Commit Graph

19529 Commits

Author SHA1 Message Date
Geoff Berry 2ddfc5e60f [DAGCombiner] Improve zextload optimization.
Summary:
Don't fold
  (zext (and (load x), cst)) -> (and (zextload x), (zext cst))
if
  (and (load x) cst)
will match as a zextload already and has additional users.

For example, the following IR:

  %load = load i32, i32* %ptr, align 8
  %load16 = and i32 %load, 65535
  %load64 = zext i32 %load16 to i64
  store i32 %load16, i32* %dst1, align 4
  store i64 %load64, i64* %dst2, align 8

used to produce the following aarch64 code:

	ldr		w8, [x0]
	and	w9, w8, #0xffff
	and	x8, x8, #0xffff
	str		w9, [x1]
	str		x8, [x2]

but with this change produces the following aarch64 code:

	ldrh		w8, [x0]
	str		w8, [x1]
	str		x8, [x2]

Reviewers: resistor, mcrosier

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D14340

llvm-svn: 252789
2015-11-11 19:42:52 +00:00
Matt Arsenault d8fed1b793 Add target preference for GatherAllAliases max depth
llvm-svn: 252775
2015-11-11 18:44:33 +00:00
Dehao Chen 54511353e3 clang-format lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
llvm-svn: 252769
2015-11-11 18:09:47 +00:00
Dehao Chen 72fdf444b7 Emit discriminator for inlined callsites.
Summary: Inlined callsites need to be emitted in debug info so that sample profile can be annotated to the correct inlined instance.

Reviewers: dnovillo, dblaikie

Subscribers: dblaikie, llvm-commits

Differential Revision: http://reviews.llvm.org/D14511

llvm-svn: 252768
2015-11-11 18:08:18 +00:00
Matthias Braun 2c98d0f477 MachineInstr: addRegisterDefReadUndef() => setRegisterDefReadUndef()
This way we can not only add but also remove read undef flags.

llvm-svn: 252678
2015-11-11 00:41:58 +00:00
Matthias Braun 4353b30542 TableGen: Emit LaneMask for register classes without subregisters as ~0u
This makes it slightly easier to handle classes with and without
subregister uniformly.

llvm-svn: 252671
2015-11-10 23:23:05 +00:00
Sanjay Patel 33ec5dbe35 less indent; NFCI
llvm-svn: 252643
2015-11-10 20:09:02 +00:00
Matt Arsenault aa118e299c LegalizeDAG: Implement promote for scalar_to_vector
This allows avoiding the default Expand behavior which
introduces stack usage. Bitcast the scalar and replace
the missing elements with undef.

This is covered by existing tests and used by a future
commit which makes 64-bit vectors legal types on AMDGPU.

llvm-svn: 252632
2015-11-10 18:48:11 +00:00
Matt Arsenault a46aa641f2 LegalizeDAG: Implement promote for insert_vector_elt
This is covered by existing tests and used by a future
commit which makes 64-bit vectors legal types on AMDGPU.

llvm-svn: 252631
2015-11-10 18:48:08 +00:00
Matt Arsenault 0b7958a59b LegalizeDAG: Implement promote for extract_vector_elt
This is for AMDGPU to implement v2i64 extract as extract of
half of a v4i32.

This is covered by existing tests and used by a future
commit which makes 64-bit vectors legal types on AMDGPU.

llvm-svn: 252630
2015-11-10 18:48:04 +00:00
Sanjay Patel 766589efdc add 'MustReduceDepth' as an objective/cost-metric for the MachineCombiner
This is one of the problems noted in PR25016:
https://llvm.org/bugs/show_bug.cgi?id=25016
and:
http://lists.llvm.org/pipermail/llvm-dev/2015-October/090998.html

The spilling problem is independent and not addressed by this patch.

The MachineCombiner was doing reassociations that don't improve or even worsen the critical path. 
This is caused by inclusion of the "slack" factor when calculating the critical path of the original
code sequence. If we don't add that, then we have a more conservative cost comparison of the old code
sequence vs. a new sequence. The more liberal calculation must be preserved, however, for the AArch64
MULADD patterns because benchmark regressions were observed without that.

