Commit Graph

206 Commits

Author SHA1 Message Date
Chandler Carruth 75ca6be1c1 [x86/MIR] Implement support for pre- and post-instruction symbols, as
well as MIR parsing support for `MCSymbol` `MachineOperand`s.

The only real way to test pre- and post-instruction symbol support is to
use them in operands, so I ended up implementing that within the patch
as well. I can split out the operand support if folks really want but it
doesn't really seem worth it.

The functional implementation of pre- and post-instruction symbols is
now *completely trivial*. Two tiny bits of code in the (misnamed)
AsmPrinter. It should be completely target independent as well. We emit
these exactly the same way as we emit basic block labels. Most of the
code here is to give full dumping, MIR printing, and MIR parsing support
so that we can write useful tests.

The MIR parsing of MC symbol operands still isn't 100%, as it forces the
symbols to be non-temporary and non-local symbols with names. However,
those names often can encode most (if not all) of the special semantics
desired, and unnamed symbols seem especially annoying to serialize and
de-serialize. While this isn't perfect or full support, it seems plenty
to write tests that exercise usage of these kinds of operands.

The MIR support for pre-and post-instruction symbols was quite
straightforward. I chose to print them out in an as-if-operand syntax
similar to debug locations as this seemed the cleanest way and let me
use nice introducer tokens rather than inventing more magic punctuation
like we use for memoperands.

However, supporting MIR-based parsing of these symbols caused me to
change the design of the symbol support to allow setting arbitrary
symbols. Without this, I don't see any reasonable way to test things
with MIR.

Differential Revision: https://reviews.llvm.org/D50833

llvm-svn: 339962
2018-08-16 23:11:05 +00:00
Michael Berg 7d1b25d053 MachineInst support mapping SDNode fast math flags for support in Back End code generation
Summary:
Machine Instruction flags for fast math support and MIR print support


Reviewers: spatel, arsenm

Reviewed By: arsenm

Subscribers: wdng

Differential Revision: https://reviews.llvm.org/D45781

llvm-svn: 331417
2018-05-03 00:07:56 +00:00
Francis Visoiu Mistrih 57fcd3454a [MIR] Add support for debug metadata for fixed stack objects
Debug var, expr and loc were only supported for non-fixed stack objects.

This patch adds the following fields to the "fixedStack:" entries, and
renames the ones from "stack:" to:

* debug-info-variable
* debug-info-expression
* debug-info-location

Differential Revision: https://reviews.llvm.org/D46032

llvm-svn: 330859
2018-04-25 18:58:06 +00:00
Francis Visoiu Mistrih 537d7eee90 [MIR] Add support for MachineFrameInfo::LocalFrameSize
MFI.LocalFrameSize was not serialized.

It is usually set from LocalStackSlotAllocation, so if that pass doesn't
run it is impossible do deduce it from the stack objects. Until now, this
information was lost.

llvm-svn: 329382
2018-04-06 08:56:25 +00:00
Puyan Lotfi 399b46c98d [MIR] Adding support for Named Virtual Registers in MIR.
llvm-svn: 328887
2018-03-30 18:15:54 +00:00
Francis Visoiu Mistrih e85b06d65f [CodeGen] Use MIR syntax for MachineMemOperand printing
Get rid of the "; mem:" suffix and use the one we use in MIR: ":: (load 2)".

rdar://38163529

Differential Revision: https://reviews.llvm.org/D42377

llvm-svn: 327580
2018-03-14 21:52:13 +00:00
Francis Visoiu Mistrih 3abf05739f [MIR] Allow frame-setup and frame-destroy on the same instruction
Nothing prevents us from having both frame-setup and frame-destroy on
the same instruction.

When merging:
* frame-setup OPCODE1
* frame-destroy OPCODE2
into
* frame-setup frame-destroy OPCODE3

we want to be able to print and parse both flags.

llvm-svn: 327442
2018-03-13 19:53:16 +00:00
Roman Tereshin 3054ecea3f [GlobalISel] Print/Parse FailedISel MachineFunction property
FailedISel MachineFunction property is part of the CodeGen pipeline
state as much as every other property, notably, Legalized,
RegBankSelected, and Selected. Let's make that part of the state also
serializable / de-serializable, so if GlobalISel aborts on some of the
functions of a large module, but not the others, it could be easily seen
and the state of the pipeline could be maintained through llc's
invocations with -stop-after / -start-after.

