Before 3.0, I'd like to add a mechanism for automatically loading a set of plugins from a config file. API suggestions welcome...
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@137717 91177308-0d34-0410-b5e6-96231b3b80d8
Allow a target assembly parser to do context sensitive constraint checking
on a potential instruction match. This will be used, for example, to handle
Thumb2 IT block parsing.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@137675 91177308-0d34-0410-b5e6-96231b3b80d8
This caused a race condition where a thread calls ~LLVMContextImpl which calls
Module::dropAllReferences which calls begin() on an empty ilist that would
create the sentinel, which racily accesses the global context.
This can not be fixed by locking inside createSentinel because the lock would
need to be shared with all users of the global context, including those that
reside outside LLVM's own code.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@137546 91177308-0d34-0410-b5e6-96231b3b80d8
This implements the 'landingpad' instruction. It's used to indicate that a basic
block is a landing pad. There are several restrictions on its use (see
LangRef.html for more detail). These restrictions allow the exception handling
code to gather the information it needs in a much more sane way.
This patch has the definition, implementation, C interface, parsing, and bitcode
support in it.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@137501 91177308-0d34-0410-b5e6-96231b3b80d8
when checking isNull(), we'd pick off the sentinel bit for the outer
PointerUnion, but would not recursively convert the inner pointerunion to bool,
so if *its* sentinel bit is set, isNull() would incorrectly return false.
No testcase, because someone hit this when they were trying to refactor code
to use PointerUnion3, but they since found a better solution.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@137428 91177308-0d34-0410-b5e6-96231b3b80d8
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.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@137384 91177308-0d34-0410-b5e6-96231b3b80d8
An algorithm for incrementally updating LoopInfo within a
LoopPassManager. The incremental update should be extremely cheap in
most cases and can be used in places where it's not feasible to
regenerate the entire loop forest.
- "Unloop" is a node in the loop tree whose last backedge has been removed.
- Perform reverse dataflow on the block inside Unloop to propagate the
nearest loop from the block's successors.
- For reducible CFG, each block in unloop is visited exactly
once. This is because unloop no longer has a backedge and blocks
within subloops don't change parents.
- Immediate subloops are summarized by the nearest loop reachable from
their exits or exits within nested subloops.
- At completion the unloop blocks each have a new parent loop, and
each immediate subloop has a new parent.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@137276 91177308-0d34-0410-b5e6-96231b3b80d8
based on ScalarEvolution without changing the induction variable phis.
This utility is the main tool of IndVarSimplifyPass, but the pass also
restructures induction variables in strange ways that are sensitive to
pass ordering. This provides a way for other loop passes to simplify
new uses of induction variables created during transformation. The
utility may be used by any pass that preserves ScalarEvolution. Soon
LoopUnroll will use it.
The net effect in this checkin is to cleanup the IndVarSimplify pass
by factoring out the SimplifyIndVar algorithm into a standalone utility.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@137197 91177308-0d34-0410-b5e6-96231b3b80d8
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.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@137190 91177308-0d34-0410-b5e6-96231b3b80d8
This function doesn't have anything to do with spill weights, and MRI
already has functions for manipulating the register class of a virtual
register.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@137123 91177308-0d34-0410-b5e6-96231b3b80d8
These the methods are target-independent since they simply scan the
memory operands. They can live in TargetInstrInfoImpl.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@137063 91177308-0d34-0410-b5e6-96231b3b80d8
inlined variable, based on the discussion in PR10542.
This explodes the runtime of several passes down the pipeline due to
a large number of "copies" remaining live across a large function. This
only shows up with both debug and opt, but when it does it creates
a many-minute compile when self-hosting LLVM+Clang. There are several
other cases that show these types of regressions.
All of this is tracked in PR10542, and progress is being made on fixing
the issue. Once its addressed, the re-instated, but until then this
restores the performance for self-hosting and other opt+debug builds.
Devang, let me know if this causes any trouble, or impedes fixing it in
any way, and thanks for working on this!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136953 91177308-0d34-0410-b5e6-96231b3b80d8
LoopPassManager. The incremental update should be extremely cheap in
most cases and can be used in places where it's not feasible to
regenerate the entire loop forest.
- "Unloop" is a node in the loop tree whose last backedge has been removed.
