Now the pass is just a tiny wrapper around the util. This lets us reuse
the logic elsewhere (done here for BuildLibCalls) instead of duplicating
it.
The next step is to have something like getOrInsertLibFunc that also
sets the attributes.
Differential Revision: http://reviews.llvm.org/D19470
llvm-svn: 267759
I tried to be as close as possible to the strongest check that
existed before; cleaning these up properly is left for future work.
Differential Revision: http://reviews.llvm.org/D19469
llvm-svn: 267758
We previously disallowed interleaved load groups that may cause us to
speculatively access memory out-of-bounds (r261331). We did this by ensuring
each load group had an access corresponding to the first and last member.
Instead of bailing out for these interleaved groups, this patch enables us to
peel off the last vector iteration, ensuring that we execute at least one
iteration of the scalar remainder loop. This solution was proposed in the
review of the previous patch.
Differential Revision: http://reviews.llvm.org/D19487
llvm-svn: 267751
This is the first of two commits for extending SLP Vectorizer to deal with aggregates.
This commit merely refactors existing logic.
http://reviews.llvm.org/D14185
llvm-svn: 267748
Added support of TTMP quads.
Reworked M0 exclusion machinery for SMRD and similar instructions
to enable usage of TTMP registers in those instructions as destinations.
Tests added.
Differential Revision: http://reviews.llvm.org/D19342
llvm-svn: 267733
Summary:
llvm-symbolizer wants to get linkage names of functions for historical
reasons. Linkage names are only recorded in the PDB for public symbols,
and the linkage name is apparently stored separately in some "public
symbol" record. We had a workaround in PDBContext which would look for
such symbols when the user requested linkage names.
However, when given an address that was truly in a private function and
public funciton, we would accidentally find nearby public symbols and
return those function names. The fix is to look for both function
symbols and public symbols and only prefer the public symbol name if the
addresses of the symbols agree.
Fixes PR27492
Reviewers: zturner
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D19571
llvm-svn: 267732
Summary:
So it appears that to guarantee some of the ordering requirements of a GLSL
memoryBarrier() executed in the shader, we need to emit an s_waitcnt.
(We can't use an s_barrier, because memoryBarrier() may appear anywhere in
the shader, in particular it may appear in non-uniform control flow.)
Reviewers: arsenm, mareko, tstellarAMD
Subscribers: arsenm, llvm-commits
Differential Revision: http://reviews.llvm.org/D19203
llvm-svn: 267729
This change adds a new hook for estimating the cost of vector extracts followed
by zero- and sign-extensions. The motivating example for this change is the
SMOV and UMOV instructions on AArch64. These instructions move data from vector
to general purpose registers while performing the corresponding extension
(sign-extend for SMOV and zero-extend for UMOV) at the same time. For these
operations, TargetTransformInfo can assume the extensions are free and only
report the cost of the vector extract. The SLP vectorizer has been updated to
make use of the new hook.
Differential Revision: http://reviews.llvm.org/D18523
llvm-svn: 267725
Possibility to specify code of hardware register kept.
Disassemble to symbolic name, if name is known.
Tests updated/added.
Differential Revision: http://reviews.llvm.org/D19335
llvm-svn: 267724
Summary:
Refine the workaround from r266877 that attempts to prevent
renaming of locals in inline assembly, so that in addition to looking
for a llvm.used local value, that there is at least one inline assembly
call in the module. Otherwise, debug functions added to the llvm.used
can block importing/exporting unnecessarily.
Reviewers: joker.eph
Subscribers: llvm-commits, joker.eph
Differential Revision: http://reviews.llvm.org/D19573
llvm-svn: 267717
Summary:
With the removal of support for lazy parsing of combined index summary
records (e.g. r267344), we no longer need to include the summary record
bitcode offset in the VST entries for definitions. Change the combined
index format to be similar to the per-module index format in using value
ids to cross-reference from the summary record to the VST entry (rather
than the summary record bitcode offset to cross-reference in the other
direction).
The visible changes are:
1) Add the value id to the combined summary records
2) Remove the summary offset from the combined VST records, which has
the following effects:
- No longer need the VST_CODE_COMBINED_GVDEFENTRY record, as all
combined index VST entries now only contain the value id and
corresponding GUID.
