Commit Graph

785 Commits

Author SHA1 Message Date
Reid Kleckner 294fa7aa9d TableGen: Use 'enum : uint64_t' for feature flags to fix -Wmicrosoft
clang-cl would warn that this value is not representable in 'int':
  enum { FeatureX = 1ULL << 31 };
All MS enums are 'ints' unless otherwise specified, so we have to use an
explicit type.  The AMDGPU target just hit 32 features, triggering this
warning.

Now that we have C++11 strong enum types, we can also eliminate the
'const uint64_t' codepath from tablegen and just use 'enum : uint64_t'.

llvm-svn: 231697
2015-03-09 20:23:14 +00:00
Eric Christopher 11e4df73c8 getRegForInlineAsmConstraint wants to use TargetRegisterInfo for
a lookup, pass that in rather than use a naked call to getSubtargetImpl.
This involved passing down and around either a TargetMachine or
TargetRegisterInfo. Update all callers/definitions around the targets
and SelectionDAG.

llvm-svn: 230699
2015-02-26 22:38:43 +00:00
Eric Christopher 23a3a7c871 Remove an argument-less call to getSubtargetImpl from TargetLoweringBase.
This required plumbing a TargetRegisterInfo through computeRegisterProperties
and into findRepresentativeClass which uses it for register class
iteration. This required passing a subtarget into a few target specific
initializations of TargetLowering.

llvm-svn: 230583
2015-02-26 00:00:24 +00:00
Tim Northover 3b6b7ca2bc CodeGen: convert CCState interface to using ArrayRefs
Everyone except R600 was manually passing the length of a static array
at each callsite, calculated in a variety of interesting ways. Far
easier to let ArrayRef handle that.

There should be no functional change, but out of tree targets may have
to tweak their calls as with these examples.

llvm-svn: 230118
2015-02-21 02:11:17 +00:00
Chandler Carruth 30d69c2e36 [PM] Remove the old 'PassManager.h' header file at the top level of
LLVM's include tree and the use of using declarations to hide the
'legacy' namespace for the old pass manager.

This undoes the primary modules-hostile change I made to keep
out-of-tree targets building. I sent an email inquiring about whether
this would be reasonable to do at this phase and people seemed fine with
it, so making it a reality. This should allow us to start bootstrapping
with modules to a certain extent along with making it easier to mix and
match headers in general.

The updates to any code for users of LLVM are very mechanical. Switch
from including "llvm/PassManager.h" to "llvm/IR/LegacyPassManager.h".
Qualify the types which now produce compile errors with "legacy::". The
most common ones are "PassManager", "PassManagerBase", and
"FunctionPassManager".

llvm-svn: 229094
2015-02-13 10:01:29 +00:00
Eric Christopher 8341358adc Since TargetLowering is already subtarget dependent just pass
in the subtarget and stash it in the class so that lookups are
easier and safer.

llvm-svn: 227819
2015-02-02 17:52:27 +00:00
Eric Christopher 1c50429923 Use the function template getSubtarget on the MachineFunction
rather than a larger explicit cast.

llvm-svn: 227818
2015-02-02 17:52:25 +00:00
Eric Christopher 40fb765888 Remove unused class variable.
llvm-svn: 227817
2015-02-02 17:52:23 +00:00
Eric Christopher 49a0fd7444 Remove unused class variable.
llvm-svn: 227816
2015-02-02 17:52:20 +00:00
Chandler Carruth c956ab6603 [multiversion] Switch the TTI queries from TargetMachine to Subtarget
now that we have a correct and cached subtarget specific to the
function.

Also, finish providing a cached per-function subtarget in the core
LLVMTargetMachine -- that layer hadn't switched over yet.

The only use of the TargetMachine was to re-lookup a subtarget for
a particular function to work around the fact that TTI was immutable.
Now that it is per-function and we haved a cached subtarget, use it.

This still leaves a few interfaces with real warts on them where we were
passing Function objects through the TTI interface. I'll remove these
and clean their usage up in subsequent commits now that this isn't
necessary.

llvm-svn: 227738
2015-02-01 14:22:17 +00:00
Chandler Carruth c340ca839c [multiversion] Remove the cached TargetMachine pointer from the
intermediate TTI implementation template and instead query up to the
derived class for both the TargetMachine and the TargetLowering.

Most of the derived types had a TLI cached already and there is no need
to store a less precisely typed target machine pointer.

