llvm-project/llvm/lib/CodeGen
Chandler Carruth d48cdbf0c3 Put the functionality for printing a value to a raw_ostream as an
operand into the Value interface just like the core print method is.
That gives a more conistent organization to the IR printing interfaces
-- they are all attached to the IR objects themselves. Also, update all
the users.

This removes the 'Writer.h' header which contained only a single function
declaration.

llvm-svn: 198836
2014-01-09 02:29:41 +00:00
..
AsmPrinter Put the functionality for printing a value to a raw_ostream as an 2014-01-09 02:29:41 +00:00
SelectionDAG Put the functionality for printing a value to a raw_ostream as an 2014-01-09 02:29:41 +00:00
AggressiveAntiDepBreaker.cpp Fix crash in AggressiveAntiDepBreaker with empty CriticalPathSet 2013-09-12 04:22:31 +00:00
AggressiveAntiDepBreaker.h Revert "Give internal classes hidden visibility." 2013-09-11 18:05:11 +00:00
AllocationOrder.cpp Assert that the target provided hints are in the allocation order. 2013-02-19 18:41:01 +00:00
AllocationOrder.h Check hint registers for interference only once before evictions 2013-12-05 21:18:40 +00:00
Analysis.cpp [stackprotector] Refactor out the end of isInTailCallPosition into the function returnTypeIsEligibleForTailCall. 2013-08-20 08:36:50 +00:00
AntiDepBreaker.h Revert "Give internal classes hidden visibility." 2013-09-11 18:05:11 +00:00
BasicTargetTransformInfo.cpp Costmodel: Add support for horizontal vector reductions 2013-09-17 18:06:50 +00:00
BranchFolding.cpp Add a RequireStructuredCFG Field to TargetMachine. 2013-12-07 01:49:19 +00:00
BranchFolding.h Revert "Give internal classes hidden visibility." 2013-09-11 18:05:11 +00:00
CMakeLists.txt [Stackmap] Liveness Analysis Pass 2013-12-14 06:53:06 +00:00
CalcSpillWeights.cpp [block-freq] Refactor LiveInterals::getSpillWeight to use the new MachineBlockFrequencyInfo methods. 2013-12-14 00:53:32 +00:00
CallingConvLower.cpp Use SmallVectorImpl& instead of SmallVector to avoid repeating small vector size. 2013-07-14 04:42:23 +00:00
CodeGen.cpp Re-sort all of the includes with ./utils/sort_includes.py so that 2014-01-07 11:48:04 +00:00
CriticalAntiDepBreaker.cpp Use SmallVectorImpl instead of SmallVector as method argument to avoid specifying vector size. 2013-07-03 05:16:59 +00:00
CriticalAntiDepBreaker.h Revert "Give internal classes hidden visibility." 2013-09-11 18:05:11 +00:00
DFAPacketizer.cpp mi-sched: Don't call MBB.size() in initSUnits. The driver already has instr count. 2013-08-23 17:48:33 +00:00
DeadMachineInstructionElim.cpp Simplify logic now that r182490 is in place. No functional change intended. 2013-05-22 23:17:36 +00:00
DwarfEHPrepare.cpp Access the TargetLoweringInfo from the TargetMachine object instead of caching it. The TLI may change between functions. No functionality change. 2013-06-19 20:51:24 +00:00
EarlyIfConversion.cpp Allow MachineTraceMetrics to be used when the model has no resources. 2013-04-02 22:27:45 +00:00
EdgeBundles.cpp
ErlangGC.cpp Add a GC plugin for Erlang 2013-03-25 13:47:46 +00:00
ExecutionDepsFix.cpp Convert register liveness tracking to work on a sub-register level instead of just register units. 2013-12-14 06:52:56 +00:00
ExpandISelPseudos.cpp
ExpandPostRAPseudos.cpp fix typo in comment 2013-10-11 15:40:14 +00:00
GCMetadata.cpp Fix GCMetadaPrinter::finishAssembly not executed, patch by Yiannis Tsiouris. 2013-02-19 16:51:44 +00:00
GCMetadataPrinter.cpp
GCStrategy.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
IfConversion.cpp Re-sort all of the includes with ./utils/sort_includes.py so that 2014-01-07 11:48:04 +00:00
InlineSpiller.cpp Re-sort all of the includes with ./utils/sort_includes.py so that 2014-01-07 11:48:04 +00:00
InterferenceCache.cpp Represent RegUnit liveness with LiveRange instance 2013-10-10 21:29:02 +00:00
InterferenceCache.h Represent RegUnit liveness with LiveRange instance 2013-10-10 21:29:02 +00:00
IntrinsicLowering.cpp Use type form of getIntPtrType. 2013-11-10 04:46:57 +00:00
JITCodeEmitter.cpp
LLVMBuild.txt Prune redundant dependencies in LLVMBuild.txt. 2013-12-11 00:30:57 +00:00
LLVMTargetMachine.cpp Move the LLVM IR asm writer header files into the IR directory, as they 2014-01-07 12:34:26 +00:00
LatencyPriorityQueue.cpp
LexicalScopes.cpp Remove capability for polymorphic destruction from LexicalScope 2013-11-20 00:54:28 +00:00