The two failing test cases now have identical asm that does what we want:
a + b + c + d ---> (a + b) + (c + d)

Differential Revision: http://reviews.llvm.org/D13417

llvm-svn: 252616
2015-11-10 16:48:53 +00:00
Andy Ayers 809cbe9ea0 Support for emitting inline stack probes
For CoreCLR on Windows, stack probes must be emitted as inline sequences that probe successive stack pages
between the current stack limit and the desired new stack pointer location. This implements support for
the inline expansion on x64.

For in-body alloca probes, expansion is done during instruction lowering. For prolog probes, a stub call
is initially emitted during prolog creation, and expanded after epilog generation, to avoid complications
that arise when introducing new machine basic blocks during prolog and epilog creation.

Added a new test case, modified an existing one to exclude non-x64 coreclr (for now).

Add test case

Fix tests

llvm-svn: 252578
2015-11-10 01:50:49 +00:00
Matt Arsenault 6d87f28afd Remove unnecessary call to getAllocatableRegClass
I'm not sure what the point of this was. I'm not sure why
you would ever define an instruction that produces an unallocatable
register class. No tests fail with this removed, and it seems like
it should be a verifier error to define such an instruction.

This was problematic for AMDGPU because it would make bad decisions
by arbitrarily changing the register class when unsetting isAllocatable
for VS_32/VS_64, which is currently set as a workaround to this problem.

AMDGPU uses the VS_32/VS_64 register classes to represent operands which
can use either VGPRs or SGPRs. When  isAllocatable is unset for these,
this would need to pick  either the SGPR or VGPR class and insert either
a copy we don't want, or an illegal copy we would need to deal with
later. A semi-arbitrary register class ordering decision is made in tablegen,
which resulted in always picking a VGPR class because it happens to have
more registers than the SGPR register class. We really just want to
use whatever register class the original register had.

llvm-svn: 252565
2015-11-10 00:30:14 +00:00
Matthias Braun 7e624d5f11 MachineVerifier: Streamline live interval related error reporting
Simply perform additional report_context() calls after a report()
instead of adding more and more overloaded variations of report().  Also
improve several instances where information was output in an ad-hoc way
probably because no matching report() overload was available.

llvm-svn: 252552
2015-11-09 23:59:33 +00:00
Matthias Braun 716b43306b MachineVerifier: Add missing linebreak
MachineInstr::print() with SkipOppers==true does not produce a
linebreak, so we have to do that in MachineVerifier::report().

llvm-svn: 252551
2015-11-09 23:59:29 +00:00
Matthias Braun 45718db0a1 MachineVerifier: MI::print has no TargetMachine overload
The code was passing a target machine pointer which degraded to a true
operand to SkipOppers.

llvm-svn: 252550
2015-11-09 23:59:25 +00:00
Matthias Braun 42b4b63056 MachineVerifier: print list of live intervals if available
llvm-svn: 252549
2015-11-09 23:59:23 +00:00
Sanjay Patel 533c10c651 add a SelectionDAG method to check if no common bits are set in two nodes; NFCI
This was suggested in:
http://reviews.llvm.org/D13956

and is a follow-on to:
http://reviews.llvm.org/rL252515
http://reviews.llvm.org/rL252519

This lets us remove logically equivalent/duplicated code from DAGCombiner and X86ISelDAGToDAG.

A corresponding function for IR instructions already exists in ValueTracking.

llvm-svn: 252539
2015-11-09 23:31:38 +00:00
David Majnemer 2652b75700 [WinEH] Don't emit CATCHRET from visitCatchPad
Instead, emit a CATCHPAD node which will get selected to a target
specific sequence.

llvm-svn: 252528
2015-11-09 23:07:48 +00:00
Reid Kleckner 64b003f05d [WinEH] Tweak funclet prologue/epilogue insertion to pass verifier
For some reason we'd never run MachineVerifier on WinEH code, and you
explicitly have to ask for it with llc. I added it to a few test cases
to get some coverage.

Fixes PR25461.

llvm-svn: 252512
2015-11-09 21:04:00 +00:00
Andrew Kaylor fdd48fa1e1 [WinEH] Re-committing r252249 (Clone funclets with multiple parents) with additional fixes for determinism problems
Differential Revision: http://reviews.llvm.org/D14454

llvm-svn: 252508
2015-11-09 19:59:02 +00:00
Oliver Stannard 563585789c [CodeGen] Always promote f16 if not legal
We don't currently have any runtime library functions for operations on
f16 values (other than conversions to and from f32 and f64), so we
should always promote it to f32, even if that is not a legal type. In
that case, the f32 values would be softened to f32 library calls.

