Commit Graph

18881 Commits

Author SHA1 Message Date
Alex Lorenz
aa0d6db1e7 MIR Printer: Use a module slot tracker to print global address operands. NFC.
This commit adopts the 'ModuleSlotTracker' class, which was surfaced in r240842,
to print the global address operands. This change ensures that the slot tracker
won't have to be recreated every time a global address operand is printed,
making the MIR printing more efficient.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241645 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-07 23:27:53 +00:00
Reid Kleckner
4fe74caa61 [WinEH] Add localaddress intrinsic instead of using frameaddress
Clang uses this for SEH finally. The new intrinsic will produce the
right value when stack realignment is required.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241643 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-07 23:23:03 +00:00
Reid Kleckner
8f32e5f0d6 Rename llvm.frameescape and llvm.framerecover to localescape and localrecover
Summary:
Initially, these intrinsics seemed like part of a family of "frame"
related intrinsics, but now I think that's more confusing than helpful.
Initially, the LangRef specified that this would create a new kind of
allocation that would be allocated at a fixed offset from the frame
pointer (EBP/RBP). We ended up dropping that design, and leaving the
stack frame layout alone.

These intrinsics are really about sharing local stack allocations, not
frame pointers. I intend to go further and add an `llvm.localaddress()`
intrinsic that returns whatever register (EBP, ESI, ESP, RBX) is being
used to address locals, which should not be confused with the frame
pointer.

Naming suggestions at this point are welcome, I'm happy to re-run sed.

Reviewers: majnemer, nicholas

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D11011

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241633 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-07 22:25:32 +00:00
Alex Lorenz
78bc2545c9 MIR Serialization: Serialize the 'dead' register machine operand flag.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241624 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-07 20:34:53 +00:00
Mehdi Amini
298a718c94 Redirect DataLayout from TargetMachine to Module in SelectionDAG
Summary:
SelectionDAG itself is not invoking directly the DataLayout in the
TargetMachine, but the "TargetLowering" class is still using it. I'll
address it in a following commit.

This change is part of a series of commits dedicated to have a single
DataLayout during compilation by using always the one owned by the
module.

Reviewers: echristo

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D11000

From: Mehdi Amini <mehdi.amini@apple.com>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241618 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-07 19:07:19 +00:00
Mehdi Amini
a77796487b Redirect DataLayout from TargetMachine to Module in GlobalMerge
Summary:
This change is part of a series of commits dedicated to have a single
DataLayout during compilation by using always the one owned by the
module.

Reviewers: echristo

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D10987

From: Mehdi Amini <mehdi.amini@apple.com>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241615 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-07 18:49:25 +00:00
Mehdi Amini
d888ac430d Redirect DataLayout from TargetMachine to Module in CodeGen Prepare
Summary:
This change is part of a series of commits dedicated to have a single
DataLayout during compilation by using always the one owned by the
module.

Reviewers: echristo

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D10986

From: Mehdi Amini <mehdi.amini@apple.com>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241614 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-07 18:45:17 +00:00
Mehdi Amini
26a2a4b4ed Redirect DataLayout from TargetMachine to Module in FastISel
Summary:
This change is part of a series of commits dedicated to have a single
DataLayout during compilation by using always the one owned by the
module.

Reviewers: echristo

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D10985

From: Mehdi Amini <mehdi.amini@apple.com>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241613 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-07 18:39:02 +00:00
Mehdi Amini
33c4d685e3 Redirect DataLayout from TargetMachine to Module in MachineFunction
Summary:
This change is part of a series of commits dedicated to have a
single DataLayout during compilation by using always the one owned by the
module.

Reviewers: echristo

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D10984

From: Mehdi Amini <mehdi.amini@apple.com>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241610 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-07 18:20:57 +00:00
Alex Lorenz
ddc6f0a433 MIR Parser: wrap 'MBBSlots' from the MI parsing functions in a struct. NFC.
This commit modifies the interface for the machine instruction parsing
functions by wrapping the parameter 'MBBSlots' in a new structure called
'PerFunctionMIParsingState'. This change is useful as in the future I will be
able to pass new parameters to the machine instruction parser just by modifying
the 'PerFunctionMIParsingState' structure instead of adding a new parameter to
each function.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241607 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-07 17:46:43 +00:00
Alex Lorenz
d0ef9f3115 MIR Parser: Verify the implicit machine register operands.
This commit verifies that the parsed machine instructions contain the implicit
register operands as specified by the MCInstrDesc. Variadic and call
instructions aren't verified.