This will in turn make it much cleaner to look up the TLI via
a per-function subtarget instead of the generic subtarget, and it will
pave the way toward pulling the subtarget used for unroll preferences
into the same form once we are *always* using the function to look up
the correct subtarget.

llvm-svn: 227737
2015-02-01 14:01:15 +00:00
Chandler Carruth 8b04c0d26a [multiversion] Switch all of the targets over to use the
TargetIRAnalysis access path directly rather than implementing getTTI.

This even removes getTTI from the interface. It's more efficient for
each target to just register a precise callback that creates their
specific TTI.

As part of this, all of the targets which are building their subtargets
individually per-function now build their TTI instance with the function
and thus look up the correct subtarget and cache it. NVPTX, R600, and
XCore currently don't leverage this functionality, but its trivial for
them to add it now.

llvm-svn: 227735
2015-02-01 13:20:00 +00:00
Chandler Carruth ee642690ea [multiversion] Remove a false freedom to leave the TargetMachine pointer
null.

For some reason some of the original TTI code supported a null target
machine. This seems to have been legacy, and I made matters worse when
refactoring this code by spreading that pattern further through the
various targets.

The TargetMachine can't actually be null, and it doesn't make sense to
support that use case. I've now consistently removed it and removed all
of the code trying to cope with that situation. This is probably good,
as several targets *didn't* cope with it being null despite the null
default argument in their constructors. =]

llvm-svn: 227734
2015-02-01 12:38:24 +00:00
Chandler Carruth d8b3e9a420 [PM] Remove a bunch of stale TTI creation method declarations. I nuked
their definitions, but forgot to clean up all the declarations which are
in different files.

llvm-svn: 227698
2015-02-01 00:22:15 +00:00
Chandler Carruth 93dcdc47db [PM] Switch the TargetMachine interface from accepting a pass manager
base which it adds a single analysis pass to, to instead return the type
erased TargetTransformInfo object constructed for that TargetMachine.

This removes all of the pass variants for TTI. There is now a single TTI
*pass* in the Analysis layer. All of the Analysis <-> Target
communication is through the TTI's type erased interface itself. While
the diff is large here, it is nothing more that code motion to make
types available in a header file for use in a different source file
within each target.

I've tried to keep all the doxygen comments and file boilerplate in line
with this move, but let me know if I missed anything.

With this in place, the next step to making TTI work with the new pass
manager is to introduce a really simple new-style analysis that produces
a TTI object via a callback into this routine on the target machine.
Once we have that, we'll have the building blocks necessary to accept
a function argument as well.

llvm-svn: 227685
2015-01-31 11:17:59 +00:00
Chandler Carruth 705b185f90 [PM] Change the core design of the TTI analysis to use a polymorphic
type erased interface and a single analysis pass rather than an
extremely complex analysis group.

The end result is that the TTI analysis can contain a type erased
implementation that supports the polymorphic TTI interface. We can build
one from a target-specific implementation or from a dummy one in the IR.

I've also factored all of the code into "mix-in"-able base classes,
including CRTP base classes to facilitate calling back up to the most
specialized form when delegating horizontally across the surface. These
aren't as clean as I would like and I'm planning to work on cleaning
some of this up, but I wanted to start by putting into the right form.

There are a number of reasons for this change, and this particular
design. The first and foremost reason is that an analysis group is
complete overkill, and the chaining delegation strategy was so opaque,
confusing, and high overhead that TTI was suffering greatly for it.
Several of the TTI functions had failed to be implemented in all places
because of the chaining-based delegation making there be no checking of
this. A few other functions were implemented with incorrect delegation.
The message to me was very clear working on this -- the delegation and
analysis group structure was too confusing to be useful here.

The other reason of course is that this is *much* more natural fit for
the new pass manager. This will lay the ground work for a type-erased
per-function info object that can look up the correct subtarget and even
cache it.

Yet another benefit is that this will significantly simplify the
interaction of the pass managers and the TargetMachine. See the future
work below.

