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We'll also need to get the CLA fixed before merging.

I have fixed the indentation problem pointed out by Owen. The other comments Owen provided are either blocked because of the need to not clobber argument registers in the critical section or me not having found a valid addressing mode that would improve performance.

During some internal testing, I noticed a need to make sure TCMalloc is defining its own rseq-related macros (rather than requiring internal functions to follow TCMalloc's implementation's in lock-step). I should have a commit landed in the tree soon to rename those, but that'll require rebasing...

I'll wait for that commit then.

Had messed up the condition, now this should work, skip the test if the version < 9. For versions 9 or newer it will still check it is using the small memory model and error otherwise.