CPU2006 Flag Description
Dell Inc. PowerEdge 2970 (AMD Opteron 2210, 1.80GHz)

Copyright © 2006. QLogic Corporation. All rights reserved.

Compilers: QLogic PathScale Compiler Suite

Implicitly Included Flags

This section contains descriptions of flags that were included implicitly by other flags, but which do not have a permanent home at SPEC.

• • -O3
  • 

  • Specify the basic level of optimization desired.
    The options can be one of the following:

    0    Turn off all optimizations.

    1    Turn on local optimizations that can be done quickly. Do peephole optimizations and instruction scheduling.

    2    Turn on extensive optimization. This is the default.
    The optimizations at this level are generally conservative, in the sense that they are virtually always beneficial and avoid changes which affect such things as floating point accuracy. In addition to the level 1 optimizations, do inner loop unrolling, if-conversion, two passes of instruction scheduling, global register allocation, dead store elimination, instruction scheduling across basic blocks, and partial redundancy elimination.

    3    Turn on aggressive optimization.
    The optimizations at this level are distinguished from -O2 by their aggressiveness, generally seeking highest-quality generated code even if it requires extensive compile time. They may include optimizations that are generally beneficial but may hurt performance.
    This includes but is not limited to turning on the Loop Nest Optimizer, -LNO:opt=1, and setting -OPT:roundoff=1:IEEE_arithmetic=2:Olimit=9000:reorg_common=ON.

    s    Specify that code size is to be given priority in tradeoffs with execution time.

    If no value is specified, 2 is assumed.

• • -ipa
  • 

  • Invoke inter-procedural analysis (IPA). Specifying this option is identical to specifying -IPA or -IPA:. Default settings for the individual IPA suboptions are used.

• • -OPT:Ofast
  • 

  • -OPT:Ofast
    Use optimizations selected to maximize performance. Although the optimizations are generally safe, they may affect floating point accuracy due to rearrangement of computations. This effectively turns on the following optimizations: -OPT:ro=2:Olimit=0:div_split=ON:alias=typed.

  • Includes:
    • -OPT:ro
    • -OPT:Olimit
    • -OPT:div_split
    • -OPT:alias
• • -OPT:ro
  • 

  • -OPT:roundoff,ro=(0|1|2|3)
    Specify the level of acceptable departure from source language floating-point, round-off, and overflow semantics. The options can be one of the following:

    0 = Inhibit optimizations that might affect the floating-point behavior. This is the default when optimization levels -O0, -O1, and -O2 are in effect.

    1 = Allow simple transformations that might cause limited round-off or overflow differences. Compounding such transformations could have more extensive effects. This is the default when -O3 is in effect.

    2 = Allow more extensive transformations, such as the reordering of reduction loops. This is the default level when -OPT:Ofast is specified.

    3 = Enable any mathematically valid transformation.

• • -OPT:Olimit
  • 

  • -OPT:Olimit=N
    Disable optimization when size of program unit is > N. When N is 0, program unit size is ignored and optimization process will not be disabled due to compile time limit. The default is 0 when -OPT:Ofast is specified, 9000 when -O3 is specified; otherwise the default is 6000.

• • -OPT:div_split
  • 

  • -OPT:div_split=(ON|OFF)
    Enable or disable changing x/y into x*(recip(y)). This is OFF by default, but enabled by -OPT:Ofast or -OPT:IEEE_arithmetic=3. This transformation generates fairly accurate code.

• • -OPT:alias
  • 

  • The -OPT: option group controls miscellaneous optimizations. These options override defaults based on the main optimization level.

    -OPT:alias=<name>
    Specify the pointer aliasing model to be used. By specifying one or more of the following for <name>, the compiler is able to make assumptions throughout the compilation:

    typed
    Assume that the code adheres to the ANSI/ISO C standard which states that two pointers of different types cannot point to the same location in memory. This is ON by default when -OPT:Ofast is specified.

    restrict
    Specify that distinct pointers are assumed to point to distinct, non-overlapping objects. This is OFF by default.

    disjoint
    Specify that any two pointer expressions are assumed to point to distinct, non-overlapping objects. This is OFF by default.

• • -fno-math-errno
  • 

  • Do not set ERRNO after calling math functions that are executed with a single instruction, e.g. sqrt. A program that relies on IEEE exceptions for math error handling may want to use this flag for speed while maintaining IEEE arithmetic compatibility. This is implied by -Ofast. The default is -fmath-errno.

• • -ffast-math
  • 

  • -ffast-math improves FP speed by relaxing ANSI & IEEE rules. -fno-fast-math tells the compiler to conform to ANSI and IEEE math rules at the expense of speed. -ffast- math implies -OPT:IEEE_arithmetic=2 -fno-math-errno. -fno-fast-math implies -OPT:IEEE_arithmetic=1 -fmath-errno.

Flag description origin markings:

	Indicates that the flag description came from the user flags file.
	Indicates that the flag description came from the suite-wide flags file.
	Indicates that the flag description came from a per-benchmark flags file.

For questions about the meanings of these flags, please contact the tester.
For other inquiries, please contact webmaster@spec.org
Copyright 2006-2014 Standard Performance Evaluation Corporation
Tested with SPEC CPU2006 v1.0.
Report generated on Tue Jul 22 11:52:09 2014 by SPEC CPU2006 flags formatter v6906.