SoftenFloatRes_FP_EXTEND now needs to check the promoted operand's type,
as it may ne a no-op or require a different library call.

getCopyFromParts and getCopyToParts now need to cope with a
floating-point value stored in a larger integer part, as is the case for
any target that needs to store an f16 value in a 32-bit integer
register.

Differential Revision: http://reviews.llvm.org/D12856

llvm-svn: 252459
2015-11-09 11:03:18 +00:00
Yaron Keren 9ffee46d45 Erase unused FunctionDIs variables after r252219.
llvm-svn: 252401
2015-11-07 10:21:25 +00:00
Joseph Tremoulet f748c8937e [WinEH] Update exception pointer registers
Summary:
The CLR's personality routine passes these in rdx/edx, not rax/eax.

Make getExceptionPointerRegister a virtual method parameterized by
personality function to allow making this distinction.

Similarly make getExceptionSelectorRegister a virtual method parameterized
by personality function, for symmetry.


Reviewers: pgavlin, majnemer, rnk

Subscribers: jyknight, dsanders, llvm-commits

Differential Revision: http://reviews.llvm.org/D14344

llvm-svn: 252383
2015-11-07 01:11:31 +00:00
Tom Stellard 05691a678e DAGCombiner: Check shouldReduceLoadWidth before combining (and (load), x) -> extload
Reviewers: resistor, arsenm

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D13805

llvm-svn: 252349
2015-11-06 21:58:37 +00:00
Quentin Colombet 9a8efc08d3 [ShrinkWrapping] Teach shrink-wrapping how to analyze RegMask.
Previously we were conservatively assuming that RegMask operands clobber
callee saved registers.

llvm-svn: 252341
2015-11-06 21:00:13 +00:00
Matthias Braun 9198c671e8 MachineScheduler: Add regpressure information to debug dump
llvm-svn: 252340
2015-11-06 20:59:02 +00:00
Reid Kleckner b8fd162fc5 [WinEH] Mark funclet entries and exits as clobbering all registers
Summary:
In this implementation, LiveIntervalAnalysis invents a few register
masks on basic block boundaries that preserve no registers. The nice
thing about this is that it prevents the prologue inserter from thinking
it needs to spill all XMM CSRs, because it doesn't see any explicit
physreg defs in the MI.

Reviewers: MatzeB, qcolombet, JosephTremoulet, majnemer

Subscribers: MatzeB, llvm-commits

Differential Revision: http://reviews.llvm.org/D14407

llvm-svn: 252318
2015-11-06 17:06:38 +00:00
NAKAMURA Takumi 9947cacebf Revert r252249 (and r252255, r252258), "[WinEH] Clone funclets with multiple parents"
It behaved flaky due to iterating pointer key values on std::set and std::map.

llvm-svn: 252279
2015-11-06 10:07:33 +00:00
Reid Kleckner e535c1f856 Range-for some LiveIntervals code under review
llvm-svn: 252267
2015-11-06 02:01:02 +00:00
Andrew Kaylor f477585a2b Fix build warnings
llvm-svn: 252255
2015-11-06 01:08:35 +00:00
Andrew Kaylor 29cd576554 [WinEH] Clone funclets with multiple parents
Windows EH funclets need to always return to a single parent funclet.  However, it is possible for earlier optimizations to combine funclets (probably based on one funclet having an unreachable terminator) in such a way that this condition is violated.

These changes add code to the WinEHPrepare pass to detect situations where a funclet has multiple parents and clone such funclets, fixing up the unwind and catch return edges so that each copy of the funclet returns to the correct parent funclet.

Differential Revision: http://reviews.llvm.org/D13274?id=39098

llvm-svn: 252249
2015-11-06 00:20:50 +00:00
Peter Collingbourne d4bff30370 DI: Reverse direction of subprogram -> function edge.
Previously, subprograms contained a metadata reference to the function they
described. Because most clients need to get or set a subprogram for a given
function rather than the other way around, this created unneeded inefficiency.

For example, many passes needed to call the function llvm::makeSubprogramMap()
to build a mapping from functions to subprograms, and the IR linker needed to
fix up function references in a way that caused quadratic complexity in the IR
linking phase of LTO.

