Specifications

46 Troubleshooting and Portability Issues Chapter 4

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Compiler Usage Guidelines for AMD64 Platforms

GCC provides switches, such as the -mieee-fp switch, to control whether or not the compiler uses

IEEE floating-point comparisons.

The user should not use the -ffast-math optimization recommended in the general optimization

guidelines in this case. Using the -ffast-math switch results in a fast but less predictable floating-

point model. The user should also be careful to not use a switch that implies -ffast-math.

Does your code need C++ exception handling?

GCC generates the extra code needed to propagate exceptions with the -fexceptions switch. For some

targets, propagating exceptions implies that GCC generates frame unwind information for all

functions. Generating frame unwind information for all functions can produce significant data-size

overhead, although it does not affect the execution of a program.

By default, GCC enables the - fexceptions option for languages like C++ that normally require

exception handling. GCC disables the -fexceptions option for languages like C that do not normally

require it. You may need, however, to enable this option when compiling C code that must

interoperate properly with exception handlers written in C++. You may also wish to disable this

option if you are compiling older C++ programs that do not use exception handling.

Do you need to unwind the stack using the frame pointer?

The frame pointer is omitted by default on 64-bit GCC compilers to improve performance. This

default omission can be reversed by using -fno-omit-frame-pointer.

4.3 Intel Compilers (64-Bit) for Linux

See section 4.9, “Intel Compilers (32-Bit) for Linux®”, on page 50 for the portability and

troubleshooting issues with this compiler.

4.4 PathScale Compilers (64-Bit) for Linux

For information on diagnosing problems with the PathScale compiler, refer to the tuning document

distributed with the PathScale compiler suite.

4.5 Intel Compilers (64-Bit) for Microsoft

Windows

See section 4.11, “Intel Compilers (32-Bit) for Microsoft® Windows®”, on page 51 for

troubleshooting errors with this compiler.