- No longer have duplicate VST entries in the case where there are
multiple definitions of a symbol (e.g. weak/linkonce), as they all
have the same value id and GUID.
An implication of #2 above is that in order to hook up an alias to the
correct aliasee based on the value id of the aliasee recorded in the
combined index alias record, we need to scan the entries in the index
for that GUID to find the one from the same module (i.e. the case where
there are multiple entries for the aliasee). But the reader no longer
has to maintain a special map to hook up the alias/aliasee.
Reviewers: joker.eph
Subscribers: joker.eph, llvm-commits
Differential Revision: http://reviews.llvm.org/D19481
llvm-svn: 267712
Extract a part of isDereferenceableAndAlignedPointer functionality to Value::getPointerDerferecnceableBytes. Currently it's a NFC, but in future I'm going to accumulate all the logic about value dereferenceability in this function similarly to Value::getPointerAlignment function (D16144).
Reviewed By: reames
Differential Revision: http://reviews.llvm.org/D17572
llvm-svn: 267708
This is required to use this function from isSafeToSpeculativelyExecute
Reviewed By: hfinkel
Differential Revision: http://reviews.llvm.org/D16231
llvm-svn: 267692
Teach Value::getPointerAlignment that allocas with no explicit alignment are aligned to preferred alignment of the allocated type.
Reviewed By: hfinkel
Differential Revision: http://reviews.llvm.org/D17569
llvm-svn: 267689
Summary:
D19403 adds a new pragma for loop distribution. This change adds
support for the corresponding metadata that the pragma is translated to
by the FE.
As part of this I had to rethink the flag -enable-loop-distribute. My
goal was to be backward compatible with the existing behavior:
A1. pass is off by default from the optimization pipeline
unless -enable-loop-distribute is specified
A2. pass is on when invoked directly from opt (e.g. for unit-testing)
The new pragma/metadata overrides these defaults so the new behavior is:
B1. A1 + enable distribution for individual loop with the pragma/metadata
B2. A2 + disable distribution for individual loop with the pragma/metadata
The default value whether the pass is on or off comes from the initiator
of the pass. From the PassManagerBuilder the default is off, from opt
it's on.
I moved -enable-loop-distribute under the pass. If the flag is
specified it overrides the default from above.
Then the pragma/metadata can further modifies this per loop.
As a side-effect, we can now also use -enable-loop-distribute=0 from opt
to emulate the default from the optimization pipeline. So to be precise
this is the new behavior:
C1. pass is off by default from the optimization pipeline
unless -enable-loop-distribute or the pragma/metadata enables it
C2. pass is on when invoked directly from opt
unless -enable-loop-distribute=0 or the pragma/metadata disables it
Reviewers: hfinkel
Subscribers: joker.eph, mzolotukhin, llvm-commits
Differential Revision: http://reviews.llvm.org/D19431
llvm-svn: 267672
Summary:
cloneLoopWithPreheader() does not update LoopInfo for sub-loop of
the original loop being cloned. Add assert to ensure no sub-loops for loop being cloned.
Reviewers: anemet, ashutosh.nema, hfinkel
Subscribers: mzolotukhin, llvm-commits
Differential Revision: http://reviews.llvm.org/D15922
llvm-svn: 267671
This reverts commit r267657, r267656, and r267655.
The test does not pass on multiple bots, I'm unsure why yet but let's unbreak them.
From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 267664
Summary:
It is incorrect to compare TripCount (which is BECount + 1)
with extraiters (or Count) to check if we should enter unrolled
loop or not, because TripCount can potentially overflow
(when BECount is max unsigned integer).
While comparing BECount with (Count - 1) is overflow safe and
therefore correct.
Reviewer: hfinkel
Differential Revision: http://reviews.llvm.org/D19256
From: Evgeny Stupachenko <evstupac@gmail.com>
llvm-svn: 267662
We run after PEI, so we need to AddPristinesAndCSRs.
In practice, that makes no difference here, because we only ask about
liveness of super-registers of defined GR8/GR16 registers, so they
can't be pristine. Still, it's the correct thing to do.
Thanks to Quentin for noticing!