Reviewers: Duncan P. N. Exon Smith

Differential Revision: http://reviews.llvm.org/D10781


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241537 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-07 02:08:46 +00:00
Juergen Ributzka
b062a9b411 [StackMap Liveness] Calling the base class' getAnalysisUsage method. NFCI.
Calling into the base class' getAnalysisUsage method after we did our pass
specific modifications. This shouldn't really matter since this is the last
pass in the pipeline anyways.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241536 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-07 02:05:18 +00:00
Juergen Ributzka
083b791eaf [StackMap Liveness] No need to cache the MachineFunction. NFC.
Don't cache the MachineFunction in the pass and range'ify some loops.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241535 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-07 02:05:15 +00:00
Sanjoy Das
0b1bc70dbf [FaultMaps] Add statistic to count the # of implicit null checks.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241521 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-06 23:32:10 +00:00
Alex Lorenz
4ec0f60807 MIR Serialization: Serialize the implicit register flag.
This commit serializes the implicit flag for the register machine operands. It
introduces two new keywords into the machine instruction syntax: 'implicit' and
'implicit-def'. The 'implicit' keyword is used for the implicit register
operands, and the 'implicit-def' keyword is used for the register operands that
have both the implicit and the define flags set.

Reviewers: Duncan P. N. Exon Smith

Differential Revision: http://reviews.llvm.org/D10709


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241519 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-06 23:07:26 +00:00
Eric Christopher
ddf4c989ee Remove JumpInstrTableInfo.h as it is no longer used.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241517 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-06 22:55:20 +00:00
Reid Kleckner
e23370402c [WinEH] Insert the EH code load before the block terminator
The previous code put the load after the terminator, leading to invalid
IR and downstream crashes. This caused http://crbug.com/506446.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241509 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-06 21:13:43 +00:00
Quentin Colombet
4bde0fa367 [TwoAddressInstructionPass] Rename a variable to match the coding style.
Spot by Bruno.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241505 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-06 20:12:54 +00:00
Alex Lorenz
edfa571cbd llc: Add a 'run-pass' option.
This commit adds a 'run-pass' option to llc, which instructs the compiler to run
one specific code generation pass only.

Llc already has the 'start-after' and the 'stop-after' options, and this new
option complements the other two by making it easier to write tests that want
to invoke a single pass only.

Reviewers: Duncan P. N. Exon Smith

Differential Revision: http://reviews.llvm.org/D10776


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241476 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-06 17:44:26 +00:00
Sanjay Patel
a71390ff3b use range-based for loops; NFCI
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241468 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-06 16:27:35 +00:00
Sanjay Patel
98d447c206 use range-based for loops; NFCI
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241463 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-06 16:19:14 +00:00
Peter Collingbourne
ce2b45bd7d IR: Do not consider available_externally linkage to be linker-weak.
From the linker's perspective, an available_externally global is equivalent
to an external declaration (per isDeclarationForLinker()), so it is incorrect
to consider it to be a weak definition.

Also clean up some logic in the dead argument elimination pass and clarify
its comments to better explain how its behavior depends on linkage,
introduce GlobalValue::isStrongDefinitionForLinker() and start using
it throughout the optimizers and backend.

Differential Revision: http://reviews.llvm.org/D10941

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241413 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-05 20:52:35 +00:00
Benjamin Kramer
54b3b4c15e [TargetLowering] StringRefize asm constraint getters.
There is some functional change here because it changes target code from
atoi(3) to StringRef::getAsInteger which has error checking. For valid
constraints there should be no difference.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241411 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-05 19:29:18 +00:00
Sanjay Patel
2244d521c0 use valid bits to avoid unnecessary machine trace metric recomputations
Although this does cut the number of traces recomputed by ~10% for the
test case mentioned in http://reviews.llvm.org/D10460, it doesn't
make a dent in the overall performance. That example needs to be more
selective when invalidating traces.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241393 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-04 15:00:28 +00:00
Yaron Keren
a450348ecc Initialize booleans CallsUnwindInit and CallsEHReturn with false instead of 0.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241324 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-03 07:56:24 +00:00
Nadav Rotem
6890be345e Fix an overly aggressive assertion in getCopyFromPartsVector.
The assertion in getCopyFromPartsVector assumed that the vector 'part' must
match the type of argument (arguments are potentially split into multiple
parts). However, in some cases the targets return a 'part' of the right size
but with a different type. We already handle this case correctly later on
and generate a bitcast. This commit just makes sure that we are actually
checking the property that we care about.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241312 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-02 23:23:52 +00:00
Akira Hatanaka
516286ff69 Use function attribute "trap-func-name" and remove TargetOptions::TrapFuncName.
This commit changes normal isel and fast isel to read the user-defined trap
function name from function attribute "trap-func-name" attached to llvm.trap or
llvm.debugtrap instead of from TargetOptions::TrapFuncName. This is needed to
use clang's command line option "-ftrap-function" for LTO and enable changing
the trap function name on a per-call-site basis.

