Add fabs() to arm64 libc
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Authored by emaste on May 13 2015, 1:14 PM.

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andrew
imp

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rS282909: Add fabs() to arm64 libc

Summary

fabs comes from libc, not libm, for historical reasons. Add a trivial C implementation for arm64.

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rS FreeBSD src repository - subversion

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emaste updated this revision to Diff 5359.May 13 2015, 1:14 PM

emaste retitled this revision from to Add fabs() to arm64 libc.

emaste updated this object.

emaste edited the test plan for this revision. (Show Details)

emaste added reviewers: andrew, imp.

Herald added a subscriber: emaste. · View Herald TranscriptMay 13 2015, 1:14 PM

We could use inline asm with the fabs instruction, but the compiler generates reasonable code:

0000000000000000 <fabs>:
   0:	1e602008 	fcmp	d0, #0.0
   4:	54000045 	b.pl	c <fabs+0xc>
   8:	1e614000 	fneg	d0, d0
   c:	d65f03c0 	ret

lib/libc/aarch64/gen/fabs.c
33 ↗	(On Diff #5359)	There should be a black newline for style (but I don't agree with that part of style(9), and should x be compared with `0.` (with a `.`) to make it a floating-point value.

This revision is now accepted and ready to land.May 13 2015, 2:06 PM

interesting, with Clang 3.7 I get:

fabs:
       0:       01 40 61 1e                                     fneg    d1, d0
       4:       08 20 60 1e                                     fcmp    d0, #0.0
       8:       20 4c 60 1e                                     fcsel   d0, d1, d0, mi
       c:       c0 03 5f d6                                     ret