Commit Graph

26 Commits

Author SHA1 Message Date
Hans Wennborg 0b39fc0d16 Revert "Teach the load analysis to allow finding available values which require" (r220277)
This seems to have caused PR21330.

llvm-svn: 220349
2014-10-21 23:49:52 +00:00
Chandler Carruth aa72a6dd3b Teach the load analysis to allow finding available values which require
inttoptr or ptrtoint cast provided there is datalayout available.
Eventually, the datalayout can just be required but in practice it will
always be there today.

To go with the ability to expose available values requiring a ptrtoint
or inttoptr cast, helpers are added to perform one of these three casts.

These smarts are necessary to finish canonicalizing loads and stores to
the operational type requirements without regressing fundamental
combines.

I've added some test cases. These should actually improve as the load
combining and store combining improves, but they may fundamentally be
highlighting some missing combines for select in addition to exercising
the specific added logic to load analysis.

llvm-svn: 220277
2014-10-21 09:00:40 +00:00
Chandler Carruth a32038b006 Fix a miscompile introduced in r220178.
The original code had an implicit assumption that if the test for
allocas or globals was reached, the two pointers were not equal. With my
changes to make the pointer analysis more powerful here, I also had to
guard against circumstances where the results weren't useful. That in
turn violated the assumption and gave rise to a circumstance in which we
could have a store with both the queried pointer and stored pointer
rooted at *the same* alloca. Clearly, we cannot ignore such a store.
There are other things we might do in this code to better handle the
case of both pointers ending up at the same alloca or global, but it
seems best to at least make the test explicit in what it intends to
check.

I've added tests for both the alloca and global case here.

llvm-svn: 220190
2014-10-20 10:03:01 +00:00
Chandler Carruth eeec35ae1c Teach the load analysis driving core instcombine logic and other bits of
logic to look through pointer casts, making them trivially stronger in
the face of loads and stores with intervening pointer casts.

I've included a few test cases that demonstrate the kind of folding
instcombine can do without pointer casts and then variations which
obfuscate the logic through bitcasts. Without this patch, the variations
all fail to optimize fully.

This is more important now than it has been in the past as I've started
moving the load canonicialization to more closely follow the value type
requirements rather than the pointer type requirements and thus this
needs to be prepared for more pointer casts. When I made the same change
to stores several test cases regressed without logic along these lines
so I wanted to systematically improve matters first.

llvm-svn: 220178
2014-10-20 00:24:14 +00:00
Chandler Carruth a801dd5799 Fix a long-standing miscompile in the load analysis that was uncovered
by my refactoring of this code.

The method isSafeToLoadUnconditionally assumes that the load will
proceed with the preferred type alignment. Given that, it has to ensure
that the alloca or global is at least that aligned. It has always done
this historically when a datalayout is present, but has never checked it
when the datalayout is absent. When I refactored the code in r220156,
I exposed this path when datalayout was present and that turned the
latent bug into a patent bug.

This fixes the issue by just removing the special case which allows
folding things without datalayout. This isn't worth the complexity of
trying to tease apart when it is or isn't safe without actually knowing
the preferred alignment.

llvm-svn: 220161
2014-10-19 08:17:50 +00:00
Chandler Carruth 8a99373812 Switch how the datalayout availability test is handled in this code to
make much more sense and in theory be more correct.

If you trace the code alllll the way back to when it was first
introduced, the comments make it slightly more clear what was going on
here. At that time, the only way Base != V was if DL (then TD) was
non-null. As a consequence, if DL *was* null, that meant we were loading
directly from the alloca or global found above the test. After
refactoring, this has become at least terribly subtle and potentially
incorrect. There are many forms of pointer manipulation that can be
traversed without DataLayout, and some of them would in fact change the
size of object being loaded vs. allocated.

Rather than this subtlety, I've hoisted the actual 'return true' bits
into the code which actually found an alloca or global and based them on
the loaded pointer being that alloca or global. This is both more clear
and safer. I've also added comments about exactly why this set of
predicates is used.

I've also corrected a misleading comment about globals -- if overridden
they may not just have a different size, they may be null and completely
unsafe to load from!

