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4561 Commits

Author SHA1 Message Date
Nemanja Ivanovic
a5dac0b623 Vector element extraction without stack operations on Power 8
This patch corresponds to review:
http://reviews.llvm.org/D12032

This patch builds onto the patch that provided scalar to vector conversions
without stack operations (D11471).
Included in this patch:

    - Vector element extraction for all vector types with constant element number
    - Vector element extraction for v16i8 and v8i16 with variable element number
    - Removal of some unnecessary COPY_TO_REGCLASS operations that ended up
      unnecessarily moving things around between registers

Not included in this patch (will be in upcoming patch):

    - Vector element extraction for v4i32, v4f32, v2i64 and v2f64 with
      variable element number
    - Vector element insertion for variable/constant element number

Testing is provided for all extractions. The extractions that are not
implemented yet are just placeholders.

llvm-svn: 249822
2015-10-09 11:12:18 +00:00
Duncan P. N. Exon Smith
a8b2dd10e2 PowerPC: Don't use getNextNode() for insertion point
Stop using `getNextNode()` to create an insertion point for machine
instructions (at least, in this one place).  Instead, use an iterator.
As a drive-by, clean up dump statements to use iterator logic.

The `getNextNode()` interface isn't actually supposed to work for
insertion points; it's supposed to return `nullptr` if this is the last
node.  It's currently broken and will "happen" to work, but if we ever
fix the function, we'll get some strange failures.

llvm-svn: 249758
2015-10-08 22:20:37 +00:00
Rafael Espindola
d32e304f9c Fix pr24486.
This extends the work done in r233995 so that now getFragment (in addition to
getSection) also works for variable symbols.

With that the existing logic to decide if a-b can be computed works even if
a or b are variables. Given that, the expression evaluation can avoid expanding
variables as aggressively and that in turn lets the relocation code see the
original variable.

In order for this to work with the asm streamer, there is now a dummy fragment
per section. It is used to assign a section to a symbol when no other fragment
exists.

This patch is a joint work by Maxim Ostapenko andy myself.

llvm-svn: 249303
2015-10-05 12:07:05 +00:00
Hal Finkel
64fd7537a1 [PowerPC] Disable shrink wrapping
Shrink wrapping is causing a self-hosting failure on PPC64/Linux. Disable for
now until the problem can be fixed.

llvm-svn: 248924
2015-09-30 17:29:03 +00:00
Nemanja Ivanovic
fd63bba5b3 Addition of interfaces the BE to conform to Table A-2 of ELF V2 ABI V1.1
This patch corresponds to review:
http://reviews.llvm.org/D13191

Back end portion of the fifth round of additions to altivec.h.

llvm-svn: 248809
2015-09-29 17:41:53 +00:00
Andrew Kaylor
8d27e2d077 Improved the interface of methods commuting operands, improved X86-FMA3 mem-folding&coalescing.
Patch by Slava Klochkov (vyacheslav.n.klochkov@intel.com)

Differential Revision: http://reviews.llvm.org/D11370

llvm-svn: 248735
2015-09-28 20:33:22 +00:00
Matthias Braun
c0bbfcbec3 MachineBasicBlock: Factor out common code into isReturnBlock()
llvm-svn: 248617
2015-09-25 21:25:19 +00:00
Sanjoy Das
c636db0b30 [SCEV] Introduce ScalarEvolution::getOne and getZero.
Summary:
It is fairly common to call SE->getConstant(Ty, 0) or
SE->getConstant(Ty, 1); this change makes such uses a little bit
briefer.

I've refactored the call sites I could find easily to use getZero /
getOne.

