Try to turn on "good" C optimization flags for various compilers and architectures, for some definition of "good". (In our case, good for FFTW and hopefully for other scientific codes. Modify as needed.)
The user can override the flags by setting the CFLAGS environment variable. The user can also specify –enable-portable-binary in order to disable any optimization flags that might result in a binary that only runs on the host architecture.
Note also that the flags assume that ANSI C aliasing rules are followed by the code (e.g. for gcc’s -fstrict-aliasing), and that floating-point computations can be re-ordered as needed.
Requires macros: AX_CHECK_COMPILE_FLAG, AX_COMPILER_VENDOR, AX_GCC_ARCHFLAG, AX_GCC_X86_CPUID.
Download the latest version of ax_cc_maxopt.m4 or browse the macro’s revision history.
Copyright © 2008 Steven G. Johnson firstname.lastname@example.org
Copyright © 2008 Matteo Frigo
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