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7c7b72a066
llvm-6502/test/Transforms
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Philip Reames 7c7b72a066 Infer known bits from dominating conditions 
This patch adds limited support in ValueTracking for inferring known bits of a value from conditional expressions which must be true to reach the instruction we're trying to optimize. At this time, the feature is off by default. Once landed, I'm hoping for feedback from others on both profitability and compile time impact.

Forms of conditional value propagation have been tried in LLVM before and have failed due to compile time problems.  In an attempt to side step that, this patch only considers conditions where the edge leaving the branch dominates the context instruction. It does not attempt full dataflow.  Even with that restriction, it handles many interesting cases:
 * Early exits from functions
 * Early exits from loops (for context instructions in the loop and after the check)
 * Conditions which control entry into loops, including multi-version loops (such as those produced during vectorization, IRCE, loop unswitch, etc..)

Possible applications include optimizing using information provided by constructs such as: preconditions, assumptions, null checks, & range checks.

This patch implements two approaches to the problem that need further benchmarking.  Approach 1 is to directly walk the dominator tree looking for interesting conditions.  Approach 2 is to inspect other uses of the value being queried for interesting comparisons.  From initial benchmarking, it appears that Approach 2 is faster than Approach 1, but this needs to be further validated.  

Differential Revision: http://reviews.llvm.org/D7708



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231879 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-10 22:43:20 +00:00
..
ADCE [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
AddDiscriminators DebugInfo: Move new hierarchy into place 2015-03-03 17:24:31 +00:00
AlignmentFromAssumptions [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
ArgumentPromotion DebugInfo: Move new hierarchy into place 2015-03-03 17:24:31 +00:00
AtomicExpand/ARM
BBVectorize [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
BDCE [BDCE] Don't forget uses of root instructions seen before the instruction itself 2015-02-18 03:12:28 +00:00
BranchFolding
CodeExtractor [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
CodeGenPrepare [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
ConstantHoisting [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
ConstantMerge Make DataLayout Non-Optional in the Module 2015-03-04 18:43:29 +00:00
ConstProp [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
CorrelatedValuePropagation [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
DeadArgElim DebugInfo: Move new hierarchy into place 2015-03-03 17:24:31 +00:00
DeadStoreElimination DebugInfo: Move new hierarchy into place 2015-03-03 17:24:31 +00:00
EarlyCSE [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
FunctionAttrs [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
GCOVProfiling DebugInfo: Move new hierarchy into place 2015-03-03 17:24:31 +00:00
GlobalDCE [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
GlobalOpt Make DataLayout Non-Optional in the Module 2015-03-04 18:43:29 +00:00
GVN [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
IndVarSimplify Make DataLayout Non-Optional in the Module 2015-03-04 18:43:29 +00:00
Inline Make DataLayout Non-Optional in the Module 2015-03-04 18:43:29 +00:00
InstCombine Infer known bits from dominating conditions 2015-03-10 22:43:20 +00:00
InstMerge [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
InstSimplify [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
Internalize [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
IPConstantProp [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
IRCE [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
JumpThreading [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
LCSSA [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
LICM DebugInfo: Move new hierarchy into place 2015-03-03 17:24:31 +00:00
LoadCombine [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
LoopDeletion [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
LoopIdiom DebugInfo: Move new hierarchy into place 2015-03-03 17:24:31 +00:00
LoopInterchange Add a new pass "Loop Interchange" 2015-03-06 10:11:25 +00:00
LoopReroll [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
LoopRotate DebugInfo: Move new hierarchy into place 2015-03-03 17:24:31 +00:00
LoopSimplify Make DataLayout Non-Optional in the Module 2015-03-04 18:43:29 +00:00
LoopStrengthReduce Make DataLayout Non-Optional in the Module 2015-03-04 18:43:29 +00:00
LoopUnroll Revert r231630 - Run LICM pass after loop unrolling pass. 2015-03-09 07:26:37 +00:00
LoopUnswitch [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
LoopVectorize Introduce runtime unrolling disable matadata and use it to mark the scalar loop from vectorization. 2015-03-09 06:14:18 +00:00
LowerAtomic [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
LowerBitSets LowerBitSets: Use byte arrays instead of bit sets to represent in-memory bit sets. 2015-03-03 00:49:28 +00:00
LowerExpectIntrinsic [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
LowerInvoke
LowerSwitch [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
Mem2Reg DebugInfo: Move new hierarchy into place 2015-03-03 17:24:31 +00:00
MemCpyOpt [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
MergeFunc [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
MetaRenamer [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
ObjCARC [objc-arc] Remove annotations code. 2015-03-06 00:34:29 +00:00
PartiallyInlineLibCalls
PhaseOrdering Make DataLayout Non-Optional in the Module 2015-03-04 18:43:29 +00:00
PlaceSafepoints PlaceSafepoints: use IRBuilder helpers 2015-02-26 00:35:56 +00:00
PruneEH Fix invalid LLVM IR in PruneEH tests 2015-02-11 02:06:47 +00:00
Reassociate [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
Reg2Mem
RewriteStatepointsForGC [RewriteStatepointsForGC] Yet more test cases for relocation 2015-03-05 22:28:06 +00:00
SampleProfile DebugInfo: Move new hierarchy into place 2015-03-03 17:24:31 +00:00
Scalarizer Make DataLayout Non-Optional in the Module 2015-03-04 18:43:29 +00:00
ScalarRepl Make DataLayout Non-Optional in the Module 2015-03-04 18:43:29 +00:00
SCCP [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
SeparateConstOffsetFromGEP/NVPTX [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
SimplifyCFG DebugInfo: Move new hierarchy into place 2015-03-03 17:24:31 +00:00
Sink [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
SLPVectorizer DebugInfo: Move new hierarchy into place 2015-03-03 17:24:31 +00:00
SROA [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
StraightLineStrengthReduce Add straight-line strength reduction to LLVM 2015-02-03 19:37:06 +00:00
StripSymbols DebugInfo: Move new hierarchy into place 2015-03-03 17:24:31 +00:00
StructurizeCFG [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
TailCallElim TRE: Just erase dead BBs and tweak the iteration loop not to increment the deleted BB iterator. 2015-02-28 16:47:27 +00:00
TailDup
Util Correctly combine alias.scope metadata by a union instead of intersecting 2015-02-08 17:07:14 +00:00