llvm-6502/lib/IR
Chandler Carruth 69774fa1c4 [LPM] A targeted but somewhat horrible fix to the legacy pass manager's
querying of the pass registry.

The pass manager relies on the static registry of PassInfo objects to
perform all manner of its functionality. I don't understand why it does
much of this. My very vague understanding is that this registry is
touched both during static initialization *and* while each pass is being
constructed. As a consequence it is hard to make accessing it not
require a acquiring some lock. This lock ends up in the hot path of
setting up, tearing down, and invaliditing analyses in the legacy pass
manager.

On most systems you can observe this as a non-trivial % of the time
spent in 'ninja check-llvm'. However, I haven't really seen it be more
than 1% in extreme cases of compiling more real-world software,
including LTO.

Unfortunately, some of the GPU JITs are seeing this taking essentially
all of their time because they have very small IR running through
a small pass pipeline very many times (at least, this is the vague
understanding I have of it).

This patch tries to minimize the cost of looking up PassInfo objects by
leveraging the fact that the objects themselves are immutable and they
are allocated separately on the heap and so don't have their address
change. It also requires a change I made the last time I tried to debug
this problem which removed the ability to de-register a pass from the
registry. This patch creates a single access path to these objects
inside the PMTopLevelManager which memoizes the result of querying the
registry. This is somewhat gross as I don't really know if
PMTopLevelManager is the *right* place to put it, and I dislike using
a mutable member to memoize things, but it seems to work.

For long-lived pass managers this should completely eliminate
the cost of acquiring locks to look into the pass registry once the
memoized cache is warm. For 'ninja check' I measured about 1.5%
reduction in CPU time and in total time on a machine with 32 hardware
threads. For normal compilation, I don't know how much this will help,
sadly. We will still pay the cost while we populate the memoized cache.
I don't think it will hurt though, and for LTO or compiles with many
small functions it should still be a win. However, for tight loops
around a pass manager with many passes and small modules, this will help
tremendously. On the AArch64 backend I saw nearly 50% reductions in time
to complete 2000 cycles of spinning up and tearing down the pipeline.
Measurements from Owen of an actual long-lived pass manager show more
along the lines of 10% improvements.

