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Commit Graph

29666 Commits

Author SHA1 Message Date
Dan Gohman
078794f61e [MC] Refactor emitELFSize to make usage more consistent. NFC.
Move the cast<MCSymbolELF> inside emitELFSize, so that: 
 - it's done in one place instead of at each call
 - it's more consistent with similar functions like EmitCOFFSafeSEH
 - ambiguity between cast<> and dyn_cast<> is avoided (which also
   eliminates an unnecessary dyn_cast call)

This also makes it easier to experiment with using ".size" directives on
non-ELF targets.

llvm-svn: 288437
2016-12-01 23:39:08 +00:00
Eugene Zelenko
341abb7066 Fix broken buildbots because of r288424 (NFC).
llvm-svn: 288426
2016-12-01 22:26:55 +00:00
Eugene Zelenko
181555a389 [ADT, Support, TableGen] Fix some Clang-tidy modernize-use-default and Include What You Use warnings; other minor fixes (NFC).
llvm-svn: 288424
2016-12-01 22:13:24 +00:00
David Blaikie
f594a55419 [debug info] Minor cleanup from D27170/r288399
llvm-svn: 288421
2016-12-01 21:59:09 +00:00
Chih-Hung Hsieh
beaba94b87 [SelectionDAG] getRawSubclassData should not return HasDebugValue.
This change fixes a regression in r279537 and
makes getRawSubclassData behave like r279536.
Without this change, the fp128-g.ll test case will have an
infinite loop involving SoftenFloatRes_LOAD.

Differential Revision: http://reviews.llvm.org/D26942

llvm-svn: 288420
2016-12-01 21:56:33 +00:00
Mehdi Amini
d9082699df Improve documentation on MSVC workaround for AlignedCharArray (NFC)
The comment only mentioned "old version of MSVC".

Differential Revision: https://reviews.llvm.org/D27312

llvm-svn: 288417
2016-12-01 20:54:29 +00:00
Philip Reames
66a2409cf2 Factor out common parts of LVI and Float2Int into ConstantRange [NFCI]
This just extracts out the transfer rules for constant ranges into a single shared point. As it happens, neither bit of code actually overlaps in terms of the handled operators, but with this change that could easily be tweaked in the future.

I also want to have this separated out to make experimenting with a eager value info implementation and possibly a ValueTracking-like fixed depth recursion peephole version. There's no reason all four of these can't share a common implementation which reduces the chances of bugs.

Differential Revision: https://reviews.llvm.org/D27294

llvm-svn: 288413
2016-12-01 20:08:47 +00:00
Dan Gohman
0eeebae7be [WebAssembly] Define more wasm binary encoding constants.
llvm-svn: 288411
2016-12-01 20:02:12 +00:00
Matthias Braun
148c29c710 Move most EH from MachineModuleInfo to MachineFunction
Recommitting r288293 with some extra fixes for GlobalISel code.

Most of the exception handling members in MachineModuleInfo is actually
per function data (talks about the "current function") so it is better
to keep it at the function instead of the module.

This is a necessary step to have machine module passes work properly.

Also:
- Rename TidyLandingPads() to tidyLandingPads()
- Use doxygen member groups instead of "//===- EH ---"... so it is clear
  where a group ends.
- I had to add an ugly const_cast at two places in the AsmPrinter
  because the available MachineFunction pointers are const, but the code
  wants to call tidyLandingPads() in between
  (markFunctionEnd()/endFunction()).

Differential Revision: https://reviews.llvm.org/D27227

llvm-svn: 288405
2016-12-01 19:32:15 +00:00
Mehdi Amini
7fcd86cce5 Fix module map to create a module for the configured header Config/abi-breaking.h
A client of a header that relies on ABI breaking should get the macro
exported there.
Before this, the unittest for Support/Error including Support/Error.h
didn't get the macro exported by the Support module, because the
latter only re-export its submodules and included module, not
textual headers.