- Perform reverse dataflow on the block inside Unloop to propagate the
nearest loop from the block's successors.
- For reducible CFG, each block in unloop is visited exactly
once. This is because unloop no longer has a backedge and blocks
within subloops don't change parents.
- Immediate subloops are summarized by the nearest loop reachable from
their exits or exits within nested subloops.
- At completion the unloop blocks each have a new parent loop, and
each immediate subloop has a new parent.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136844 91177308-0d34-0410-b5e6-96231b3b80d8
but it solves a layering violation since things in Support are not supposed to
use things in Transforms.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136726 91177308-0d34-0410-b5e6-96231b3b80d8
externally visable, create a local symbol to use in the CFE. If not, use the
function label itself.
Fixes PR10420.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136716 91177308-0d34-0410-b5e6-96231b3b80d8
The 'unwind' function is going away with the new EH rewrite. This is step 0 in
keeping front-ends from using it.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136683 91177308-0d34-0410-b5e6-96231b3b80d8
This adds the 'resume' instruction class, IR parsing, and bitcode reading and
writing. The 'resume' instruction resumes propagation of an existing (in-flight)
exception whose unwinding was interrupted with a 'landingpad' instruction (to be
added later).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136589 91177308-0d34-0410-b5e6-96231b3b80d8
This flag is true from isel to register allocation when the machine
function is required to be in SSA form. The TwoAddressInstructionPass
and PHIElimination passes clear the flag.
The SSA flag wil be used by the machine code verifier to check for SSA
form, and eventually an assertion can enforce it in +Asserts builds.
This will catch the common target error of creating machine code with
multiple defs of a virtual register.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136532 91177308-0d34-0410-b5e6-96231b3b80d8
Create a std::string wrapper for use as a DenseMap key. DenseMap is
not safe in generate with strings, so this wrapper indicates that only
strings guaranteed not to have certain values should be used in the
DenseMap.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136481 91177308-0d34-0410-b5e6-96231b3b80d8
working on x86 (at least for trivial testcases); other architectures will
need more work so that they actually emit the appropriate instructions for
orderings stricter than 'monotonic'. (As far as I can tell, the ARM, PPC,
Mips, and Alpha backends need such changes.)
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136457 91177308-0d34-0410-b5e6-96231b3b80d8
AddLandingPadInfo takes a landingpad instruction and grabs all of the
information from it that it needs for EH table generation.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136429 91177308-0d34-0410-b5e6-96231b3b80d8
'atomicrmw' instructions, which allow representing all the current atomic
rmw intrinsics.
The allowed operands for these instructions are heavily restricted at the
moment; we can probably loosen it a bit, but supporting general
first-class types (where it makes sense) might get a bit complicated,
given how SelectionDAG works.
As an initial cut, these operations do not support specifying an alignment,
but it would be possible to add if we think it's useful. Specifying an
alignment lower than the natural alignment would be essentially
impossible to support on anything other than x86, but specifying a greater
alignment would be possible. I can't think of any useful optimizations which
would use that information, but maybe someone else has ideas.
Optimizer/codegen support coming soon.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136404 91177308-0d34-0410-b5e6-96231b3b80d8
of the empty key for U. This shouldn't really matter because the tombstone key
for the pair was still distinct from every other key, but it is odd. Patch by
Michael Ilseman!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136336 91177308-0d34-0410-b5e6-96231b3b80d8
* InvokeInst: Get the landingpad instruction associated with this invoke.
* LandingPadInst: A method to reserve extra space for clauses.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136325 91177308-0d34-0410-b5e6-96231b3b80d8
If true and 'model' parameter is not an absolute path, a temp directory will be prepended.
Make it true by default to match current behaviour.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136310 91177308-0d34-0410-b5e6-96231b3b80d8
exit. Added an interfaces for querying either the loop's exact/max
backedge taken count or a specific loop exit's not-taken count.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136100 91177308-0d34-0410-b5e6-96231b3b80d8
This is just a LangRef entry and reading/writing/memory representation; optimizer+codegen support coming soon.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136009 91177308-0d34-0410-b5e6-96231b3b80d8
This makes TargetRegisterClass slightly slower. Next step will be making contains faster.
