If the size of an AST entry changes, we also need to make sure we perform
necessary alias set merges, as the new size may overlap pointers in other sets.
We happen to run into this with memset, because memset allows an entry for a
i8* pointer to have a decidedly non-i8 size.
This fixes PR27262.
Differential Revision: http://reviews.llvm.org/D18939
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266381 91177308-0d34-0410-b5e6-96231b3b80d8
Some SIMD implementations are not IEEE-754 compliant, for example ARM's NEON.
This patch teaches the loop vectorizer to only allow transformations of loops
that either contain no floating-point operations or have enough allowance
flags supporting lack of precision (ex. -ffast-math, Darwin).
For that, the target description now has a method which tells us if the
vectorizer is allowed to handle FP math without falling into unsafe
representations, plus a check on every FP instruction in the candidate loop
to check for the safety flags.
This commit makes LLVM behave like GCC with respect to ARM NEON support, but
it stops short of fixing the underlying problem: sub-normals. Neither GCC
nor LLVM have a flag for allowing sub-normal operations. Before this patch,
GCC only allows it using unsafe-math flags and LLVM allows it by default with
no way to turn it off (short of not using NEON at all).
As a first step, we push this change to make it safe and in sync with GCC.
The second step is to discuss a new sub-normal's flag on both communitues
and come up with a common solution. The third step is to improve the FastMath
flags in LLVM to encode sub-normals and use those flags to restrict NEON FP.
Fixes PR16275.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266363 91177308-0d34-0410-b5e6-96231b3b80d8
https://llvm.org/bugs/show_bug.cgi?id=27105
We can check if all bits outside of a constant mask are set with a
single constant.
As noted in the bug report, although this form should be considered the
canonical IR, backends may want to transform this into an 'andn' / 'andc'
comparison against zero because that could be a single machine instruction.
Differential Revision: http://reviews.llvm.org/D18842
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266362 91177308-0d34-0410-b5e6-96231b3b80d8
At some point, ARM stopped getting any benefit from ConstantHoisting because
the pass called a different variant of getIntImmCost. Reimplementing the
correct variant revealed some problems, however:
+ ConstantHoisting was modifying switch statements. This is simply invalid,
the cases must remain integer constants no matter the notional cost.
+ ConstantHoisting was mangling alloca instructions in the entry block. These
should be handled by FrameLowering, so constants actually have a cost of 0.
Worse, the resulting bitcasts meant they became dynamic allocas.
rdar://25707382
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266260 91177308-0d34-0410-b5e6-96231b3b80d8
LLVM optimization passes may reduce a profiled target expression
to a constant. Removing runtime calls at such instrumentation points
would help speedup the runtime of the instrumented program.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266229 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
To be able to work accurately on the reference graph when taking decision
about internalizing, promoting, renaming, etc. We need to have the alias
information explicit.
Reviewers: tejohnson
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D18836
From: Mehdi Amini <mehdi.amini@apple.com>
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266214 91177308-0d34-0410-b5e6-96231b3b80d8
This patch fixes calculating of builtin_object_size if it depends on a
condition. Before this patch compiler did not know how to calculate the
object size when it finds a condition that cannot be eliminated.
This patch enables calculating of builtin_object_size even in case when
condition cannot be eliminated by choosing minimum or maximum value as a
result from condition. Choosing minimum or maximum value from condition
is based on the second argument of __builtin_object_size function.
Patch by Strahinja Petrovic.
Differential Revision: http://reviews.llvm.org/D18438
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266193 91177308-0d34-0410-b5e6-96231b3b80d8
Remove an ad-hoc transform in InstCombine and replace it with more
general machinery (ValueTracking, InstructionSimplify and VectorUtils).
This fixes PR27332.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266175 91177308-0d34-0410-b5e6-96231b3b80d8
This bug was introduced with:
http://reviews.llvm.org/rL262269
AVX masked loads are specified to set vector lanes to zero when the high bit of the mask
element for that lane is zero:
"If the mask is 0, the corresponding data element is set to zero in the load form of these
instructions, and unmodified in the store form." --Intel manual
Differential Revision: http://reviews.llvm.org/D19017
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266148 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
For correct handling of alias to nameless
function, we need to be able to refer them through a GUID in the summary.
Here we name them using a hash of the non-private global names in the module.
Reviewers: tejohnson
Subscribers: joker.eph, llvm-commits
Differential Revision: http://reviews.llvm.org/D18883
From: Mehdi Amini <mehdi.amini@apple.com>
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266132 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
Let keep llvm-as "dumb": it converts textual IR to bitcode. This
commit removes the dependency from llvm-as to libLLVMAnalysis.