Differential Revision: http://reviews.llvm.org/D7213

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@227299 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-28 09:47:21 +00:00
..
AsmWriter.cpp IR: DwarfNode => DebugNode, NFC 2015-01-22 22:47:44 +00:00
AsmWriter.h IR: Implement uselistorder assembly directives 2014-08-19 21:30:15 +00:00
AttributeImpl.h Canonicalize header guards into a common format. 2014-08-13 16:26:38 +00:00
Attributes.cpp Revert accidentally committed r217107 2014-09-03 23:38:05 +00:00
AutoUpgrade.cpp [X86] Use i8 immediate for comparison type on AVX512 packed integer instructions. This matches floating point equivalents. Includes autoupgrade support to convert old code. 2015-01-25 23:26:02 +00:00
BasicBlock.cpp The leak detector is dead, long live asan and valgrind. 2014-12-22 13:00:36 +00:00
CMakeLists.txt Revert GCStrategy ownership changes 2015-01-26 18:26:35 +00:00
Comdat.cpp IR: Add COMDATs to the IR 2014-06-27 18:19:56 +00:00
ConstantFold.cpp ConstantFold: Shifting undef by zero results in undef 2014-12-18 23:54:43 +00:00
ConstantFold.h Canonicalize header guards into a common format. 2014-08-13 16:26:38 +00:00
ConstantRange.cpp
Constants.cpp Reapply "LLVMContext: Store APInt/APFloat directly into the ConstantInt/FP DenseMaps." 2014-12-06 13:12:56 +00:00
ConstantsContext.h IR: De-duplicate code for replacing operands in place 2014-08-19 19:13:30 +00:00
Core.cpp IR: Split Metadata from Value 2014-12-09 18:38:53 +00:00
DataLayout.cpp DataLayout: Provide nicer diagnostics for malformed strings 2014-12-10 02:36:41 +00:00
DebugInfo.cpp DebugInfo: Fix use after return found by asan. 2015-01-24 19:55:23 +00:00
DebugLoc.cpp IR: Cleanup dead code, NFC 2015-01-16 17:31:29 +00:00
DiagnosticInfo.cpp IR: Split Metadata from Value 2014-12-09 18:38:53 +00:00
DiagnosticPrinter.cpp Fix typos in comments, NFC 2014-08-29 21:53:01 +00:00
DIBuilder.cpp Reapply "IR: Simplify DIBuilder's HeaderBuilder API, NFC" 2015-01-20 05:02:42 +00:00
Dominators.cpp [PM] Port domtree to the new pass manager (at last). 2015-01-14 10:19:28 +00:00
Function.cpp Revert GCStrategy ownership changes 2015-01-26 18:26:35 +00:00
GCOV.cpp llvm-cov: Don't use llvm::outs() in library code 2015-01-23 23:09:27 +00:00
Globals.cpp The leak detector is dead, long live asan and valgrind. 2014-12-22 13:00:36 +00:00
GVMaterializer.cpp
InlineAsm.cpp [inline asm] Add a check in InlineAsm::ConstraintInfo::Parse to make sure '{' 2014-09-05 22:30:32 +00:00
Instruction.cpp The leak detector is dead, long live asan and valgrind. 2014-12-22 13:00:36 +00:00
Instructions.cpp IR: Split Metadata from Value 2014-12-09 18:38:53 +00:00
IntrinsicInst.cpp IR: Split Metadata from Value 2014-12-09 18:38:53 +00:00
IRBuilder.cpp Intrinsics: introduce llvm_any_ty aka ValueType Any 2015-01-22 20:14:38 +00:00
IRPrintingPasses.cpp [PM] Switch the new pass manager to use a reference-based API for IR 2015-01-05 02:47:05 +00:00
LegacyPassManager.cpp [LPM] A targeted but somewhat horrible fix to the legacy pass manager's 2015-01-28 09:47:21 +00:00
LLVMBuild.txt
LLVMContext.cpp Fix LLVMContext to match what MDKind names that the LL parser permits. Fixes PR21799! 2014-12-11 02:10:28 +00:00
LLVMContextImpl.cpp Revert GCStrategy ownership changes 2015-01-26 18:26:35 +00:00
LLVMContextImpl.h Revert GCStrategy ownership changes 2015-01-26 18:26:35 +00:00
Makefile
Mangler.cpp Silencing an "enumeral and non-enumeral type in conditional expression" warning; NFC. 2014-10-28 13:12:13 +00:00
MDBuilder.cpp IR: Return unique_ptr from MDNode::getTemporary() 2015-01-19 21:30:18 +00:00
Metadata.cpp IR: Change GenericDwarfNode::getHeader() to StringRef 2015-01-22 23:10:55 +00:00
MetadataTracking.cpp IR: Store RAUW support and Context in the same pointer, NFC 2015-01-19 19:02:06 +00:00
Module.cpp The leak detector is dead, long live asan and valgrind. 2014-12-22 13:00:36 +00:00
module.modulemap [modules] Add module maps for LLVM. These are not quite ready for prime-time 2014-05-21 02:46:14 +00:00
Pass.cpp Refactoring cl::parser construction and initialization. 2015-01-22 21:01:12 +00:00
PassManager.cpp [PM] Push the debug option for the new pass manager into the opt tool 2015-01-13 22:42:38 +00:00
PassRegistry.cpp [PM] Remove an unused and rather expensive mapping from an analysis 2014-10-06 00:30:59 +00:00
Statepoint.cpp Intrinsics: introduce llvm_any_ty aka ValueType Any 2015-01-22 20:14:38 +00:00
SymbolTableListTraitsImpl.h Canonicalize header guards into a common format. 2014-08-13 16:26:38 +00:00
Type.cpp Turn some DenseMaps that are only used for set operations into DenseSets. 2014-12-06 19:22:54 +00:00
TypeFinder.cpp IR: Split Metadata from Value 2014-12-09 18:38:53 +00:00
Use.cpp Fix a URL (NFC) 2014-08-21 21:09:24 +00:00
UseListOrder.cpp verify-uselistorder: Force -preserve-bc-use-list-order 2014-08-19 21:08:27 +00:00
User.cpp IR: Cleanup comments for Value, User, and MDNode 2014-10-15 20:28:31 +00:00
Value.cpp Cleaup ValueHandle to no longer keep a PointerIntPair for the Value*. 2015-01-09 00:48:47 +00:00
ValueSymbolTable.cpp IR: Split Metadata from Value 2014-12-09 18:38:53 +00:00
ValueTypes.cpp
Verifier.cpp Intrinsics: introduce llvm_any_ty aka ValueType Any 2015-01-22 20:14:38 +00:00