This change reverses the direction of the edge by storing the subprogram as
function-level metadata and removing DISubprogram's function field.

Since this is an IR change, a bitcode upgrade has been provided.

Fixes PR23367. An upgrade script for textual IR for out-of-tree clients is
attached to the PR.

Differential Revision: http://reviews.llvm.org/D14265

llvm-svn: 252219
2015-11-05 22:03:56 +00:00
Reid Kleckner 6ddae31045 [WinEH] Fix funclet prologues with stack realignment
We already had a test for this for 32-bit SEH catchpads, but those don't
actually create funclets. We had a bug that only appeared in funclet
prologues, where we would establish EBP and ESI as our FP and BP, and
then downstream prologue code would overwrite them.

While I was at it, I fixed Win64+funclets+stackrealign. This issue
doesn't come up as often there due to the ABI requring 16 byte stack
alignment, but now we can rest easy that AVX and WinEH will work well
together =P.

llvm-svn: 252210
2015-11-05 21:09:49 +00:00
Sanjay Patel 387e66e79f replace MachineCombinerPattern namespace and enum with enum class; NFCI
Also, remove an enum hack where enum values were used as indexes into an array.

We may want to make this a real class to allow pattern-based queries/customization (D13417).

llvm-svn: 252196
2015-11-05 19:34:57 +00:00
Eugene Zelenko ffec81ca00 Fix some Clang-tidy modernize warnings, other minor fixes.
Fixed warnings are: modernize-use-override, modernize-use-nullptr and modernize-redundant-void-arg.

Differential revision: http://reviews.llvm.org/D14312

llvm-svn: 252087
2015-11-04 22:32:32 +00:00
Cong Hou 23a3bf0147 Add new interfaces to MBB for manipulating successors with probabilities instead of weights. NFC.
This is part-1 of the patch that replaces all edge weights in MBB by
probabilities, which only adds new interfaces. No functional changes.

Differential revision: http://reviews.llvm.org/D13908

llvm-svn: 252083
2015-11-04 21:37:58 +00:00
Igor Laevsky 35fe692025 [StatepointLowering] Remove distinction between call and invoke safepoints
There is no point in having invoke safepoints handled differently than the
call safepoints. All relevant decisions could be made by looking at whether
or not gc.result and gc.relocate lay in a same basic block. This change will
 allow to lower call safepoints with relocates and results in a different 
basic blocks. See test case for example.

Differential Revision: http://reviews.llvm.org/D14158

llvm-svn: 252028
2015-11-04 01:16:10 +00:00
Peter Collingbourne 94d778697a CodeGen, Target: Move Mach-O-specific symbol name logic to Mach-O lowering.
A profile of an LTO link of Chrome revealed that we were spending some
~30-50% of execution time in the function Constant::getRelocationInfo(),
which is called from TargetLoweringObjectFile::getKindForGlobal() and in turn
from TargetMachine::getNameWithPrefix().

It turns out that we only need the result of getKindForGlobal() when
targeting Mach-O, so this change moves the relevant part of the logic to
TargetLoweringObjectFileMachO.

NFCI.

Differential Revision: http://reviews.llvm.org/D14168

llvm-svn: 252014
2015-11-03 23:40:03 +00:00
Simon Pilgrim 191ac7c679 [SelectionDAG] Use existing constant nodes instead of recreating them. NFC.
llvm-svn: 251990
2015-11-03 22:21:38 +00:00
Rafael Espindola 43e2e251ea Delete dead code.
llvm-svn: 251960
2015-11-03 18:55:58 +00:00
Igor Laevsky f637b4a52e [CodegenPrepare] Do not rematerialize gc.relocates across different basic blocks
Differential Revision: http://reviews.llvm.org/D14258

llvm-svn: 251957
2015-11-03 18:37:40 +00:00
Michael Kuperstein 73dc85293f [X86] Generate .cfi_adjust_cfa_offset correctly when pushing arguments
When push instructions are being used to pass function arguments on
the stack, and either EH or debugging are enabled, we need to generate
.cfi_adjust_cfa_offset directives appropriately. For (synch) EH, it is
enough for the CFA offset to be correct at every call site, while
for debugging we want to be correct after every push.