Hopefully this confuses the next reader a bit less. I don't have any
test cases or anything, the patch is motivated strictly to improve the
readability of the code.

llvm-svn: 220156
2014-10-19 00:42:16 +00:00
Chandler Carruth 38e98d5782 Rename 'TD' to 'DL' in this function as the argument is now a DataLayout
argument.

llvm-svn: 220151
2014-10-18 23:47:22 +00:00
Chandler Carruth 1f27f03849 Fix the other comment to use modern doxygen style and be a bit more
direct. Notably, comment on the fact that the loaded type is significant
in that it determines how wide of an access must be safe.

llvm-svn: 220150
2014-10-18 23:46:17 +00:00
Chandler Carruth be49df3d2c More formatting cleanup brought to you by clang-format.
llvm-svn: 220149
2014-10-18 23:41:25 +00:00
Chandler Carruth b56052f44d Clean up doxygen syntax and reword comments to flow better, have a brief
section, and not have unfinished sentence fragments.

llvm-svn: 220147
2014-10-18 23:31:55 +00:00
Chandler Carruth d67244df4e Clean up the formatting and trailing whitespace of a routine before
editting it.

llvm-svn: 220146
2014-10-18 23:19:03 +00:00
Hal Finkel cc39b67530 AA metadata refactoring (introduce AAMDNodes)
In order to enable the preservation of noalias function parameter information
after inlining, and the representation of block-level __restrict__ pointer
information (etc.), additional kinds of aliasing metadata will be introduced.
This metadata needs to be carried around in AliasAnalysis::Location objects
(and MMOs at the SDAG level), and so we need to generalize the current scheme
(which is hard-coded to just one TBAA MDNode*).

This commit introduces only the necessary refactoring to allow for the
introduction of other aliasing metadata types, but does not actually introduce
any (that will come in a follow-up commit). What it does introduce is a new
AAMDNodes structure to hold all of the aliasing metadata nodes associated with
a particular memory-accessing instruction, and uses that structure instead of
the raw MDNode* in AliasAnalysis::Location, etc.

No functionality change intended.

llvm-svn: 213859
2014-07-24 12:16:19 +00:00
Craig Topper 9f008867c0 [C++11] More 'nullptr' conversion. In some cases just using a boolean check instead of comparing to nullptr.
llvm-svn: 206243
2014-04-15 04:59:12 +00:00
Dan Gohman 20a2ae9df5 Change GetPointerBaseWithConstantOffset's DataLayout argument from a
reference to a pointer, so that it can handle the case where DataLayout
is not available and behave conservatively.

llvm-svn: 174024
2013-01-31 02:00:45 +00:00
Chandler Carruth 9fb823bbd4 Move all of the header files which are involved in modelling the LLVM IR
into their new header subdirectory: include/llvm/IR. This matches the
directory structure of lib, and begins to correct a long standing point
of file layout clutter in LLVM.

There are still more header files to move here, but I wanted to handle
them in separate commits to make tracking what files make sense at each
layer easier.

The only really questionable files here are the target intrinsic
tablegen files. But that's a battle I'd rather not fight today.

I've updated both CMake and Makefile build systems (I think, and my
tests think, but I may have missed something).

I've also re-sorted the includes throughout the project. I'll be
committing updates to Clang, DragonEgg, and Polly momentarily.

llvm-svn: 171366
2013-01-02 11:36:10 +00:00
Nuno Lopes 69dcc7deec use ValueTracking's GetPointerBaseWithConstantOffset() function instead of a local implementation
llvm-svn: 171307
2012-12-31 17:42:11 +00:00
Micah Villmow cdfe20b97f Move TargetData to DataLayout.
llvm-svn: 165402
2012-10-08 16:38:25 +00:00
Chris Lattner 87fa77bd8a enhance jump threading to preserve TBAA information when PRE'ing loads,
fixing rdar://11039258, an issue that came up when inspecting clang's 
bootstrapped codegen.

llvm-svn: 152635
2012-03-13 18:07:41 +00:00
Eli Friedman 4419cd2464 Add some comments here because the lack of a check for volatile/atomic here is a bit unusual.
llvm-svn: 137662
2011-08-15 21:56:39 +00:00
Jay Foad bf904773bb Convert TargetData::getIndexedOffset to use ArrayRef.
llvm-svn: 135478
2011-07-19 14:01:37 +00:00
Chris Lattner 229907cd11 land David Blaikie's patch to de-constify Type, with a few tweaks.
llvm-svn: 135375
2011-07-18 04:54:35 +00:00
Hans Wennborg 060b994a29 Test commit.
llvm-svn: 132558
2011-06-03 17:15:37 +00:00
Jay Foad 7c14a558fe Don't include Operator.h from InstrTypes.h.
llvm-svn: 129271
2011-04-11 09:35:34 +00:00
Dan Gohman a4fcd2418d Move Value::getUnderlyingObject to be a standalone
function so that it can live in Analysis instead of
VMCore.

llvm-svn: 121885
2010-12-15 20:02:24 +00:00
Dan Gohman f372cf869b Reapply r116831 and r116839, converting AliasAnalysis to use
uint64_t, plus fixes for places I missed before.

llvm-svn: 116875
2010-10-19 22:54:46 +00:00
Dan Gohman 826bdf8c10 Move FindAvailableLoadedValue isSafeToLoadUnconditionally out of
lib/Transforms/Utils and into lib/Analysis so that Analysis passes
can use them.

llvm-svn: 104949
2010-05-28 16:19:17 +00:00