Reviewers: hfinkel, majnemer, reames

Subscribers: sanjoy, llvm-commits

Differential Revision: http://reviews.llvm.org/D12947

llvm-svn: 248362
2015-09-23 01:59:04 +00:00
NAKAMURA Takumi
162c68483b Prune trailing whitespaces.
llvm-svn: 248265
2015-09-22 11:19:03 +00:00
NAKAMURA Takumi
dd4e00ed1e Untabify.
llvm-svn: 248264
2015-09-22 11:15:07 +00:00
NAKAMURA Takumi
28276df470 Reformat blank lines.
llvm-svn: 248263
2015-09-22 11:14:39 +00:00
NAKAMURA Takumi
a6e5b048c7 Reformat comment lines.
llvm-svn: 248262
2015-09-22 11:14:12 +00:00
NAKAMURA Takumi
8c11e8767b Reformat.
llvm-svn: 248261
2015-09-22 11:13:55 +00:00
NAKAMURA Takumi
65f46936a1 Fix utf8 chars.
llvm-svn: 248259
2015-09-22 11:10:08 +00:00
Chad Rosier
432f88b93e [Machine Combiner] Refactor machine reassociation code to be target-independent.
No functional change intended.
Patch by Haicheng Wu <haicheng@codeaurora.org>!

http://reviews.llvm.org/D12887
PR24522

llvm-svn: 248164
2015-09-21 15:09:11 +00:00
Eric Christopher
a096f8ec12 constify the Function parameter to the TTI creation callback and
propagate to all callers/users/etc.

llvm-svn: 247864
2015-09-16 23:38:13 +00:00
Sanjay Patel
a84e4eb51a propagate fast-math-flags on DAG nodes
After D10403, we had FMF in the DAG but disabled by default. Nick reported no crashing errors after some stress testing, 
so I enabled them at r243687. However, Escha soon notified us of a bug not covered by any in-tree regression tests: 
if we don't propagate the flags, we may fail to CSE DAG nodes because differing FMF causes them to not match. There is
one test case in this patch to prove that point.

This patch hopes to fix or leave a 'TODO' for all of the in-tree places where we create nodes that are FMF-capable. I 
did this by putting an assert in SelectionDAG.getNode() to find any FMF-capable node that was being created without FMF
( D11807 ). I then ran all regression tests and test-suite and confirmed that everything passes.

This patch exposes remaining work to get DAG FMF to be fully functional: (1) add the flags to non-binary nodes such as
FCMP, FMA and FNEG; (2) add the flags to intrinsics; (3) use the flags as conditions for transforms rather than the
current global settings.

Differential Revision: http://reviews.llvm.org/D12095

llvm-svn: 247815
2015-09-16 16:31:21 +00:00
Daniel Sanders
a6be0437bb Revert r247692: Replace Triple with a new TargetTuple in MCTargetDesc/* and related. NFC.
Eric has replied and has demanded the patch be reverted.

llvm-svn: 247702
2015-09-15 16:17:27 +00:00
Daniel Sanders
2df05b7d7d Re-commit r247683: Replace Triple with a new TargetTuple in MCTargetDesc/* and related. NFC.
Summary:
This is the first patch in the series to migrate Triple's (which are ambiguous)
to TargetTuple's (which aren't).

For the moment, TargetTuple simply passes all requests to the Triple object it
holds. Once it has replaced Triple, it will start to implement the interface in
a more suitable way.

This change makes some changes to the public C++ API. In particular,
InitMCSubtargetInfo(), createMCRelocationInfo(), and createMCSymbolizer()
now take TargetTuples instead of Triples. The other public C++ API's have
been left as-is for the moment to reduce patch size.

This commit also contains a trivial patch to clang to account for the C++ API
change. Thanks go to Pavel Labath for fixing LLDB for me.

Reviewers: rengolin

Subscribers: jyknight, dschuff, arsenm, rampitec, danalbert, srhines, javed.absar, dsanders, echristo, emaste, jholewinski, tberghammer, ted, jfb, llvm-commits, rengolin

Differential Revision: http://reviews.llvm.org/D10969

llvm-svn: 247692
2015-09-15 14:08:28 +00:00
Daniel Sanders
e42ee9384a Revert r247684 - Replace Triple with a new TargetTuple ...
LLDB needs to be updated in the same commit.

llvm-svn: 247686
2015-09-15 13:46:21 +00:00
Daniel Sanders
f247476e1e Replace Triple with a new TargetTuple in MCTargetDesc/* and related. NFC.
Summary:
This is the first patch in the series to migrate Triple's (which are ambiguous)
to TargetTuple's (which aren't).