The downside of this change is that it is very, very verbose. I'm going
to work to improve that, but it is somewhat an implementation necessity
in C++ to do type erasure. =/ I discussed this design really extensively
with Eric and Hal prior to going down this path, and afterward showed
them the result. No one was really thrilled with it, but there doesn't
seem to be a substantially better alternative. Using a base class and
virtual method dispatch would make the code much shorter, but as
discussed in the update to the programmer's manual and elsewhere,
a polymorphic interface feels like the more principled approach even if
this is perhaps the least compelling example of it. ;]

Ultimately, there is still a lot more to be done here, but this was the
huge chunk that I couldn't really split things out of because this was
the interface change to TTI. I've tried to minimize all the other parts
of this. The follow up work should include at least:

1) Improving the TargetMachine interface by having it directly return
   a TTI object. Because we have a non-pass object with value semantics
   and an internal type erasure mechanism, we can narrow the interface
   of the TargetMachine to *just* do what we need: build and return
   a TTI object that we can then insert into the pass pipeline.
2) Make the TTI object be fully specialized for a particular function.
   This will include splitting off a minimal form of it which is
   sufficient for the inliner and the old pass manager.
3) Add a new pass manager analysis which produces TTI objects from the
   target machine for each function. This may actually be done as part
   of #2 in order to use the new analysis to implement #2.
4) Work on narrowing the API between TTI and the targets so that it is
   easier to understand and less verbose to type erase.
5) Work on narrowing the API between TTI and its clients so that it is
   easier to understand and less verbose to forward.
6) Try to improve the CRTP-based delegation. I feel like this code is
   just a bit messy and exacerbating the complexity of implementing
   the TTI in each target.

Many thanks to Eric and Hal for their help here. I ended up blocked on
this somewhat more abruptly than I expected, and so I appreciate getting
it sorted out very quickly.

Differential Revision: http://reviews.llvm.org/D7293

llvm-svn: 227669
2015-01-31 03:43:40 +00:00
Rafael Espindola ba31e27f0a Compute the ELF SectionKind from the flags.
Any code creating an MCSectionELF knows ELF and already provides the flags.

SectionKind is an abstraction used by common code that uses a plain
MCSection.

Use the flags to compute the SectionKind. This removes a lot of
guessing and boilerplate from the MCSectionELF construction.

llvm-svn: 227476
2015-01-29 17:33:21 +00:00
Eric Christopher 8b7706517c Move DataLayout back to the TargetMachine from TargetSubtargetInfo
derived classes.

Since global data alignment, layout, and mangling is often based on the
DataLayout, move it to the TargetMachine. This ensures that global
data is going to be layed out and mangled consistently if the subtarget
changes on a per function basis. Prior to this all targets(*) have
had subtarget dependent code moved out and onto the TargetMachine.

*One target hasn't been migrated as part of this change: R600. The
R600 port has, as a subtarget feature, the size of pointers and
this affects global data layout. I've currently hacked in a FIXME
to enable progress, but the port needs to be updated to either pass
the 64-bitness to the TargetMachine, or fix the DataLayout to
avoid subtarget dependent features.

llvm-svn: 227113
2015-01-26 19:03:15 +00:00
Rafael Espindola 12ca34f53f Bring r226038 back.
No change in this commit, but clang was changed to also produce trivial comdats when
needed.

Original message:

Don't create new comdats in CodeGen.

This patch stops the implicit creation of comdats during codegen.

Clang now sets the comdat explicitly when it is required. With this patch clang and gcc
now produce the same result in pr19848.

llvm-svn: 226467
2015-01-19 15:16:06 +00:00
Chandler Carruth d450056c78 [PM] Replace the Pass argument to SplitEdge with specific analyses used
and updated.

This may appear to remove handling for things like alias analysis when
splitting critical edges here, but in fact no callers of SplitEdge
relied on this. Similarly, all of them wanted to preserve LCSSA if there
was any update of the loop info. That makes the interface much simpler.

With this, all of BasicBlockUtils.h is free of Pass arguments and
prepared for the new pass manager. This is tho majority of utilities
that relied on pass arguments.

llvm-svn: 226459
2015-01-19 12:36:53 +00:00
David Blaikie 9459832ebd std::unique_ptrify the MCStreamer argument to createAsmPrinter
llvm-svn: 226414
2015-01-18 20:29:04 +00:00
Timur Iskhodzhanov 60b721363c Revert r226242 - Revert Revert Don't create new comdats in CodeGen
This breaks AddressSanitizer (ninja check-asan) on Windows

llvm-svn: 226251
2015-01-16 08:38:45 +00:00
Rafael Espindola 67a79e72f5 Revert "Revert Don't create new comdats in CodeGen"
This reverts commit r226173, adding r226038 back.