Darwin does not support this well, so don't use pushes whenever it
would be required.

Differential Revision: http://reviews.llvm.org/D13767

llvm-svn: 251904
2015-11-03 08:17:25 +00:00
Matthias Braun 6f4ed269b9 RegisterPressure: Improve assert message
llvm-svn: 251885
2015-11-03 01:53:36 +00:00
Matthias Braun 11859b5c8f RegisterPressure: Slightly nicer pressure diff dumping
llvm-svn: 251884
2015-11-03 01:53:33 +00:00
Matthias Braun 93563e7032 ScheduleDAGInstrs: Remove IsPostRA flag; NFC
ScheduleDAGInstrs doesn't behave differently before or after register
allocation. It was only used in a method of MachineSchedulerBase which
behaved differently in MachineScheduler/PostMachineScheduler. Change
this to let MachineScheduler/PostMachineScheduler just pass in a
parameter to that function.

The order of the LiveIntervals* and bool RemoveKillFlags paramters have
been switched to make out-of-tree code fail instead of unintentionally
passing a value intended for the IsPostRA flag to the (previously
following and default initialized) RemoveKillFlags.

Differential Revision: http://reviews.llvm.org/D14245

llvm-svn: 251883
2015-11-03 01:53:29 +00:00
Sanjay Patel 0ed9aeaa5f [CGP] widen switch condition and case constants to target's register width (2nd try)
This is a redo of r251849 except the tests have been split into arch-specific folders
to hopefully make the bots happy.

This is a follow-up from the discussion in D12965. The block-at-a-time limitation of
SelectionDAG also came up in D13297.

Without the InstCombine change from D12965, I don't expect this patch to make any
difference in the real world because InstCombine does not shrink cases like this in
visitSwitchInst(). But we need to have this CGP safety harness in place before
proceeding with any shrinkage in D12965, so we won't generate extra extends for compares.

I've opted for IR regression tests in the patch because that seems like a clearer way to
test the transform, but PowerPC CodeGen for an i16 widening test is shown below. x86
will need more work to solve: https://llvm.org/bugs/show_bug.cgi?id=22473

Before:
BB#0:
  mr 4, 3
  extsh. 3, 4
  ble 0, .LBB0_5
 BB#1:
  cmpwi  3, 99
  bgt    0, .LBB0_9
 BB#2:
  rlwinm 4, 4, 0, 16, 31      <--- 32-bit mask/extend
  li 3, 0
  cmplwi         4, 1
  beqlr 0
 BB#3:
  cmplwi         4, 10
  bne    0, .LBB0_12
 BB#4:
  li 3, 1
  blr
.LBB0_5:
  rlwinm 3, 4, 0, 16, 31      <--- 32-bit mask/extend
  cmplwi         3, 65436
  beq    0, .LBB0_13
 BB#6:
  cmplwi         3, 65526
  beq    0, .LBB0_15
 BB#7:
  cmplwi         3, 65535
  bne    0, .LBB0_12
 BB#8:
  li 3, 4
  blr
.LBB0_9:
  rlwinm 3, 4, 0, 16, 31      <--- 32-bit mask/extend
  cmplwi         3, 100
  beq    0, .LBB0_14
...

After:
BB#0:
  rlwinm 4, 3, 0, 16, 31      <--- mask/extend to 32-bit and then use that for comparisons
  cmpwi  4, 999
  ble 0, .LBB0_5
 BB#1:
  lis 3, 0
  ori 3, 3, 65525
  cmpw   4, 3
  bgt    0, .LBB0_9
 BB#2:
  cmplwi         4, 1000
  beq    0, .LBB0_14
 BB#3:
  cmplwi         4, 65436
  bne    0, .LBB0_13
 BB#4:
  li 3, 6
  blr
.LBB0_5:
  li 3, 0
  cmplwi         4, 1
  beqlr 0
 BB#6:
  cmplwi         4, 10
  beq    0, .LBB0_12
 BB#7:
  cmplwi         4, 100
  bne    0, .LBB0_13
 BB#8:
  li 3, 2
  blr
.LBB0_9:
  cmplwi         4, 65526
  beq    0, .LBB0_15
 BB#10:
  cmplwi         4, 65535
  bne    0, .LBB0_13
...


