Commit Graph

2293 Commits

Author SHA1 Message Date
Rafael Espindola
6c449e8fa6 Remove dead declarations.
Patch by Tobias Güntner.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205119 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-30 02:33:01 +00:00
Duncan P. N. Exon Smith
27e1ca8189 blockfreq: Implement Pass::releaseMemory()
Implement Pass::releaseMemory() in BlockFrequencyInfo and
MachineBlockFrequencyInfo.  Just delete the private implementation when
not in use.  Switch to a std::unique_ptr to make the logic more clear.

<rdar://problem/14292693>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204741 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-25 18:01:38 +00:00
Juergen Ributzka
d3cf783ed1 [Constant Hoisting] Make the constant materialization cost operand dependent
Extend the target hook to take also the operand index into account when
calculating the cost of the constant materialization.

Related to <rdar://problem/16381500>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204435 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-21 06:04:45 +00:00
Juergen Ributzka
ee3242ed0b Revert "[Constant Hoisting] Extend coverage of the constant hoisting pass."
I will break this up into smaller pieces for review and recommit.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204393 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-20 20:17:13 +00:00
Juergen Ributzka
228c72a841 [Constant Hoisting] Extend coverage of the constant hoisting pass.
This commit extends the coverage of the constant hoisting pass, adds additonal
debug output and updates the function names according to the style guide.

Related to <rdar://problem/16381500>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204389 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-20 19:55:52 +00:00
Benjamin Kramer
dabc5073b2 Remove copy ctors that did the same thing as the default one.
The code added nothing but potentially disabled move semantics and made
types non-trivially copyable.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203563 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-11 11:32:49 +00:00
Chandler Carruth
31da39e479 [LCG] Make this call graph a fully regular type by giving it assignment
as well. I don't see any particular need but it imposes no cost to
support it and it makes the API cleaner.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203448 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-10 08:08:59 +00:00
Chandler Carruth
b94ad9729b [LCG] Make the iterator move constructable (and thus movable in general)
now that there is essentially no cost to doing so. Yay C++11.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203447 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-10 08:08:47 +00:00
Chandler Carruth
673fbf14a6 [LCG] One more formatting fix that I failed to get into the prior
commit. Sorry for the churn, just trying to keep it out of any
functionality changed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203438 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-10 02:50:21 +00:00
Chandler Carruth
436906ab3c [TTI] There is actually no realistic way to pop TTI implementations off
the stack of the analysis group because they are all immutable passes.
This is made clear by Craig's recent work to use override
systematically -- we weren't overriding anything for 'finalizePass'
because there is no such thing.

This is kind of a lame restriction on the API -- we can no longer push
and pop things, we just set up the stack and run. However, I'm not
invested in building some better solution on top of the existing
(terrifying) immutable pass and legacy pass manager.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203437 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-10 02:45:14 +00:00
Nico Weber
f456d37c4f "Mac OS/X" -> "Mac OS X" spelling fixes for llvm.
Patch from Sean McBride <sean@rogue-research.com>!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203258 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-07 18:08:54 +00:00
Benjamin Kramer
c1dafe8dc3 [C++11] Replace LLVM-style type traits with C++11 standard ones.
No functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203242 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-07 14:42:25 +00:00
Ahmed Charles
f4ccd11075 Replace OwningPtr<T> with std::unique_ptr<T>.
This compiles with no changes to clang/lld/lldb with MSVC and includes
overloads to various functions which are used by those projects and llvm
which have OwningPtr's as parameters. This should allow out of tree
projects some time to move. There are also no changes to libs/Target,
which should help out of tree targets have time to move, if necessary.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203083 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-06 05:51:42 +00:00
Chandler Carruth
67f6bf70d2 [Layering] Move InstVisitor.h into the IR library as it is pretty
obviously coupled to the IR.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203064 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-06 03:23:41 +00:00
Chandler Carruth
2e816f0d56 [C++11] Make this interface accept const Use pointers and use override
to ensure we don't mess up any of the overrides. Necessary for cleaning
up the Value use iterators and enabling range-based traversing of use
lists.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202958 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-05 10:21:48 +00:00
Craig Topper
c37e6c0734 [C++11] Add 'override' keyword to virtual methods that override their base class.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202945 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-05 07:30:04 +00:00
Chandler Carruth
19d764fb05 [Modules] Move the ConstantRange class into the IR library. This is
a bit surprising, as the class is almost entirely abstracted away from
any particular IR, however it encodes the comparsion predicates which
mutate ranges as ICmp predicate codes. This is reasonable as they're
used for both instructions and constants. Thus, it belongs in the IR
library with instructions and constants.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202838 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-04 12:24:34 +00:00
Chandler Carruth
d90488f7e8 [Modules] Move the TargetFolder into the Analysis library. Historically,
this would have been required because of the use of DataLayout, but that
has moved into the IR proper. It is still required because this folder
uses the constant folding in the analysis library (which uses the
datalayout) as the more aggressive basis of its folder.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202832 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-04 11:59:06 +00:00
Chandler Carruth
03e36d752c [Modules] Move CFG.h to the IR library as it defines graph traits over
IR types.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202827 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-04 11:45:46 +00:00
Chandler Carruth
eb3d76da81 [Modules] Move ValueHandle into the IR library where Value itself lives.
Move the test for this class into the IR unittests as well.

