Commit Graph

5457 Commits

Author SHA1 Message Date
Meador Inge
c2e331275b instcombine: Migrate fwrite optimizations
This patch migrates the fwrite optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168892 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-29 15:45:39 +00:00
Meador Inge
28d52913ab instcombine: Migrate fprintf optimizations
This patch migrates the fprintf optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168891 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-29 15:45:33 +00:00
Bill Wendling
bf2ad736c7 When we delete a dead basic block, see if any of its successors are dead and
delete those as well.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168829 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-28 23:23:48 +00:00
Meador Inge
69ea027e04 instcombine: Migrate sprintf optimizations
This patch migrates the sprintf optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168677 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-27 05:57:54 +00:00
Meador Inge
d7aa3231f7 instcombine: Migrate printf optimizations
This patch migrates the printf optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168604 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-26 20:37:20 +00:00
Meador Inge
38c4441797 instcombine: Migrate toascii optimizations
This patch migrates the toascii optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168580 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-26 03:38:52 +00:00
Meador Inge
017bb750ab instcombine: Migrate isascii optimizations
This patch migrates the isascii optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168579 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-26 03:10:07 +00:00
Meador Inge
a0798ec377 instcombine: Migrate isdigit optimizations
This patch migrates the isdigit optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168578 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-26 02:31:59 +00:00
Meador Inge
dfb3b1a779 instcombine: Migrate *abs optimizations
This patch migrates the *abs optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168574 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-26 00:24:07 +00:00
Meador Inge
15d099a790 instcombine: Migrate ffs* optimizations
This patch migrates the ffs* optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168571 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-25 20:45:27 +00:00
Benjamin Kramer
4ccb49a838 CodeGenPrepare: Move ret duplication out of the instruction iteration loop.
It can delete the block, and the loop continues on free'd memory.
No change in output. Found by valgrind.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168525 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-23 19:17:06 +00:00
Chandler Carruth
07df765e65 PR14055: Implement support for sub-vector operations in SROA.
Now if we can transform an alloca into a single vector value, but it has
subvector, non-element accesses, we form the appropriate shufflevectors
to allow SROA to proceed. This fixes PR14055 which pointed out a very
common pattern that SROA couldn't handle -- mixed vec3 and vec4
operations on a single alloca.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168418 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-21 08:16:30 +00:00
Chandler Carruth
3a902d0ae7 Use LLVM_ENABLE_DUMP for the variables used in printing as well as the
printing functions themselves.

Part of PR14324 (which should have just been a patch to the list, but
hey...)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168362 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-20 10:23:07 +00:00
Chandler Carruth
176792990e Fix PR14132 and handle OOB loads speculated throuh PHI nodes.
The issue is that we may end up with newly OOB loads when speculating
a load into the predecessors of a PHI node, and this confuses the new
integer splitting logic in some cases, triggering an assertion failure.
In fact, the branch in question must be dead code as it loads from
a too-narrow alloca. Add code to handle this gracefully and leave the
requisite FIXMEs for both optimizing more aggressively and doing more to
aid sanitizing invalid code which triggers these patterns.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168361 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-20 10:02:19 +00:00
Chandler Carruth
a1237b16c9 Add a comment to associate a FIXME with a PR where it is matters.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168347 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-20 01:27:48 +00:00
Chandler Carruth
f5837aacd4 Rework the rewriting of loads and stores for vector and integer allocas
to properly handle the combinations of these with split integer loads
and stores. This essentially replaces Evan's r168227 by refactoring the
code in a different way, and trynig to mirror that refactoring in both
the load and store sides of the rewriting.

Generally speaking there was some really problematic duplicated code
here that led to poorly founded assumptions and then subtle bugs. Now
much of the code actually flows through and follows a more consistent
style and logical path. There is still a tiny bit of duplication on the
store side of things, but it is much less bad.

This also changes the logic to never re-use a load or store instruction
as that was simply too error prone in practice.

I've added a few tests (one a reduction of the one in Evan's original
patch, which happened to be the same as the report in PR14349). I'm
going to look at adding a few more tests for things I found and fixed in
passing (such as the volatile tests in the vectorizable predicate).