We'll add back summary in llvm-as if we get to a textual
representation for it at some point. In the meantime, opt seems
like a better place for that.
Reviewers: tejohnson
Subscribers: joker.eph, llvm-commits
Differential Revision: http://reviews.llvm.org/D19032
From: Mehdi Amini <mehdi.amini@apple.com>
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266131 91177308-0d34-0410-b5e6-96231b3b80d8
(Recommit of r266002, with r266011, r266016, and not accidentally
including an extra unused/uninitialized element in LibcallRoutineNames)
AtomicExpandPass can now lower atomic load, atomic store, atomicrmw, and
cmpxchg instructions to __atomic_* library calls, when the target
doesn't support atomics of a given size.
This is the first step towards moving all atomic lowering from clang
into llvm. When all is done, the behavior of __sync_* builtins,
__atomic_* builtins, and C11 atomics will be unified.
Previously LLVM would pass everything through to the ISelLowering
code. There, unsupported atomic instructions would turn into __sync_*
library calls. Because of that behavior, Clang currently avoids emitting
llvm IR atomic instructions when this would happen, and emits __atomic_*
library functions itself, in the frontend.
This change makes LLVM able to emit __atomic_* libcalls, and thus will
eventually allow clang to depend on LLVM to do the right thing.
It is advantageous to do the new lowering to atomic libcalls in
AtomicExpandPass, before ISel time, because it's important that all
atomic operations for a given size either lower to __atomic_*
libcalls (which may use locks), or native instructions which won't. No
mixing and matching.
At the moment, this code is enabled only for SPARC, as a
demonstration. The next commit will expand support to all of the other
targets.
Differential Revision: http://reviews.llvm.org/D18200
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266115 91177308-0d34-0410-b5e6-96231b3b80d8
This is a resubmittion of 263158 change.
This patch fixes the problem which occurs when loop-vectorize tries to use @llvm.masked.load/store intrinsic for a non-default addrspace pointer. It fails with "Calling a function with a bad signature!" assertion in CallInst constructor because it tries to pass a non-default addrspace pointer to the pointer argument which has default addrspace.
The fix is to add pointer type as another overloaded type to @llvm.masked.load/store intrinsics.
Reviewed By: reames
Differential Revision: http://reviews.llvm.org/D17270
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266086 91177308-0d34-0410-b5e6-96231b3b80d8
They broke the msan bot.
Original message:
Add __atomic_* lowering to AtomicExpandPass.
AtomicExpandPass can now lower atomic load, atomic store, atomicrmw,and
cmpxchg instructions to __atomic_* library calls, when the target
doesn't support atomics of a given size.
This is the first step towards moving all atomic lowering from clang
into llvm. When all is done, the behavior of __sync_* builtins,
__atomic_* builtins, and C11 atomics will be unified.
Previously LLVM would pass everything through to the ISelLowering
code. There, unsupported atomic instructions would turn into __sync_*
library calls. Because of that behavior, Clang currently avoids emitting
llvm IR atomic instructions when this would happen, and emits __atomic_*
library functions itself, in the frontend.
This change makes LLVM able to emit __atomic_* libcalls, and thus will
eventually allow clang to depend on LLVM to do the right thing.
It is advantageous to do the new lowering to atomic libcalls in
AtomicExpandPass, before ISel time, because it's important that all
atomic operations for a given size either lower to __atomic_*
libcalls (which may use locks), or native instructions which won't. No
mixing and matching.
At the moment, this code is enabled only for SPARC, as a
demonstration. The next commit will expand support to all of the other
targets.
Differential Revision: http://reviews.llvm.org/D18200
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266062 91177308-0d34-0410-b5e6-96231b3b80d8
`allocsize` is a function attribute that allows users to request that
LLVM treat arbitrary functions as allocation functions.
This patch makes LLVM accept the `allocsize` attribute, and makes
`@llvm.objectsize` recognize said attribute.
The review for this was split into two patches for ease of reviewing:
D18974 and D14933. As promised on the revisions, I'm landing both
patches as a single commit.
Differential Revision: http://reviews.llvm.org/D14933
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266032 91177308-0d34-0410-b5e6-96231b3b80d8
r237193 fix handling of alloca size / align in MergeFunctions, but only tested one and didn't follow FunctionComparator::cmpOperations's usual comparison pattern. It also didn't update Instruction.cpp:haveSameSpecialState which I'll do separately.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266022 91177308-0d34-0410-b5e6-96231b3b80d8
Add StackProtector to SafeStack. This adds limited protection against
data corruption in the caller frame. Current implementation treats
all stack protector levels as -fstack-protector-all.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266004 91177308-0d34-0410-b5e6-96231b3b80d8
AtomicExpandPass can now lower atomic load, atomic store, atomicrmw, and
cmpxchg instructions to __atomic_* library calls, when the target
doesn't support atomics of a given size.
