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Jun Bum Lim af56683019 [CodeGen] Add a new pass for PostRA sink
Summary:
This pass sinks COPY instructions into a successor block, if the COPY is not
used in the current block and the COPY is live-in to a single successor
(i.e., doesn't require the COPY to be duplicated).  This avoids executing the
the copy on paths where their results aren't needed.  This also exposes
additional opportunites for dead copy elimination and shrink wrapping.

These copies were either not handled by or are inserted after the MachineSink
pass. As an example of the former case, the MachineSink pass cannot sink
COPY instructions with allocatable source registers; for AArch64 these type
of copy instructions are frequently used to move function parameters (PhyReg)
into virtual registers in the entry block..

For the machine IR below, this pass will sink %w19 in the entry into its
successor (%bb.1) because %w19 is only live-in in %bb.1.

```
   %bb.0:
      %wzr = SUBSWri %w1, 1
      %w19 = COPY %w0
      Bcc 11, %bb.2
    %bb.1:
      Live Ins: %w19
      BL @fun
      %w0 = ADDWrr %w0, %w19
      RET %w0
    %bb.2:
      %w0 = COPY %wzr
      RET %w0
```
As we sink %w19 (CSR in AArch64) into %bb.1, the shrink-wrapping pass will be
able to see %bb.0 as a candidate.

With this change I observed 12% more shrink-wrapping candidate and 13% more dead copies deleted  in spec2000/2006/2017 on AArch64.

Reviewers: qcolombet, MatzeB, thegameg, mcrosier, gberry, hfinkel, john.brawn, twoh, RKSimon, sebpop, kparzysz

Reviewed By: sebpop

Subscribers: evandro, sebpop, sfertile, aemerson, mgorny, javed.absar, kristof.beyls, llvm-commits

Differential Revision: https://reviews.llvm.org/D41463

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@328237 91177308-0d34-0410-b5e6-96231b3b80d8
2018-03-22 20:06:47 +00:00
bindings [bindings/go] Add a missing , in the test code to fix a go compile 2018-03-17 15:12:52 +00:00
cmake Accept any filepath in llvm_check_source_file_list 2018-03-19 21:35:30 +00:00
docs Document optforfuzzing attribute created in r328214. 2018-03-22 19:50:10 +00:00
examples [ORC] Re-apply r327566 with a fix for test-global-ctors.ll. 2018-03-15 00:30:14 +00:00
include [CodeGen] Add a new pass for PostRA sink 2018-03-22 20:06:47 +00:00
lib [CodeGen] Add a new pass for PostRA sink 2018-03-22 20:06:47 +00:00
projects [cmake] Support moving debuginfo-tests to llvm/projects 2017-12-12 17:06:08 +00:00
resources
runtimes [CMake] Support for cross-compilation when build runtimes 2018-01-08 23:50:59 +00:00
test [CodeGen] Add a new pass for PostRA sink 2018-03-22 20:06:47 +00:00
tools [llvm-mca] Minor refactoring. NFCI 2018-03-22 14:14:49 +00:00
unittests Revert "[InstrProf] Support for external functions in text format." 2018-03-22 15:29:55 +00:00
utils vim: rename singlethread to syncscope 2018-03-22 16:39:54 +00:00
.arcconfig [llvm] Set up .arcconfig to point to Diffusion L repository 2018-01-12 15:37:41 +00:00
.clang-format
.clang-tidy
.gitattributes [MC] Fix regression tests on Windows when git “core.autocrlf” is set to true. 2017-11-17 21:59:43 +00:00
.gitignore gitignore: Ignore .vs folder (VS2017 config files) 2017-04-08 00:16:58 +00:00
CMakeLists.txt Ensure that DataTypes.h is installed now that it's moved to llvm-c 2018-03-21 18:21:57 +00:00
CODE_OWNERS.TXT Update my email addresses, NFC. 2017-10-26 10:16:54 +00:00
configure
CREDITS.TXT Add myself to CREDITS.txt 2018-01-29 17:02:34 +00:00
LICENSE.TXT Bump year to 2017 in LICENSE.txt 2017-01-12 18:02:42 +00:00
llvm.spec.in
LLVMBuild.txt
README.txt Test commit access 2017-08-18 02:39:28 +00:00
RELEASE_TESTERS.TXT Update my email addresses, NFC. 2017-10-26 10:16:54 +00:00

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