Follow-up to r267495.
llvm-svn: 267658
This effectively adds back the extractelt combine removed by r262358:
the direct case can still occur (because x86_mmx is special, see
r262446), but it's the indirect case that's now superseded by the
generic combine.
llvm-svn: 267651
In the case where isLegalAddressingMode is used for cases
not related to addressing modes, such as pure adds and muls,
it should not be using address space 0. LSR already passes -1
as the address space in these cases.
llvm-svn: 267645
Summary:
If the linker requested to preserve a linkonce function, we should
honor this even if we drop all uses.
Reviewers: dexonsmith
Subscribers: llvm-commits, joker.eph
Differential Revision: http://reviews.llvm.org/D19527
From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 267644
This splits out the per-loop functionality from the Pass class.
With this the fact whether the loop is forced-distribute with the new
metadata/pragma can be cached in the per-loop class rather than passed
around.
llvm-svn: 267643
When encountering a non-local pointer, LVI would eagerly scan the block for dereferences of the given object to prove the pointer to be non null. That's all well and good, but *then* we'd go recurse through our input blocks. As a result, we could end up scanning each and every block we traverse, even if the final definition was obviously non null or we found a constant value somewhere up the chain. The previous code papered over this by using the isKnownNonNull routine from value tracking. This made the duplication less painful in the common case.
Instead, we know do the block scan only *after* we've gotten the recursive results back. This lets us stop scanning individual blocks as soon as we've determined it to be non-null in any predecessor block and use our usual merge rules to propagate that information cheaply through successor blocks. For a pointer which can be found non-null, this does strictly less work and sometimes substaintially so.
Note that the case where we *can't* prove something non-null is still the really expensive case. We end up scanning each and every block looking for a dereference and never end up finding one.
llvm-svn: 267642
is defined!
The users were checking the proper thing (Defined + PartialDeadDef), but the
information may have been wrong for other use cases, so fix that.
llvm-svn: 267641
the prologue.
Do not use basic blocks that have EFLAGS live-in as prologue if we need
to realign the stack. Realigning the stack uses AND instruction and this
clobbers EFLAGS.
An other alternative would have been to save and restore EFLAGS around
the stack realignment code, but this is likely inefficient.
Fixes PR27531.
llvm-svn: 267634
Previously we were recursing on our operands for unary and binary operators regardless of whether we knew how to reason about the operator in question. This has the effect of doing a potentially large amount of work, only to throw it away. By checking whether the operation is one LVI can handle, we can cut short the search and return the (overdefined) answer more quickly. The quality of the results produced should not change.
llvm-svn: 267626
As pointed out by John Regehr over in http://reviews.llvm.org/D19485, LVI was being incredibly stupid about applying its transfer rules. Rather than gathering local facts from the expression itself, it was simply giving up entirely if one of the inputs was overdefined. This greatly impacts the precision of the overall analysis and makes it far more fragile as well.
This patch builds on 267609 which did the same thing for unary casts.
llvm-svn: 267620
NVPTXLowerKernelArgs is required for correctness, so it should not be guarded
by CodeGenOpt::None.
NVPTXPeephole is optimization only, so it should be skipped when
CodeGenOpt::None.
llvm-svn: 267619
Essentially, I was using the wrong size function. For types which were sized, but not primitive, I wasn't getting a useful size for the operand and failed an assert. I fixed this, and also added a guard that the input is a sized type. Test case is for the original mistake. I'm not sure how to actually exercise the sized type check.
llvm-svn: 267618
We need the default ratio to be sufficiently large that it triggers transforms
based on block frequency info (BFI) and plays well with the recently introduced
BranchProbability used by CGP.
Differential Revision: http://reviews.llvm.org/D19435
llvm-svn: 267615
As pointed out by John Regehr over in http://reviews.llvm.org/D19485, LVI was being incredibly stupid about applying its transfer rules. Rather than gathering local facts from the expression itself, it was simply giving up entirely if one of the inputs was overdefined. This greatly impacts the precision of the overall analysis and makes it far more fragile as well.
This patch implements only the unary operation case. Once this is in, I'll implement the same for the binary operations.
Differential Revision: http://reviews.llvm.org/D19492
llvm-svn: 267609
The destination buffer that sprintf uses is restrict qualified, we do
not need to worry about derived pointers referenced via format
specifiers.