This uncovers that ValueMap too is in the IR library. Ironically, the
unittest for ValueMap is useless in the Support library (honestly, so
was the ValueHandle test) and so it already lives in the IR unittests.
Mmmm, tasty layering.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202821 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-04 11:17:44 +00:00
Chandler Carruth
4bbfbdf7d7 [Modules] Move CallSite into the IR library where it belogs. It is
abstracting between a CallInst and an InvokeInst, both of which are IR
concepts.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202816 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-04 11:01:28 +00:00
Chandler Carruth
876ac60880 [Modules] Move InstIterator out of the Support library, where it had no
business.

This header includes Function and BasicBlock and directly uses the
interfaces of both classes. It has to do with the IR, it even has that
in the name. =] Put it in the library it belongs to.

This is one step toward making LLVM's Support library survive a C++
modules bootstrap.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202814 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-04 10:30:26 +00:00
Chandler Carruth
1decd56b8d [cleanup] Re-sort all the includes with utils/sort_includes.py.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202811 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-04 10:07:28 +00:00
Tobias Grosser
75c86c9e9a [C++11] Add a basic block range view for RegionInfo
This also switches the users in LLVM to ensure this functionality is tested.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202705 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-03 13:00:39 +00:00
Chandler Carruth
0a3eef53d7 [C++11] Switch all uses of the llvm_move macro to use std::move
directly, and remove the macro.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202612 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-02 04:08:41 +00:00
Chandler Carruth
bc1bddb4c6 [C++11] Remove the use of LLVM_HAS_RVALUE_REFERENCES from the rest of
the core LLVM libraries.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202582 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-01 09:32:03 +00:00
Paul Robinson
cf84b5ba5e Constify the Optnone checks in IR passes.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202213 91177308-0d34-0410-b5e6-96231b3b80d8
2014-02-26 01:23:26 +00:00
Rafael Espindola
356deb5ecd Use DataLayout from the module when easily available.
Eventually DataLayoutPass should go away, but for now that is the only easy
way to get a DataLayout in some APIs. This patch only changes the ones that
have easy access to a Module.

One interesting issue with sometimes using DataLayoutPass and sometimes
fetching it from the Module is that we have to make sure they are equivalent.
We can get most of the way there by always constructing the pass with a Module.
In fact, the pass could be changed to point to an external DataLayout instead
of owning one to make this stricter.

