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When the Natural Optimizer has been activated, you can specify checks by setting the options explained in this section.

The options cannot be used for specifying statements to be optimized.

This document covers the following topics:

• List of Options

• PGEN Option

• Influence of other Natural Parameters

List of Options

The following table lists and describes NOC options. Default values are underlined (this is the value that will be assumed if the option is not present).

A NOC option consists of a string surrounded by brackets or single quotation marks (except in the Natural OPTIONS statement), with options separated by commas. Some options have values, while the very existence of some options in the option string is sufficient to modify the environment.

The following rules apply:

• Optional clauses are surrounded by square brackets [ ].

• Choices are surrounded by curly braces { }.

• Each choice is separated by vertical lines "|".

• Only one of these choices can be specified;

  ON is equivalent to Y (Yes),

  OFF to N (No).

• Options specified without the optional clause ON or OFF (if applicable), or their equivalent values, are interpreted as set to ON. For example, OVFLW is identical to OVFLW=ON.

• Except for the option OFF, any specified option switches on optimizing (as if ON was specified) and the default values apply. For example, INDEX is identical to ON,INDEX.

Warning: For INDEX, INDX, OVFLW, and RANGE: Apply values OFF and N with care. Suppressing overflow checking or array index checking may allow incorrect programs to lead to unpredictable results, storage corruption, or abnormal terminating. See also the Example of INDEX and OVFLW below which demonstrates the impact of INDEX and OVFLW.

Below is information on:

• Example of INDEX and OVFLW

• Optimum Code Generation

Example of INDEX and OVFLW

DEFINE DATA LOCAL
...
1 P1 (P1/9)
...
1 P3 (P3/9)
...
1 I (I4)
1 J (I4)
1 K (I4)
1 L (I4) 
END-DEFINE
...
P1(I:J) := P3(K:L)
...
END

Explanation of Example

With INDX=ON or INDEX=ON set, code is generated to verify that I, J, K and L are within the ranges defined for P1 and P3 respectively.

With INDX=ON or RANGE=ON set, code is generated to verify that I:J and K:L denote ranges of the same length.

With OVFLW=ON set, code is generated to verify that the value of P3 fits into the corresponding P1 variable.

For example: Value 100 would cause an overflow here.

Example Error Situation:

If one of the occurrences of P3 contains the value 100, with OVFLW=OFF set, the value assigned to the corresponding P1 occurrence will be zero. If the index variable I is zero or greater than 9, with INDX=OFF set, storage areas that do not belong to Array P1 will be corrupted. If these options (OVFLW and INDX) are set to ON, a Natural error occurs like it does in standard Natural runtime.

For the NOC option specified above, additional code is generated. However, this is well compensated for by the advantage of a check that, for example, protects against hard-to-debug errors. Undetected errors can, of course, lead to unpredictable results.

Optimum Code Generation

To assure that the least amount of code is generated and thus achieve optimum performance, use:

OPT='NODBG,NOSGNTR,SIGNCHCK=OFF,ZD=OFF'

However, only apply this setting to programming objects that have been thoroughly debugged; see also the Warning.

PGEN Option

The PGEN option causes the Natural Optimizer Compiler to output the generated code and internal Natural structures. Thus, code and structures can be examined, for example, for bug fixing, performance review and support issues.

An understanding of IBM's /370 assembler is required to interpret the results produced by the PGEN option.

We recommend that you use this option with the assistance of your local Software AG representative.

Below is information on:

• Setting PGEN

• Sub-Options of the PGEN Option

• Output of the PGEN Option

• Working with the PGEN Output

Setting PGEN

To use the PGEN facility, set the PGEN option when activating on the Optimizer Compiler.

Since the buffer is kept in memory, it is possible that the user thread will not be big enough to hold the trace information. In this case, try setting PGEN on only for the portion of the program which is to be traced, for example:

Various options affect the content of the output. The basic PGEN option causes a formatted listing of Natural source lines and a disassembly of the corresponding code to be generated and kept in memory for extraction by the NOCSHOW utility as described below, under Output of the PGEN Option.

The TRSTMT, TRGPT, TRMPT and TRVDT options cause hex dumps of internal data structures associated with each line to be output.

The TRBASES and TRCACHE options cause information on base registers and cache variables to be printed out. 

Sub-Options of the PGEN Option

The following table describes the options when PGEN=ON. For an explanation of the syntax used see the introduction to List of Options above.

See also the examples below.

Output of the PGEN Option

There are two places to where the Natural Optimizer Compiler can direct the output of PGEN:

• internal Buffer
• User Exit NOCPRINT

internal Buffer

The contents of this buffer is overwritten each time a CHECK, CAT, STOW or RUN command is executed. A system utility NOCSHOW is provided whereby the contents of this buffer can be viewed, searched or printed.

To invoke the NOCSHOW utility

• Enter the direct command NOCSHOW after a CHECK, STOW, CAT or RUN where the Natural Optimizer Compiler has been active. 

The following PF keys are available on the screen:

User Exit NOCPRINT

If TREXT=ON is specified, the Natural Optimizer Compiler passes every output line to the user exit NOCPRINT instead of adding it to the trace buffer.

NOCPRINT is invoked following normal OS register conventions. Register 1 points to a full word containing the address of the 81 byte print line with ANSI carriage control characters in position 1. Register 13 points to an area of 18*4 bytes which may be used as a save area. Register 14 contains the return address and Register 15 contains the entry address of NOCPRINT.