LiveDebugVariables.cpp Remove capability for polymorphic destruction from LexicalScope 2013-11-20 00:54:28 +00:00
LiveDebugVariables.h Revert "Give internal classes hidden visibility." 2013-09-11 18:05:11 +00:00
LiveInterval.cpp Print register in LiveInterval::print() 2013-10-10 21:29:05 +00:00
LiveIntervalAnalysis.cpp [block-freq] Rename getEntryFrequency() -> getEntryFreq() to match getBlockFreq() in all *BlockFrequencyInfo*. 2013-12-14 02:37:38 +00:00
LiveIntervalUnion.cpp
LivePhysRegs.cpp Convert register liveness tracking to work on a sub-register level instead of just register units. 2013-12-14 06:52:56 +00:00
LiveRangeCalc.cpp Work on LiveRange instead of LiveInterval where possible 2013-10-10 21:28:57 +00:00
LiveRangeCalc.h LiveRangeCalc.h: Update a description corresponding to r192396. [-Wdocumentation] 2013-10-11 04:52:03 +00:00
LiveRangeEdit.cpp CalcSpillWeights: give a better describing name to calculateSpillWeights 2013-11-11 19:04:45 +00:00
LiveRegMatrix.cpp Represent RegUnit liveness with LiveRange instance 2013-10-10 21:29:02 +00:00
LiveStackAnalysis.cpp
LiveVariables.cpp Use SmallVectorImpl& instead of SmallVector to avoid repeating small vector size. 2013-07-11 16:22:38 +00:00
LocalStackSlotAllocation.cpp [stackprotector] Use analysis from the StackProtector pass for stack layout in PEI a nd LocalStackSlot passes. 2013-12-19 03:17:11 +00:00
MachineBasicBlock.cpp Put the functionality for printing a value to a raw_ostream as an 2014-01-09 02:29:41 +00:00
MachineBlockFrequencyInfo.cpp [block-freq] Rename getEntryFrequency() -> getEntryFreq() to match getBlockFreq() in all *BlockFrequencyInfo*. 2013-12-14 02:37:38 +00:00
MachineBlockPlacement.cpp Add a LLVM_DUMP_METHOD macro. 2014-01-03 22:53:37 +00:00
MachineBranchProbabilityInfo.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
MachineCSE.cpp Disabled subregister copy coalescing during MachineCSE. 2013-12-17 19:29:36 +00:00
MachineCodeEmitter.cpp
MachineCopyPropagation.cpp Simplify logic now that r182490 is in place. No functional change intended. 2013-05-22 23:17:36 +00:00
MachineDominators.cpp
MachineFunction.cpp Put the functionality for printing a value to a raw_ostream as an 2014-01-09 02:29:41 +00:00
MachineFunctionAnalysis.cpp
MachineFunctionPass.cpp [stackprotector] Use analysis from the StackProtector pass for stack layout in PEI a nd LocalStackSlot passes. 2013-12-19 03:17:11 +00:00
MachineFunctionPrinterPass.cpp
MachineInstr.cpp Put the functionality for printing a value to a raw_ostream as an 2014-01-09 02:29:41 +00:00
MachineInstrBundle.cpp Move an assertion so it doesn't dereference end(). 2013-01-04 22:17:31 +00:00
MachineLICM.cpp Replace some unnecessary vector copies with references. 2013-09-15 22:04:42 +00:00
MachineLoopInfo.cpp
MachineModuleInfo.cpp Use pointers to the MCAsmInfo and MCRegInfo. 2013-06-18 07:20:20 +00:00
MachineModuleInfoImpls.cpp
MachinePassRegistry.cpp
MachinePostDominators.cpp
MachineRegisterInfo.cpp Re-sort all of the includes with ./utils/sort_includes.py so that 2014-01-07 11:48:04 +00:00
MachineSSAUpdater.cpp Use SmallVectorImpl& instead of SmallVector to avoid repeating small vector size. 2013-07-14 04:42:23 +00:00
MachineScheduler.cpp CodeGen: silence a C++11 feature warning 2013-12-28 22:47:55 +00:00
MachineSink.cpp MachineSink: Fix and tweak critical-edge breaking heuristic. 2013-10-14 16:57:17 +00:00
MachineTraceMetrics.cpp Machine Model: Add MicroOpBufferSize and resource BufferSize. 2013-06-15 04:49:57 +00:00
MachineVerifier.cpp Fix confusing machine verifier error. 2013-11-15 22:18:19 +00:00
Makefile
OcamlGC.cpp
OptimizePHIs.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
PHIElimination.cpp Rename LiveRange to LiveInterval::Segment 2013-10-10 21:28:43 +00:00
PHIEliminationUtils.cpp
PHIEliminationUtils.h Fixed another place in CodeGen where we had a typo in our editor C++ filetype declaration. 2013-08-12 20:52:06 +00:00
Passes.cpp Move the LLVM IR asm writer header files into the IR directory, as they 2014-01-07 12:34:26 +00:00
PeepholeOptimizer.cpp [Peephole] Rewrite copies to avoid cross register banks copies. 2013-09-13 18:26:31 +00:00
PostRASchedulerList.cpp Move the PostRA scheduler's fixupKills function for reuse. 2013-12-28 21:56:55 +00:00
ProcessImplicitDefs.cpp Fix typo 2013-10-04 16:52:58 +00:00
PrologEpilogInserter.cpp Re-sort all of the includes with ./utils/sort_includes.py so that 2014-01-07 11:48:04 +00:00