This is the first step towards moving all atomic lowering from clang
into llvm. When all is done, the behavior of __sync_* builtins,
__atomic_* builtins, and C11 atomics will be unified.
Previously LLVM would pass everything through to the ISelLowering
code. There, unsupported atomic instructions would turn into __sync_*
library calls. Because of that behavior, Clang currently avoids emitting
llvm IR atomic instructions when this would happen, and emits __atomic_*
library functions itself, in the frontend.
This change makes LLVM able to emit __atomic_* libcalls, and thus will
eventually allow clang to depend on LLVM to do the right thing.
It is advantageous to do the new lowering to atomic libcalls in
AtomicExpandPass, before ISel time, because it's important that all
atomic operations for a given size either lower to __atomic_*
libcalls (which may use locks), or native instructions which won't. No
mixing and matching.
At the moment, this code is enabled only for SPARC, as a
demonstration. The next commit will expand support to all of the other
targets.
Differential Revision: http://reviews.llvm.org/D18200
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266002 91177308-0d34-0410-b5e6-96231b3b80d8
This patch ensures that when we detect first-order recurrences, we reject a phi
node if its previous value is also a phi node. During vectorization the initial
and previous values of the recurrence are shuffled together to create the value
for the current iteration. However, phi nodes are not widened like other
instructions. This fixes PR27246.
Differential Revision: http://reviews.llvm.org/D18971
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265983 91177308-0d34-0410-b5e6-96231b3b80d8
See PR27315
r265913: "[IndVars] Eliminate op.with.overflow when possible"
r265912: "[SCEV] See through op.with.overflow intrinsics"
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265950 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
This is the first step in also serializing the index out to LLVM
assembly.
The per-module summary written to bitcode is moved out of the bitcode
writer and to a new analysis pass (ModuleSummaryIndexWrapperPass).
The pass itself uses a new builder class to compute index, and the
builder class is used directly in places where we don't have a pass
manager (e.g. llvm-as).
Because we are computing summaries outside of the bitcode writer, we no
longer can use value ids created by the bitcode writer's
ValueEnumerator. This required changing the reference graph edge type
to use a new ValueInfo class holding a union between a GUID (combined
index) and Value* (permodule index). The Value* are converted to the
appropriate value ID during bitcode writing.
Also, this enables removal of the BitWriter library's dependence on the
Analysis library that was previously required for the summary computation.
Reviewers: joker.eph
Subscribers: joker.eph, llvm-commits
Differential Revision: http://reviews.llvm.org/D18763
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265941 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
If we can prove that an op.with.overflow intrinsic does not overflow, we
can get rid of the intrinsic, and replace it with non-wrapping
arithmetic.
Reviewers: atrick, regehr
Subscribers: sanjoy, mcrosier, llvm-commits
Differential Revision: http://reviews.llvm.org/D18685
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265913 91177308-0d34-0410-b5e6-96231b3b80d8
The behavior here was buggy -- we'd forget the calling convention after
inlining a callsite calling llvm.deoptimize.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265867 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
The llvm cos intrinsic currently does not propagate undef's. This change
transforms cos(undef) to null value or 0.
There are 2 test cases added as well.
Patch by Anna Thomas!
Reviewers: sanjoy
Subscribers: majnemer, llvm-commits
Differential Revision: http://reviews.llvm.org/D18863
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265825 91177308-0d34-0410-b5e6-96231b3b80d8
We had a select of a cast of a select but attempted to replace the outer
select with the inner select dispite their incompatible types.
Patch by Anton Korobeynikov!
This fixes PR27236.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265805 91177308-0d34-0410-b5e6-96231b3b80d8
InstCombine cannot effectively remove redundant assumptions without them
registered in the assumption cache. The vectorizer can create identical
assumptions but doesn't register them with the cache, resulting in
slower compile times because InstCombine tries to reason about a lot
more assumptions.
Fix this by registering the cloned assumptions.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265800 91177308-0d34-0410-b5e6-96231b3b80d8
This re-commits r265535 which was reverted in r265541 because it
broke the windows bots. The problem was that we had a PointerIntPair
which took a pointer to a struct allocated with new. The problem
was that new doesn't provide sufficient alignment guarantees.