This patch has survived bootstrap, and modulo one bugfix survived
Duncan's test suite, but let me know if anything else explodes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168346 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-20 01:12:50 +00:00
Duncan Sands
820b52572f Remove the last bit of constant folding from LinearizeExprTree (most of it was
removed in commit 168035, but I missed this bit).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168292 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-18 20:15:36 +00:00
Duncan Sands
b8e1111fbf Fix PR14060, an infinite loop in reassociate. The problem was that one of the
operands of the expression being written was wrongly thought to be reusable as
an inner node of the expression resulting in it turning up as both an inner node
*and* a leaf, creating a cycle in the def-use graph.  This would have caused the
verifier to blow up if things had gotten that far, however it managed to provoke
an infinite loop first.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168291 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-18 19:27:01 +00:00
Evan Cheng
fd22019ec3 Teach SROA rewriteVectorizedStoreInst to handle cases when the loaded value is narrower than the stored value. rdar://12713675
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168227 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-17 00:05:06 +00:00
Duncan Sands
7ecfcc1639 Fix a crash observed by Shuxin Yang. The issue here is that LinearizeExprTree,
the utility for extracting a chain of operations from the IR, thought that it
might as well combine any constants it came across (rather than just returning
them along with everything else).  On the other hand, the factorization code
would like to see the individual constants (this is quite reasonable: it is
much easier to pull a factor of 3 out of 2*3 than it is to pull it out of 6;
you may think 6/3 isn't so hard, but due to overflow it's not as easy to undo
multiplications of constants as it may at first appear).  This patch therefore
makes LinearizeExprTree stupider: it now leaves optimizing to the optimization
part of reassociate, and sticks to just analysing the IR.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168035 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-15 09:58:38 +00:00
Meador Inge
2920a71663 instcombine: Migrate math library call simplifications
This patch migrates the math library call simplifications from the
simplify-libcalls pass into the instcombine library call simplifier.

I have typically migrated just one simplifier at a time, but the math
simplifiers are interdependent because:

   1. CosOpt, PowOpt, and Exp2Opt all depend on UnaryDoubleFPOpt.
   2. CosOpt, PowOpt, Exp2Opt, and UnaryDoubleFPOpt all depend on
      the option -enable-double-float-shrink.

These two factors made migrating each of these simplifiers individually
more of a pain than it would be worth.  So, I migrated them all together.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167815 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-13 04:16:17 +00:00
Shuxin Yang
4df2826166 revert r167740
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167787 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-13 00:08:49 +00:00
Shuxin Yang
0a46bf13a3 This change is to fix rdar://12571717 which is about assertion in Reassociate pass.
The assertion is trigged when the Reassociater tries to transform expression
     ... + 2 * n * 3 + 2 * m + ...
  into:
     ... + 2 * (n*3 + m).

In the process of the transformation, a helper routine folds the constant 2*3 into 6,
confusing optimizer which is trying the to eliminate the common factor 2, and cannot
find 2 any more. 

Review is pending. But I'd like commit first in order to help those who are waiting 
for this fix. 


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167740 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-12 19:34:11 +00:00
Meador Inge
b798edd791 Delete a stale comment. No functional change.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167698 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-12 00:28:15 +00:00
Meador Inge
26ebe398f2 instcombine: Migrate memset optimizations
This patch migrates the memset optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167689 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-11 06:49:03 +00:00
Meador Inge
d7cb600514 instcombine: Migrate memmove optimizations
This patch migrates the memmove optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167687 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-11 06:22:40 +00:00
Meador Inge
11b04b40f2 instcombine: Migrate memcpy optimizations
This patch migrates the memcpy optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167686 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-11 05:54:34 +00:00
Meador Inge
bb51ec8b62 instcombine: Migrate memcmp optimizations
This patch migrates the memcmp optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167683 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-11 05:11:20 +00:00
Meador Inge
6e1591a5d5 instcombine: Migrate strstr optimizations
This patch migrates the strstr optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167682 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-11 03:51:48 +00:00
Meador Inge
5464ee7eaa instcombine: Migrate strcspn optimizations
This patch migrates the strcspn optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167675 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-10 15:16:48 +00:00
Meador Inge
7629de3326 instcombine: Migrate strspn optimizations
This patch migrates the strspn optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167568 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-08 01:33:50 +00:00
Chandler Carruth
a864748284 Revert the switch of loop-idiom to use the new dependence analysis.
The new analysis is not yet ready for prime time. It has a *critical*
flawed assumption, and some troubling shortages of testing. Until it's
been hammered into better shape, let's stick with the working code. This
should be easy to revert itself when the analysis is ready.

Fixes PR14241, a miscompile of any memcpy-able loop which uses a pointer
as the induction mechanism. If you have been seeing miscompiles in this
revision range, you really want to test with this backed out. The
results of this miscompile are a bit subtle as they can lead to
downstream passes concluding things are impossible which are in fact
possible.

Thanks to David Blaikie for the majority of the reduction of this
miscompile. I'll be checking in the test case in a non-revert commit.

