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4db527032a
llvm-6502/lib/Transforms/Scalar
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Sanjoy Das 4db527032a [IndVars] Try to use existing values in RewriteLoopExitValues. 
Summary:
In RewriteLoopExitValues, before expanding out an SCEV expression using
SCEVExpander, try to see if an existing LLVM IR expression already
computes the value we're interested in.  If so use that existing
expression.

Apart from reducing IndVars' reliance on the rest of the compilation
pipeline, this also prevents IndVars from concluding some expressions as
"high cost" when they're not.  For instance,
`InductiveRangeCheckElimination` often emits code of the following form:

```
len = umin(len_A, len_B)

loop:
  ...
  if (i++ < len)
    goto loop

outside_loop:
    use(i)
```

`SCEVExpander` refuses to rewrite the use of `i` in `outside_loop`,
since it thinks the value of `i` on loop exit, `len`, is a high cost
expansion since it contains an `umax` in it.  With this change,
`IndVars` can see that it can re-use `len` instead of creating a new
expression to compute `umin(len_A, len_B)`.

I considered putting this cleverness in `SCEVExpander`, but I was
worried that it may then have a deterimental effect on other passes
that use it.  So I decided it was better to just do this in the one
place where it seems like an obviously good idea, with the intent of
generalizing later if needed.

Reviewers: atrick, reames

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D10782

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241838 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-09 18:46:12 +00:00
..
ADCE.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
AlignmentFromAssumptions.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
BDCE.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
CMakeLists.txt Add a speculative execution pass 2015-05-15 17:54:48 +00:00
ConstantHoisting.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
ConstantProp.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
CorrelatedValuePropagation.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
DCE.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
DeadStoreElimination.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
EarlyCSE.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
FlattenCFGPass.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
Float2Int.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
GVN.cpp GVN: If a branch has two identical successors, we cannot declare either dead. 2015-06-25 18:32:02 +00:00
InductiveRangeCheckElimination.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
IndVarSimplify.cpp [IndVars] Try to use existing values in RewriteLoopExitValues. 2015-07-09 18:46:12 +00:00
JumpThreading.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
LICM.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
LLVMBuild.txt Update libdeps since TLI was moved from Target to Analysis in r226078. 2015-01-15 05:21:00 +00:00
LoadCombine.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
LoopDeletion.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
LoopDistribute.cpp [LoopDist] Improve variable names and comments in LoopVersioning class, NFC 2015-06-22 22:59:40 +00:00
LoopIdiomRecognize.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
LoopInstSimplify.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
LoopInterchange.cpp Rename Reduction variables/structures to Recurrence. 2015-06-16 18:07:34 +00:00
LoopRerollPass.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
LoopRotation.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
LoopStrengthReduce.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
LoopUnrollPass.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
LoopUnswitch.cpp This change fixes three bugs in loop unswitching. This change causes an 81% speed-up on a benchmark that is based on EigenConvolutionKernel2D from Eigen3, where the lack of loop unswitching blocks hoisting of loads out of a nested loop (see bug 23816 for how loop unswitching and load hoisting are related). 2015-06-23 18:26:50 +00:00
LowerAtomic.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
LowerExpectIntrinsic.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
Makefile
MemCpyOptimizer.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
MergedLoadStoreMotion.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
NaryReassociate.cpp [NaryReassociate] enhances nsw by leveraging @llvm.assume 2015-07-01 03:38:49 +00:00
PartiallyInlineLibCalls.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
PlaceSafepoints.cpp Rename llvm.frameescape and llvm.framerecover to localescape and localrecover 2015-07-07 22:25:32 +00:00
Reassociate.cpp [Reassociate] Don't propogate flags when creating negations 2015-06-24 21:27:36 +00:00
Reg2Mem.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
RewriteStatepointsForGC.cpp [RewriteStatepointsForGC] Generalized vector phi/select handling for base pointers 2015-06-26 22:47:37 +00:00
SampleProfile.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
Scalar.cpp Add a speculative execution pass 2015-05-15 17:54:48 +00:00
Scalarizer.cpp Revert 239644. 2015-06-13 01:08:00 +00:00
ScalarReplAggregates.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
SCCP.cpp Revert "Revert r241570, it caused PR24053" 2015-07-07 18:49:41 +00:00
SeparateConstOffsetFromGEP.cpp SeparateConstOffsetFromGEP: Pass address space to isLegalAddressingMode 2015-06-07 20:17:44 +00:00
SimplifyCFGPass.cpp fix typos; NFC 2015-06-24 20:42:33 +00:00
Sink.cpp [PM/AA] Remove the Location typedef from the AliasAnalysis class now 2015-06-17 07:18:54 +00:00
SpeculativeExecution.cpp [Speculation] NFC: more header comments 2015-05-19 20:52:45 +00:00
SROA.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00
StraightLineStrengthReduce.cpp [SLSR] S's basis must have the same type as S 2015-06-28 17:45:05 +00:00
StructurizeCFG.cpp Change range-based for-loops to be -Wrange-loop-analysis clean. 2015-04-15 01:21:15 +00:00
TailRecursionElimination.cpp Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC) 2015-06-23 09:49:53 +00:00