Commit Graph

76 Commits

Author SHA1 Message Date
Mark Heffernan 2beab5f0b4 This patch de-pessimizes the calculation of loop trip counts in
ScalarEvolution in the presence of multiple exits. Previously all
loops exits had to have identical counts for a loop trip count to be
considered computable. This pessimization was implemented by calling
getBackedgeTakenCount(L) rather than getExitCount(L, ExitingBlock)
inside of ScalarEvolution::getSmallConstantTripCount() (see the FIXME
in the comments of that function). The pessimization was added to fix
a corner case involving undefined behavior (pr/16130). This patch more
precisely handles the undefined behavior case allowing the pessimization
to be removed.

ControlsExit replaces IsSubExpr to more precisely track the case where
undefined behavior is expected to occur. Because undefined behavior is
tracked more precisely we can remove MustExit from ExitLimit. MustExit
was used to track the case where the limit was computed potentially
assuming undefined behavior even if undefined behavior didn't necessarily
occur.

llvm-svn: 219517
2014-10-10 17:39:11 +00:00
Duncan P. N. Exon Smith c46cfcbbc6 LoopUnroll: Create sub-loops in LoopInfo
`LoopUnrollPass` says that it preserves `LoopInfo` -- make it so.  In
particular, tell `LoopInfo` about copies of inner loops when unrolling
the outer loop.

Conservatively, also tell `ScalarEvolution` to forget about the original
versions of these loops, since their inputs may have changed.

Fixes PR20987.

llvm-svn: 219241
2014-10-07 21:19:00 +00:00
Kevin Qin fc02e3c363 Use a loop to simplify the runtime unrolling prologue.
Runtime unrolling will create a prologue to execute the extra
iterations which is can't divided by the unroll factor. It
generates an if-then-else sequence to jump into a factor -1
times unrolled loop body, like

    extraiters = tripcount % loopfactor
    if (extraiters == 0) jump Loop:
    if (extraiters == loopfactor) jump L1
    if (extraiters == loopfactor-1) jump L2
    ...
    L1:  LoopBody;
    L2:  LoopBody;
    ...
    if tripcount < loopfactor jump End
    Loop:
    ...
    End:

It means if the unroll factor is 4, the loop body will be 7
times unrolled, 3 are in loop prologue, and 4 are in the loop.
This commit is to use a loop to execute the extra iterations
in prologue, like

        extraiters = tripcount % loopfactor
        if (extraiters == 0) jump Loop:
        else jump Prol
 Prol:  LoopBody;
        extraiters -= 1                 // Omitted if unroll factor is 2.
        if (extraiters != 0) jump Prol: // Omitted if unroll factor is 2.
        if (tripcount < loopfactor) jump End
 Loop:
 ...
 End:

Then when unroll factor is 4, the loop body will be copied by
only 5 times, 1 in the prologue loop, 4 in the original loop.
And if the unroll factor is 2, new loop won't be created, just
as the original solution.

llvm-svn: 218604
2014-09-29 11:15:00 +00:00
David Peixotto 472b05b36c Ignore annotation function calls in cost computation
The annotation instructions are dropped during codegen and have no
impact on size.  In some cases, the annotations were preventing the
unroller from unrolling a loop because the annotation calls were
pushing the cost over the unrolling threshold.

Differential Revision: http://reviews.llvm.org/D5335

llvm-svn: 218525
2014-09-26 17:48:40 +00:00
Hal Finkel 57f03dda49 Add functions for finding ephemeral values
This adds a set of utility functions for collecting 'ephemeral' values. These
are LLVM IR values that are used only by @llvm.assume intrinsics (directly or
indirectly), and thus will be removed prior to code generation, implying that
they should be considered free for certain purposes (like inlining). The
inliner's cost analysis, and a few other passes, have been updated to account
for ephemeral values using the provided functionality.