To make MIR printable and generally to not to break it too much too
soon, this patch also defers cleaning up the vreg -> LLT map until
ResetMachineFunctionPass.

To make MIR with FailedISel: true also machine verifiable, machine
verifier is changed so it treats a MIR-module as non-regbankselected and
non-selected if there is FailedISel property set.

Reviewers: qcolombet, ab

Reviewed By: dsanders

Subscribers: javed.absar, rovka, kristof.beyls, llvm-commits

Differential Revision: https://reviews.llvm.org/D42877

llvm-svn: 326343
2018-02-28 17:55:45 +00:00
Francis Visoiu Mistrih e4718e84e8 [MIR] Add support for addrspace in MIR
Add support for printing / parsing the addrspace of a MachineMemOperand.

Fixes PR35970.

Differential Revision: https://reviews.llvm.org/D42502

llvm-svn: 323521
2018-01-26 11:47:28 +00:00
Francis Visoiu Mistrih 548add992e [CodeGen] Unify printing format of debug-location in both MIR and -debug
Use "debug-location" instead of "; dbg:" in MI::print.

llvm-svn: 322936
2018-01-19 11:44:42 +00:00
Francis Visoiu Mistrih eb3f76fc83 [CodeGen][NFC] Rename IsVerbose to IsStandalone in Machine*::print
Committed r322867 too soon.

Differential Revision: https://reviews.llvm.org/D42239

llvm-svn: 322868
2018-01-18 18:05:15 +00:00
Francis Visoiu Mistrih 378b5f3de6 [CodeGen] Print RegClasses on MI in verbose mode
r322086 removed the trailing information describing reg classes for each
register.

This patch adds printing reg classes next to every register when
individual operands/instructions/basic blocks are printed. In the case
of dumping MIR or printing a full function, by default don't print it.

Differential Revision: https://reviews.llvm.org/D42239

llvm-svn: 322867
2018-01-18 17:59:06 +00:00
Francis Visoiu Mistrih ecd0b83312 [CodeGen][NFC] Correct case for printSubRegIdx
llvm-svn: 322541
2018-01-16 10:53:11 +00:00
Puyan Lotfi fe6c9cbb24 [MIR] Repurposing '$' sigil used by external symbols. Replacing with '&'.
Planning to add support for named vregs. This puts is in a conundrum since
physregs are named as well. To rectify this we need to use a sigil other than
'%' for physregs in MIR. We've settled on using '$' for physregs but first we
must repurpose it from external symbols using it, which is what this commit is
all about. We think '&' will have familiar semantics for C/C++ users.

llvm-svn: 322146
2018-01-10 00:56:48 +00:00
Francis Visoiu Mistrih dbf2c48fc7 [MIR] Add support for the frame-destroy MachineInstr flag
We are printing / parsing the `frame-setup` MachineInstr flag but not
the `frame-destroy` one.

Differential Revision: https://reviews.llvm.org/D41509

llvm-svn: 322071
2018-01-09 11:33:22 +00:00
Francis Visoiu Mistrih f81727d138 [CodeGen] Move printing MO_BlockAddress operands to MachineOperand::print
Work towards the unification of MIR and debug output by refactoring the
interfaces.

llvm-svn: 321113
2017-12-19 21:47:14 +00:00
Francis Visoiu Mistrih cb2683d46a [CodeGen] Move printing MO_IntrinsicID operands to MachineOperand::print
Work towards the unification of MIR and debug output by refactoring the
interfaces.

llvm-svn: 321112
2017-12-19 21:47:10 +00:00
Francis Visoiu Mistrih bbd610ae92 [CodeGen] Move printing MO_IntrinsicID operands to MachineOperand::print
Work towards the unification of MIR and debug output by refactoring the
interfaces.