For the moment, TargetTuple simply passes all requests to the Triple object it
holds. Once it has replaced Triple, it will start to implement the interface in
a more suitable way.

This change makes some changes to the public C++ API. In particular,
InitMCSubtargetInfo(), createMCRelocationInfo(), and createMCSymbolizer()
now take TargetTuples instead of Triples. The other public C++ API's have
been left as-is for the moment to reduce patch size.

This commit also contains a trivial patch to clang to account for the C++ API
change.

Reviewers: rengolin

Subscribers: jyknight, dschuff, arsenm, rampitec, danalbert, srhines, javed.absar, dsanders, echristo, emaste, jholewinski, tberghammer, ted, jfb, llvm-commits, rengolin

Differential Revision: http://reviews.llvm.org/D10969

llvm-svn: 247683
2015-09-15 13:17:40 +00:00
Daniel Sanders
68efbaf9b2 Fix namespace indentation and missing blank lines before 'public:' in *MCAsmInfo.h. NFC.
This is to reduce noise in a following commit.

Also fixes a couple missing spaces before the reference operator.

llvm-svn: 247679
2015-09-15 12:27:06 +00:00
NAKAMURA Takumi
2140c9830e PPCFrameLowering::emitEpilogue(): Avoid manipulating MBBI on iterator end.
It caused crash in MachineInstr::hasPropertyInBundle() since r247237.

llvm-svn: 247395
2015-09-11 08:20:56 +00:00
Cong Hou
16bf52a24c Pass BranchProbability/BlockMass by value instead of const& as they are small. NFC.
llvm-svn: 247357
2015-09-10 23:10:42 +00:00
Kit Barton
8bde6cb866 Enable the shrink wrapping optimization for PPC64.
The changes in this patch are as follows:
  1. Modify the emitPrologue and emitEpilogue methods to work properly when the prologue and epilogue blocks are not the first/last blocks in the function
  2. Fix a bug in PPCEarlyReturn optimization caused by an empty entry block in the function
  3. Override the runShrinkWrap PredicateFtor (defined in TargetMachine) to check whether shrink wrapping should run:
      Shrink wrapping will run on PPC64 (Little Endian and Big Endian) unless -enable-shrink-wrap=false is specified on command line

A new test case, ppc-shrink-wrapping.ll was created based on the existing shrink wrapping tests for x86, arm, and arm64.

Phabricator review: http://reviews.llvm.org/D11817

llvm-svn: 247237
2015-09-10 01:55:44 +00:00
Chandler Carruth
d7003090ac [PM/AA] Rebuild LLVM's alias analysis infrastructure in a way compatible
with the new pass manager, and no longer relying on analysis groups.

This builds essentially a ground-up new AA infrastructure stack for
LLVM. The core ideas are the same that are used throughout the new pass
manager: type erased polymorphism and direct composition. The design is
as follows:

- FunctionAAResults is a type-erasing alias analysis results aggregation
  interface to walk a single query across a range of results from
  different alias analyses. Currently this is function-specific as we
  always assume that aliasing queries are *within* a function.

- AAResultBase is a CRTP utility providing stub implementations of
  various parts of the alias analysis result concept, notably in several
  cases in terms of other more general parts of the interface. This can
  be used to implement only a narrow part of the interface rather than
  the entire interface. This isn't really ideal, this logic should be
  hoisted into FunctionAAResults as currently it will cause
  a significant amount of redundant work, but it faithfully models the
  behavior of the prior infrastructure.

- All the alias analysis passes are ported to be wrapper passes for the
  legacy PM and new-style analysis passes for the new PM with a shared
  result object. In some cases (most notably CFL), this is an extremely
  naive approach that we should revisit when we can specialize for the
  new pass manager.

- BasicAA has been restructured to reflect that it is much more
  fundamentally a function analysis because it uses dominator trees and
  loop info that need to be constructed for each function.