Unfortunately, the C api passes a DataLayout, so it has to be up to the caller
to make sure the pass and the module are in sync.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202204 91177308-0d34-0410-b5e6-96231b3b80d8
2014-02-25 23:25:17 +00:00
Rafael Espindola
ec89b9fb9e Make some DataLayout pointers const.
No functionality change. Just reduces the noise of an upcoming patch.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202087 91177308-0d34-0410-b5e6-96231b3b80d8
2014-02-24 23:12:18 +00:00
Rafael Espindola
ac69459e0f Replace the F_Binary flag with a F_Text one.
After this I will set the default back to F_None. The advantage is that
before this patch forgetting to set F_Binary would corrupt a file on windows.
Forgetting to set F_Text produces one that cannot be read in notepad, which
is a better failure mode :-)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202052 91177308-0d34-0410-b5e6-96231b3b80d8
2014-02-24 18:20:12 +00:00
Rafael Espindola
843efd49b7 Don't make F_None the default.
This will make it easier to switch the default to being binary files.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202042 91177308-0d34-0410-b5e6-96231b3b80d8
2014-02-24 15:07:20 +00:00
Mingjie Xing
3fd813ef42 Fix a typo in a comment.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201633 91177308-0d34-0410-b5e6-96231b3b80d8
2014-02-19 03:20:46 +00:00
Rafael Espindola
39d8dcb53b Rename some member variables from TD to DL.
TargetData was renamed DataLayout back in r165242.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201581 91177308-0d34-0410-b5e6-96231b3b80d8
2014-02-18 15:33:12 +00:00
Arnold Schwaighofer
2ced33808e SCEVExpander: Try hard not to create derived induction variables in other loops
During LSR of one loop we can run into a situation where we have to expand the
start of a recurrence of a loop induction variable in this loop. This start
value is a value derived of the induction variable of a preceeding loop. SCEV
has cannonicalized this value to a different recurrence than the recurrence of
the preceeding loop's induction variable (the type and/or step direction) has
changed). When we come to instantiate this SCEV we created a second induction
variable in this preceeding loop.  This patch tries to base such derived
induction variables of the preceeding loop's induction variable.

This helps twolf on arm and seems to help scimark2 on x86.

Reapply with a fix for the case of a value derived from a pointer.

radar://15970709

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201496 91177308-0d34-0410-b5e6-96231b3b80d8
2014-02-16 15:49:50 +00:00
Arnold Schwaighofer
a9db46bf3e Revert "SCEVExpander: Try hard not to create derived induction variables in other loops"
This reverts commit r201465. It broke an arm bot.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201466 91177308-0d34-0410-b5e6-96231b3b80d8
2014-02-15 18:16:56 +00:00
Arnold Schwaighofer
e672548602 SCEVExpander: Try hard not to create derived induction variables in other loops
During LSR of one loop we can run into a situation where we have to expand the
start of a recurrence of a loop induction variable in this loop. This start
value is a value derived of the induction variable of a preceeding loop. SCEV
has cannonicalized this value to a different recurrence than the recurrence of
the preceeding loop's induction variable (the type and/or step direction) has
changed). When we come to instantiate this SCEV we created a second induction
variable in this preceeding loop.  This patch tries to base such derived
induction variables of the preceeding loop's induction variable.

This helps twolf on arm and seems to help scimark2 on x86.

radar://15970709

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201465 91177308-0d34-0410-b5e6-96231b3b80d8
2014-02-15 17:11:56 +00:00
Andrea Di Biagio
029a76b0a2 [Vectorizer] Add a new 'OperandValueKind' in TargetTransformInfo called
'OK_NonUniformConstValue' to identify operands which are constants but
not constant splats.

The cost model now allows returning 'OK_NonUniformConstValue'
for non splat operands that are instances of ConstantVector or
ConstantDataVector.

With this change, targets are now able to compute different costs
for instructions with non-uniform constant operands.
For example, On X86 the cost of a vector shift may vary depending on whether
the second operand is a uniform or non-uniform constant.

This patch applies the following changes:
 - The cost model computation now takes into account non-uniform constants;
 - The cost of vector shift instructions has been improved in
   X86TargetTransformInfo analysis pass;
 - BBVectorize, SLPVectorizer and LoopVectorize now know how to distinguish
   between non-uniform and uniform constant operands.

