03.アセンブラーの使い方とアセンブリー・リストの見方 – 「メインフレーム・コンピューター」で遊ぼう

下記のサンプル・ソースコードをアセンブルした際のアセンブリー・リストに、簡単な見方を示した資料を作りました。アセンブラー・プログラムは他の言語と違って、区分データセットに格納したソース・コードのメンバー内容だけを見てもデバッグできません。構文エラーであっても、実行時の異常終了であっても必ずアセンブリー・リストを見てデバッグする癖を付けることを勧めます。異常終了時や期待した実行結果にならない時、ダンプ・リストを解析してのデバッグであれば機械語コードと照らし合わせる場面も生じます。正しく動いてデバッグの必要が無い場合でも、自分が書いたソース命令がどのような機械語コードに変換されたかをアセンブリー・リストで見ていれば、ダンプ解析に必要なスキルも身に付けやすくなります。

HLASMアセンブリー・リストの見方（pdf）

***********************************************************************
*        z/Architecture & z/OS Assembler Learning Program             *
*        =====================================================        *
*        Program member name GO is fixed. That is created by          *
*        ASMCL/ASMCLG HLASM Standard Procedure.                       *
***********************************************************************
*                                  *----------------------------------*
*                                  *  HOUSE-KEEPING PROCEDURE         *
*                                  *----------------------------------*
MAINPROG CSECT ,                        DEFINE CONTROL SECTION
         USING *,R12                    DEFINE OUR BASE REGISTER=12
         SAVE  (14,12),,                SAVE CALLER REGISTERS          +
               'MAINPROG(ALP:z/OS Assembler Learning Program)BUILD:&SYS+
               DATE-&SYSTIME'
         LR    R12,R15                  GR12 --> OUR BASE ADDRESS
         LR    R15,R13                  COPY CALLER SAVEAREA ADDRESS
         LA    R13,GPRSAVEA             LOAD OUR RSA(SAVEAREA) ADDRESS
         ST    R15,4(,R13)              SAVE CALLER'S SAVEAREA ADDRESS +
                                                      INTO OUR SAVEAREA
         ST    R13,8(,R15)              CHAIN OUR RSA INTO CALLER'S    +
                                                  SAVEAREA FOR SA TRACE
         L     R1,0(,R1)                LOAD EXEC PARM FIELD ADDRESS
         LH    R0,0(,R1)                GR0 ---> PARM TEXT LENGTH
         LA    R1,2(,R1)                GR1 ---> BEGIN OF PARM TEXT
         SPACE ,
***********************************************************************
*        AVAILABLE YOUR ASSEMBLER LANGUAGE CODE AT HERE.              *
*        =====================================================        *
*        GR0 ---> EXEC PARAMETER TEXT LENGTH                          *
*        GR1 ---> EXEC PARAMETER TEXT ADDRESS                         *
*        GR13 --> OUR REGISTER SAVEAREA(RSA)                          *
***********************************************************************
MAINPROC DS    0H
         L     R2,=A(X'22222222')       GR2 <--- X'22222222'
         L     R3,=A(X'33333333')       GR3 <--- X'33333333'
         L     R4,=A(X'44444444')       GR4 <--- X'44444444'
         L     R5,=A(X'55555555')       GR5 <--- X'55555555'
         L     R6,=A(X'66666666')       GR6 <--- X'66666666'
         L     R7,=A(X'77777777')       GR7 <--- X'77777777'
         L     R8,=A(X'88888888')       GR8 <--- X'88888888'
         L     R9,=A(X'99999999')       GR9 <--- X'99999999'
         L     R10,=A(X'AAAAAAAA')      GR10 <-- X'AAAAAAAA'
         L     R11,=A(X'BBBBBBBB')      GR11 <-- X'BBBBBBBB'

         L     R0,FWORD1                LOAD FWORD1
         ST    R0,DWORD                 STORE IT INTO DWORD
         LH    R1,HWORD1                LOAD HWORD1
         ST    R1,DWORD+4               STORE IT INTO DWORD+4