All of the references to getting alias analysis results have been
updated to use the new aggregation interface. All the preservation and
other pass management code has been updated accordingly.

The way the FunctionAAResultsWrapperPass works is to detect the
available alias analyses when run, and add them to the results object.
This means that we should be able to continue to respect when various
passes are added to the pipeline, for example adding CFL or adding TBAA
passes should just cause their results to be available and to get folded
into this. The exception to this rule is BasicAA which really needs to
be a function pass due to using dominator trees and loop info. As
a consequence, the FunctionAAResultsWrapperPass directly depends on
BasicAA and always includes it in the aggregation.

This has significant implications for preserving analyses. Generally,
most passes shouldn't bother preserving FunctionAAResultsWrapperPass
because rebuilding the results just updates the set of known AA passes.
The exception to this rule are LoopPass instances which need to preserve
all the function analyses that the loop pass manager will end up
needing. This means preserving both BasicAAWrapperPass and the
aggregating FunctionAAResultsWrapperPass.

Now, when preserving an alias analysis, you do so by directly preserving
that analysis. This is only necessary for non-immutable-pass-provided
alias analyses though, and there are only three of interest: BasicAA,
GlobalsAA (formerly GlobalsModRef), and SCEVAA. Usually BasicAA is
preserved when needed because it (like DominatorTree and LoopInfo) is
marked as a CFG-only pass. I've expanded GlobalsAA into the preserved
set everywhere we previously were preserving all of AliasAnalysis, and
I've added SCEVAA in the intersection of that with where we preserve
SCEV itself.

One significant challenge to all of this is that the CGSCC passes were
actually using the alias analysis implementations by taking advantage of
a pretty amazing set of loop holes in the old pass manager's analysis
management code which allowed analysis groups to slide through in many
cases. Moving away from analysis groups makes this problem much more
obvious. To fix it, I've leveraged the flexibility the design of the new
PM components provides to just directly construct the relevant alias
analyses for the relevant functions in the IPO passes that need them.
This is a bit hacky, but should go away with the new pass manager, and
is already in many ways cleaner than the prior state.

Another significant challenge is that various facilities of the old
alias analysis infrastructure just don't fit any more. The most
significant of these is the alias analysis 'counter' pass. That pass
relied on the ability to snoop on AA queries at different points in the
analysis group chain. Instead, I'm planning to build printing
functionality directly into the aggregation layer. I've not included
that in this patch merely to keep it smaller.

Note that all of this needs a nearly complete rewrite of the AA
documentation. I'm planning to do that, but I'd like to make sure the
new design settles, and to flesh out a bit more of what it looks like in
the new pass manager first.

Differential Revision: http://reviews.llvm.org/D12080

llvm-svn: 247167
2015-09-09 17:55:00 +00:00
Eric Christopher
a3c9004b9c Fix the PPC CTR Loop pass to look for calls to the intrinsics that
read CTR and count them as reading the CTR.

llvm-svn: 247083
2015-09-08 22:14:58 +00:00
Hal Finkel
2e0ee83cd9 [PowerPC] Don't commute trivial rlwimi instructions
To commute a trivial rlwimi instructions (meaning one with a full mask and zero
shift), we'd need to ability to form an all-zero mask (instead of an all-one
mask) using rlwimi. We can't represent this, however, and we'll miscompile code
if we try.

The code quality problem that this highlights (that SDAG simplification can
lead to us generating an ISD::OR node with a constant zero LHS) will be fixed
as a follow-up.

Fixes PR24719.

llvm-svn: 246937
2015-09-06 04:17:30 +00:00
Hal Finkel
2d02d8085a [PowerPC] Fix and(or(x, c1), c2) -> rlwimi generation
PPCISelDAGToDAG has a transformation that generates a rlwimi instruction from
an input pattern that looks like this:

  and(or(x, c1), c2)

but the associated logic does not work if there are bits that are 1 in c1 but 0
in c2 (these are normally canonicalized away, but that can't happen if the 'or'
has other users. Make sure we abort the transformation if such bits are
discovered.

