Commit Graph

8 Commits

Author SHA1 Message Date
Max Kazantsev 68b2ad7e63 [NFC] Add missing test case, some test renaming
llvm-svn: 346295
2018-11-07 05:58:10 +00:00
Max Kazantsev ea35455d9e [NFC] Add tests for loop-simplifycfg for further development
llvm-svn: 345713
2018-10-31 11:28:23 +00:00
Alina Sbirlea 8b83d68544 Update MemorySSA in LoopSimplifyCFG.
Summary:
Add MemorySSA as a dependency to LoopSimplifyCFG and preserve it.
Disabled by default until all passes preserve MemorySSA.

Reviewers: bogner, chandlerc

Subscribers: sanjoy, jlebar, Prazek, george.burgess.iv, llvm-commits

Differential Revision: https://reviews.llvm.org/D50911

llvm-svn: 340445
2018-08-22 20:10:21 +00:00
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
David Green e6a9c24878 [LoopSimplifyCFG] Invalidate SCEV in LoopSimplifyCFG
LoopSimplifyCFG, being a loop pass, needs to preserve scalar
evolution. This invalidates SE for the loops altered during
block merging.

Differential Revision: https://reviews.llvm.org/D48258

llvm-svn: 335036
2018-06-19 09:43:36 +00:00
Justin Bogner da0fe183c3 LPM: Drop require<loops> from these tests, it's redundant. NFC
The LoopPassManager needs to calculate the loops analysis in order to
iterate over the loops at all. Requiring it is redundant and just adds
noise to the RUN lines here.

llvm-svn: 269097
2016-05-10 18:28:10 +00:00
Justin Bogner ab6a513b4e PM: Port LoopSimplifyCFG to the new pass manager
llvm-svn: 268446
2016-05-03 21:47:32 +00:00
Fiona Glaser b417d464e6 Add LoopSimplifyCFG pass
Loop transformations can sometimes fail because the loop, while in
valid rotated LCSSA form, is not in a canonical CFG form. This is
an extremely simple pass that just merges obviously redundant
blocks, which can be used to fix some known failure cases. In the
future, it may be enhanced with more cases (and have code shared with
SimplifyCFG).

This allows us to run LoopSimplifyCFG -> LoopRotate -> LoopUnroll,
so that SimplifyCFG cleans up the loop before Rotate tries to run.

Not currently used in the pass manager, since this pass doesn't do
anything unless you can hook it up in an LPM with other loop passes.
It'll be added once Chandler cleans up things to allow this.

Tested in a custom pipeline out of tree to confirm it works in
practice (in addition to the included trivial test).

llvm-svn: 259256
2016-01-29 22:35:36 +00:00