Differential Revision: http://reviews.llvm.org/D13532

llvm-svn: 251857
2015-11-02 23:22:49 +00:00
Sanjay Patel dfc825eb36 revert r251849; need to move tests to arch-specific folders
llvm-svn: 251851
2015-11-02 23:05:20 +00:00
Sanjay Patel b90a078de9 [CGP] widen switch condition and case constants to target's register width
This is a follow-up from the discussion in D12965. The block-at-a-time limitation of 
SelectionDAG also came up in D13297.

Without the InstCombine change from D12965, I don't expect this patch to make any 
difference in the real world because InstCombine does not shrink cases like this in
visitSwitchInst(). But we need to have this CGP safety harness in place before
proceeding with any shrinkage in D12965, so we won't generate extra extends for compares.

I've opted for IR regression tests in the patch because that seems like a clearer way to
test the transform, but PowerPC CodeGen for an i16 widening test is shown below. x86
will need more work to solve: https://llvm.org/bugs/show_bug.cgi?id=22473

Before:
BB#0:
  mr 4, 3
  extsh. 3, 4
  ble 0, .LBB0_5
 BB#1: 
  cmpwi	 3, 99
  bgt	 0, .LBB0_9
 BB#2:            
  rlwinm 4, 4, 0, 16, 31      <--- 32-bit mask/extend
  li 3, 0
  cmplwi	 4, 1
  beqlr 0
 BB#3:            
  cmplwi	 4, 10
  bne	 0, .LBB0_12
 BB#4:                      
  li 3, 1
  blr
.LBB0_5:                             
  rlwinm 3, 4, 0, 16, 31      <--- 32-bit mask/extend
  cmplwi	 3, 65436
  beq	 0, .LBB0_13
 BB#6:                            
  cmplwi	 3, 65526
  beq	 0, .LBB0_15
 BB#7:                       
  cmplwi	 3, 65535
  bne	 0, .LBB0_12
 BB#8:                       
  li 3, 4
  blr
.LBB0_9:                       
  rlwinm 3, 4, 0, 16, 31      <--- 32-bit mask/extend
  cmplwi	 3, 100
  beq	 0, .LBB0_14
...

After:
BB#0:        
  rlwinm 4, 3, 0, 16, 31      <--- mask/extend to 32-bit and then use that for comparisons
  cmpwi	 4, 999
  ble 0, .LBB0_5
 BB#1:          
  lis 3, 0
  ori 3, 3, 65525
  cmpw	 4, 3
  bgt	 0, .LBB0_9
 BB#2:         
  cmplwi	 4, 1000
  beq	 0, .LBB0_14
 BB#3:    
  cmplwi	 4, 65436
  bne	 0, .LBB0_13
 BB#4:       
  li 3, 6
  blr
.LBB0_5:   
  li 3, 0
  cmplwi	 4, 1
  beqlr 0
 BB#6: 
  cmplwi	 4, 10
  beq	 0, .LBB0_12
 BB#7:             
  cmplwi	 4, 100
  bne	 0, .LBB0_13
 BB#8:             
  li 3, 2
  blr
.LBB0_9:       
  cmplwi	 4, 65526
  beq	 0, .LBB0_15
 BB#10:      
  cmplwi	 4, 65535
  bne	 0, .LBB0_13
...


Differential Revision: http://reviews.llvm.org/D13532

llvm-svn: 251849
2015-11-02 22:46:24 +00:00
Cong Hou b90b9e0531 In MachineBlockPlacement, filter cold blocks off the loop chain when profile data is available.
In the current BB placement algorithm, a loop chain always contains all loop blocks. This has a drawback that cold blocks in the loop may be inserted on a hot function path, hence increasing branch cost and also reducing icache locality.

Consider a simple example shown below:

A
|
B⇆C
|
D

When B->C is quite cold, the best BB-layout should be A,B,D,C. But the current implementation produces A,C,B,D.

This patch filters those cold blocks off from the loop chain by comparing the ratio:

LoopBBFreq / LoopFreq

to 20%: if it is less than 20%, we don't include this BB to the loop chain. Here LoopFreq is the frequency of the loop when we reduce the loop into a single node. In general we have more cold blocks when the loop has few iterations. And vice versa.


Differential revision: http://reviews.llvm.org/D11662

llvm-svn: 251833
2015-11-02 21:24:00 +00:00