Fixes PR24704.

llvm-svn: 246900
2015-09-05 00:02:59 +00:00
Hal Finkel
1b270f3e9b [PowerPC] Enable interleaved-access vectorization
This adds a basic cost model for interleaved-access vectorization (and a better
default for shuffles), and enables interleaved-access vectorization by default.
The relevant difference from the default cost model for interleaved-access
vectorization, is that on PPC, the shuffles that end up being used are *much*
cheaper than modeling the process with insert/extract pairs (which are
quite expensive, especially on older cores).

llvm-svn: 246824
2015-09-04 00:10:41 +00:00
Hal Finkel
60a2a5bada [PowerPC] Always use aggressive interleaving on the A2
On the A2, with an eye toward QPX unaligned-load merging, we should always use
aggressive interleaving. It is generally superior to only using concatenation
unrolling.

llvm-svn: 246819
2015-09-03 23:23:00 +00:00
Hal Finkel
978e2d8bf0 [PowerPC] Try harder to find a base+offset when looking for consecutive accesses
When forming permutation-based unaligned vector loads, we need to know whether
it is valid to read ahead of the requested address by a full vector length.
Doing so is more efficient (and allows for more CSE with later loads), but
could trigger a page fault if invalid. To determine validity, we look for other
loads in the same block that access the relevant address range.

The relevant point here is that we need to do this as part of the process of
forming permutation-based vector loads, and this happens quite early in the
SDAG pipeline - specifically before many of the address calculations are fully
canonicalized. As a result, we need to try harder to recognize base+offset
address computations, because they still might appear as chain of adds
(base+offset+offset, for example). To account for this, we'll look through
chains of adds, accumulating the constant offsets.

llvm-svn: 246813
2015-09-03 22:37:44 +00:00
Hal Finkel
e0c4d702bd [PowerPC] Include the permutation cost for unaligned vector loads
Pre-P8, when we generate code for unaligned vector loads (for Altivec and QPX
types), even when accounting for the combining that takes place for multiple
consecutive such loads, there is at least one load instructions and one
permutation for each load. Make sure the cost reported reflects the cost of the
permutes as well.

llvm-svn: 246807
2015-09-03 21:23:18 +00:00
Hal Finkel
e53c76127a [PowerPC] Compute the MMO offset for an unaligned load with signed arithmetic
If you compute the MMO offset using unsigned arithmetic, you end up with a
large positive offset instead of a small negative one. In theory, this could
cause bad instruction-scheduling decisions later.

I noticed this by inspection from the debug output, and using that for the
regression test is the best I can do right now.

llvm-svn: 246805
2015-09-03 21:12:15 +00:00
Hal Finkel
4a4ac3736c [PowerPC] Cleanup cost model for unaligned vector loads/stores
I'm adding a regression test to better cover code generation for unaligned
vector loads and stores, but there's no functional change to the code
generation here. There is an improvement to the cost model for unaligned vector
loads and stores, mostly for QPX (for which we were not previously accounting
for the permutation-based loads), and the cost model implementation is cleaner.

llvm-svn: 246712
2015-09-02 21:03:28 +00:00
Hal Finkel
daef1ea7bc [PowerPC] Don't always consider P8Altivec-only masks in LowerVECTOR_SHUFFLE
LowerVECTOR_SHUFFLE needs to decide whether to pass a vector shuffle off to the
TableGen-generated matching code, and it does this by testing the same
predicates used by the TableGen files. Unfortunately, when we added new
P8Altivec-only predicates, we started universally testing them in
LowerVECTOR_SHUFFLE, and if then matched when targeting a system prior to a P8,
we'd end up with a selection failure.

llvm-svn: 246675
2015-09-02 16:52:37 +00:00
Reid Kleckner
0edf7445db [EH] Handle non-Function personalities like unknown personalities
Also delete and simplify a lot of MachineModuleInfo code that used to be
needed to handle personalities on landingpads.  Now that the personality
is on the LLVM Function, we no longer need to track it this way on MMI.
Certainly it should not live on LandingPadInfo.

llvm-svn: 246478
2015-08-31 20:02:16 +00:00
Hal Finkel
8f9c81dcf5 [PowerPC] Fixup SELECT_CC (and SETCC) patterns with i1 comparison operands
There were really two problems here. The first was that we had the truth tables
for signed i1 comparisons backward. I imagine these are not very common, but if
you have:
  setcc i1 x, y, LT
this has the '0 1' and the '1 0' results flipped compared to:
  setcc i1 x, y, ULT
because, in the signed case, '1 0' is really '-1 0', and the answer is not the
same as in the unsigned case.