No change in this commit, but clang was changed to also produce trivial comdats for
costructors, destructors and vtables when needed.

Original message:

Don't create new comdats in CodeGen.

This patch stops the implicit creation of comdats during codegen.

Clang now sets the comdat explicitly when it is required. With this patch clang and gcc
now produce the same result in pr19848.

llvm-svn: 226242
2015-01-16 02:22:55 +00:00
Timur Iskhodzhanov f5adf13fac Revert Don't create new comdats in CodeGen
It breaks AddressSanitizer on Windows.

llvm-svn: 226173
2015-01-15 16:14:34 +00:00
Rafael Espindola fad1639a12 Don't create new comdats in CodeGen.
This patch stops the implicit creation of comdats during codegen.

Clang now sets the comdat explicitly when it is required. With this patch clang and gcc
now produce the same result in pr19848.

llvm-svn: 226038
2015-01-14 20:55:48 +00:00
Ahmed Bougacha 2b6917b020 [SelectionDAG] Allow targets to specify legality of extloads' result
type (in addition to the memory type).

The *LoadExt* legalization handling used to only have one type, the
memory type.  This forced users to assume that as long as the extload
for the memory type was declared legal, and the result type was legal,
the whole extload was legal.

However, this isn't always the case.  For instance, on X86, with AVX,
this is legal:
    v4i32 load, zext from v4i8
but this isn't:
    v4i64 load, zext from v4i8
Whereas v4i64 is (arguably) legal, even without AVX2.

Note that the same thing was done a while ago for truncstores (r46140),
but I assume no one needed it yet for extloads, so here we go.

Calls to getLoadExtAction were changed to add the value type, found
manually in the surrounding code.

Calls to setLoadExtAction were mechanically changed, by wrapping the
call in a loop, to match previous behavior.  The loop iterates over
the MVT subrange corresponding to the memory type (FP vectors, etc...).
I also pulled neighboring setTruncStoreActions into some of the loops;
those shouldn't make a difference, as the additional types are illegal.
(e.g., i128->i1 truncstores on PPC.)

No functional change intended.

Differential Revision: http://reviews.llvm.org/D6532

llvm-svn: 225421
2015-01-08 00:51:32 +00:00
Matthias Braun 7e37a5f523 [CodeGen] Add print and verify pass after each MachineFunctionPass by default
Previously print+verify passes were added in a very unsystematic way, which is
annoying when debugging as you miss intermediate steps and allows bugs to stay
unnotice when no verification is performed.

To make this change practical I added the possibility to explicitely disable
verification. I used this option on all places where no verification was
performed previously (because alot of places actually don't pass the
MachineVerifier).
In the long term these problems should be fixed properly and verification
enabled after each pass. I'll enable some more verification in subsequent
commits.

This is the 2nd attempt at this after realizing that PassManager::add() may
actually delete the pass.

llvm-svn: 224059
2014-12-11 21:26:47 +00:00
Rafael Espindola 01c73610d0 This reverts commit r224043 and r224042.
check-llvm was failing.

llvm-svn: 224045
2014-12-11 20:03:57 +00:00
Matthias Braun a7c82a9f1d [CodeGen] Add print and verify pass after each MachineFunctionPass by default
Previously print+verify passes were added in a very unsystematic way, which is
annoying when debugging as you miss intermediate steps and allows bugs to stay
unnotice when no verification is performed.

To make this change practical I added the possibility to explicitely disable
verification. I used this option on all places where no verification was
performed previously (because alot of places actually don't pass the
MachineVerifier).
In the long term these problems should be fixed properly and verification
enabled after each pass. I'll enable some more verification in subsequent
commits.

llvm-svn: 224042
2014-12-11 19:42:05 +00:00
Craig Topper c50d64b07b Replace neverHasSideEffects=1 with hasSideEffects=0 in all .td files.
llvm-svn: 222801
2014-11-26 00:46:26 +00:00
Reid Kleckner 357600eab5 Add out of line virtual destructors to all LLVMTargetMachine subclasses
These recently all grew a unique_ptr<TargetLoweringObjectFile> member in
r221878.  When anyone calls a virtual method of a class, clang-cl
requires all virtual methods to be semantically valid. This includes the
implicit virtual destructor, which triggers instantiation of the
unique_ptr destructor, which fails because the type being deleted is
incomplete.