Added a new test to verify that the output of opt
'-cost-model -analyze' is valid in the following configurations: SSE2,
SSE4.1, AVX, AVX2.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201272 91177308-0d34-0410-b5e6-96231b3b80d8
2014-02-12 23:43:47 +00:00
Benjamin Kramer
cb27441554 ScalarEvolution: Analyze trip count of loops with a switch guarding the exit.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201159 91177308-0d34-0410-b5e6-96231b3b80d8
2014-02-11 15:44:32 +00:00
Chandler Carruth
f47fd2f22a [PM] Fix horrible typos that somehow didn't cause a failure in a C++11
build but spectacularly changed behavior of the C++98 build. =]

This shows my one problem with not having unittests -- basic API
expectations aren't well exercised by the integration tests because they
*happen* to not come up, even though they might later. I'll probably add
a basic unittest to complement the integration testing later, but
I wanted to revive the bots.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200905 91177308-0d34-0410-b5e6-96231b3b80d8
2014-02-06 05:17:02 +00:00
Chandler Carruth
57732bff1e [PM] Add a new "lazy" call graph analysis pass for the new pass manager.
The primary motivation for this pass is to separate the call graph
analysis used by the new pass manager's CGSCC pass management from the
existing call graph analysis pass. That analysis pass is (somewhat
unfortunately) over-constrained by the existing CallGraphSCCPassManager
requirements. Those requirements make it *really* hard to cleanly layer
the needed functionality for the new pass manager on top of the existing
analysis.

However, there are also a bunch of things that the pass manager would
specifically benefit from doing differently from the existing call graph
analysis, and this new implementation tries to address several of them:

- Be lazy about scanning function definitions. The existing pass eagerly
  scans the entire module to build the initial graph. This new pass is
  significantly more lazy, and I plan to push this even further to
  maximize locality during CGSCC walks.
- Don't use a single synthetic node to partition functions with an
  indirect call from functions whose address is taken. This node creates
  a huge choke-point which would preclude good parallelization across
  the fanout of the SCC graph when we got to the point of looking at
  such changes to LLVM.
- Use a memory dense and lightweight representation of the call graph
  rather than value handles and tracking call instructions. This will
  require explicit update calls instead of some updates working
  transparently, but should end up being significantly more efficient.
  The explicit update calls ended up being needed in many cases for the
  existing call graph so we don't really lose anything.
- Doesn't explicitly model SCCs and thus doesn't provide an "identity"
  for an SCC which is stable across updates. This is essential for the
  new pass manager to work correctly.
- Only form the graph necessary for traversing all of the functions in
  an SCC friendly order. This is a much simpler graph structure and
  should be more memory dense. It does limit the ways in which it is
  appropriate to use this analysis. I wish I had a better name than
  "call graph". I've commented extensively this aspect.

This is still very much a WIP, in fact it is really just the initial
bits. But it is about the fourth version of the initial bits that I've
implemented with each of the others running into really frustrating
problms. This looks like it will actually work and I'd like to split the
actual complexity across commits for the sake of my reviewers. =] The
rest of the implementation along with lots of wiring will follow
somewhat more rapidly now that there is a good path forward.

Naturally, this doesn't impact any of the existing optimizer. This code
is specific to the new pass manager.

A bunch of thanks are deserved for the various folks that have helped
with the design of this, especially Nick Lewycky who actually sat with
me to go through the fundamentals of the final version here.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200903 91177308-0d34-0410-b5e6-96231b3b80d8
2014-02-06 04:37:03 +00:00
Paul Robinson
2684ddd72e Disable most IR-level transform passes on functions marked 'optnone'.
Ideally only those transform passes that run at -O0 remain enabled,
in reality we get as close as we reasonably can.
Passes are responsible for disabling themselves, it's not the job of
the pass manager to do it for them.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200892 91177308-0d34-0410-b5e6-96231b3b80d8
2014-02-06 00:07:05 +00:00
Duncan P. N. Exon Smith
42e0bc88a3 Clean up whitespace
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200579 91177308-0d34-0410-b5e6-96231b3b80d8
2014-01-31 21:45:51 +00:00
Juergen Ributzka
efbb39740c [TLI] Add a new hook to TargetLowering to query the target if a load of a constant should be converted to simply the constant itself.
Before this patch we used getIntImmCost from TargetTransformInfo to determine if
a load of a constant should be converted to just a constant, but the threshold
for this was set to an arbitrary value. This value works well for the two
targets (X86 and ARM) that implement this target-hook, but it isn't
target-independent at all.