Hopefully, it'll also fix the build with local submodule visibility,
since the LLVM_Utils contains two submodules: ADT and Support. They
both include abi-breaking.h that defines a symbol. The textual
inclusion lead to a double definition of the symbol which broke
the parent module.

Differential Revision: https://reviews.llvm.org/D27273

llvm-svn: 288400
2016-12-01 19:08:38 +00:00
Greg Clayton
82231cda69 This change removes the dependency on DwarfDebug that was used for DW_FORM_ref_addr by making a new DIEUnit class in DIE.cpp.
The DIEUnit class represents a compile or type unit and it owns the unit DIE as an instance variable. This allows anyone with a DIE, to get the unit DIE, and then get back to its DIEUnit without adding any new ivars to the DIE class. Why was this needed? The DIE class has an Offset that is always the CU relative DIE offset, not the "offset in debug info section" as was commented in the header file (the comment has been corrected). This is great for performance because most DIE references are compile unit relative and this means most code that accessed the DIE's offset didn't need to make it into a compile unit relative offset because it already was. When we needed to emit a DW_FORM_ref_addr though, we needed to find the absolute offset of the DIE by finding the DIE's compile/type unit. This class did have the absolute debug info/type offset and could be added to the CU relative offset to compute the absolute offset. With this change we can easily get back to a DIE's DIEUnit which will have this needed offset. Prior to this is required having a DwarfDebug and required calling:

DwarfCompileUnit *DwarfDebug::lookupUnit(const DIE *CU) const;
Now we can use the DIEUnit class to do so without needing DwarfDebug. All clients now use DIEUnit objects (the DwarfDebug stack and the DwarfLinker). A follow on patch for the DWARF generator will also take advantage of this.

Differential Revision: https://reviews.llvm.org/D27170

llvm-svn: 288399
2016-12-01 18:56:29 +00:00
Alexey Bataev
7135b5ad24 [SLP] Fixed cost model for horizontal reduction.
Currently when cost of scalar operations is evaluated the vector type is
used for scalar operations. Patch fixes this issue and fixes evaluation
of the vector operations cost.
Several test showed that vector cost model is too optimistic. It
allowed vectorization of 8 or less add/fadd operations, though scalar
code is faster. Actually, only for 16 or more operations vector code
provides better performance.

Differential Revision: https://reviews.llvm.org/D26277

llvm-svn: 288398
2016-12-01 18:42:42 +00:00
Mandeep Singh Grang
1bd40d6822 [llvm] Implement support for -defsym assembler option
Summary:
Changes to llvm-mc to move common logic to separate function.

Related clang patch: https://reviews.llvm.org/D26213

Reviewers: rafael, t.p.northover, colinl, echristo, rengolin

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D26214

llvm-svn: 288396
2016-12-01 18:42:04 +00:00
Adam Nemet
c8b56276e7 [GVN, OptDiag] Print the interesting instructions involved in missed load-elimination
[recommitting after the fix in r288307]

This includes the intervening store and the load/store that we're trying
to forward from in the optimization remark for the missed load
elimination.

This is hooked up under a new mode in ORE that allows for compile-time
budget for a bit more analysis to print more insightful messages.  This
mode is currently enabled for -fsave-optimization-record (-Rpass is
trickier since it is controlled in the front-end).

With this we can now print the red remark in http://lab.llvm.org:8080/artifacts/opt-view_test-suite/build/SingleSource/Benchmarks/Dhrystone/CMakeFiles/dry.dir/html/_org_test-suite_SingleSource_Benchmarks_Dhrystone_dry.c.html#L446

Differential Revision: https://reviews.llvm.org/D26490

llvm-svn: 288381
2016-12-01 17:34:50 +00:00
Adam Nemet
05eccda0d4 [GVN, OptDiag] Include the value that is forwarded in load elimination
[recommitting after the fix in r288307]

This requires some changes to the opt-diag API.  Hal and I have
discussed this at the Dev Meeting and came up with a streaming delimiter
(setExtraArgs) to solve this.

Arguments after this delimiter are only included in the optimization
records and not in the remarks printed in the compiler output.  (Note,
how in the test the content of the YAML file changes but the remarks on
the compiler output don't.)