This is just part of the ongoing saga of PR20337, which is affecting
Blink as well. Because the MSVC ABI doesn't have key functions, we end
up referencing the vtable and implicit destructor on any virtual call
through a class. We don't actually end up emitting the dtor, so it'd be
good if we could avoid this unneeded type completion work.

llvm-svn: 222480
2014-11-20 23:37:18 +00:00
Aditya Nandakumar 3053155652 We can get the TLOF from the TargetMachine - so constructor no longer requires TargetLoweringObjectFile to be passed.
llvm-svn: 221926
2014-11-13 21:29:21 +00:00
Aditya Nandakumar a27193297f This patch changes the ownership of TLOF from TargetLoweringBase to TargetMachine so that different subtargets could share the TLOF effectively
llvm-svn: 221878
2014-11-13 09:26:31 +00:00
Rafael Espindola 7fc5b87480 Pass an ArrayRef to MCDisassembler::getInstruction.
With this patch MCDisassembler::getInstruction takes an ArrayRef<uint8_t>
instead of a MemoryObject.

Even on X86 there is a maximum size an instruction can have. Given
that, it seems way simpler and more efficient to just pass an ArrayRef
to the disassembler instead of a MemoryObject and have it do a virtual
call every time it wants some extra bytes.

llvm-svn: 221751
2014-11-12 02:04:27 +00:00
Rafael Espindola 4aa6bea7a2 Misc style fixes. NFC.
This fixes a few cases of:

* Wrong variable name style.
* Lines longer than 80 columns.
* Repeated names in comments.
* clang-format of the above.

This make the next patch a lot easier to read.

llvm-svn: 221615
2014-11-10 18:11:10 +00:00
Reid Kleckner da00cf5f73 Work around bugs in MSVC "14" CTP 3's conversion logic
It appears to ignore or find ambiguous MachineInstrBuilder's conversion
operators that allow conversion to MachineInstr* and
MachineBasicBlock::bundle_iterator.

As a workaround, add an explicit way to get the MachineInstr.

llvm-svn: 221017
2014-10-31 23:19:46 +00:00
Robin Morisset e2de06bef6 Erase fence insertion from SelectionDAGBuilder.cpp (NFC)
Summary:
Backends can use setInsertFencesForAtomic to signal to the middle-end that
montonic is the only memory ordering they can accept for
stores/loads/rmws/cmpxchg. The code lowering those accesses with a stronger
ordering to fences + monotonic accesses is currently living in
SelectionDAGBuilder.cpp. In this patch I propose moving this logic out of it
for several reasons:
- There is lots of redundancy to avoid: extremely similar logic already
  exists in AtomicExpand.
- The current code in SelectionDAGBuilder does not use any target-hooks, it
  does the same transformation for every backend that requires it
- As a result it is plain *unsound*, as it was apparently designed for ARM.
  It happens to mostly work for the other targets because they are extremely
  conservative, but Power for example had to switch to AtomicExpand to be
  able to use lwsync safely (see r218331).
- Because it produces IR-level fences, it cannot be made sound ! This is noted
  in the C++11 standard (section 29.3, page 1140):
```
Fences cannot, in general, be used to restore sequential consistency for atomic
operations with weaker ordering semantics.
```
It can also be seen by the following example (called IRIW in the litterature):
```
atomic<int> x = y = 0;
int r1, r2, r3, r4;
Thread 0:
  x.store(1);
Thread 1:
  y.store(1);
Thread 2:
  r1 = x.load();
  r2 = y.load();
Thread 3:
  r3 = y.load();
  r4 = x.load();
```
r1 = r3 = 1 and r2 = r4 = 0 is impossible as long as the accesses are all seq_cst.
But if they are lowered to monotonic accesses, no amount of fences can prevent it..

This patch does three things (I could cut it into parts, but then some of them
would not be tested/testable, please tell me if you would prefer that):
- it provides a default implementation for emitLeadingFence/emitTrailingFence in
terms of IR-level fences, that mimic the original logic of SelectionDAGBuilder.
As we saw above, this is unsound, but the best that can be done without knowing
the targets well (and there is a comment warning about this risk).
- it then switches Mips/Sparc/XCore to use AtomicExpand, relying on this default
implementation (that exactly replicates the logic of SelectionDAGBuilder, so no
functional change)
- it finally erase this logic from SelectionDAGBuilder as it is dead-code.