Now targets have the possibility to decide directly if this optimization should
be performed. The default value is set to false to preserve the current
behavior. The target hook has been moved to TargetLowering, which removed the
last use and need of TargetTransformInfo in SelectionDAG.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200271 91177308-0d34-0410-b5e6-96231b3b80d8
2014-01-28 01:20:14 +00:00
Nick Lewycky
f2282cac95 Teach SCEV to handle more cases of 'and X, CST', specifically where CST is any number of contiguous 1 bits in a row, with any number of leading and trailing 0 bits.
Unfortunately, this in turn led to some lower quality SCEVs due to some different paths through expression simplification, so add getUDivExactExpr and use it. This fixes all instances of the problems that I found, but we can make that function smarter as necessary.

Merge test "xor-and.ll" into "and-xor.ll" since I needed to update it anyways. Test 'nsw-offset.ll' analyzes a little deeper, %n now gets a scev in terms of %no instead of a SCEVUnknown.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200203 91177308-0d34-0410-b5e6-96231b3b80d8
2014-01-27 10:04:03 +00:00
Juergen Ributzka
943ce55f39 Revert "Revert "Add Constant Hoisting Pass" (r200034)"
This reverts commit r200058 and adds the using directive for
ARMTargetTransformInfo to silence two g++ overload warnings.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200062 91177308-0d34-0410-b5e6-96231b3b80d8
2014-01-25 02:02:55 +00:00
Hans Wennborg
503793e834 Revert "Add Constant Hoisting Pass" (r200034)
This commit caused -Woverloaded-virtual warnings. The two new
TargetTransformInfo::getIntImmCost functions were only added to the superclass,
and to the X86 subclass. The other targets were not updated, and the
warning highlighted this by pointing out that e.g. ARMTTI::getIntImmCost was
hiding the two new getIntImmCost variants.

We could pacify the warning by adding "using TargetTransformInfo::getIntImmCost"
to the various subclasses, or turning it off, but I suspect that it's wrong to
leave the functions unimplemnted in those targets. The default implementations
return TCC_Free, which I don't think is right e.g. for ARM.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200058 91177308-0d34-0410-b5e6-96231b3b80d8
2014-01-25 01:18:18 +00:00
Juergen Ributzka
96172cb4a4 Add Constant Hoisting Pass
Retry commit r200022 with a fix for the build bot errors. Constant expressions
have (unlike instructions) module scope use lists and therefore may have users
in different functions. The fix is to simply ignore these out-of-function uses.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200034 91177308-0d34-0410-b5e6-96231b3b80d8
2014-01-24 20:18:00 +00:00
Juergen Ributzka
dc6f9b9a4f Revert "Add Constant Hoisting Pass"
This reverts commit r200022 to unbreak the build bots.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200024 91177308-0d34-0410-b5e6-96231b3b80d8
2014-01-24 18:40:30 +00:00
Juergen Ributzka
fb282c68b7 Add Constant Hoisting Pass
This pass identifies expensive constants to hoist and coalesces them to
better prepare it for SelectionDAG-based code generation. This works around the
limitations of the basic-block-at-a-time approach.

First it scans all instructions for integer constants and calculates its
cost. If the constant can be folded into the instruction (the cost is
TCC_Free) or the cost is just a simple operation (TCC_BASIC), then we don't
consider it expensive and leave it alone. This is the default behavior and
the default implementation of getIntImmCost will always return TCC_Free.

If the cost is more than TCC_BASIC, then the integer constant can't be folded
into the instruction and it might be beneficial to hoist the constant.
Similar constants are coalesced to reduce register pressure and
materialization code.

When a constant is hoisted, it is also hidden behind a bitcast to force it to
be live-out of the basic block. Otherwise the constant would be just
duplicated and each basic block would have its own copy in the SelectionDAG.
The SelectionDAG recognizes such constants as opaque and doesn't perform
certain transformations on them, which would create a new expensive constant.

This optimization is only applied to integer constants in instructions and
simple (this means not nested) constant cast experessions. For example:
%0 = load i64* inttoptr (i64 big_constant to i64*)

Reviewed by Eric

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200022 91177308-0d34-0410-b5e6-96231b3b80d8
2014-01-24 18:23:08 +00:00
Juergen Ributzka
342a479f8d Doxify comments
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200020 91177308-0d34-0410-b5e6-96231b3b80d8
2014-01-24 18:22:55 +00:00