The second problem was that we did not have patterns (at all) for the unsigned
comparisons select_cc nodes for i1 comparison operands. This was the specific
cause of PR24552. These had to be added (and a missing Altivec promotion added
as well) to make sure these function for all types. I've added a bunch more
test cases for these patterns, and there are a few FIXMEs in the test case
regarding code-quality.

Fixes PR24552.

llvm-svn: 246400
2015-08-30 22:12:50 +00:00
Hal Finkel
e59e834a2a [MIR Serialization] static -> static const in getSerializable*MachineOperandTargetFlags
Make the arrays 'static const' instead of just 'static'. Post-commit review
comment from Roman Divacky on IRC. NFC.

llvm-svn: 246376
2015-08-30 08:07:29 +00:00
Hal Finkel
1e41909d2b [PowerPC/MIR Serialization] Target flags serialization support
Add support for MIR serialization of PowerPC-specific operand target flags
(based on the generic infrastructure added in r244185 and r245383).

I won't even pretend that this is good test coverage, but this includes the
regression test associated with r246372. Adding an MIR test for that fix is far
superior to adding an IR-level test because particular instruction-scheduling
decisions are necessary in order to expose the bug, and using an MIR test we
can start the pipeline post-scheduling.

llvm-svn: 246373
2015-08-30 07:50:35 +00:00
Hal Finkel
6c9166ae70 [PowerPC] Don't assume ADDISdtprelHA's source is r3
Even through ADDISdtprelHA generally has r3 as its source register, it is
possible for the instruction scheduler to move things around such that some
other register is the source. We need to print the actual source register, not
always r3. Fixes PR24394.

The test case will come in a follow-up commit because it depends on MIR
target-flags parsing.

llvm-svn: 246372
2015-08-30 07:44:05 +00:00
Hal Finkel
719ae331a6 [PowerPC] Remove unnecessary braces in PPCVSXFMAMutate
Address Eric's post-commit review of r245741. NFC.

llvm-svn: 246121
2015-08-26 23:41:53 +00:00
Matthias Braun
cfe46ab1cf FastISel: Use finishCondBranch() for ARM,Mips,PowerPC FastISel
Note that after this change branch probabilities are preserved now.

llvm-svn: 245998
2015-08-26 01:55:47 +00:00
Hal Finkel
d1f0f5ba25 [PowerPC] PPCVSXFMAMutate should ignore trivial-copy addends
We might end up with a trivial copy as the addend, and if so, we should ignore
the corresponding FMA instruction. The trivial copy can be coalesced away later,
so there's nothing to do here. We should not, however, assert. Fixes PR24544.

llvm-svn: 245907
2015-08-24 23:48:28 +00:00
Bill Schmidt
a2ec47b475 [PPC64LE] Fix PR24546 - Swap optimization and debug values
This patch fixes PR24546, which demonstrates a segfault during the VSX
swap removal pass.  The problem is that debug value instructions were
not excluded from the list of instructions to be analyzed for webs of
related computation.  I've added the test case from the PR as a crash
test in test/CodeGen/PowerPC.

llvm-svn: 245862
2015-08-24 19:27:27 +00:00
Hal Finkel
8f05a818d7 [PowerPC] PPCVSXFMAMutate should not segfault on undef input registers
When PPCVSXFMAMutate would look at the input addend register, it would get its
input value number. This would fail, however, if the register was undef,
causing a segfault. Don't segfault (just skip such FMA instructions).