Also add support for printing with a null TargetIntrinsicInfo and no
MachineFunction.

llvm-svn: 321111
2017-12-19 21:47:05 +00:00
Francis Visoiu Mistrih 3b265c8fcf [CodeGen] Move printing MO_FPImmediate operands to MachineOperand::print
Work towards the unification of MIR and debug output by refactoring the
interfaces.

llvm-svn: 321110
2017-12-19 21:47:00 +00:00
Francis Visoiu Mistrih 8122660226 [CodeGen] Refactor printOffset from MO and MIRPrinter
llvm-svn: 321109
2017-12-19 21:46:55 +00:00
Francis Visoiu Mistrih 874ae6faa5 [CodeGen] Move printing MO_CFIIndex operands to MachineOperand::print
Work towards the unification of MIR and debug output by refactoring the
interfaces.

Before this patch we printed "<call frame instruction>" in the debug
output.

llvm-svn: 321084
2017-12-19 16:51:52 +00:00
Matthias Braun f1caa2833f MachineFunction: Return reference from getFunction(); NFC
The Function can never be nullptr so we can return a reference.

llvm-svn: 320884
2017-12-15 22:22:58 +00:00
Francis Visoiu Mistrih 0b5bdceabf [CodeGen] Print stack object references as %(fixed-)stack.0 in both MIR and debug output
Work towards the unification of MIR and debug output by printing
`%stack.0` instead of `<fi#0>`, and `%fixed-stack.0` instead of
`<fi#-4>` (supposing there are 4 fixed stack objects).

Only debug syntax is affected.

Differential Revision: https://reviews.llvm.org/D41027

llvm-svn: 320827
2017-12-15 16:33:45 +00:00
Francis Visoiu Mistrih 5de20e039e [MIR] Add support for missing CFI directives
The following CFI directives are suported by MC but not by MIR:

* .cfi_rel_offset
* .cfi_adjust_cfa_offset
* .cfi_escape
* .cfi_remember_state
* .cfi_restore_state
* .cfi_undefined
* .cfi_register
* .cfi_window_save

Add support for printing, parsing and update tests.

Differential Revision: https://reviews.llvm.org/D41230

llvm-svn: 320819
2017-12-15 15:17:18 +00:00
Francis Visoiu Mistrih 3c99371c6e [CodeGen] Print MCSymbol operands as <mcsymbol sym> in both MIR and debug output
Work towards the unification of MIR and debug output by printing
`<mcsymbol sym>` instead of `<MCSym=sym>`.

Only debug syntax is affected.

llvm-svn: 320685
2017-12-14 10:03:23 +00:00
Francis Visoiu Mistrih 2db59382db [CodeGen] Move printing MO_Metadata operands to MachineOperand::print
Work towards the unification of MIR and debug output by refactoring the
interfaces.

llvm-svn: 320684
2017-12-14 10:03:18 +00:00
Francis Visoiu Mistrih bdaf8bfa99 [CodeGen] Print live-out register lists as liveout(...) in both MIR and debug output
Work towards the unification of MIR and debug output by printing
`liveout(...)` instead of `<regliveout>`.

Only debug syntax is affected.

llvm-svn: 320683
2017-12-14 10:03:14 +00:00
Francis Visoiu Mistrih 5df3bbf3e6 [CodeGen] Print global addresses as @foo in both MIR and debug output
Work towards the unification of MIR and debug output by printing
`@foo` instead of `<ga:@foo>`.

Also print target flags in the MIR format since most of them are used on
global address operands.

Only debug syntax is affected.

llvm-svn: 320682
2017-12-14 10:03:09 +00:00
Francis Visoiu Mistrih e76c5fcd70 [CodeGen] Print external symbols as $symbol in both MIR and debug output
Work towards the unification of MIR and debug output by printing
`$symbol` instead of `<es:symbol>`.

Only debug syntax is affected.

llvm-svn: 320681
2017-12-14 10:02:58 +00:00
Francis Visoiu Mistrih b41dbbe325 [CodeGen] Print jump-table index operands as %jump-table.0 in both MIR and debug output
Work towards the unification of MIR and debug output by printing `%jump-table.0` instead of `<jt#0>`.