This functionality is important for the usability of @llvm.assume, because it
limits the "non-local" side-effects of adding llvm.assume on inlining, loop
unrolling, etc. (these are hints, and do not generate code, so they should not
directly contribute to estimates of execution cost).

llvm-svn: 217335
2014-09-07 13:49:57 +00:00
Mark Heffernan 8ec1474f7f After unrolling a loop with llvm.loop.unroll.count metadata (unroll factor
hint) the loop unroller replaces the llvm.loop.unroll.count metadata with
llvm.loop.unroll.disable metadata to prevent any subsequent unrolling
passes from unrolling more than the hint indicates.  This patch fixes
an issue where loop unrolling could be disabled for other loops as well which
share the same llvm.loop metadata.

llvm-svn: 213900
2014-07-24 22:36:40 +00:00
Mark Heffernan 9e112443b6 Do not add unroll disable metadata after unrolling pass for loops with #pragma clang loop unroll(full).
llvm-svn: 213789
2014-07-23 20:05:44 +00:00
Mark Heffernan e6b4ba1c41 In unroll pragma syntax and loop hint metadata, change "enable" forms to a new form using the string "full".
llvm-svn: 213772
2014-07-23 17:31:37 +00:00
Mark Heffernan 053a68688a Remove unroll pragma metadata after it is used.
llvm-svn: 213412
2014-07-18 21:04:33 +00:00
Eli Bendersky 5d5e18da3e Rename loop unrolling and loop vectorizer metadata to have a common prefix.
[LLVM part]

These patches rename the loop unrolling and loop vectorizer metadata
such that they have a common 'llvm.loop.' prefix.  Metadata name
changes:

llvm.vectorizer.* => llvm.loop.vectorizer.*
llvm.loopunroll.* => llvm.loop.unroll.*

This was a suggestion from an earlier review
(http://reviews.llvm.org/D4090) which added the loop unrolling
metadata. 

Patch by Mark Heffernan.

llvm-svn: 211710
2014-06-25 15:41:00 +00:00
Benjamin Kramer 0bf086f80f LoopUnrollRuntime: Check for overflow in the trip count calculation.
Fixes PR19823.

llvm-svn: 211436
2014-06-21 13:46:25 +00:00
Eli Bendersky ff90324599 Teach LoopUnrollPass to respect loop unrolling hints in metadata.
[This is resubmitting r210721, which was reverted due to suspected breakage
which turned out to be unrelated].

Some extra review comments were addressed. See D4090 and D4147 for more details.

The Clang change that produces this metadata was committed in r210667

Patch by Mark Heffernan.

llvm-svn: 211076
2014-06-16 23:53:02 +00:00
Eli Bendersky dc6de2ce29 Revert r210721 as it causes breakage in internal builds (and possibly GDB).
llvm-svn: 210807
2014-06-12 18:05:39 +00:00
Eli Bendersky 899bef099f Teach LoopUnrollPass to respect loop unrolling hints in metadata.
See http://reviews.llvm.org/D4090 for more details.

The Clang change that produces this metadata was committed in r210667

Patch by Mark Heffernan.

llvm-svn: 210721
2014-06-11 23:15:35 +00:00
Alp Toker d3d017cf00 Reduce verbiage of lit.local.cfg files
We can just split targets_to_build in one place and make it immutable.

llvm-svn: 210496
2014-06-09 22:42:55 +00:00
Dinesh Dwivedi d266cb1a0b LCSSA should be performed on the outermost affected loop while unrolling loop.
During loop-unroll, loop exits from the current loop may end up in in different
outer loop. This requires to re-form LCSSA recursively for one level down from
the outer most loop where loop exits are landed during unroll. This fixes PR18861.

Differential Revision: http://reviews.llvm.org/D2976

llvm-svn: 209796
2014-05-29 06:47:23 +00:00
Hal Finkel 6532c20faa Move late partial-unrolling thresholds into the processor definitions
The old method used by X86TTI to determine partial-unrolling thresholds was
messy (because it worked by testing target features), and also would not
correctly identify the target CPU if certain target features were disabled.
After some discussions on IRC with Chandler et al., it was decided that the
processor scheduling models were the right containers for this information
(because it is often tied to special uop dispatch-buffer sizes).