This implements the green GVN message with a bug fix at line
http://lab.llvm.org:8080/artifacts/opt-view_test-suite/build/SingleSource/Benchmarks/Dhrystone/CMakeFiles/dry.dir/html/_org_test-suite_SingleSource_Benchmarks_Dhrystone_dry.c.html#L446

The fix is that now we properly include the constant value in the
message: "load of type i32 eliminated in favor of 7"

Differential Revision: https://reviews.llvm.org/D26489

llvm-svn: 288380
2016-12-01 17:34:44 +00:00
Adam Nemet
ecf9aaa497 [GVN] Basic optimization remark support
[recommitting after the fix in r288307]

Follow-on patches will add more interesting cases.

The goal of this patch-set is to get the GVN messages printed in
opt-viewer from Dhrystone as was presented in my Dev Meeting talk.  This
is the optimization view for the function (the last remark in the
function has a bug which is fixed in this series):
http://lab.llvm.org:8080/artifacts/opt-view_test-suite/build/SingleSource/Benchmarks/Dhrystone/CMakeFiles/dry.dir/html/_org_test-suite_SingleSource_Benchmarks_Dhrystone_dry.c.html#L430

Differential Revision: https://reviews.llvm.org/D26488

llvm-svn: 288370
2016-12-01 16:40:32 +00:00
Eric Christopher
4e57c02b4a Temporarily Revert "Move most EH from MachineModuleInfo to MachineFunction"
This apprears to have broken the global isel bot:
http://lab.llvm.org:8080/green/job/clang-stage1-cmake-RA-globalisel_build/5174/console

This reverts commit r288293.

llvm-svn: 288322
2016-12-01 07:50:12 +00:00
Peter Collingbourne
7f3cfca4ed Object: Add SF_Executable symbol flag.
This allows us to remove a few uses of IRObjectFile::getSymbolGV() in
llvm-nm.

While here change host-dependent logic in llvm-nm to target-dependent
logic.

Differential Revision: https://reviews.llvm.org/D27075

llvm-svn: 288320
2016-12-01 06:53:47 +00:00
Peter Collingbourne
cfd25fdfa1 Object: Extract a ModuleSymbolTable class from IRObjectFile.
This class represents a symbol table built from in-memory IR. It provides
access to GlobalValues and should only be used if such access is required
(e.g. in the LTO implementation). We will eventually change IRObjectFile
to read from a bitcode symbol table rather than using ModuleSymbolTable,
so it would not be able to expose the module.

Differential Revision: https://reviews.llvm.org/D27073

llvm-svn: 288319
2016-12-01 06:51:47 +00:00
Peter Collingbourne
dfb6dfca5e Bitcode: Introduce BitcodeModule::{has,get}Summary().
These are equivalent to hasGlobalValueSummary() and getModuleSummaryIndex().

Differential Revision: https://reviews.llvm.org/D27242

llvm-svn: 288317
2016-12-01 06:00:53 +00:00
Peter Collingbourne
7f0f3ad816 LTO: Remove ModuleLoader, make loadModuleFromBuffer static and move into its only client, ThinLTOCodeGenerator.
This is no longer the recommended way to load modules for importing, so it should not be public API.

Differential Revision: https://reviews.llvm.org/D27292

llvm-svn: 288316
2016-12-01 05:52:32 +00:00
Adam Nemet
2a29152193 [GVN] When merging blocks update LoopInfo if it's available
If LoopInfo is available during GVN, BasicAA will use it.  However
MergeBlockIntoPredecessor does not update LI as it merges blocks.

This didn't use to cause problems because LI was freed before
GVN/BasicAA.  Now with OptimizationRemarkEmitter, the lifetime of LI is
extended so LI needs to be kept up-to-date during GVN.