Fixes the test case from PR24542 (although that may have been over-reduced).

llvm-svn: 245741
2015-08-21 21:34:24 +00:00
Hal Finkel
b8e2581942 [PowerPC] Fix value type on XVCMPEQDP for v2f64 comparisons
XVCMPEQDP is used for VSX v2f64 equality comparisons, but the value type needs
to be v2i64 (as that's the corresponding SETCC type).

Fixes PR24225.

llvm-svn: 245535
2015-08-20 03:02:02 +00:00
Hal Finkel
c4b6cee81f [PowerPC] Fix the int2fp(fp2int(x)) DAGCombine to ignore ppc_fp128
This DAGCombine was creating custom SDAG nodes with an illegal ppc_fp128
operand type because it was triggering on f64/f32 int2fp(fp2int(ppc_fp128 x)),
but shouldn't (it should only apply to f32/f64 types). The result was a crash.

llvm-svn: 245530
2015-08-20 01:18:20 +00:00
Nemanja Ivanovic
9f042b959b Temporary fix for the self-host failures introduced by rL244921.
This revision has introduced an issue that only affects bootstrapped compiler
when it is printing the ASM. I am working on resolving the issue, but in the
meantime, I'm disabling the legalization of scalar_to_vector operation for v2i64
and the associated testing until I can get this fixed.

llvm-svn: 245481
2015-08-19 19:04:47 +00:00
Chandler Carruth
4d1e1851a4 [PM] Port ScalarEvolution to the new pass manager.
This change makes ScalarEvolution a stand-alone object and just produces
one from a pass as needed. Making this work well requires making the
object movable, using references instead of overwritten pointers in
a number of places, and other refactorings.

I've also wired it up to the new pass manager and added a RUN line to
a test to exercise it under the new pass manager. This includes basic
printing support much like with other analyses.

But there is a big and somewhat scary change here. Prior to this patch
ScalarEvolution was never *actually* invalidated!!! Re-running the pass
just re-wired up the various other analyses and didn't remove any of the
existing entries in the SCEV caches or clear out anything at all. This
might seem OK as everything in SCEV that can uses ValueHandles to track
updates to the values that serve as SCEV keys. However, this still means
that as we ran SCEV over each function in the module, we kept
accumulating more and more SCEVs into the cache. At the end, we would
have a SCEV cache with every value that we ever needed a SCEV for in the
entire module!!! Yowzers. The releaseMemory routine would dump all of
this, but that isn't realy called during normal runs of the pipeline as
far as I can see.

To make matters worse, there *is* actually a key that we don't update
with value handles -- there is a map keyed off of Loop*s. Because
LoopInfo *does* release its memory from run to run, it is entirely
possible to run SCEV over one function, then over another function, and
then lookup a Loop* from the second function but find an entry inserted
for the first function! Ouch.

To make matters still worse, there are plenty of updates that *don't*
trip a value handle. It seems incredibly unlikely that today GVN or
another pass that invalidates SCEV can update values in *just* such
a way that a subsequent run of SCEV will incorrectly find lookups in
a cache, but it is theoretically possible and would be a nightmare to
debug.

With this refactoring, I've fixed all this by actually destroying and
recreating the ScalarEvolution object from run to run. Technically, this
could increase the amount of malloc traffic we see, but then again it is
also technically correct. ;] I don't actually think we're suffering from
tons of malloc traffic from SCEV because if we were, the fact that we
never clear the memory would seem more likely to have come up as an
actual problem before now. So, I've made the simple fix here. If in fact
there are serious issues with too much allocation and deallocation,
I can work on a clever fix that preserves the allocations (while
clearing the data) between each run, but I'd prefer to do that kind of
optimization with a test case / benchmark that shows why we need such
cleverness (and that can test that we actually make it faster). It's
possible that this will make some things faster by making the SCEV
caches have higher locality (due to being significantly smaller) so
until there is a clear benchmark, I think the simple change is best.

Differential Revision: http://reviews.llvm.org/D12063

llvm-svn: 245193
2015-08-17 02:08:17 +00:00