         LH    R1,HWORD2                LOAD HWORD2
         CVD   R1,DWORD                 CONVERT IT TO PACKED-DECIMAL

         MVC   WORKAREA(10),CHAR2       MOVE CHAR2 TO WORKAREA

         SLR   R14,R14                  CLEAR WORKREG
         LA    R15,5                    LOAD LOOP COUNT
LOOP     DS    0H
         AHI   R14,+1                   INCREMENT R14
         BCT   R15,LOOP                 DO UNTIL R15=0                 +
                              USE CURRENT GR15 AS COMPLETION CODE(CC=0)
***********************************************************************
*                                  *----------------------------------*
*                                  *  PROGRAM EXIT PROCEDURE          *
*                                  *  ==============================  *
*                                  *  GR15 --> COMPLETION CODE(RETCD  *
*                                  *----------------------------------*
EXITPROC DS    0H                       EXIT PROCEDURE AT HERE
         L     R13,4(,R13)              LOAD CALLER'S SAVEAREA ADDRESS
         RETURN (14,12),T,RC=(15)       RESTORE CALLER'S REGISTERS     +
                                        AND RETURN TO CALLER WITH RETCD
***********************************************************************
*        DATA AREA                                                    *
***********************************************************************
GPRSAVEA DS    18F                      STANDARD GPR SAVEAREA(18WORDS)
*---------------------------------------------------------------------*
*        AVAILABLE YOUR ASSEMBLER LANGUAGE DATA AT HERE.              *
*---------------------------------------------------------------------*
DATAAREA DS    0D                       USER DATA AREA START AT HERE
DWORD    DC    D'0'                     x0000000000000000
FWORD1   DC    F'12345'                 x00003039
FWORD2   DC    FL3'-875'                xFFFC95
HWORD1   DC    H'6789'                  x1A85
HWORD2   DC    H'-123'                  xFF85
*
CHAR1    DC    C'A'                     'A'
CHAR2    DC    CL10'ABCDEFGH'           'ABCDEFGH  '
CHAR3    DC    3CL2'XY'                 'XYXYXY'
CHAR4    DC    CL8'12345'               '12345   '
HEX1     DC    X'00'                    x00
HEX2     DC    XL4'123'                 x00000123
PACK1    DC    P'12345'                 x12345C
PACK2    DC    PL6'+3456789'            x00003456789C
PACK3    DC    P'-875'                  x875D
PACK4    DC    PL3'-875'                x00875D
ZONE1    DC    ZL8'12345'               '   1234E'
*
ADDR1    DC    A(GPRSAVEA)              x00000xxx
ADDR2    DC    AL3(CHAR1)               x000xxx
*---------------------------------------------------------------------*
WORKAREA DS    XL256                    --- 256BYTES WORKING AREA ---
*---------------------------------------------------------------------*
         YREGS ,                        EXPAND GPR EQUATIONS(z/OS ONLY)
         END

100

101

102

103

***********************************************************************

* z/Architecture & z/OS Assembler Learning Program *

* ===================================================== *

* Program member name GO is fixed. That is created by *

* ASMCL/ASMCLG HLASM Standard Procedure. *

***********************************************************************

* *----------------------------------*

* * HOUSE-KEEPING PROCEDURE *

* *----------------------------------*

MAINPROG CSECT , DEFINE CONTROL SECTION

USING *,R12 DEFINE OUR BASE REGISTER=12

SAVE (14,12),, SAVE CALLER REGISTERS +

'MAINPROG(ALP:z/OS Assembler Learning Program)BUILD:&SYS+

DATE-&SYSTIME'

