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A new suboption added to -qprefetch for XL C/C++ for AIX, V12.1 and XL Fortran for AIX, V14.1

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A new suboption dscr has been added to the -qprefetch option. This page contains the syntax and parameter descriptions of this suboption.


You can specify a value for the dscr suboption to improve the runtime performance of your applications. The compiler sets the Data Stream Control Register (DSCR) to the specified dscr value to control the hardware prefetch engine. The value is valid only when the optimization level is -O3 or greater and the high-order transformation (HOT) is in effect. The default value of dscr is 0.

The value that you specify for dscr must be 0 or greater, and representable as a 64-bit unsigned integer. Otherwise, the compiler issues a warning message and sets dscr to 0. The compiler accepts both decimal and hexadecimal numbers, and a hexadecimal number requires the prefix of 0x. The value range depends on your system architecture. See the product information about the POWER Architecture for details. If you specify multiple dscr values, the last one takes effect.

Syntax diagram
                      V                                   |     
          |             |    .-noassistthread-----------. |   |   
          |             +-=--+-assistthread--=--+-SMT-+-+-+   |   
          |             |                       '-CMP-'   |   |   
          |             |    .-noaggressive-.             |   |   
          |             +-=--+-aggressive---+-------------+   |   
          |             '-=--dscr--=--
value---------------'   |   
>>- -q----+-noprefetch----------------------------------------+--><
Default: -qprefetch=noassistthread:noaggressive:dscr=0

Cross reference information
Segment Product Component Platform Version Edition
Software Development XL C for AIX Documentation AIX 12.1 Not Applicable
Software Development XL C/C++ for AIX Documentation AIX 12.1 Not Applicable
Software Development XL Fortran for AIX Documentation AIX 14.1 Not Applicable

Document information

More support for: XL C/C++

Software version: 12.1

Operating system(s): AIX

Reference #: 1635114

Modified date: 28 June 2013