Only debug syntax is affected.

llvm-svn: 320566
2017-12-13 10:30:59 +00:00
Francis Visoiu Mistrih b3a0d51374 [CodeGen] Print target index operands as target-index(target-specific) + 8 in both MIR and debug output
Work towards the unification of MIR and debug output by printing `target-index(target-specific) + 8` instead of `<ti#0+8>` and `target-index(target-specific) + 8` instead of `<ti#0-8>`.

Only debug syntax is affected.

llvm-svn: 320565
2017-12-13 10:30:51 +00:00
Francis Visoiu Mistrih 26ae8a6582 [CodeGen] Print constant pool index operands as %const.0 + 8 in both MIR and debug output
Work towards the unification of MIR and debug output by printing
`%const.0 + 8` instead of `<cp#0+8>` and `%const.0 - 8` instead of
`<cp#0-8>`.

Only debug syntax is affected.

Differential Revision: https://reviews.llvm.org/D41116

llvm-svn: 320564
2017-12-13 10:30:45 +00:00
Francis Visoiu Mistrih 440f69c95a [CodeGen] Move printing MO_Immediate operands to MachineOperand::print
Work towards the unification of MIR and debug output by refactoring the
interfaces.

Add support for operand subreg index as an immediate to debug printing
and use ::print in the MIRPrinter.

Differential Review: https://reviews.llvm.org/D40965

llvm-svn: 320209
2017-12-08 22:53:21 +00:00
Francis Visoiu Mistrih f4bd295576 [CodeGen] Move printing MO_MachineBasicBlock operands to MachineOperand::print
Work towards the unification of MIR and debug output by refactoring the
interfaces.

llvm-svn: 320141
2017-12-08 11:48:02 +00:00
Francis Visoiu Mistrih 6c4ca713f1 [CodeGen] Move printing MO_CImmediate operands to MachineOperand::print
Work towards the unification of MIR and debug output by refactoring the
interfaces.

llvm-svn: 320140
2017-12-08 11:40:06 +00:00
Francis Visoiu Mistrih a8a83d150f [CodeGen] Use MachineOperand::print in the MIRPrinter for MO_Register.
Work towards the unification of MIR and debug output by refactoring the
interfaces.

For MachineOperand::print, keep a simple version that can be easily called
from `dump()`, and a more complex one which will be called from both the
MIRPrinter and MachineInstr::print.

Add extra checks inside MachineOperand for detached operands (operands
with getParent() == nullptr).

https://reviews.llvm.org/D40836

* find . \( -name "*.mir" -o -name "*.cpp" -o -name "*.h" -o -name "*.ll" -o -name "*.s" \) -type f -print0 | xargs -0 sed -i '' -E 's/kill: ([^ ]+) ([^ ]+)<def> ([^ ]+)/kill: \1 def \2 \3/g'
* find . \( -name "*.mir" -o -name "*.cpp" -o -name "*.h" -o -name "*.ll" -o -name "*.s" \) -type f -print0 | xargs -0 sed -i '' -E 's/kill: ([^ ]+) ([^ ]+) ([^ ]+)<def>/kill: \1 \2 def \3/g'
* find . \( -name "*.mir" -o -name "*.cpp" -o -name "*.h" -o -name "*.ll" -o -name "*.s" \) -type f -print0 | xargs -0 sed -i '' -E 's/kill: def ([^ ]+) ([^ ]+) ([^ ]+)<def>/kill: def \1 \2 def \3/g'
* find . \( -name "*.mir" -o -name "*.cpp" -o -name "*.h" -o -name "*.ll" -o -name "*.s" \) -type f -print0 | xargs -0 sed -i '' -E 's/<def>//g'
* find . \( -name "*.mir" -o -name "*.cpp" -o -name "*.h" -o -name "*.ll" -o -name "*.s" \) -type f -print0 | xargs -0 sed -i '' -E 's/([^ ]+)<kill>/killed \1/g'
* find . \( -name "*.mir" -o -name "*.cpp" -o -name "*.h" -o -name "*.ll" -o -name "*.s" \) -type f -print0 | xargs -0 sed -i '' -E 's/([^ ]+)<imp-use,kill>/implicit killed \1/g'
* find . \( -name "*.mir" -o -name "*.cpp" -o -name "*.h" -o -name "*.ll" -o -name "*.s" \) -type f -print0 | xargs -0 sed -i '' -E 's/([^ ]+)<dead>/dead \1/g'
* find . \( -name "*.mir" -o -name "*.cpp" -o -name "*.h" -o -name "*.ll" -o -name "*.s" \) -type f -print0 | xargs -0 sed -i '' -E 's/([^ ]+)<def[ ]*,[ ]*dead>/dead \1/g'
* find . \( -name "*.mir" -o -name "*.cpp" -o -name "*.h" -o -name "*.ll" -o -name "*.s" \) -type f -print0 | xargs -0 sed -i '' -E 's/([^ ]+)<imp-def[ ]*,[ ]*dead>/implicit-def dead \1/g'
* find . \( -name "*.mir" -o -name "*.cpp" -o -name "*.h" -o -name "*.ll" -o -name "*.s" \) -type f -print0 | xargs -0 sed -i '' -E 's/([^ ]+)<imp-def>/implicit-def \1/g'
* find . \( -name "*.mir" -o -name "*.cpp" -o -name "*.h" -o -name "*.ll" -o -name "*.s" \) -type f -print0 | xargs -0 sed -i '' -E 's/([^ ]+)<imp-use>/implicit \1/g'
* find . \( -name "*.mir" -o -name "*.cpp" -o -name "*.h" -o -name "*.ll" -o -name "*.s" \) -type f -print0 | xargs -0 sed -i '' -E 's/([^ ]+)<internal>/internal \1/g'
* find . \( -name "*.mir" -o -name "*.cpp" -o -name "*.h" -o -name "*.ll" -o -name "*.s" \) -type f -print0 | xargs -0 sed -i '' -E 's/([^ ]+)<undef>/undef \1/g'

