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Alina Sbirlea dfd14adeb0 Generalize MergeBlockIntoPredecessor. Replace uses of MergeBasicBlockIntoOnlyPred. 
Summary:
Two utils methods have essentially the same functionality. This is an attempt to merge them into one.
1. lib/Transforms/Utils/Local.cpp : MergeBasicBlockIntoOnlyPred
2. lib/Transforms/Utils/BasicBlockUtils.cpp : MergeBlockIntoPredecessor

Prior to the patch:
1. MergeBasicBlockIntoOnlyPred
Updates either DomTree or DeferredDominance
Moves all instructions from Pred to BB, deletes Pred
Asserts BB has single predecessor
If address was taken, replace the block address with constant 1 (?)

2. MergeBlockIntoPredecessor
Updates DomTree, LoopInfo and MemoryDependenceResults
Moves all instruction from BB to Pred, deletes BB
Returns if doesn't have a single predecessor
Returns if BB's address was taken

After the patch:
Method 2. MergeBlockIntoPredecessor is attempting to become the new default:
Updates DomTree or DeferredDominance, and LoopInfo and MemoryDependenceResults
Moves all instruction from BB to Pred, deletes BB
Returns if doesn't have a single predecessor
Returns if BB's address was taken

Uses of MergeBasicBlockIntoOnlyPred that need to be replaced:

1. lib/Transforms/Scalar/LoopSimplifyCFG.cpp
Updated in this patch. No challenges.

2. lib/CodeGen/CodeGenPrepare.cpp
Updated in this patch.
  i. eliminateFallThrough is straightforward, but I added using a temporary array to avoid the iterator invalidation.
  ii. eliminateMostlyEmptyBlock(s) methods also now use a temporary array for blocks
Some interesting aspects:
  - Since Pred is not deleted (BB is), the entry block does not need updating.
  - The entry block was being updated with the deleted block in eliminateMostlyEmptyBlock. Added assert to make obvious that BB=SinglePred.
  - isMergingEmptyBlockProfitable assumes BB is the one to be deleted.
  - eliminateMostlyEmptyBlock(BB) does not delete BB on one path, it deletes its unique predecessor instead.
  - adding some test owner as subscribers for the interesting tests modified:
    test/CodeGen/X86/avx-cmp.ll
    test/CodeGen/AMDGPU/nested-loop-conditions.ll
    test/CodeGen/AMDGPU/si-annotate-cf.ll
    test/CodeGen/X86/hoist-spill.ll
    test/CodeGen/X86/2006-11-17-IllegalMove.ll

3. lib/Transforms/Scalar/JumpThreading.cpp
Not covered in this patch. It is the only use case using the DeferredDominance.
I would defer to Brian Rzycki to make this replacement.

Reviewers: chandlerc, spatel, davide, brzycki, bkramer, javed.absar

Subscribers: qcolombet, sanjoy, nemanjai, nhaehnle, jlebar, tpr, kbarton, RKSimon, wmi, arsenm, llvm-commits

Differential Revision: https://reviews.llvm.org/D48202

llvm-svn: 335183
 		2018-06-20 22:01:04 +00:00
clang Related to PR37768: improve diagnostics for class name shadowing. 2018-06-20 21:58:20 +00:00
clang-tools-extra [clangd] Use workspace root path as hint path for resolving URIs in workspace/symbol 2018-06-19 09:33:53 +00:00
compiler-rt [TSan] fix build and couple of unit tests on FreeBSD 2018-06-20 20:17:44 +00:00
debuginfo-tests [debuginfo-tests] Always use the system python to invoke llgdb.py. 2018-06-10 19:38:26 +00:00
libclc Update copyright year to 2018. 2018-06-18 12:22:17 +00:00
libcxx [CMake] Convert paths to the right form in standalone builds on Windows 2018-06-20 21:03:34 +00:00
libcxxabi [CMake] Convert paths to the right form in standalone builds on Windows 2018-06-20 20:59:18 +00:00
libunwind [CMake] Convert paths to the right form in standalone builds on Windows 2018-06-20 20:53:19 +00:00
lld [ELF][MIPS] Fill a primary-GOT as much as possible 2018-06-20 15:58:48 +00:00
lldb Improve SBThread's stepping API using SBError parameter. 2018-06-20 21:43:16 +00:00
llgo Update copyright year to 2018. 2018-06-18 12:22:17 +00:00
llvm Generalize MergeBlockIntoPredecessor. Replace uses of MergeBasicBlockIntoOnlyPred. 2018-06-20 22:01:04 +00:00
openmp minor: fixed typo in debug print 2018-06-20 15:54:11 +00:00
parallel-libs Update copyright year to 2018. 2018-06-18 12:22:17 +00:00
polly Move ScopInfo to isl++ 2018-06-19 08:13:53 +00:00
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README.md

Low Level Virtual Machine (LLVM)

This directory and its subdirectories contain source code for LLVM, a toolkit for the construction of highly optimized compilers, optimizers, and runtime environments.