Revesions reverted here:

r167045: LoopIdiom: Fix a serious missed optimization: we only turned
         top-level loops into memmove.
r166877: LoopIdiom: Add checks to avoid turning memmove into an infinite
         loop.
r166875: LoopIdiom: Recognize memmove loops.
r166874: LoopIdiom: Replace custom dependence analysis with
         DependenceAnalysis.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167286 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-02 08:33:25 +00:00
Duncan Sands
d295c9729d Fix an obvious typo that causes an assertion failure when running
test/Transforms/GVN/rle.ll if the (currently disabled) check for a
pointer type in getIntPtrType is turned on.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167285 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-02 07:49:32 +00:00
Chandler Carruth
426c2bf5cd Revert the majority of the next patch in the address space series:
r165941: Resubmit the changes to llvm core to update the functions to
         support different pointer sizes on a per address space basis.

Despite this commit log, this change primarily changed stuff outside of
VMCore, and those changes do not carry any tests for correctness (or
even plausibility), and we have consistently found questionable or flat
out incorrect cases in these changes. Most of them are probably correct,
but we need to devise a system that makes it more clear when we have
handled the address space concerns correctly, and ideally each pass that
gets updated would receive an accompanying test case that exercises that
pass specificaly w.r.t. alternate address spaces.

However, from this commit, I have retained the new C API entry points.
Those were an orthogonal change that probably should have been split
apart, but they seem entirely good.

In several places the changes were very obvious cleanups with no actual
multiple address space code added; these I have not reverted when
I spotted them.

In a few other places there were merge conflicts due to a cleaner
solution being implemented later, often not using address spaces at all.
In those cases, I've preserved the new code which isn't address space
dependent.

This is part of my ongoing effort to clean out the partial address space
code which carries high risk and low test coverage, and not likely to be
finished before the 3.2 release looms closer. Duncan and I would both
like to see the above issues addressed before we return to these
changes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167222 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-01 09:14:31 +00:00
Chandler Carruth
ece6c6bb63 Revert the series of commits starting with r166578 which introduced the
getIntPtrType support for multiple address spaces via a pointer type,
and also introduced a crasher bug in the constant folder reported in
PR14233.

These commits also contained several problems that should really be
addressed before they are re-committed. I have avoided reverting various
cleanups to the DataLayout APIs that are reasonable to have moving
forward in order to reduce the amount of churn, and minimize the number
of commits that were reverted. I've also manually updated merge
conflicts and manually arranged for the getIntPtrType function to stay
in DataLayout and to be defined in a plausible way after this revert.

Thanks to Duncan for working through this exact strategy with me, and
Nick Lewycky for tracking down the really annoying crasher this
triggered. (Test case to follow in its own commit.)

After discussing with Duncan extensively, and based on a note from
Micah, I'm going to continue to back out some more of the more
problematic patches in this series in order to ensure we go into the
LLVM 3.2 branch with a reasonable story here. I'll send a note to
llvmdev explaining what's going on and why.

Summary of reverted revisions:

r166634: Fix a compiler warning with an unused variable.
r166607: Add some cleanup to the DataLayout changes requested by
         Chandler.
r166596: Revert "Back out r166591, not sure why this made it through
         since I cancelled the command. Bleh, sorry about this!
r166591: Delete a directory that wasn't supposed to be checked in yet.
r166578: Add in support for getIntPtrType to get the pointer type based
         on the address space.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167221 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-01 08:07:29 +00:00
Jakub Staszak
5801ff93e3 Don't insert and erase load instruction. Simply create (new) and delete it.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167196 91177308-0d34-0410-b5e6-96231b3b80d8
2012-11-01 01:10:43 +00:00
Meador Inge
e0f1dca1c8 instcombine: Migrate strto* optimizations
This patch migrates the strto* optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167119 91177308-0d34-0410-b5e6-96231b3b80d8
2012-10-31 14:58:26 +00:00
Meador Inge
08684d1f06 instcombine: Migrate strpbrk optimizations
This patch migrates the strpbrk optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167105 91177308-0d34-0410-b5e6-96231b3b80d8
2012-10-31 04:29:58 +00:00
Meador Inge
57cfd71f88 instcombine: Migrate strlen optimizations
This patch migrates the strlen optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167103 91177308-0d34-0410-b5e6-96231b3b80d8
2012-10-31 03:33:06 +00:00
Meador Inge
a0885fb882 instcombine: Migrate strncpy optimizations
This patch migrates the strncpy optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167102 91177308-0d34-0410-b5e6-96231b3b80d8
2012-10-31 03:33:00 +00:00
Meador Inge
e6d781fd3c instcombine: Migrate stpcpy optimizations
This patch migrates the stpcpy optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.  Note that the
__stpcpy_chk simplifications were migrated in a previous commit.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167083 91177308-0d34-0410-b5e6-96231b3b80d8
2012-10-31 00:20:56 +00:00
Chandler Carruth
70dace3052 Fix PR14212: For some strange reason I treated vectors differently from
integers in that the code to handle split alloca-wide integer loads or
stores doesn't come first. It should, for the same reasons as with
integers, and the PR attests to that. Also had to fix a busted assert in
that this test case also covers.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167051 91177308-0d34-0410-b5e6-96231b3b80d8
2012-10-30 20:52:40 +00:00
Benjamin Kramer
415f869cf3 LoopIdiom: Fix a serious missed optimization: we only turned top-level loops into memmove.
Thanks to Preston Briggs for catching this!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167045 91177308-0d34-0410-b5e6-96231b3b80d8
2012-10-30 19:49:39 +00:00
Hans Wennborg
04d7d13d30 Use TargetTransformInfo to control switch-to-lookup table transformation
When the switch-to-lookup tables transform landed in SimplifyCFG, it
was pointed out that this could be inappropriate for some targets.
Since there was no way at the time for the pass to know anything about
the target, an awkward reverse-transform was added in CodeGenPrepare
that turned lookup tables back into switches for some targets.