The user exit NOCPRINT can be written in any language which supports the register conventions described above. It must be linked to the Natural nucleus together with the Natural Optimizer Compiler nucleus.

Working with the PGEN Output

This section provides hints and explanations on how to interpret the output created with the PGEN option.

• At the top of the PGEN output are some disassembled lines which do not appear to belong to any source line. These are the instructions which make up the prologue, which is executed whenever control passes from non-optimized to optimized code. Permanent base registers are loaded and control is passed to the correct point in the prologue. See Example Section A below.

• Sometimes a lot of source lines are printed without any code. This is because the Natural compiler puts a single line number in the object of statements which may span more than one line. See Example Section B below.

• If the NODBG=OFF (default) has been specified, a sequence of instructions is generated at the start of each Natural statement:

  BALR R9,R11
  DC X'....' 
  

  This sequence sets the line number (in case of error) and checks whether the TEST mode is switched ON. Without this sequence, debugging of NOC-compiled statements by the Natural Debugger is not possible. See Example Section C below.

• Sometimes there is a line break between disassembled lines. This break indicates an internal statement separation. It happens because often a single Natural statement will generate multiple internal (pseudo-code) statements.

Example Section A:

   000000 5880 D354           L     R8,RTADR+4
   000004 5870 D370           L     R7,RTADR+32
   000008 4810 6006           LH    R1,6(,R6)
   00000C 1F60                SLR   R6,R0
   00000E 47F1 A000           BC    15,0(R1,R10)

Example Section B:

    0010 OPTIONS MCG=(PGEN=ON,TRGPT=ON)  
    0020 DEFINE DATA LOCAL
    0030 1 I(I4)
    0040 1 P(P7.2)
    0050 1 T(P7.2)
    0060 END-DEFINE
    0070 *
  
    0080 SETTIME
    0090 *
  
   000012 45E0 B040           BAL   R14,RETH   
   000016 0036                DC    X'0036'
  
    0100 FOR I=1 TO 100000

Example Section C:

000018 059B                BALR  R9,R11
   00001A 003E                DC    X'003E'
   00001C D203 7000 833B      MVC   I,#VAR033B
  
   000022 059B                BALR  R9,R11
   000024 004C                DC    X'004C'
   000026 47F0 A040           BC    15,64(,R10)
  
   00002A 059B                BALR  R9,R11
   00002C 005A                DC    X'005A'
   00002E BFFF 8343           ICM   R15,15,#VAR0343
   000032 BF0F 7000           ICM   R0,15,I
   000036 1A0F                AR    R0,R15
   000038 BE0F 7000           STCM  R0,15,I
  
   00003C 059B                BALR  R9,R11
   00003E 006C                DC    X'006C'
   000040 BFFF 833F           ICM   R15,15,#VAR033F
   000044 BF0F 7000           ICM   R0,15,I
   000048 190F                CR    R0,R15
   00004A 4720 A066           BC    2,102(,R10)
  
    0110   ADD 1.00 TO P
  
   00004E 059B                BALR  R9,R11
   000050 0082                DC    X'0082'
   000052 FA41 7004 8347      AP    P,#VAR0347
   000058 DC00 7008 B488      TR    P+4(1),PSGNTR
  
    0120 END-FOR
    0130 *
  
   00005E 059B                BALR  R9,R11
   000060 0094                DC    X'0094'
   000062 47F0 A02A           BC    15,42(,R10)
  
    0140 T:=*TIMD(0080)
  
   000066 059B                BALR  R9,R11
   000068 009C                DC    X'009C'
   00006A 45E0 B0D8           BAL   R14,SYSFUNC
   00006E 0330 B881           DC    X'0330B881'
  
   000072 F246 7009 8330      PACK  T,#VAR0330
   000078 F040 7009 0002      SRP   T,2,0
   00007E DC00 700D B488      TR    T+4(1),PSGNTR
  
    0150 T:=T / 10
    0160 *
  
   000084 059B                BALR  R9,R11
   000086 00AE                DC    X'00AE'
   000088 F864 D100 7009      ZAP   OP1(7),T
   00008E F811 D130 8349      ZAP   WORK2(2),#VAR0349
   000094 45E0 B104           BAL   R14,ZDCHECK
   000098 F240 7009 B355      PACK  T,ZEROZ
   00009E 47F0 E01C           BC    15,28(,R14)
   0000A2 FD61 D100 8349      DP    OP1(7),#VAR0349
   0000A8 D204 7009 D100      MVC   T,OP1
   0000AE DC00 700D B488      TR    T+4(1),PSGNTR
  
    0170 DISPLAY 'ELAPSED TIME (S)' T
  
   0000B4 45E0 B040           BAL   R14,RETH
   0000B8 00C0                DC    X'00C0'
  
    0180 END

Influence of other Natural Parameters

The global parameter ZD influences the behavior of the NOC compiler. See the description of the ZD option as described under List of Options above.

The COMPOPT parameter PSIGNF (see also the system command COMPOPT in the Natural System Commands documentation) influences the behavior by forcing the signs of positive packed decimal numbers to F if ON, and to C if OFF. The parameter is applied if NOSGNTR=OFF is specified.

See the chart below for packed data (Format P) ":"

For numeric data (Format N) the signs are always normalized to F, regardless of the settings of NOSGNTR and PSIGNF.

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