GCC optimization flags for Intel Atom [closed]

Answer 1

Just like for Pentium 4:

-march=prescott -O2 -pipe -fomit-frame-pointer

Answer 2

I've a script that auto selects the appropriate flags for your CPU and compiler combination. I've just updated it to support Intel Atom:

http://www.pixelbeat.org/scripts/gcccpuopt

Update: I previously specified -march=prescott for Atom, but looking more into it shows that Atom is merom ISA compliant, therefore -march=core2 is more appropriate. Note however that Atoms are in-order cores, the last of those being the original pentium. Therefore it's probably better to -mtune=pentium as well. Unfortunately I don't have an Atom to test. I would really appreciate if anyone could benchmark the diff between:

-march=core2 -mfpmath=sse -O3
-march=core2 -mtune=pentium -mfpmath=sse -O3

Update: Here are a couple of nice articles on low level optimization for Atom:

• http://virtualdub.org/blog/pivot/entry.php?id=286
• http://virtualdub.org/blog/pivot/entry.php?id=287

Answer 3

Well, the Gentoo wiki states for the prescott:

http://en.gentoo-wiki.com/wiki/Safe_Cflags/Intel#Atom_N270

CHOST="i686-pc-linux-gnu"

CFLAGS="-march=prescott -O2 -pipe -fomit-frame-pointer"

CXXFLAGS="${CFLAGS}"

Answer 4

I don't know if GCC has any Atom-specific optimization flags yet, but the Atom core is supposed to be very similar to the original Pentium, with the very significant addition of the MMX/SSE/SSE2/SSE3/SSSE3 instruction sets. Of course, these only make a significant difference if your code is floating-point or DSP-heavy.

Perhaps you could try:

gcc -O2 -march=pentium -mmmx -msse -msse2 -msse3 -mssse3 -mfpmath=sse

Answer 5

GCC 4.5 will contain the -march=atom and -mtune=atom options.

Source: http://gcc.gnu.org/gcc-4.5/changes.html

Answer 6

From Intel, Getting Started with MID

When using GCC to compile, there are a few recommended flags to use:

• -O2 or -O1: O2 flag optimizes for speed, while the -O1 flag optimizes for size
• -msse3
• -march=core2
• -mfpmath=sse