Differential Revision: https://reviews.llvm.org/D27288

llvm-svn: 288307
2016-12-01 03:56:43 +00:00
Ivan Krasin
a46f4c6583 Use trigrams to speed up SpecialCaseList.
Summary:
it's often the case when the rules in the SpecialCaseList
are of the form hel.o*bar. That gives us a chance to build
trigram index to quickly discard 99% of inputs without
running a full regex. A similar idea was used in Google Code Search
as described in the blog post:
https://swtch.com/~rsc/regexp/regexp4.html

The check is defeated, if there's at least one regex
more complicated than that. In this case, all inputs
will go through the regex. That said, the real-world
rules are often simple or can be simplied. That considerably
speeds up compiling Chromium with CFI and UBSan.

As measured on Chromium's content_message_generator.cc:

before, CFI: 44 s
after, CFI: 23 s
after, CFI, no blacklist: 23 s (~1% slower, but 3 runs were unable to show the difference)
after, regular compilation to bitcode: 23 s

Reviewers: pcc

Subscribers: mgorny, llvm-commits

Differential Revision: https://reviews.llvm.org/D27188

llvm-svn: 288303
2016-12-01 02:54:54 +00:00
Peter Collingbourne
56451c8fb1 LTO: Remove Symbol::getIRName().
Its only use was in the LTO implementation. Also document
Symbol::getName().

llvm-svn: 288302
2016-12-01 02:51:12 +00:00
Matthias Braun
6a2832f1f2 Move most EH from MachineModuleInfo to MachineFunction
Most of the exception handling members in MachineModuleInfo is actually
per function data (talks about the "current function") so it is better
to keep it at the function instead of the module.

This is a necessary step to have machine module passes work properly.

Also:
- Rename TidyLandingPads() to tidyLandingPads()
- Use doxygen member groups instead of "//===- EH ---"... so it is clear
  where a group ends.
- I had to add an ugly const_cast at two places in the AsmPrinter
  because the available MachineFunction pointers are const, but the code
  wants to call tidyLandingPads() in between
  (markFunctionEnd()/endFunction()).

Differential Revision: https://reviews.llvm.org/D27227

llvm-svn: 288293
2016-11-30 23:49:01 +00:00
Matthias Braun
566827a026 Move VariableDbgInfo from MachineModuleInfo to MachineFunction
VariableDbgInfo is per function data, so it makes sense to have it with
the function instead of the module.

This is a necessary step to have machine module passes work properly.

Differential Revision: https://reviews.llvm.org/D27186

llvm-svn: 288292
2016-11-30 23:48:50 +00:00
Matthias Braun
ced7bf3e1d Move FrameInstructions from MachineModuleInfo to MachineFunction
This is per function data so it is better kept at the function instead
of the module.

This is a necessary step to have machine module passes work properly.

Differential Revision: https://reviews.llvm.org/D27185

llvm-svn: 288291
2016-11-30 23:48:42 +00:00
Matthias Braun
c909de5624 MCStreamer: Use "cfi" for CFI related temp labels.
Choosing a "cfi" name makes the intend a bit clearer in an assembly dump
and more importantly the assembly dumps are slightly more stable as the
numbers don't move around anymore when unrelated code calls
createTempSymbol() more or less often.
As they are temp labels the name doesn't influence the generated object
code.

Differential Revision: https://reviews.llvm.org/D27244

llvm-svn: 288290
2016-11-30 23:48:26 +00:00
Eugene Zelenko
f6dfd4f698 Fix some Clang-tidy modernize-use-default and Include What You Use warnings; other minor fixes (NFC).
llvm-svn: 288285
2016-11-30 23:10:42 +00:00
David Callahan
a4726764ec Only computeRelativePath() on new members
Summary:
When using thin archives, and processing the same archive multiple times, we were mangling existing entries.  The root cause is that we were calling computeRelativePath() more than once.   Here, we only call it when adding new members to an archive.

Note that D27218 changes the way thin archives are printed, and will break the new unit test included here.  Depending on which one lands first, the other will need to be slightly modified.