This reverts commit r267580.
llvm-svn: 267605
The DBI stream contains a lot of bookkeeping information for other
streams. In particular it contains information about section contributions
and linked modules. This patch is a first attempt at parsing some of the
information out of the DBI stream. It currently only parses and dumps the
headers of the DBI stream, so none of the module data or section
contribution data is pulled out.
This is just a proof of concept that we understand the basic properties of
the DBI stream's metadata, and followup patches will try to extract more
detailed information out.
Differential Revision: http://reviews.llvm.org/D19500
Reviewed By: majnemer, ruiu
llvm-svn: 267585
When a block is tail-duplicated, the PHI nodes from that block are
replaced with appropriate COPY instructions. When those PHI nodes
contained use operands with subregisters, the subregisters were
dropped from the COPY instructions, resulting in incorrect code.
Keep track of the subregister information and use this information
when remapping instructions from the duplicated block.
Differential Revision: http://reviews.llvm.org/D19337
llvm-svn: 267583
sprintf doesn't read or copy the terminating null byte from it's string
operands. sprintf will append it's own after processing all of the
format specifiers.
This fixes PR27526.
llvm-svn: 267580
This is part of solving PR27344:
https://llvm.org/bugs/show_bug.cgi?id=27344
CGP should undo the SimplifyCFG transform for the same reason that earlier patches have used this
same mechanism: it's possible that passes between SimplifyCFG and CGP may be able to optimize the
IR further with a select in place.
For the TLI hook default, >99% taken or not taken is chosen as the default threshold for a highly
predictable branch. Even the most limited HW branch predictors will be correct on this branch almost
all the time, so even a massive mispredict penalty perf loss would be overcome by the win from all
the times the branch was predicted correctly.
As a follow-up, we could make the default target hook less conservative by using the SchedMachineModel's
MispredictPenalty. Or we could just let targets override the default by implementing the hook with that
and other target-specific options. Note that trying to statically determine mispredict rates for
close-to-balanced profile weight data is generally impossible if the HW is sufficiently advanced. Ie,
50/50 taken/not-taken might still be 100% predictable.
Finally, note that this patch as-is will not solve PR27344 because the current __builtin_unpredictable()
branch weight default values are 4 and 64. A proposal to change that is in D19435.
Differential Revision: http://reviews.llvm.org/D19488
llvm-svn: 267572
In gcc, \ escapes every character in response files. It is true that this makes
it harder to mention Windows files in rsp files, but not doing this means clang
disagrees with gcc, and also disagrees with the shell (on non-Windows) which
rsp file quoting is supposed to match. clang isn't free to choose what to do
here.
In general, the idea for response files is to take bits of your command line
and write them to a file unchanged, and have things work the same way. Since
the command line would've been interpreted by the shell, things in the rsp file
need to be subject to the same shell quoting rules.
People who want to put Windows-style paths in their response files either need
to do any of:
* escape their backslashes
* or use clang-cl which uses cl.exe/cmd.exe quoting rules
* pass --rsp-quoting=windows to clang to tell it to use
cl.exe/cmd.exe quoting rules for response files.
Fixes PR27464.
http://reviews.llvm.org/D19417
llvm-svn: 267556
Support for SDWA instructions for VOP1 and VOP2 encoding.
Not done yet:
- converters for support optional operands and modifiers
- VOPC
- sext() modifier
- intrinsics
- VOP2b (see vop_dpp.s)
- V_MAC_F32 (see vop_dpp.s)
Differential Revision: http://reviews.llvm.org/D19360
llvm-svn: 267553
Handle MachineBasicBlock as a memory displacement operand in the LEA optimization pass.
Differential Revision: http://reviews.llvm.org/D19409
llvm-svn: 267551
If the linker specifically requested for a linkonce to be preserved,
we need to make sure we won't drop it even if all the uses in the
current module disappear.
From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 267543
print-stack-trace.cc test failure of compiler-rt has been fixed by
r266869 (http://reviews.llvm.org/D19148), so reenable sibling call
optimization on ppc64
Reviewers: nemanjai kbarton
llvm-svn: 267527
Summary:
Instead of using maximum IR weight as the basic block weight, this patch uses the voting algorithm to find the most likely weight for the basic block. This can effectively avoid the cases when some IRs are annotated incorrectly due to code motion of the profiled binary.
This patch also updates propagate.ll unittest to include discriminator in the input file so that it is testing something meaningful.