This does represent a small functionality change:
 - For generic x86-64 (which uses the SB model and, thus, will get some
   unrolling).
 - For AMD cores (because they still currently use the SB scheduling model)
 - For Haswell (based on benchmarking by Louis Gerbarg, it was decided to bump
   the default threshold to 50; we're working on a test case for this).
Otherwise, nothing has changed for any other targets. The logic, however, has
been moved into BasicTTI, so other targets may now also opt-in to this
functionality simply by setting LoopMicroOpBufferSize in their processor
model definitions.

llvm-svn: 208289
2014-05-08 09:14:44 +00:00
Benjamin Kramer 9130cb8547 LoopUnroll: If we're doing partial unrolling, use the PartialThreshold to limit unrolling.
Otherwise we use the same threshold as for complete unrolling, which is
way too high. This made us unroll any loop smaller than 150 instructions
by 8 times, but only if someone specified -march=core2 or better,
which happens to be the default on darwin.

llvm-svn: 207940
2014-05-04 19:12:38 +00:00
Diego Novillo cd64780d18 Fix vectorization remarks.
This patch changes the vectorization remarks to also inform when
vectorization is possible but not beneficial.

Added tests to exercise some loop remarks.

llvm-svn: 207574
2014-04-29 20:06:10 +00:00
Hal Finkel 2eed29f3c8 Implement X86TTI::getUnrollingPreferences
This provides an initial implementation of getUnrollingPreferences for x86.
getUnrollingPreferences is used by the generic (concatenation) unroller, which
is distinct from the unrolling done by the loop vectorizer. Many modern x86
cores have some kind of uop cache and loop-stream detector (LSD) used to
efficiently dispatch small loops, and taking full advantage of this requires
unrolling small loops (small here means 10s of uops).

These caches also have limits on the number of taken branches in the loop, and
so we also cap the loop unrolling factor based on the maximum "depth" of the
loop. This is currently calculated with a partial DFS traversal (partial
because it will stop early if the path length grows too much). This is still an
approximation, and one that is both conservative (because it does not account
for branches eliminated via block placement) and optimistic (because it is only
recording the maximum depth over minimum paths). Nevertheless, because the
loops that fit in these uop caches are so small, it is not clear how much the
details matter.

The original set of patches posted for review produced the following test-suite
performance results (from the TSVC benchmark) at that time:
  ControlLoops-dbl - 13% speedup
  ControlLoops-flt - 15% speedup
  Reductions-dbl - 7.5% speedup

llvm-svn: 205348
2014-04-01 18:50:34 +00:00
Hal Finkel 71780ec4fd Implement TTI getUnrollingPreferences for PowerPC
The PowerPC A2 core greatly benefits from aggressive concatenation unrolling;
use the new getUnrollingPreferences to enable this by default when targeting
the PPC A2 core.

llvm-svn: 190549
2013-09-11 21:20:40 +00:00
Daniel Dunbar 9efbedfd35 [tests] Cleanup initialization of test suffixes.
- Instead of setting the suffixes in a bunch of places, just set one master
   list in the top-level config. We now only modify the suffix list in a few
   suites that have one particular unique suffix (.ml, .mc, .yaml, .td, .py).

 - Aside from removing the need for a bunch of lit.local.cfg files, this enables
   4 tests that were inadvertently being skipped (one in
   Transforms/BranchFolding, a .s file each in DebugInfo/AArch64 and
   CodeGen/PowerPC, and one in CodeGen/SI which is now failing and has been
   XFAILED).

 - This commit also fixes a bunch of config files to use config.root instead of
   older copy-pasted code.

llvm-svn: 188513
2013-08-16 00:37:11 +00:00
Stephen Lin c89a0ececb Fixup to r186268 and r186269: don't append -LABEL to CHECK-NOT. No functionality change.
llvm-svn: 186271
2013-07-14 02:10:57 +00:00
Stephen Lin c1c7a1309c Update Transforms tests to use CHECK-LABEL for easier debugging. No functionality change.
This update was done with the following bash script:

  find test/Transforms -name "*.ll" | \
  while read NAME; do
    echo "$NAME"
    if ! grep -q "^; *RUN: *llc" $NAME; then
      TEMP=`mktemp -t temp`
      cp $NAME $TEMP
      sed -n "s/^define [^@]*@\([A-Za-z0-9_]*\)(.*$/\1/p" < $NAME | \
      while read FUNC; do
        sed -i '' "s/;\(.*\)\([A-Za-z0-9_]*\):\( *\)@$FUNC\([( ]*\)\$/;\1\2-LABEL:\3@$FUNC(/g" $TEMP
      done
      mv $TEMP $NAME
    fi
  done

llvm-svn: 186268
2013-07-14 01:42:54 +00:00
Stephen Lin 2e105ff8b7 Modify two Transforms tests to explicitly check for full function names in some cases, rather than just a common prefix. No functionality change.
(This is to avoid confusing a scripted mass update of these tests to use CHECK-LABEL)

llvm-svn: 186267
2013-07-14 01:38:19 +00:00
Andrew Trick ee9143acf5 Prevent loop-unroll from making assumptions about undefined behavior.
Fixes rdar:14036816, PR16130.

There is an opportunity to compute precise trip counts for 'or'
expressions and multi-exit loops.
rdar:14038809: Optimize trip count computation for multi-exit loops.

To do this we need to record the fact that ExitLimit assumes NSW. When
it does not we can safely assume that the loop trip count is the
minimum ExitLimt across all subexpressions and loop exits.

llvm-svn: 183060
2013-05-31 23:34:46 +00:00
Jan Wen Voung 6dc3076080 Revert the test moves from 176733. Use "REQUIRES: asserts" instead.
llvm-svn: 176873
2013-03-12 16:27:52 +00:00
Jan Wen Voung 7857a64909 Disable statistics on Release builds and move tests that depend on -stats.
Summary:
Statistics are still available in Release+Asserts (any +Asserts builds),
and stats can also be turned on with LLVM_ENABLE_STATS.

Move some of the FastISel stats that were moved under DEBUG()
back out of DEBUG(), since stats are disabled across the board now.

Many tests depend on grepping "-stats" output.  Move those into
a orig_dir/Stats/. so that they can be marked as unsupported
when building without statistics.

Differential Revision: http://llvm-reviews.chandlerc.com/D486

llvm-svn: 176733
2013-03-08 22:56:31 +00:00
James Molloy 4f6fb953a7 Add a new attribute, 'noduplicate'. If a function contains a noduplicate call, the call cannot be duplicated - Jump threading, loop unrolling, loop unswitching, and loop rotation are inhibited if they would duplicate the call.
Similarly inlining of the function is inhibited, if that would duplicate the call (in particular inlining is still allowed when there is only one callsite and the function has internal linkage).

llvm-svn: 170704
2012-12-20 16:04:27 +00:00
Hal Finkel 30bd9346a0 getSmallConstantTripMultiple should never return zero.
When the trip count is -1, getSmallConstantTripMultiple could return zero,
and this would cause runtime loop unrolling to assert. Instead of returning
zero, one is now returned (consistent with the existing overflow cases).
Fixes PR14167.

llvm-svn: 166612
2012-10-24 19:46:44 +00:00
Benjamin Kramer 205d70ed28 Fix tests that didn't test anything.
llvm-svn: 164686
2012-09-26 09:51:39 +00:00
Andrew Trick 4442bfe559 Fix 12513: Loop unrolling breaks with indirect branches.
Take this opportunity to generalize the indirectbr bailout logic for
loop transformations. CFG transformations will never get indirectbr
right, and there's no point trying.

llvm-svn: 154386
2012-04-10 05:14:42 +00:00
Hongbin Zheng e1fd20172b Add testcase for r154007, when a function has the optsize attribute,
the loop should be unrolled according the value of OptSizeUnrollThreshold.

llvm-svn: 154014
2012-04-04 13:24:40 +00:00
Andrew Trick db149f9e73 Remove redundant -enable-iv-rewrite=false flags from test cases.
llvm-svn: 153255
2012-03-22 17:09:04 +00:00
Eli Bendersky 924f9a671d Replace all instances of dg.exp file with lit.local.cfg, since all tests are run with LIT now and now Dejagnu. dg.exp is no longer needed.
Patch reviewed by Daniel Dunbar. It will be followed by additional cleanup patches.

llvm-svn: 150664
2012-02-16 06:28:33 +00:00
Andrew Trick d04d152998 Add -unroll-runtime for unrolling loops with run-time trip counts.
Patch by Brendon Cahoon!