PrologEpilogInserter.h Remove the --shrink-wrap option. 2013-10-31 14:07:59 +00:00
PseudoSourceValue.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
README.txt Correct wrong register in this example, pointed out by Baoshan Pang. 2013-06-07 08:30:55 +00:00
RegAllocBase.cpp DEBUG shouldEvict decisions 2013-11-22 19:07:42 +00:00
RegAllocBase.h [weak vtables] Remove a bunch of weak vtables 2013-11-19 00:57:56 +00:00
RegAllocBasic.cpp CalcSpillWeights: give a better describing name to calculateSpillWeights 2013-11-11 19:04:45 +00:00
RegAllocFast.cpp Explicitly request unsigned enum types when desired 2013-10-08 20:15:11 +00:00
RegAllocGreedy.cpp [RegAlloc] Make tryInstructionSplit less aggressive. 2014-01-02 22:47:22 +00:00
RegAllocPBQP.cpp [block-freq] Refactor LiveInterals::getSpillWeight to use the new MachineBlockFrequencyInfo methods. 2013-12-14 00:53:32 +00:00
RegisterClassInfo.cpp Make comment more explicit. 2013-12-17 02:18:02 +00:00
RegisterCoalescer.cpp Print register in LiveInterval::print() 2013-10-10 21:29:05 +00:00
RegisterCoalescer.h
RegisterPressure.cpp increase the accuracy of register pressure computation in the presence of dead definitions by using live intervals, if available, to identify dead definitions and proceed accordingly. 2013-11-08 22:46:28 +00:00
RegisterScavenging.cpp RegScavenger should not exclude undef uses 2013-07-11 05:55:57 +00:00
ScheduleDAG.cpp Use SmallVectorImpl instead of SmallVector for iterators and references to avoid specifying the vector size unnecessarily. 2013-07-03 05:11:49 +00:00
ScheduleDAGInstrs.cpp Conservatively handle multiple MMOs in MIsNeedChainEdge 2014-01-08 21:52:02 +00:00
ScheduleDAGPrinter.cpp Put the functionality for printing a value to a raw_ostream as an 2014-01-09 02:29:41 +00:00
ScoreboardHazardRecognizer.cpp
ShadowStackGC.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
SjLjEHPrepare.cpp Reformat code with clang-format. 2013-09-23 20:57:47 +00:00
SlotIndexes.cpp Make some fixes for LiveInterval repair with debug info. Debug value 2013-02-23 10:25:25 +00:00
SpillPlacement.cpp [block-freq] Rename getEntryFrequency() -> getEntryFreq() to match getBlockFreq() in all *BlockFrequencyInfo*. 2013-12-14 02:37:38 +00:00
SpillPlacement.h [block-freq] Store MBFI as a field on SpillPlacement so we can access it to get the entry frequency while processing data. 2013-12-14 00:25:47 +00:00
Spiller.cpp Replacing HUGE_VALF with llvm::huge_valf in order to work around a warning triggered in MSVC 12. 2013-11-13 00:15:44 +00:00
Spiller.h
SplitKit.cpp Work on LiveRange instead of LiveInterval where possible 2013-10-10 21:28:57 +00:00
SplitKit.h Revert "Give internal classes hidden visibility." 2013-09-11 18:05:11 +00:00
StackColoring.cpp Correct word hyphenations 2013-12-05 05:44:44 +00:00
StackMapLivenessAnalysis.cpp [Stackmap] Liveness Analysis Pass 2013-12-14 06:53:06 +00:00
StackMaps.cpp llvm.experimental.stackmap: fix encoding of large constants. 2014-01-09 00:22:31 +00:00
StackProtector.cpp Re-sort all of the includes with ./utils/sort_includes.py so that 2014-01-07 11:48:04 +00:00
StackSlotColoring.cpp [block-freq] Refactor LiveInterals::getSpillWeight to use the new MachineBlockFrequencyInfo methods. 2013-12-14 00:53:32 +00:00
TailDuplication.cpp Remove several unused variables. 2013-10-01 13:32:03 +00:00
TargetFrameLoweringImpl.cpp
TargetInstrInfo.cpp Remove redundant fold call introduced in r195944. Thanks very much to Juergen 2014-01-02 19:38:41 +00:00
TargetLoweringBase.cpp Disable compare sinking in CodeGenPrepare when multiple condition registers are available 2014-01-02 21:13:43 +00:00
TargetLoweringObjectFileImpl.cpp Move the llvm mangler to lib/IR. 2014-01-07 21:19:40 +00:00
TargetOptionsImpl.cpp Re-sort all of the includes with ./utils/sort_includes.py so that 2014-01-07 11:48:04 +00:00
TargetRegisterInfo.cpp PrintVRegOrUnit 2013-08-23 17:48:53 +00:00
TargetSchedule.cpp IfConverter: Use TargetSchedule for instruction latencies 2013-09-30 15:28:56 +00:00
TwoAddressInstructionPass.cpp Allow MachineCSE to coalesce trivial subregister copies the same way that it coalesces normal copies. 2013-12-17 04:50:45 +00:00
UnreachableBlockElim.cpp Remove the very substantial, largely unmaintained legacy PGO 2013-10-02 15:42:23 +00:00
VirtRegMap.cpp [VirtRegMap] Fix for PR17825. Do not ignore noreturn definitions when setting 2013-11-08 18:14:17 +00:00