This pattern was already present before r265535 and it just happened
to work. To fix this, we now separate the PointerToIntPair from the
ExitNotTakenInfo struct into a pointer and a bool.
Original commit message:
Summary:
When the backedge taken codition is computed from an icmp, SCEV can
deduce the backedge taken count only if one of the sides of the icmp
is an AddRecExpr. However, due to sign/zero extensions, we sometimes
end up with something that is not an AddRecExpr.
However, we can use SCEV predicates to produce a 'guarded' expression.
This change adds a method to SCEV to get this expression, and the
SCEV predicate associated with it.
In HowManyGreaterThans and HowManyLessThans we will now add a SCEV
predicate associated with the guarded backedge taken count when the
analyzed SCEV expression is not an AddRecExpr. Note that we only do
this as an alternative to returning a 'CouldNotCompute'.
We use new feature in Loop Access Analysis and LoopVectorize to analyze
and transform more loops.
Reviewers: anemet, mzolotukhin, hfinkel, sanjoy
Subscribers: flyingforyou, mcrosier, atrick, mssimpso, sanjoy, mzolotukhin, llvm-commits
Differential Revision: http://reviews.llvm.org/D17201
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265786 91177308-0d34-0410-b5e6-96231b3b80d8
This reverts commit r265765, reapplying r265759 after changing a call from
LocalAsMetadata::get to ValueAsMetadata::get (and adding a unit test). When a
local value is mapped to a constant (like "i32 %a" => "i32 7"), the new debug
intrinsic operand may no longer be pointing at a local.
http://lab.llvm.org:8080/green/job/clang-stage1-configure-RA_build/19020/
The previous coommit message follows:
--
This is a partial re-commit -- maybe more of a re-implementation -- of
r265631 (reverted in r265637).
This makes RF_IgnoreMissingLocals behave (almost) consistently between
the Value and the Metadata hierarchy. In particular:
- MapValue returns nullptr or "metadata !{}" for missing locals in
MetadataAsValue/LocalAsMetadata bridging paris, depending on
the RF_IgnoreMissingLocals flag.
- MapValue doesn't memoize LocalAsMetadata-related results.
- MapMetadata no longer deals with LocalAsMetadata or
RF_IgnoreMissingLocals at all. (This wasn't in r265631 at all, but
I realized during testing it would make the patch simpler with no
loss of generality.)
r265631 went too far, making both functions universally ignore
RF_IgnoreMissingLocals. This broke building (e.g.) compiler-rt.
Reassociate (and possibly other passes) don't currently maintain
dominates-use invariants for metadata operands, resulting in IR like
this:
define void @foo(i32 %arg) {
call void @llvm.some.intrinsic(metadata i32 %x)
%x = add i32 1, i32 %arg
}
If the inliner chooses to inline @foo into another function, then
RemapInstruction will call `MapValue(metadata i32 %x)` and assert that
the return is not nullptr.
I've filed PR27273 to add a Verifier check and fix the underlying
problem in the optimization passes.
As a workaround, return `!{}` instead of nullptr for unmapped
LocalAsMetadata when RF_IgnoreMissingLocals is unset. Otherwise, match
the behaviour of r265631.
Original commit message:
ValueMapper: Make LocalAsMetadata match function-local Values
Start treating LocalAsMetadata similarly to function-local members of
the Value hierarchy in MapValue and MapMetadata.
- Don't memoize them.
- Return nullptr if they are missing.
This also cleans up ConstantAsMetadata to stop listening to the
RF_IgnoreMissingLocals flag.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265768 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
Fixes PR26774.
If you're aware of the issue, feel free to skip the "Motivation"
section and jump directly to "This patch".
Motivation:
I define "refinement" as discarding behaviors from a program that the
optimizer has license to discard. So transforming:
```
void f(unsigned x) {
unsigned t = 5 / x;
(void)t;
}
```
to
```
void f(unsigned x) { }
```
is refinement, since the behavior went from "if x == 0 then undefined
else nothing" to "nothing" (the optimizer has license to discard
undefined behavior).
Refinement is a fundamental aspect of many mid-level optimizations done
by LLVM. For instance, transforming `x == (x + 1)` to `false` also
involves refinement since the expression's value went from "if x is
`undef` then { `true` or `false` } else { `false` }" to "`false`" (by
definition, the optimizer has license to fold `undef` to any non-`undef`
value).
Unfortunately, refinement implies that the optimizer cannot assume
that the implementation of a function it can see has all of the
behavior an unoptimized or a differently optimized version of the same
function can have. This is a problem for functions with comdat
linkage, where a function can be replaced by an unoptimized or a
differently optimized version of the same source level function.