Out-of-tree projects currently using TargetOptions::TrapFuncName to specify the
trap function name should attach attribute "trap-func-name" to the call sites
of llvm.trap and llvm.debugtrap instead.

rdar://problem/21225723

Differential Revision: http://reviews.llvm.org/D10832


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241305 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-02 22:13:27 +00:00
Pawel Bylica
074d71dea6 Reapply r240291: Fix shl folding in DAG combiner.
The code responsible for shl folding in the DAGCombiner was assuming incorrectly that all constants are less than 64 bits. This patch simply changes the way values are compared.

It has been reverted previously because of some problems with comparing APInt with raw uint64_t. That has been fixed/changed with r241204.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241254 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-02 11:44:54 +00:00
Sanjoy Das
d0872b393c [NFC] Make the Statepoint class more like CallSite
Summary: Rename some methods to make Statepoint look more like CallSite.

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D10756

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241235 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-02 02:53:45 +00:00
Quentin Colombet
a1a323c637 [TwoAddressInstructionPass] Try 3 Addr Conversion After Commuting.
TwoAddressInstructionPass stops after a successful commuting but 3 Addr
conversion might be good for some cases.
 
Consider:

int foo(int a, int b) {
  return a + b;
}

Before this commit, we emit:

addl	%esi, %edi
movl	%edi, %eax
ret

After this commit, we try 3 Addr conversion:

leal	(%rsi,%rdi), %eax
ret

Patch by Volkan Keles <vkeles@apple.com>!

Differential Revision: http://reviews.llvm.org/D10851


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241206 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-01 23:12:13 +00:00
Reid Kleckner
8a1df9b25f [WinEH] Use llvm.x86.seh.recoverfp in WinEHPrepare
Don't pattern match for frontend outlined finally calls on non-x64
platforms. The 32-bit runtime uses a different funclet prototype.  Now,
the frontend is pre-outlining the finally bodies so that it ends up
doing most of the heavy lifting for variable capturing. We're just
outlining the callsite, and adapting the frameaddress(0) call to line up
the frame pointer recovery.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241186 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-01 20:59:25 +00:00
Sanjay Patel
7472456fe9 add a cl::opt override for TargetLoweringBase's JumpIsExpensive
This patch is not intended to change existing codegen behavior for any target. 
It just exposes the JumpIsExpensive setting on the command-line to allow for
easier testing and emergency overrides.

Also, change the existing regression test to use FileCheck, explicitly specify
the jump-is-expensive option, and use more precise checks.

Differential Revision: http://reviews.llvm.org/D10846



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241179 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-01 18:10:20 +00:00
David Blaikie
b99e0eb947 Revert "[DWARF] Fix debug info generation for function static variables, typedefs, and records"
Caused PR24008

This reverts commit 37cb5f1c2d.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241176 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-01 18:07:16 +00:00
Matthias Braun
08f65f9d69 LivePhysRegs: Add support to add pristine registers when populating with live-in/live-out registers.
Differential Revision: http://reviews.llvm.org/D10139

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241172 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-01 17:17:17 +00:00
Benjamin Kramer
a2b83fd687 [AsmPrinter] Hide implementation details
NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241169 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-01 16:18:16 +00:00
Benjamin Kramer
3690da1dfa [SDAG] Give InstrEmitter hidden visibility
NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241165 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-01 14:55:10 +00:00
Benjamin Kramer
b453775cc2 [CodeGen] Reduce visibility of implementation details
NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241164 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-01 14:47:39 +00:00
Michael Kuperstein
37cb5f1c2d [DWARF] Fix debug info generation for function static variables, typedefs, and records
Function static variables, typedefs and records (class, struct or union) declared inside
a lexical scope were associated with the function as their parent scope, rather than the
lexical scope they are defined or declared in.

This fixes PR19238

Patch by: amjad.aboud@intel.com
Differential Revision: http://reviews.llvm.org/D9758

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241153 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-01 12:33:11 +00:00
Reid Kleckner
34c6bb0ef0 [SEH] Add new intrinsics for recovering and restoring parent frames
The incoming EBP value established by the runtime is actually a pointer
to the end of the EH registration object, and not the true parent
function frame pointer. Clang doesn't need llvm.x86.seh.exceptioninfo
anymore because we know that the exception info pointer is at a fixed
offset from this incoming EBP.

The llvm.x86.seh.recoverfp intrinsic takes an EBP value provided by the
EH runtime and returns a pointer that is usable with llvm.framerecover.