README.txt

//===---------------------------------------------------------------------===//

Common register allocation / spilling problem:

        mul lr, r4, lr
        str lr, [sp, #+52]
        ldr lr, [r1, #+32]
        sxth r3, r3
        ldr r4, [sp, #+52]
        mla r4, r3, lr, r4

can be:

        mul lr, r4, lr
        mov r4, lr
        str lr, [sp, #+52]
        ldr lr, [r1, #+32]
        sxth r3, r3
        mla r4, r3, lr, r4

and then "merge" mul and mov:

        mul r4, r4, lr
        str r4, [sp, #+52]
        ldr lr, [r1, #+32]
        sxth r3, r3
        mla r4, r3, lr, r4

It also increase the likelihood the store may become dead.

//===---------------------------------------------------------------------===//

bb27 ...
        ...
        %reg1037 = ADDri %reg1039, 1
        %reg1038 = ADDrs %reg1032, %reg1039, %NOREG, 10
    Successors according to CFG: 0x8b03bf0 (#5)

bb76 (0x8b03bf0, LLVM BB @0x8b032d0, ID#5):
    Predecessors according to CFG: 0x8b0c5f0 (#3) 0x8b0a7c0 (#4)
        %reg1039 = PHI %reg1070, mbb<bb76.outer,0x8b0c5f0>, %reg1037, mbb<bb27,0x8b0a7c0>

Note ADDri is not a two-address instruction. However, its result %reg1037 is an
operand of the PHI node in bb76 and its operand %reg1039 is the result of the
PHI node. We should treat it as a two-address code and make sure the ADDri is
scheduled after any node that reads %reg1039.