Eventually TargetRegisterClass will be killed entirely.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135835 91177308-0d34-0410-b5e6-96231b3b80d8
function on the TargetRegistry. Also clean it up and use the modern LLVM
utility libraries available instead of rolling a few things manually.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135756 91177308-0d34-0410-b5e6-96231b3b80d8
register extra version information to be printed. This is designed to
allow those tools which link in various targets to also print those
registered targets under --version.
Currently this printing logic is embedded into the Support library
directly; a huge layering violation. This is the first step to hoisting
it out into the tools without adding lots of duplicated code.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135755 91177308-0d34-0410-b5e6-96231b3b80d8
There is still a bit more refactoring left to do in Targets. But we are now very
close to fixing all the layering issues in MC.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135611 91177308-0d34-0410-b5e6-96231b3b80d8
- Introduce JITDefault code model. This tells targets to set different default
code model for JIT. This eliminates the ugly hack in TargetMachine where
code model is changed after construction.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135580 91177308-0d34-0410-b5e6-96231b3b80d8
TargetLoweringObjectFileImpl down to MCObjectFileInfo.
TargetAsmInfo is done to one last method. It's *almost* gone!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135569 91177308-0d34-0410-b5e6-96231b3b80d8
(including compilation, assembly). Move relocation model Reloc::Model from
TargetMachine to MCCodeGenInfo so it's accessible even without TargetMachine.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135468 91177308-0d34-0410-b5e6-96231b3b80d8
errors like the one corrected by r135261. Migrate all LLVM callers of the old
constructor to the new one.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135431 91177308-0d34-0410-b5e6-96231b3b80d8
to MCRegisterInfo. Also initialize the mapping at construction time.
This patch eliminate TargetRegisterInfo from TargetAsmInfo. It's another step
towards fixing the layering violation.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135424 91177308-0d34-0410-b5e6-96231b3b80d8
They mostly mirror the ArrayRef constructors, with two exceptions:
* There's no function mirroring the default constructor because it wouldn't have any parameters to deduce the right ArrayRef<T> from.
* There's an explicit SmallVector<T> overload in addition to the SmallVectorImpl<T> overload. Without it, the single-element overload would try to create an ArrayRef<Smallvector<T> > because it's a better match according to the overloading rules. (And both overloads are used in the current tree, so neither is redundant)
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135389 91177308-0d34-0410-b5e6-96231b3b80d8
related bug fixes and corresponding assertions for uninitialized data
and missing NULL check. Test cases will be included with the new LFTR.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135333 91177308-0d34-0410-b5e6-96231b3b80d8
This gets rid of some of the gory splitting details in RAGreedy and
makes them available to future SplitKit clients.
Slightly generalize the functionality to support multi-way splitting.
Specifically, SplitEditor::splitLiveThroughBlock() supports switching
between different register intervals in a block.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135307 91177308-0d34-0410-b5e6-96231b3b80d8
- No ELF or COFF implementation yet, I don't have a way to test that.
Should be straightforward to add though.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135288 91177308-0d34-0410-b5e6-96231b3b80d8
which was just replaceAllUsesWith without some assertions. It was
needed back when type refinement was alive.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135253 91177308-0d34-0410-b5e6-96231b3b80d8
- The actual values are from the MCOI::OperandType enum.
- Teach tblgen to read it from the instruction definition.
- This is a better implementation of the hacks in edis.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135197 91177308-0d34-0410-b5e6-96231b3b80d8
TargetAsmInfo, which in turn pulls in TargetRegisterInfo, etc. :-( There are
other cases of violations, but this is probably the worst.
This patch is but one small step towards fixing this. 500 more steps to go. :-(
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135131 91177308-0d34-0410-b5e6-96231b3b80d8
Update the debug output interface for MCParsedAsmOperand to have a print()
method which takes an output stream argument, an << operator which invokes
the print method using the given stream, and a dump() method which prints
the operand to the dbgs() stream. This makes the interface more consistent
with the rest of LLVM, and more convenient to use at the debugger command
line.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135043 91177308-0d34-0410-b5e6-96231b3b80d8
ExtractValueInst APIs to use ArrayRef: a new constructor taking a
(begin, end) range, and operators == and != for element-wise comparison.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135039 91177308-0d34-0410-b5e6-96231b3b80d8
an assert on Darwin llvm-gcc builds.