Reviewers: rafael, davide

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D27217

llvm-svn: 288280
2016-11-30 22:32:58 +00:00
Joel Jones
0d9a67f578 [AArch64] Refactor LSE support as feature separate from V8.1a support.
Summary:
This is preparation for ThunderX processors that have Large
System Extension (LSE) atomic instructions, but not the 
other instructions introduced by V8.1a.
This will mimic changes to GCC as described here:
https://gcc.gnu.org/ml/gcc-patches/2015-06/msg00388.html

LSE instructions are: LD/ST<op>, CAS*, SWP

Reviewers: t.p.northover, echristo, jmolloy, rengolin

Subscribers: aemerson, mehdi_amini

Differential Revision: https://reviews.llvm.org/D26621

llvm-svn: 288279
2016-11-30 22:25:24 +00:00
Matthias Braun
32bde7b907 Clarify rules for reserved regs, fix aarch64 ones.
No test case necessary as the problematic condition is checked with the
newly introduced assertAllSuperRegsMarked() function.

Differential Revision: https://reviews.llvm.org/D26648

llvm-svn: 288277
2016-11-30 22:17:10 +00:00
Michael Kuperstein
c222d94c24 [LoopUnroll] Implement profile-based loop peeling
This implements PGO-driven loop peeling.

The basic idea is that when the average dynamic trip-count of a loop is known,
based on PGO, to be low, we can expect a performance win by peeling off the
first several iterations of that loop.
Unlike unrolling based on a known trip count, or a trip count multiple, this
doesn't save us the conditional check and branch on each iteration. However,
it does allow us to simplify the straight-line code we get (constant-folding,
etc.). This is important given that we know that we will usually only hit this
code, and not the actual loop.

This is currently disabled by default.

Differential Revision: https://reviews.llvm.org/D25963

llvm-svn: 288274
2016-11-30 21:13:57 +00:00
Derek Schuff
30f006473b [WebAssembly] Add llvm-objdump support for wasm file format
This is the first part of an effort to add wasm binary
support across all llvm tools.

Patch by Sam Clegg

Differential Revision: https://reviews.llvm.org/D26172

llvm-svn: 288251
2016-11-30 16:49:11 +00:00
Adam Nemet
285ae7786d Revert "[GVN] Basic optimization remark support"
This reverts commit r288210.

The failure on the stage2 LTO build is back.

llvm-svn: 288226
2016-11-30 01:14:35 +00:00
Adam Nemet
acff41aed1 [GVN] Basic optimization remark support
[recommiting patches one-by-one to see which breaks the stage2 LTO bot]

Follow-on patches will add more interesting cases.

The goal of this patch-set is to get the GVN messages printed in
opt-viewer from Dhrystone as was presented in my Dev Meeting talk.  This
is the optimization view for the function (the last remark in the
function has a bug which is fixed in this series):
http://lab.llvm.org:8080/artifacts/opt-view_test-suite/build/SingleSource/Benchmarks/Dhrystone/CMakeFiles/dry.dir/html/_org_test-suite_SingleSource_Benchmarks_Dhrystone_dry.c.html#L430

Differential Revision: https://reviews.llvm.org/D26488

llvm-svn: 288210
2016-11-29 22:37:01 +00:00
Peter Collingbourne
52fcea9a2e Add llvm-modextract tool.
This program is for testing features that rely on multi-module bitcode files.
It takes a multi-module bitcode file, extracts one of the modules and writes
it to the output file.

Differential Revision: https://reviews.llvm.org/D26778

llvm-svn: 288201
2016-11-29 21:54:33 +00:00
Peter Collingbourne
19a350cfed Bitcode: Introduce BitcodeWriter interface.
This interface allows clients to write multiple modules to a single
bitcode file. Also introduce the llvm-cat utility which can be used
to create a bitcode file containing multiple modules.

Differential Revision: https://reviews.llvm.org/D26179

llvm-svn: 288195
2016-11-29 20:43:47 +00:00
Adam Nemet
aa8eea6427 Revert "[GVN] Basic optimization remark support"
This reverts commit r288046.