This extends the existing LoopUnroll and LoopUnrollPass. Brendon
measured no regressions in the llvm test suite with -unroll-runtime
enabled. This implementation works by using the existing loop
unrolling code to unroll the loop by a power-of-two (default 8). It
generates an if-then-else sequence of code prior to the loop to
execute the extra iterations before entering the unrolled loop.

llvm-svn: 146245
2011-12-09 06:19:40 +00:00
Andrew Trick 6b4d578f54 Fix a corner case in updating LoopInfo after fully unrolling an outer loop.
The loop tree's inclusive block lists are painful and expensive to
update. (I have no idea why they're inclusive). The design was
supposed to handle this case but the implementation missed it and my
unit tests weren't thorough enough.

Fixes PR11335: loop unroll update.

llvm-svn: 144970
2011-11-18 03:42:41 +00:00
Nick Lewycky d48ab84556 Don't try to loop on iterators that are potentially invalidated inside the loop. Fixes PR11361!
llvm-svn: 144454
2011-11-12 03:09:12 +00:00
Andrew Trick bf51f97c28 Unit test for r140919, loop unroll heuristics.
llvm-svn: 141049
2011-10-04 00:07:02 +00:00
Andrew Trick 74111ee07f Reapply r139759. Disable IV rewriting by default. See PR10916.
llvm-svn: 139842
2011-09-15 20:58:37 +00:00
Andrew Trick f9f68b816b [indvars] Revert r139579 until 401.bzip -arch i386 miscompilation is fixed. PR10920.
llvm-svn: 139583
2011-09-13 05:23:49 +00:00
Andrew Trick 061d811c51 Disable IV rewriting by default. See PR10916.
llvm-svn: 139579
2011-09-13 03:23:21 +00:00
Andrew Trick 183013d8d4 Rename -disable-iv-rewrite to -enable-iv-rewrite=false in preparation for default change.
llvm-svn: 139517
2011-09-12 18:28:44 +00:00
Andrew Trick 310a448cfe Test case update for unroll-scev.
llvm-svn: 139037
2011-09-02 21:21:03 +00:00
Andrew Trick 4a31ba3bae -unroll-scev flag removal
llvm-svn: 139010
2011-09-02 17:36:14 +00:00
Jakub Staszak 057d423e4b ConstantVector returns arbitrary value for the wrong index.
This fixes PR10813.

llvm-svn: 139006
2011-09-02 15:43:43 +00:00
Andrew Trick 2d8494a030 A slew of unit tests for the recent LoopInfo::updateUnloop feature
checked in at r137276 and r137341.

llvm-svn: 137385
2011-08-11 23:38:09 +00:00
Andrew Trick 2b6860f0a1 Allow loop unrolling to get known trip counts from ScalarEvolution.
SCEV unrolling can unroll loops with arbitrary induction variables. It
is a prerequisite for -disable-iv-rewrite performance. It is also
easily handles loops of arbitrary structure including multiple exits
and is generally more robust.

This is under a temporary option to avoid affecting default
behavior for the next couple of weeks. It is needed so that I can
checkin unit tests for updateUnloop.

llvm-svn: 137384
2011-08-11 23:36:16 +00:00
Andrew Trick 4d0040baf8 Invoke SimplifyIndVar when we partially unroll a loop. Fixes PR10534.
llvm-svn: 137203
2011-08-10 04:29:49 +00:00
Andrew Trick b72bbe2a92 Fix the LoopUnroller to handle nontrivial loops and partial unrolling.
These are not individual bug fixes. I had to rewrite a good chunk of
the unroller to make it sane. I think it was getting lucky on trivial
completely unrolled loops with no early exits. I included some fairly
simple unit tests for partial unrolling. I didn't do much stress
testing, so it may not be perfect, but should be usable now.

llvm-svn: 137190
2011-08-10 00:28:10 +00:00