Assertion failed: (castIsValid(op, S, Ty) && "Invalid cast!"), function Create, file /Users/buildslave/zorg/buildbot/smooshlab/slave-0.8/build.llvm-gcc-i386-darwin9-RA/llvm.src/lib/VMCore/Instructions.cpp, li\
ne 2067.
etc.
http://smooshlab.apple.com:8013/builders/llvm-gcc-i386-darwin9-RA/builds/2354
--- Reverse-merging r134893 into '.':
U include/llvm/Target/TargetData.h
U include/llvm/DerivedTypes.h
U tools/bugpoint/ExtractFunction.cpp
U unittests/Support/TypeBuilderTest.cpp
U lib/Target/ARM/ARMGlobalMerge.cpp
U lib/Target/TargetData.cpp
U lib/VMCore/Constants.cpp
U lib/VMCore/Type.cpp
U lib/VMCore/Core.cpp
U lib/Transforms/Utils/CodeExtractor.cpp
U lib/Transforms/Instrumentation/ProfilingUtils.cpp
U lib/Transforms/IPO/DeadArgumentElimination.cpp
U lib/CodeGen/SjLjEHPrepare.cpp
--- Reverse-merging r134888 into '.':
G include/llvm/DerivedTypes.h
U include/llvm/Support/TypeBuilder.h
U include/llvm/Intrinsics.h
U unittests/Analysis/ScalarEvolutionTest.cpp
U unittests/ExecutionEngine/JIT/JITTest.cpp
U unittests/ExecutionEngine/JIT/JITMemoryManagerTest.cpp
U unittests/VMCore/PassManagerTest.cpp
G unittests/Support/TypeBuilderTest.cpp
U lib/Target/MBlaze/MBlazeIntrinsicInfo.cpp
U lib/Target/Blackfin/BlackfinIntrinsicInfo.cpp
U lib/VMCore/IRBuilder.cpp
G lib/VMCore/Type.cpp
U lib/VMCore/Function.cpp
G lib/VMCore/Core.cpp
U lib/VMCore/Module.cpp
U lib/AsmParser/LLParser.cpp
U lib/Transforms/Utils/CloneFunction.cpp
G lib/Transforms/Utils/CodeExtractor.cpp
U lib/Transforms/Utils/InlineFunction.cpp
U lib/Transforms/Instrumentation/GCOVProfiling.cpp
U lib/Transforms/Scalar/ObjCARC.cpp
U lib/Transforms/Scalar/SimplifyLibCalls.cpp
U lib/Transforms/Scalar/MemCpyOptimizer.cpp
G lib/Transforms/IPO/DeadArgumentElimination.cpp
U lib/Transforms/IPO/ArgumentPromotion.cpp
U lib/Transforms/InstCombine/InstCombineCompares.cpp
U lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
U lib/Transforms/InstCombine/InstCombineCalls.cpp
U lib/CodeGen/DwarfEHPrepare.cpp
U lib/CodeGen/IntrinsicLowering.cpp
U lib/Bitcode/Reader/BitcodeReader.cpp
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134949 91177308-0d34-0410-b5e6-96231b3b80d8
and MCSubtargetInfo.
- Added methods to update subtarget features (used when targets automatically
detect subtarget features or switch modes).
- Teach X86Subtarget to update MCSubtargetInfo features bits since the
MCSubtargetInfo layer can be shared with other modules.
- These fixes .code 16 / .code 32 support since mode switch is updated in
MCSubtargetInfo so MC code emitter can do the right thing.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134884 91177308-0d34-0410-b5e6-96231b3b80d8
patch brings numerous advantages to LLVM. One way to look at it
is through diffstat:
109 files changed, 3005 insertions(+), 5906 deletions(-)
Removing almost 3K lines of code is a good thing. Other advantages
include:
1. Value::getType() is a simple load that can be CSE'd, not a mutating
union-find operation.
2. Types a uniqued and never move once created, defining away PATypeHolder.
3. Structs can be "named" now, and their name is part of the identity that
uniques them. This means that the compiler doesn't merge them structurally
which makes the IR much less confusing.
4. Now that there is no way to get a cycle in a type graph without a named
struct type, "upreferences" go away.
5. Type refinement is completely gone, which should make LTO much MUCH faster
in some common cases with C++ code.