Ideally, each target would define its own override for emitLeading/TrailingFence
using target-specific fences, but I do not know the Sparc/Mips/XCore memory model
well enough to do this, and they appear to be dealing fine with the ARM-inspired
default expansion for now (probably because they are overly conservative, as
Power was). If anyone wants to compile fences more agressively on these
platforms, the long comment should make it clear why he should first override
emitLeading/TrailingFence.

Test Plan: make check-all, no functional change

Reviewers: jfb, t.p.northover

Subscribers: aemerson, llvm-commits

Differential Revision: http://reviews.llvm.org/D5474

llvm-svn: 219957
2014-10-16 20:34:57 +00:00
Benjamin Kramer e12a6bac32 Eliminate some deep std::vector copies. NFC.
llvm-svn: 218999
2014-10-03 18:33:16 +00:00
Aaron Ballman 0bb041b5f4 Reverting NFC changes from r218050. Instead, the warning was disabled for GCC in r218059, so these changes are no longer required.
llvm-svn: 218062
2014-09-18 17:34:23 +00:00
Aaron Ballman 11fa97fa32 Fixing a bunch of -Woverloaded-virtual warnings due to hiding getSubtargetImpl from the base class. NFC.
llvm-svn: 218050
2014-09-18 13:27:14 +00:00
Benjamin Kramer 8c90fd71f7 Add override to overriden virtual methods, remove virtual keywords.
No functionality change. Changes made by clang-tidy + some manual cleanup.

llvm-svn: 217028
2014-09-03 11:41:21 +00:00
Craig Topper fd38cbebda Remove 'virtual' keyword from methods markedwith 'override' keyword.
llvm-svn: 216823
2014-08-30 16:48:34 +00:00
Rafael Espindola d610ba99cb Remove HasLEB128.
We already require CFI, so it should be safe to require .leb128 and .uleb128.

llvm-svn: 215712
2014-08-15 14:01:07 +00:00
Benjamin Kramer a7c40ef022 Canonicalize header guards into a common format.
Add header guards to files that were missing guards. Remove #endif comments
as they don't seem common in LLVM (we can easily add them back if we decide
they're useful)

Changes made by clang-tidy with minor tweaks.

llvm-svn: 215558
2014-08-13 16:26:38 +00:00
Pete Cooper c18261d467 Fix a whole bunch of binary literals which were the wrong size. All were being silently zero extended to the correct width.
The commit after this changes { } and 0bxx literals to be of type bits<n> and not int.  This means we need to write exactly the right number of bits, and not rely on the values being silently zero extended for us.

llvm-svn: 215082
2014-08-07 05:46:54 +00:00
Eric Christopher b5217507c7 Remove the target machine from CCState. Previously it was only used
to get the subtarget and that's accessible from the MachineFunction
now. This helps clear the way for smaller changes where we getting
a subtarget will require passing in a MachineFunction/Function as
well.

llvm-svn: 214988
2014-08-06 18:45:26 +00:00
Eric Christopher fc6de428c8 Have MachineFunction cache a pointer to the subtarget to make lookups
shorter/easier and have the DAG use that to do the same lookup. This
can be used in the future for TargetMachine based caching lookups from
the MachineFunction easily.

Update the MIPS subtarget switching machinery to update this pointer
at the same time it runs.

llvm-svn: 214838
2014-08-05 02:39:49 +00:00
Pedro Artigas ec7cbd7d14 Changed the liveness tracking in the RegisterScavenger
to use register units instead of registers.

reviewed by Jakob Stoklund Olesen.

llvm-svn: 214798
2014-08-04 23:07:49 +00:00
Eric Christopher d913448b38 Remove the TargetMachine forwards for TargetSubtargetInfo based
information and update all callers. No functional change.

llvm-svn: 214781
2014-08-04 21:25:23 +00:00
Louis Gerbarg 67474e3755 Make sure no loads resulting from load->switch DAGCombine are marked invariant
Currently when DAGCombine converts loads feeding a switch into a switch of
addresses feeding a load the new load inherits the isInvariant flag of the left
side. This is incorrect since invariant loads can be reordered in cases where it
is illegal to reoarder normal loads.

This patch adds an isInvariant parameter to getExtLoad() and updates all call
sites to pass in the data if they have it or false if they don't. It also
changes the DAGCombine to use that data to make the right decision when
creating the new load.

llvm-svn: 214449
2014-07-31 21:45:05 +00:00