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gcc
Gabriel Southern
Gabriel Southern

Reputation: 10073

gcc __sync builtins and x86

I was looking at a question about atomic compare and swap and gcc intrinsics. I noticed that an answer quoted from the gcc manual (note the answer I looked at quoted from an earlier version of gcc but I've linked to the latest versions manual because I had checked to see if anything changed). However, when I looked at the text in the manual I saw that it appears to reference Itanium rather than x86:

The following builtins are intended to be compatible with those described in the Intel Itanium Processor-specific Application Binary Interface, section 7.4. As such, they depart from the normal GCC practice of using the “__builtin_” prefix, and further that they are overloaded such that they work on multiple types.

My question is why does gcc reference Itanium documentation and does that effect how the intrinsics work on x86? Are there any differences or is it safe to assume that even though the gcc manual references the Itanium manual that everything the gcc manual describes will work correctly on an x86 system?

Upvotes: 2

Views: 421

Answers (1)

Brett Hale
Brett Hale

Reputation: 22378

My understanding is that a lot of gcc's ABI decisions (the egcs fork) were based on the ABI specs for the good ship Itanic. This included the name mangling conventions for C++ symbols. There was a large effort (Project Trillian) to have IA-64 Linux (and GCC) ready to go when the actual processor became available. The semantics are intended to be platform-independent, though they will be replaced by the __atomic builtins.

Upvotes: 1

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