6. Types are now generally immutable, so we can use "Type *" instead
"const Type *" everywhere.
Downsides of this patch are that it removes some functions from the C API,
so people using those will have to upgrade to (not yet added) new API.
"LLVM 3.0" is the right time to do this.
There are still some cleanups pending after this, this patch is large enough
as-is.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134829 91177308-0d34-0410-b5e6-96231b3b80d8
CPU, and feature string. Parsing some asm directives can change
subtarget state (e.g. .code 16) and it must be reflected in other
modules (e.g. MCCodeEmitter). That is, the MCSubtargetInfo instance
must be shared.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134795 91177308-0d34-0410-b5e6-96231b3b80d8
RAGreedy::tryAssign will now evict interference from the preferred
register even when another register is free.
To support this, add the EvictionCost struct that counts how many hints
are broken by an eviction. We don't want to break one hint just to
satisfy another.
Rename canEvict to shouldEvict, and add the first bit of eviction policy
that doesn't depend on spill weights: Always make room in the preferred
register as long as the evictees can be split and aren't already
assigned to their preferred register.
Also make the CSR avoidance more accurate. When looking for a cheaper
register it is OK to use a new volatile register. Only CSR aliases that
have never been used before should be avoided.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134735 91177308-0d34-0410-b5e6-96231b3b80d8
This allows the (many) pseudo-instructions we have that map onto a single
real instruction to have their expansion during MC lowering handled
automatically instead of the current cumbersome manual expansion required.
These sorts of pseudos are common when an instruction is used in situations
that require different MachineInstr flags (isTerminator, isBranch, et. al.)
than the generic instruction description has. For example, using a move
to the PC to implement a branch.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134704 91177308-0d34-0410-b5e6-96231b3b80d8
We have to do this in DAGBuilder instead of DAGCombiner, because the exact bit is lost after building.
struct foo { char x[24]; };
long bar(struct foo *a, struct foo *b) { return a-b; }
is now compiled into
movl 4(%esp), %eax
subl 8(%esp), %eax
sarl $3, %eax
imull $-1431655765, %eax, %eax
instead of
movl 4(%esp), %eax
subl 8(%esp), %eax
movl $715827883, %ecx
imull %ecx
movl %edx, %eax
shrl $31, %eax
sarl $2, %edx
addl %eax, %edx
movl %edx, %eax
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134695 91177308-0d34-0410-b5e6-96231b3b80d8
- Each target asm parser now creates its own MCSubtatgetInfo (if needed).
- Changed AssemblerPredicate to take subtarget features which tablegen uses
to generate asm matcher subtarget feature queries. e.g.
"ModeThumb,FeatureThumb2" is translated to
"(Bits & ModeThumb) != 0 && (Bits & FeatureThumb2) != 0".
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134678 91177308-0d34-0410-b5e6-96231b3b80d8
numbers should be printed instead of symbolic register names in
MCAsmStreamer::EmitRegisterName. This is necessary because some versions of
GNU assembler won't accept code in which symbolic register names are used in
cfi directives. There is no change in behavior unless the flag is explicitly
set to true by a backend.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134635 91177308-0d34-0410-b5e6-96231b3b80d8
hasPredecessorHelper function allows predecessors to be cached to speed up
repeated invocations. This fixes PR10186.
X.isPredecessorOf(Y) now just calls Y.hasPredecessor(X)
Y.hasPredecessor(X) calls Y.hasPredecessorHelper(X, Visited, Worklist) with
empty Visited and Worklist sets (i.e. no caching over invocations).
Y.hasPredecessorHelper(X, Visited, Worklist) caches search state in Visited
and Worklist to speed up repeated calls. The Visited set is searched for X
before going to the worklist to further search the DAG if necessary.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134592 91177308-0d34-0410-b5e6-96231b3b80d8
vec.insert(vec.begin(), vec[3]);
The issue was that vec[3] returns a reference into the vector, which is invalidated when insert() memmove's the elements down to make space. The method needs to specifically detect and handle this case to correctly match std::vector's semantics.
Thanks to Howard Hinnant for clarifying the correct behavior, and explaining how std::vector solves this problem.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134554 91177308-0d34-0410-b5e6-96231b3b80d8