For instance, FunctionAttrs cannot assume a comdat function is
actually `readnone` even if it does not have any loads or stores in
it; since there may have been loads and stores in the "original
function" that were refined out in the currently visible variant, and
at the link step the linker may in fact choose an implementation with
a load or a store. As an example, consider a function that does two
atomic loads from the same memory location, and writes to memory only
if the two values are not equal. The optimizer is allowed to refine
this function by first CSE'ing the two loads, and the folding the
comparision to always report that the two values are equal. Such a
refined variant will look like it is `readonly`. However, the
unoptimized version of the function can still write to memory (since
the two loads //can// result in different values), and selecting the
unoptimized version at link time will retroactively invalidate
transforms we may have done under the assumption that the function
does not write to memory.
Note: this is not just a problem with atomics or with linking
differently optimized object files. See PR26774 for more realistic
examples that involved neither.
This patch:
This change introduces a new set of linkage types, predicated as
`GlobalValue::mayBeDerefined` that returns true if the linkage type
allows a function to be replaced by a differently optimized variant at
link time. It then changes a set of IPO passes to bail out if they see
such a function.
Reviewers: chandlerc, hfinkel, dexonsmith, joker.eph, rnk
Subscribers: mcrosier, llvm-commits
Differential Revision: http://reviews.llvm.org/D18634
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265762 91177308-0d34-0410-b5e6-96231b3b80d8
This is a partial re-commit -- maybe more of a re-implementation -- of
r265631 (reverted in r265637).
This makes RF_IgnoreMissingLocals behave (almost) consistently between
the Value and the Metadata hierarchy. In particular:
- MapValue returns nullptr or "metadata !{}" for missing locals in
MetadataAsValue/LocalAsMetadata bridging paris, depending on
the RF_IgnoreMissingLocals flag.
- MapValue doesn't memoize LocalAsMetadata-related results.
- MapMetadata no longer deals with LocalAsMetadata or
RF_IgnoreMissingLocals at all. (This wasn't in r265631 at all, but
I realized during testing it would make the patch simpler with no
loss of generality.)
r265631 went too far, making both functions universally ignore
RF_IgnoreMissingLocals. This broke building (e.g.) compiler-rt.
Reassociate (and possibly other passes) don't currently maintain
dominates-use invariants for metadata operands, resulting in IR like
this:
define void @foo(i32 %arg) {
call void @llvm.some.intrinsic(metadata i32 %x)
%x = add i32 1, i32 %arg
}
If the inliner chooses to inline @foo into another function, then
RemapInstruction will call `MapValue(metadata i32 %x)` and assert that
the return is not nullptr.
I've filed PR27273 to add a Verifier check and fix the underlying
problem in the optimization passes.
As a workaround, return `!{}` instead of nullptr for unmapped
LocalAsMetadata when RF_IgnoreMissingLocals is unset. Otherwise, match
the behaviour of r265631.
Original commit message:
ValueMapper: Make LocalAsMetadata match function-local Values
Start treating LocalAsMetadata similarly to function-local members of
the Value hierarchy in MapValue and MapMetadata.
- Don't memoize them.
- Return nullptr if they are missing.
This also cleans up ConstantAsMetadata to stop listening to the
RF_IgnoreMissingLocals flag.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265759 91177308-0d34-0410-b5e6-96231b3b80d8
When GVN wants to re-interpret an already available value in a smaller
type, it needs to right-shift the value on big-endian systems to ensure
the correct bytes are accessed. The shift value is the difference of
the sizes of the two types.
This is correct as long as both types occupy multiples of full bytes.
However, when one of them is a sub-byte type like i1, this no longer
holds true: we still need to shift, but only to access the correct
*byte*. Accessing bits within the byte requires no shift in either
endianness; e.g. an i1 resides in the least-significant bit of its
containing byte on both big- and little-endian systems.
Therefore, the appropriate shift value to be used is the difference of
the *storage* sizes of the two types. This is already handled correctly
in one place where such a shift takes place (GetStoreValueForLoad), but
is incorrect in two other places: GetLoadValueForLoad and
CoerceAvailableValueToLoadType.
This patch changes both places to use the storage size as well.
Differential Revision: http://reviews.llvm.org/D18662
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265684 91177308-0d34-0410-b5e6-96231b3b80d8
Updating dominators for exit-blocks of the unrolled loops is not enough,
as shown in PR27157. The proper way is to update dominators for all
dominance-children of original loop blocks.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265605 91177308-0d34-0410-b5e6-96231b3b80d8