//===---------------------------------------------------------------------===//

Use local info (i.e. register scavenger) to assign it a free register to allow
reuse:
        ldr r3, [sp, #+4]
        add r3, r3, #3
        ldr r2, [sp, #+8]
        add r2, r2, #2
        ldr r1, [sp, #+4]  <==
        add r1, r1, #1
        ldr r0, [sp, #+4]
        add r0, r0, #2

//===---------------------------------------------------------------------===//

LLVM aggressively lift CSE out of loop. Sometimes this can be negative side-
effects:

R1 = X + 4
R2 = X + 7
R3 = X + 15

loop:
load [i + R1]
...
load [i + R2]
...
load [i + R3]

Suppose there is high register pressure, R1, R2, R3, can be spilled. We need
to implement proper re-materialization to handle this:

R1 = X + 4
R2 = X + 7
R3 = X + 15

loop:
R1 = X + 4  @ re-materialized
load [i + R1]
...
R2 = X + 7 @ re-materialized
load [i + R2]
...
R3 = X + 15 @ re-materialized
load [i + R3]

Furthermore, with re-association, we can enable sharing:

R1 = X + 4
R2 = X + 7
R3 = X + 15

loop:
T = i + X
load [T + 4]
...
load [T + 7]
...
load [T + 15]
//===---------------------------------------------------------------------===//

It's not always a good idea to choose rematerialization over spilling. If all
the load / store instructions would be folded then spilling is cheaper because
it won't require new live intervals / registers. See 2003-05-31-LongShifts for
an example.

//===---------------------------------------------------------------------===//

With a copying garbage collector, derived pointers must not be retained across
collector safe points; the collector could move the objects and invalidate the
derived pointer. This is bad enough in the first place, but safe points can
crop up unpredictably. Consider:

        %array = load { i32, [0 x %obj] }** %array_addr
        %nth_el = getelementptr { i32, [0 x %obj] }* %array, i32 0, i32 %n
        %old = load %obj** %nth_el
        %z = div i64 %x, %y
        store %obj* %new, %obj** %nth_el

If the i64 division is lowered to a libcall, then a safe point will (must)
appear for the call site. If a collection occurs, %array and %nth_el no longer
point into the correct object.

The fix for this is to copy address calculations so that dependent pointers
are never live across safe point boundaries. But the loads cannot be copied
like this if there was an intervening store, so may be hard to get right.

Only a concurrent mutator can trigger a collection at the libcall safe point.
So single-threaded programs do not have this requirement, even with a copying
collector. Still, LLVM optimizations would probably undo a front-end's careful
work.

//===---------------------------------------------------------------------===//

The ocaml frametable structure supports liveness information. It would be good
to support it.

//===---------------------------------------------------------------------===//

The FIXME in ComputeCommonTailLength in BranchFolding.cpp needs to be
revisited. The check is there to work around a misuse of directives in inline
assembly.

//===---------------------------------------------------------------------===//

It would be good to detect collector/target compatibility instead of silently
doing the wrong thing.

//===---------------------------------------------------------------------===//

It would be really nice to be able to write patterns in .td files for copies,
which would eliminate a bunch of explicit predicates on them (e.g. no side 
effects).  Once this is in place, it would be even better to have tblgen 
synthesize the various copy insertion/inspection methods in TargetInstrInfo.

//===---------------------------------------------------------------------===//

Stack coloring improvements:

1. Do proper LiveStackAnalysis on all stack objects including those which are
   not spill slots.
2. Reorder objects to fill in gaps between objects.
   e.g. 4, 1, <gap>, 4, 1, 1, 1, <gap>, 4 => 4, 1, 1, 1, 1, 4, 4

//===---------------------------------------------------------------------===//

The scheduler should be able to sort nearby instructions by their address. For
example, in an expanded memset sequence it's not uncommon to see code like this:

  movl $0, 4(%rdi)
  movl $0, 8(%rdi)
  movl $0, 12(%rdi)
  movl $0, 0(%rdi)

Each of the stores is independent, and the scheduler is currently making an
arbitrary decision about the order.

//===---------------------------------------------------------------------===//

Another opportunitiy in this code is that the $0 could be moved to a register:

  movl $0, 4(%rdi)
  movl $0, 8(%rdi)
  movl $0, 12(%rdi)
  movl $0, 0(%rdi)

This would save substantial code size, especially for longer sequences like
this. It would be easy to have a rule telling isel to avoid matching MOV32mi
if the immediate has more than some fixed number of uses. It's more involved
to teach the register allocator how to do late folding to recover from
excessive register pressure.