Use a single 'ld' to read the jmpbuf magic values instead of 'la; ld'.
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Authored by jhb on Dec 3 2019, 10:18 PM.

Details

Reviewers

br
mhorne
jrtc27

Commits

rS355402: Use a single 'ld' to read the jmpbuf magic values instead of 'la; ld'.

Summary

This saves an instruction in each case.

Test Plan

tests in /usr/tests/lib/libc/setjmp pass

Diff Detail

Repository

rS FreeBSD src repository - subversion

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Lint Not Applicable

Unit

Tests Not Applicable

Event Timeline

jhb created this revision.Dec 3 2019, 10:18 PM

Harbormaster completed remote builds in B27923: Diff 65181.Dec 3 2019, 10:18 PM

jhb added a reviewer: jrtc27.Dec 3 2019, 10:19 PM

This is particularly beneficial as, for PIC code, which this will almost always be, la expands to auipc/ld to index the GOT, so we save a level of unnecessary indirection too. (This could have been lla instead to save the indirection but still take 2 instructions just to do the address calculation.)

jhb added a child revision: D22658: Use "far" calls and branches so that lld uses valid relocations..Dec 3 2019, 10:28 PM

br accepted this revision.Dec 4 2019, 2:40 PM

This revision is now accepted and ready to land.Dec 4 2019, 2:40 PM

Closed by commit rS355402: Use a single 'ld' to read the jmpbuf magic values instead of 'la; ld'. (authored by jhb). · Explain WhyDec 4 2019, 8:51 PM

This revision was automatically updated to reflect the committed changes.

jhb added a commit: rS355402: Use a single 'ld' to read the jmpbuf magic values instead of 'la; ld'..

Herald added a subscriber: imp. · View Herald TranscriptDec 4 2019, 8:51 PM