Trying to see if the revert fixes a compiler crash during a stage2 LTO
build with a GVN backtrace.

llvm-svn: 288179
2016-11-29 18:32:04 +00:00
Adam Nemet
dca038fdfb Revert "[GVN, OptDiag] Include the value that is forwarded in load elimination"
This reverts commit r288047.

Trying to see if the revert fixes a compiler crash during a stage2 LTO
build with a GVN backtrace.

llvm-svn: 288178
2016-11-29 18:32:00 +00:00
Adam Nemet
ee7ff0a4cd Revert "[GVN, OptDiag] Print the interesting instructions involved in missed load-elimination"
This reverts commit r288090.

Trying to see if the revert fixes a compiler crash during a stage2 LTO
build with a GVN backtrace.

llvm-svn: 288177
2016-11-29 18:31:53 +00:00
NAKAMURA Takumi
fd2258bf45 Suppress abi-breaking.h on cygming, for now.
FIXME: Implement checks without weak for them.
llvm-svn: 288168
2016-11-29 17:32:58 +00:00
Chandler Carruth
2001edc7fd [PM] Fix a bad invalid densemap iterator bug in the new invalidation
logic.

Yup, the invalidation logic has an invalid iterator bug. Can't make this
stuff up.

We can recursively insert things into the map so we can't cache the
iterator into that map across those recursive calls. We did this
differently in two places. I have an end-to-end test that triggers at
least one of them. I'm going to work on a nice minimal test case that
triggers these, but I didn't want to leave the bug in the tree while
I tried to trigger it.

Also, the dense map iterator checking stuff we have now is awesome. =D

llvm-svn: 288135
2016-11-29 12:54:34 +00:00
Malcolm Parsons
2eb7118041 [StringRef] Use default member initializers and = default.
Summary: This makes the default constructor implicitly constexpr and noexcept.

Reviewers: zturner, beanz

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D27094

llvm-svn: 288131
2016-11-29 10:53:18 +00:00
Alexey Bataev
62124599cb [SLPVectorizer] Improved support of partial tree vectorization.
Currently SLP vectorizer tries to vectorize a binary operation and dies
immediately after unsuccessful the first unsuccessfull attempt. Patch
tries to improve the situation, trying to vectorize all binary
operations of all children nodes in the binop tree.

Differential Revision: https://reviews.llvm.org/D25517

llvm-svn: 288115
2016-11-29 08:21:14 +00:00
Peter Collingbourne
73ec8f79de Bitcode: Change expected layout of module blocks.
We now expect each module's identification block to appear immediately before
the module block. Any module block that appears without an identification block
immediately before it is interpreted as if it does not have a module block.

Also change the interpretation of VST and function offsets in bitcode.
The offset is always taken as relative to the start of the identification
(or module if not present) block, minus one word. This corresponds to the
historical interpretation of offsets, i.e. relative to the start of the file.

These changes allow for bitcode modules to be concatenated by copying bytes.

Differential Revision: https://reviews.llvm.org/D27184

llvm-svn: 288098
2016-11-29 02:27:04 +00:00
Adam Nemet
cc71c27f30 [GVN, OptDiag] Print the interesting instructions involved in missed load-elimination
This includes the intervening store and the load/store that we're trying
to forward from in the optimization remark for the missed load
elimination.

This is hooked up under a new mode in ORE that allows for compile-time
budget for a bit more analysis to print more insightful messages.  This
mode is currently enabled for -fsave-optimization-record (-Rpass is
trickier since it is controlled in the front-end).

With this we can now print the red remark in http://lab.llvm.org:8080/artifacts/opt-view_test-suite/build/SingleSource/Benchmarks/Dhrystone/CMakeFiles/dry.dir/html/_org_test-suite_SingleSource_Benchmarks_Dhrystone_dry.c.html#L446

Differential Revision: https://reviews.llvm.org/D26490

llvm-svn: 288090
2016-11-29 00:09:22 +00:00
Mehdi Amini
c518a52036 Put ABI breaking test in Error checking behind LLVM_ENABLE_ABI_BREAKING_CHECKS
This macro is supposed to be the one controlling the compatibility
of ABI breaks induced when enabling or disabling assertions in LLVM.