Reviewers: davidxl, dnovillo
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D19301
llvm-svn: 267519
When SimplifyCFG merges identical instructions from both sides of a diamond, it
can preserve !llvm.mem.parallel_loop_access (as it does with most of the other
metadata). There's no real data or control dependency change in this case.
llvm-svn: 267515
I really thought we were doing this already, but we were not. Given this input:
void Test(int *res, int *c, int *d, int *p) {
for (int i = 0; i < 16; i++)
res[i] = (p[i] == 0) ? res[i] : res[i] + d[i];
}
we did not vectorize the loop. Even with "assume_safety" the check that we
don't if-convert conditionally-executed loads (to protect against
data-dependent deferenceability) was not elided.
One subtlety: As implemented, it will still prefer to use a masked-load
instrinsic (given target support) over the speculated load. The choice here
seems architecture specific; the best option depends on how expensive the
masked load is compared to a regular load. Ideally, using the masked load still
reduces unnecessary memory traffic, and so should be preferred. If we'd rather
do it the other way, flipping the order of the checks is easy.
The LangRef is updated to make explicit that llvm.mem.parallel_loop_access also
implies that if conversion is okay.
Differential Revision: http://reviews.llvm.org/D19512
llvm-svn: 267514
Summary:
We don't use MinLatency any more since r184032.
Reviewers: atrick, hfinkel, mcrosier
Differential Revision: http://reviews.llvm.org/D19474
llvm-svn: 267502
Pass all of the state we need around as arguments, so that these
functions are easier to reuse. There is one part of this that is
unusual: we pass around a functor to look up a DomTree for a function.
This will be a necessary abstraction when we try to use this code in
both the legacy and the new pass manager.
llvm-svn: 267498
Kill-flags, which computeRegisterLiveness uses, are not reliable.
LivePhysRegs is.
Differential Revision: http://reviews.llvm.org/D19472
llvm-svn: 267495
The SparcV8 fneg and fabs instructions interestingly come only in a
single-float variant. Since the sign bit is always the topmost bit no
matter what size float it is, you simply operate on the high
subregister, as if it were a single float.
However, the layout of double-floats in the float registers is reversed
on little-endian CPUs, so that the high bits are in the second
subregister, rather than the first.
Thus, this expansion must check the endianness to use the correct
subregister.
llvm-svn: 267489
This patch is what was the "instcombine" portion of D14185, with an additional
test added (see julia_pseudovec in test/Transforms/InstCombine/insert-val-extract-elem.ll).
The patch causes instcombine to replace sequences of extractelement-insertvalue-store
that act essentially like a bitcast followed by a store.
Differential review: http://reviews.llvm.org/D14260
llvm-svn: 267482
Add a typedef for the std::map<GlobalValue::GUID, GlobalValueSummary *>
map that is passed around to identify summaries for values defined in a
particular module. This shortens up declarations in a variety of places.
llvm-svn: 267471
log2(Mask) is smaller than 32, we must use the 32-bit variant because the 64-bit
variant cannot encode it. Therefore, set the subreg part accordingly.
[AArch64] Fix optimizeCondBranch logic.
The opcode for the optimized branch does not depend on the size
of the activate bits in the AND masks, but the AND opcode itself.
Indeed, we need to use a X or W variant based on the AND variant
not based on whether the mask fits into the related variant.
Otherwise, we may end up using the W variant of the optimized branch
for 64-bit register inputs!
This fixes the last make check verifier issues for AArch64: PR27479.
llvm-svn: 267465
This replaces use of std::error_code and ErrorOr in the ORC RPC support library
with Error and Expected. This required updating the OrcRemoteTarget API, Client,
and server code, as well as updating the Orc C API.
This patch also fixes several instances where Errors were dropped.
llvm-svn: 267457
Use the operand for how long to wait. This is somewhat
distasteful, since it would be better to just emit s_nop
with the right argument in the first place. This would require
changing TII::insertNoop to emit N operands, which would be easy.
