AArch64 -> ARM64 merge status

James Molloy James.Molloy at arm.com
Fri Apr 25 09:59:05 PDT 2014

Hi all,

The AArch64->ARM64 merge is progressing at a rapid pace. Below I have taken the requirements drawn up in Edinburgh (which were sent to the list for comment) and annotated them with the current progress.

The TL;DR is that we still have a couple of issues outstanding but we're well on track for removing AArch64 (and re-bikeshedding ARM64) for the 3.5 release!

Times are incredibly approximate and are in man-days/weeks.

·         Requirement: No regressions

o   Correctness

§  [2w] Regression tests

·         All AArch64 Clang regression tests in Driver/, Sema/, Basic/ and Preprocessor/ ported. Only those in CodeGen{,CXX}/ left.

·         Most LLVM regression tests ported. A couple of more intricate tests remain, along with the MC tests which may be a headache to dig through.

§  [?] QuIC internal tests

·         Nightly runs show 11 test failures. Some compile-time (front-end issues), link-time and runtime (miscomparison) failures too.

§  [2d] ARM internal tests

·         All our test suites apart from Emperor and Perennial are passing.

·         Emperor mentioned below, Perennial runs ongoing.

§  [0d] Apple internal tests

·         Tim says we're "looking reasonable" here :)

·         This only blocks a "go/no-go", and there are no actual actions here at the moment (according to Tim)

§  [DONE] LLVM test suite

§  [1d] MC Hammer

·         One issue with aliasing remains. Patch being sent out to the list Friday.

§  [3d] Emperor

·         One issue still outstanding. Patch being sent to the list very shortly.

·         This is a random test suite so has the possibility to uncover more problems. Our acceptance criterion is 3 days runtime without finding any bugs.

o   Performance

§  No precise fixed performance baseline

§  [DONE] Investigate significant performance regressions - justify fix/not fix.

·         No performance blockers reported.

·         Requirement: Feature parity

o   [1-2w] Big endian

§  This comes in two parts. Big endian support with no NEON is almost completely ported - the last patches are being sent to the list on Friday.

§  NEON support for Big Endian hasn't been committed to AArch64. There's a whole kettle of fish there, that probably have about 1-2 weeks of effort left to fix. But this shouldn't be a merge completion blocker.

o   [2d] Support for no fpu/no neon/ no crc

§  Support has been ported, but some regression tests from AArch64 haven't been ported over to ARM64 yet. There is at least one ISel crash that I can see, so there's still at least some effort left here.

o   [DONE] A53 scheduler

§  The A53 scheduler has been ported across and ARM64 now has as much of a schedule as AArch64 does.

o   [DONE-ish] Inline assembly

§  All work done - One patch has seen contention from Eric and Jim so may have to be reverted. No big deal if it is though.

o   [DONE] Predefines

§  All predefines and driver flags should be correct.

o   [?] Conditionalise cyclone/Darwin

§  Not done yet, but noone's raised any issues about it so perhaps there isn't much to do!

o   [?] ADRP CSE

§  This optimization, being worked on by Jiangning, has been half ported to ARM64. But it hasn't been committed to AArch64 yet, so it can't be considered a merge blocker.

o   [2d] fastcc & guaranteed tail opt

o   [1d?] Post-increment NEON ld/st

§  Kevin is now working on this



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