LR R12,R15 GR12 --> OUR BASE ADDRESS

LR R15,R13 COPY CALLER SAVEAREA ADDRESS

LA R13,GPRSAVEA LOAD OUR RSA(SAVEAREA) ADDRESS

ST R15,4(,R13) SAVE CALLER'S SAVEAREA ADDRESS +

INTO OUR SAVEAREA

ST R13,8(,R15) CHAIN OUR RSA INTO CALLER'S +

SAVEAREA FOR SA TRACE

L R1,0(,R1) LOAD EXEC PARM FIELD ADDRESS

LH R0,0(,R1) GR0 ---> PARM TEXT LENGTH

LA R1,2(,R1) GR1 ---> BEGIN OF PARM TEXT

SPACE ,

***********************************************************************

* AVAILABLE YOUR ASSEMBLER LANGUAGE CODE AT HERE. *

* ===================================================== *

* GR0 ---> EXEC PARAMETER TEXT LENGTH *

* GR1 ---> EXEC PARAMETER TEXT ADDRESS *

* GR13 --> OUR REGISTER SAVEAREA(RSA) *

***********************************************************************

MAINPROC DS 0H

L R2,=A(X'22222222') GR2 <--- X'22222222'

L R3,=A(X'33333333') GR3 <--- X'33333333'

L R4,=A(X'44444444') GR4 <--- X'44444444'

L R5,=A(X'55555555') GR5 <--- X'55555555'

L R6,=A(X'66666666') GR6 <--- X'66666666'

L R7,=A(X'77777777') GR7 <--- X'77777777'

L R8,=A(X'88888888') GR8 <--- X'88888888'

L R9,=A(X'99999999') GR9 <--- X'99999999'

L R10,=A(X'AAAAAAAA') GR10 <-- X'AAAAAAAA'

L R11,=A(X'BBBBBBBB') GR11 <-- X'BBBBBBBB'

L R0,FWORD1 LOAD FWORD1

ST R0,DWORD STORE IT INTO DWORD

LH R1,HWORD1 LOAD HWORD1

ST R1,DWORD+4 STORE IT INTO DWORD+4

LH R1,HWORD2 LOAD HWORD2

CVD R1,DWORD CONVERT IT TO PACKED-DECIMAL

MVC WORKAREA(10),CHAR2 MOVE CHAR2 TO WORKAREA

SLR R14,R14 CLEAR WORKREG

LA R15,5 LOAD LOOP COUNT

LOOP DS 0H

AHI R14,+1 INCREMENT R14

BCT R15,LOOP DO UNTIL R15=0 +

USE CURRENT GR15 AS COMPLETION CODE(CC=0)

***********************************************************************

* *----------------------------------*

* * PROGRAM EXIT PROCEDURE *

* * ============================== *

* * GR15 --> COMPLETION CODE(RETCD *

* *----------------------------------*

EXITPROC DS 0H EXIT PROCEDURE AT HERE

L R13,4(,R13) LOAD CALLER'S SAVEAREA ADDRESS

RETURN (14,12),T,RC=(15) RESTORE CALLER'S REGISTERS +

AND RETURN TO CALLER WITH RETCD

***********************************************************************

* DATA AREA *

***********************************************************************

GPRSAVEA DS 18F STANDARD GPR SAVEAREA(18WORDS)

*---------------------------------------------------------------------*

* AVAILABLE YOUR ASSEMBLER LANGUAGE DATA AT HERE. *

*---------------------------------------------------------------------*

DATAAREA DS 0D USER DATA AREA START AT HERE

DWORD DC D'0' x0000000000000000

FWORD1 DC F'12345' x00003039

FWORD2 DC FL3'-875' xFFFC95

HWORD1 DC H'6789' x1A85

HWORD2 DC H'-123' xFF85

CHAR1 DC C'A' 'A'

CHAR2 DC CL10'ABCDEFGH' 'ABCDEFGH '

CHAR3 DC 3CL2'XY' 'XYXYXY'

CHAR4 DC CL8'12345' '12345 '

HEX1 DC X'00' x00

HEX2 DC XL4'123' x00000123

PACK1 DC P'12345' x12345C

PACK2 DC PL6'+3456789' x00003456789C

PACK3 DC P'-875' x875D

PACK4 DC PL3'-875' x00875D

ZONE1 DC ZL8'12345' ' 1234E'

ADDR1 DC A(GPRSAVEA) x00000xxx

ADDR2 DC AL3(CHAR1) x000xxx

*---------------------------------------------------------------------*

WORKAREA DS XL256 --- 256BYTES WORKING AREA ---

*---------------------------------------------------------------------*

YREGS , EXPAND GPR EQUATIONS(z/OS ONLY)

END