Slightly more problematic is the post-RA scheduler and hazard recognizer
represent nops as a single null node, and would require inventing
another way of representing N nops.
llvm-svn: 267456
There has been much recent confusion about the partition in the lattice between constant and non-constant values. Hopefully, documenting this will prevent confusion going forward.
llvm-svn: 267440
This function handled both unary and binary operators. Cloning and specializing leads to much easier to follow code with minimal duplicatation.
llvm-svn: 267438
Previously findClosestSuitableAluInstr was only considering the base register when checking the current instruction for suitability. Expand check to consider the offset if the offset is a register.
llvm-svn: 267424
visitAND, when folding and (load) forgets to check which output of
an indexed load is involved, happily folding the updated address
output on the following testcase:
target datalayout = "e-m:e-i64:64-n32:64"
target triple = "powerpc64le-unknown-linux-gnu"
%typ = type { i32, i32 }
define signext i32 @_Z8access_pP1Tc(%typ* %p, i8 zeroext %type) {
%b = getelementptr inbounds %typ, %typ* %p, i64 0, i32 1
%1 = load i32, i32* %b, align 4
%2 = ptrtoint i32* %b to i64
%3 = and i64 %2, -35184372088833
%4 = inttoptr i64 %3 to i32*
%_msld = load i32, i32* %4, align 4
%zzz = add i32 %1, %_msld
ret i32 %zzz
}
Fix this by checking ResNo.
I've found a few more places that currently neglect to check for
indexed load, and tightened them up as well, but I don't have test
cases for them. In fact, they might not be triggerable at all,
at least with current targets. Still, better safe than sorry.
Differential Revision: http://reviews.llvm.org/D19202
llvm-svn: 267420
Commit r266977 was reason for failing LLVM test suite with error message: fatal error: error in backend: Cannot select: t17: i32 = rotr t2, t11 ...
llvm-svn: 267418
Summary:
The expression is detected as a redundant expression.
Turn out, this is probably a bug.
```
/home/etienneb/llvm/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp:306:26: warning: both side of operator are equivalent [misc-redundant-expression]
if (isSMRD(*FirstLdSt) && isSMRD(*FirstLdSt)) {
```
Reviewers: rnk, tstellarAMD
Subscribers: arsenm, cfe-commits
Differential Revision: http://reviews.llvm.org/D19460
llvm-svn: 267415
We didn't have logic to correctly handle CFGs where there was more than
one EH-pad successor (these are novel with WinEH).
There were situations where a register was live in one exceptional
successor but not another but the code as written would only consider
the first exceptional successor it found.
This resulted in split points which were insufficiently early if an
invoke was present.
This fixes PR27501.
N.B. This removes getLandingPadSuccessor.
llvm-svn: 267412
Summary:
This patch adds support for the X asm constraint.
To do this, we lower the constraint to either a "w" or "r" constraint
depending on the operand type (both constraints are supported on ARM).
Fixes PR26493
Reviewers: t.p.northover, echristo, rengolin
Subscribers: joker.eph, jgreenhalgh, aemerson, rengolin, llvm-commits
Differential Revision: http://reviews.llvm.org/D19061
llvm-svn: 267411
The current logic assumes that any constant global will never be SRA'd. I presume this is because normally constant globals can be pushed into their uses and deleted. However, that sometimes can't happen (which is where you really want SRA, so the elements that can be eliminated, are!).
There seems to be no reason why we can't SRA constants too, so let's do it.
llvm-svn: 267393
If several regions cover the same area of code, we have to restore
the combined value for that area when return from a nested region.
This patch achieves that by combining regions before calling buildSegments.
Differential Revision: http://reviews.llvm.org/D18610
llvm-svn: 267390
Summary:
This implements a new method of run-time checking the NoWrap
SCEV predicates, which should be easier to optimize and nicer
for targets that don't correctly handle multiplication/addition
of large integer types (like i128).
If the AddRec is {a,+,b} and the backedge taken count is c,
the idea is to check that |b| * c doesn't have unsigned overflow,
and depending on the sign of b, that:
a + |b| * c >= a (b >= 0) or
a - |b| * c <= a (b <= 0)
where the comparisons above are signed or unsigned, depending on
the flag that we're checking.
The advantage of doing this is that we avoid extending to a larger
type and we avoid the multiplication of large types (multiplying
i128 can be expensive).
Reviewers: sanjoy
Subscribers: llvm-commits, mzolotukhin
Differential Revision: http://reviews.llvm.org/D19266
llvm-svn: 267389