The macro is enabled by default in assertions build, so this commit
won't disable the tests.

Differential Revision: https://reviews.llvm.org/D26700

llvm-svn: 288087
2016-11-28 22:57:11 +00:00
Mehdi Amini
cfa184f7d2 Add link-time detection of LLVM_ABI_BREAKING_CHECKS mismatch
The macro LLVM_ENABLE_ABI_BREAKING_CHECKS is moved to a new header
abi-breaking.h, from llvm-config.h. Only headers that are using the
macro are including this new header.

LLVM will define a symbol, either EnableABIBreakingChecks or
DisableABIBreakingChecks depending on the configuration setting for
LLVM_ABI_BREAKING_CHECKS.

The abi-breaking.h header will add weak references to these symbols in
every clients that includes this header. This should ensure that
a mismatch triggers a link failure (or a load time failure for DSO).

On MSVC, the pragma "detect_mismatch" is used instead.

Differential Revision: https://reviews.llvm.org/D26876

llvm-svn: 288082
2016-11-28 22:23:53 +00:00
Chandler Carruth
84780666b4 [PM] Extend the explicit 'invalidate' method API on analysis results to
accept an Invalidator that allows them to invalidate themselves if their
dependencies are in turn invalidated.

Rather than recording the dependency graph ahead of time when analysis
get results from other analyses, this simply lets each result trigger
the immediate invalidation of any analyses they actually depend on. They
do this in a way that has three nice properties:

1) They don't have to handle transitive dependencies because the
   infrastructure will recurse for them.
2) The invalidate methods are still called only once. We just
   dynamically discover the necessary topological ordering, everything
   is memoized nicely.
3) The infrastructure still provides a default implementation and can
   access it so that only analyses which have dependencies need to do
   anything custom.

To make this work at all, the invalidation logic also has to defer the
deletion of the result objects themselves so that they can remain alive
until we have collected the complete set of results to invalidate.

A unittest is added here that has exactly the dependency pattern we are
concerned with. It hit the use-after-free described by Sean in much
detail in the long thread about analysis invalidation before this
change, and even in an intermediate form of this change where we failed
to defer the deletion of the result objects.

There is an important problem with doing dependency invalidation that
*isn't* solved here: we don't *enforce* that results correctly
invalidate all the analyses whose results they depend on.

I actually looked at what it would take to do that, and it isn't as hard
as I had thought but the complexity it introduces seems very likely to
outweigh the benefit. The technique would be to provide a base class for
an analysis result that would be populated with other results, and
automatically provide the invalidate method which immediately does the
correct thing. This approach has some nice pros IMO:
- Handles the case we care about and nothing else: only *results*
  that depend on other analyses trigger extra invalidation.
- Localized to the result rather than centralized in the analysis
  manager.
- Ties the storage of the reference to another result to the triggering
  of the invalidation of that analysis.
- Still supports extending invalidation in customized ways.

But the down sides here are:
- Very heavy-weight meta-programming is needed to provide this base
  class.
- Requires a pretty awful API for accessing the dependencies.

Ultimately, I fear it will not pull its weight. But we can re-evaluate
this at any point if we start discovering consistent problems where the
invalidation and dependencies get out of sync. It will fit as a clean
layer on top of the facilities in this patch that we can add if and when
we need it.

Note that I'm not really thrilled with the names for these APIs... The
name "Invalidator" seems ok but not great. The method name "invalidate"
also. In review some improvements were suggested, but they really need
*other* uses of these terms to be updated as well so I'm going to do
that in a follow-up commit.

I'm working on the actual fixes to various analyses that need to use
these, but I want to try to get tests for each of them so we don't
regress. And those changes are seperable and obvious so once this goes
in I should be able to roll them out throughout LLVM.

Many thanks to Sean, Justin, and others for help reviewing here.

Differential Revision: https://reviews.llvm.org/D23738

llvm-svn: 288077
2016-11-28 22:04:31 +00:00