The llvm.x86.seh.restoreframe intrinsic is inserted by the 32-bit
specific preparation pass in blocks targetted by the EH runtime. It
re-establishes any physical registers used by the parent function to
address the stack, such as the frame, base, and stack pointers.

Neither of these intrinsics correctly handle stack realignment prologues
yet, but it's possible to add that later.

Reviewers: majnemer

Differential Revision: http://reviews.llvm.org/D10848

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241125 91177308-0d34-0410-b5e6-96231b3b80d8
2015-06-30 22:46:59 +00:00
Sanjoy Das
e1e95c11b8 [FaultMaps] Let the frontend pre-select implicit null check candidates.
Summary:
This change introduces a !make.implicit metadata that allows the
frontend to pre-select the set of explicit null checks that will be
considered for transformation into implicit null checks.

The reason for not using profiling data instead of !make.implicit is
explained in the change to `FaultMaps.rst`.

Reviewers: atrick, reames, pgavlin, JosephTremoulet

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D10824

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241116 91177308-0d34-0410-b5e6-96231b3b80d8
2015-06-30 21:22:32 +00:00
Peter Collingbourne
fd8c98591d COFF: Do not assign linker-weak symbols to selectany comdat sections.
It is mandatory to specify a comdat in order to receive comdat semantics
for a symbol. We were previously getting this wrong in -function-sections
mode; linker-weak symbols were being emitted in a selectany comdat. This
change causes such symbols to use a noduplicates comdat instead, fixing
the inconsistency.

Also correct an inaccuracy in the docs.

Differential Revision: http://reviews.llvm.org/D10828

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241103 91177308-0d34-0410-b5e6-96231b3b80d8
2015-06-30 19:10:31 +00:00
Alex Lorenz
eceef384d6 Fix compilation failure introduced in r241093.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241096 91177308-0d34-0410-b5e6-96231b3b80d8
2015-06-30 18:32:02 +00:00
Alex Lorenz
73d2cc5b8e MIR Serialization: Serialize MBB successors.
This commit implements serialization of the machine basic block successors. It
uses a YAML flow sequence that contains strings that have the MBB references.
The MBB references in those strings use the same syntax as the MBB machine
operands in the machine instruction strings.

Reviewers: Duncan P. N. Exon Smith

Differential Revision: http://reviews.llvm.org/D10699


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241093 91177308-0d34-0410-b5e6-96231b3b80d8
2015-06-30 18:16:42 +00:00
Alex Lorenz
ba4660cb83 MIR Printer: extract the code that prints MBB references into a new method. NFC.
This commit enables the MIR printer to reuse the code that prints MBB
references.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241087 91177308-0d34-0410-b5e6-96231b3b80d8
2015-06-30 18:00:16 +00:00
Alex Lorenz
403c3312c3 MIR Parser: refactor error reporting for machine instruction parser errors. NFC.
This commit extracts the code that reports an error that's produced by the
machine instruction parser into a new method that can be reused in other places.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241086 91177308-0d34-0410-b5e6-96231b3b80d8
2015-06-30 17:55:00 +00:00
Alex Lorenz
939f023bf9 MIR Parser: make the machine instruction parsing interface more consistent. NFC.
This commit refactors the interface for machine instruction parser. It adopts
the pattern of returning a bool and passing in the result in the first argument
that is used by the other parsing methods for the the method 'parse' and the
function 'parseMachineInstr'.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241085 91177308-0d34-0410-b5e6-96231b3b80d8
2015-06-30 17:47:50 +00:00
Alex Lorenz
1991c597a4 MIR Parser: adopt the 'maybeLex...' pattern. NFC.
This commit refactors the machine instruction lexer so that the lexing
functions use the 'maybeLex...' pattern, where they determine if they
can lex the current token by themselves.

Reviewers: Sean Silva

Differential Revision: http://reviews.llvm.org/D10817


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241078 91177308-0d34-0410-b5e6-96231b3b80d8
2015-06-30 16:51:29 +00:00
Sanjay Patel
5601e30a77 use range-based for loops; NFCI
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241076 91177308-0d34-0410-b5e6-96231b3b80d8
2015-06-30 16:30:22 +00:00
Adrian Prantl
85cd16c88e Debug info: Add dwarf backend support for DIModule.
rdar://problem/20965932

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241034 91177308-0d34-0410-b5e6-96231b3b80d8
2015-06-30 02:13:04 +00:00
Matthias Braun
1a5b04c725 RegisterCoalescer: Cleanup empty subranges after shrinkToUses()
A call to removeEmptySubranges() is necessary after every operation that
potentially removes all segments from a subregister range; this case in
the register coalescer was missing.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241027 91177308-0d34-0410-b5e6-96231b3b80d8
2015-06-30 00:33:44 +00:00