 1,2,-3 # 34220003
0 16 | COM dfmt 00000028 703e00ff andi. andil.30,1,0xFF # 703e00ff
0 17 | COM dfmt 0000002c 2b9401f4 cmpli 7,20,500 # 2b9401f4
0 18 | COM dfmt 00000030 0c2501a4 twlgti tlgti 5,420 # 0c2501a4
0 19 | COM dfmt 00000034 34220003 addic. ai. 1,2,3 # 34220003
0 20 | COM dfmt 00000038 2c9ff380 cmpi 1,31,-3200 # 2c9ff380
0 21 | COM dfmt 0000003c 281f0c80 cmpli 0,31,3200 # 281f0c80
0 22 | COM dfmt 00000040 8ba5000c lbz 29,d1 # 8ba5000c
0 23 | COM dfmt 00000044 85e5000c lwzu lu 15,d1 # 85e5000c
0 24 | COM dfmt 00000048 1df5fec0 mulli muli 15,21,-320 # 1df5fec0
0 25 | COM dfmt 0000004c 62af0140 ori oril 15,21,320 # 62af0140
0 26 | COM dfmt 00000050 91e5000c stw st 15,d1 # 91e5000c
0 27 | COM dfmt 00000054 bde5000c stmw stm 15,d1 # bde5000c
0 28 | COM dfmt 00000058 95e5000c stwu stu 15,d1 # 95e5000c
0 29 | COM dfmt 0000005c 69ef0960 xori xoril 15,15,2400 # 69ef0960
0 30 | COM dfmt 00000060 6d8c0960 xoris xoriu 12,12,2400 # 6d8c0960
0 31 | COM dfmt 00000064 3a9eff38 addi 20,30,-200 # 3a9eff38
0 32 |
0 33 | .csect also[RW]
0 34 | data:
0 35 | COM also 00000000 00000000 .long 0,0,0
| 00000004 ....
| COM also 00000008 00000000
0 36 | COM also 0000000c 00000003 d1:.long 3,4,5 # d1 = 0xC = 12
| COM also 00000010 00000004
| COM also 00000014 00000005
0 37 | COM also 00000018 00000068 d0: .long data # d0 = 0x18 = 24
0 38 | COM also 0000001c 00000000 data2: .space 36
| 00000020 ....
| COM also 0000003c 000000000
39 | COM also 00000040 000023e0 d8: .long 9184 # d8 = 0x40 = 64
0 40 | COM also 00000044 ffffffff d9: .long 0xFFFFFFFF # d9 = 0x44
0 41 | #
0 42 | # 0000 00000000 00000000 00000000 00000003
0 43 | # 0010 00000004 00000005 0000000C 00000000
0 44 | # 0020 00000000 00000000 00000000 00000000
0 45 | # 0030 000023E0
The following assembler listing uses the pwr assembly mode.
The source program uses PowerPC® mnemonics. The assembler listing
has a POWER® family mnemonic cross-reference.
L_dfmt_2.s V4.0 01/26/1994
File# Line# Mode Name Loc Ctr Object Code POWER Source
0 1 | #%% -L
0 2 | .machine "pwr"
0 3 | .csect dfmt[PR]
0 4 | .using data,5
0 5 | PWR dfmt 00000000 8025000c l lwz 1,d1
0 6 | PWR dfmt 00000004 b8650018 lm lmw 3,d0
0 7 | PWR dfmt 00000008 b0e50040 sth 7,d8
0 8 | PWR dfmt 0000000c 80230020 l lwz 1,0x20(3)
0 9 | PWR dfmt 00000010 30220003 ai addic 1,2,3
0 10 | PWR dfmt 00000014 0cd78300 ti twi 6,23,-32000
0 11 | PWR dfmt 00000018 2c070af0 cmpi 0,7,2800
0 12 | PWR dfmt 0000001c 2c070af0 cmpi 0,0,7,2800
0 13 | PWR dfmt 00000020 30220003 si subic 1,2,-3
0 14 | PWR dfmt 00000024 34220003 si. subic. 1,2,-3
0 15 | PWR dfmt 00000028 703e00ff andil. andi. 30,1,0xFF
0 16 | PWR dfmt 0000002c 2b9401f4 cmpli 7,20,500
0 17 | PWR dfmt 00000030 0c2501a4 tlgti twlgti 5,420
0 18 | PWR dfmt 00000034 34220003 ai. addic. 1,2,3
0 19 | PWR dfmt 00000038 2c9ff380 cmpi 1,31,-3200
0 20 | PWR dfmt 0000003c 281f0c80 cmpli 0,31,3200
0 21 | PWR dfmt 00000040 8ba5000c lbz 29,d1
0 22 | PWR dfmt 00000044 85e5000c lu lwzu 15,d1
0 23 | PWR dfmt 00000048 1df5fec0 muli mulli 15,21,-320
0 24 | PWR dfmt 0000004c 62af0140 oril ori 15,21,320
0 25 | PWR dfmt 00000050 91e5000c st stw 15,d1
0 26 | PWR dfmt 00000054 bde5000c stm stmw 15,d1
0 27 | PWR dfmt 00000058 95e5000c stu stwu 15,d1
0 28 | PWR dfmt 0000005c 69ef0960 xoril xori 15,15,2400
0 29 | PWR dfmt 00000060 6d8c0960 xoriu xoris 12,12,2400
0 30 | PWR dfmt 00000064 3a9eff38 addi 20,30,-200
0 31 |
0 32 |
0 33 | .csect also[RW]
0 34 | data:
0 35 | PWR also 00000000 00000000 .long 0,0,0
| 00000004 ....
| PWR also 00000008 00000000
0 36 | PWR also 0000000c 00000003 d1: long 3,4,5
| PWR also 00000010 00000004 # d1 = 0xc = 12
| PWR also 00000014 00000005
0 37 | PWR also 00000018 00000068 d0: long data # d0 = 0x18 = 24
0 38 | PWR also 0000001c 00000000 data2: space 36
| 00000020 ....
| PWR also 0000003c 00000000
0 39 | PWR also 00000040 000023e0 d8: long 9184 # d8 = 0x40 = 64
0 40 | PWR also 00000044 ffffffff d9: long 0xFFFFFFFF # d9 = 0x44
0 41 | #
0 42 | # 0000 00000000 00000000 00000000 00000003
0 43 | # 0010 00000004 00000005 0000000C 00000000
0 44 | # 0020 00000000 00000000 00000000 00000000
0 45 | # 0030 000023E0