This patch uses the new TargetTransformInfo to determine if a
switch should be transformed, and removes
CodeGenPrepare::ConvertLoadToSwitch.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167011 91177308-0d34-0410-b5e6-96231b3b80d8
2012-10-30 11:23:25 +00:00
Ulrich Weigand
e669c930a6 In various places throughout the code generator, there were special
checks to avoid performing compile-time arithmetic on PPCDoubleDouble.

Now that APFloat supports arithmetic on PPCDoubleDouble, those checks
are no longer needed, and we can treat the type like any other.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@166958 91177308-0d34-0410-b5e6-96231b3b80d8
2012-10-29 18:35:49 +00:00
Duncan Sands
7ed4f94c13 Remove a wrapper around getIntPtrType added to GVN by Hal in commit 166624 (the
wrapper returns a vector of integers when passed a vector of pointers) by having
getIntPtrType itself return a vector of integers in this case.  Outside of this
wrapper, I didn't find anywhere in the codebase that was relying on the old
behaviour for vectors of pointers, so give this a whirl through the buildbots.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@166939 91177308-0d34-0410-b5e6-96231b3b80d8
2012-10-29 17:31:46 +00:00
Benjamin Kramer
badffcf8fd LoopIdiom: Add checks to avoid turning memmove into an infinite loop.
I don't think this is possible with the current implementation but that may change eventually.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@166877 91177308-0d34-0410-b5e6-96231b3b80d8
2012-10-27 15:18:28 +00:00
Benjamin Kramer
d11c5d08a5 LoopIdiom: Recognize memmove loops.
This turns loops like
  for (unsigned i = 0; i != n; ++i)
    p[i] = p[i+1];
into memmove, which has a highly optimized implementation in most libcs.

This was really easy with the new DependenceAnalysis :)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@166875 91177308-0d34-0410-b5e6-96231b3b80d8
2012-10-27 14:25:51 +00:00
Benjamin Kramer
96c8735e28 LoopIdiom: Replace custom dependence analysis with DependenceAnalysis.
Requires a lot less code and complexity on loop-idiom's side and the more
precise analysis can catch more cases, like the one I included as a test case.
This also fixes the edge-case miscompilation from PR9481.

Compile time performance seems to be slightly worse, but this is mostly due
to an extra LCSSA run scheduled by the PassManager and should be fixed there.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@166874 91177308-0d34-0410-b5e6-96231b3b80d8
2012-10-27 14:25:44 +00:00
Chandler Carruth
a2b88163af Teach SROA how to split whole-alloca integer loads and stores into
smaller integer loads and stores.

The high-level motivation is that the frontend sometimes generates
a single whole-alloca integer load or store during ABI lowering of
splittable allocas. We need to be able to break this apart in order to
see the underlying elements and properly promote them to SSA values. The
hope is that this fixes some performance regressions on x86-32 with the
new SROA pass.

Unfortunately, this causes quite a bit of churn in the test cases, and
bloats some IR that comes out. When we see an alloca that consists soley
of bits and bytes being extracted and re-inserted, we now do some
splitting first, before building widened integer "bucket of bits"
representations. These are always well folded by instcombine however, so
this shouldn't actually result in missed opportunities.

If this splitting of all-integer allocas does cause problems (perhaps
due to smaller SSA values going into the RA), we could potentially go to
some extreme measures to only do this integer splitting trick when there
are non-integer component accesses of an alloca, but discovering this is
quite expensive: it adds yet another complete walk of the recursive use
tree of the alloca.

Either way, I will be watching build bots and LNT bots to see what
fallout there is here. If anyone gets x86-32 numbers before & after this
change, I would be very interested.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@166662 91177308-0d34-0410-b5e6-96231b3b80d8
2012-10-25 04:37:07 +00:00