llvm-svn: 320022
2017-12-07 10:40:31 +00:00
Francis Visoiu Mistrih 25528d6de7 [CodeGen] Unify MBB reference format in both MIR and debug output
As part of the unification of the debug format and the MIR format, print
MBB references as '%bb.5'.

The MIR printer prints the IR name of a MBB only for block definitions.

* find . \( -name "*.mir" -o -name "*.cpp" -o -name "*.h" -o -name "*.ll" \) -type f -print0 | xargs -0 sed -i '' -E 's/BB#" << ([a-zA-Z0-9_]+)->getNumber\(\)/" << printMBBReference(*\1)/g'
* find . \( -name "*.mir" -o -name "*.cpp" -o -name "*.h" -o -name "*.ll" \) -type f -print0 | xargs -0 sed -i '' -E 's/BB#" << ([a-zA-Z0-9_]+)\.getNumber\(\)/" << printMBBReference(\1)/g'
* find . \( -name "*.txt" -o -name "*.s" -o -name "*.mir" -o -name "*.cpp" -o -name "*.h" -o -name "*.ll" \) -type f -print0 | xargs -0 sed -i '' -E 's/BB#([0-9]+)/%bb.\1/g'
* grep -nr 'BB#' and fix

Differential Revision: https://reviews.llvm.org/D40422

llvm-svn: 319665
2017-12-04 17:18:51 +00:00
Zachary Turner 8065f0b975 Mark all library options as hidden.
These command line options are not intended for public use, and often
don't even make sense in the context of a particular tool anyway. About
90% of them are already hidden, but when people add new options they
forget to hide them, so if you were to make a brand new tool today, link
against one of LLVM's libraries, and run tool -help you would get a
bunch of junk that doesn't make sense for the tool you're writing.

This patch hides these options. The real solution is to not have
libraries defining command line options, but that's a much larger effort
and not something I'm prepared to take on.

Differential Revision: https://reviews.llvm.org/D40674

llvm-svn: 319505
2017-12-01 00:53:10 +00:00
Francis Visoiu Mistrih c71cced0aa [CodeGen] Always use `printReg` to print registers in both MIR and debug
output

As part of the unification of the debug format and the MIR format,
always use `printReg` to print all kinds of registers.

Updated the tests using '_' instead of '%noreg' until we decide which
one we want to be the default one.

Differential Revision: https://reviews.llvm.org/D40421

llvm-svn: 319445
2017-11-30 16:12:24 +00:00
Daniel Sanders 17d277b734 [mir] Print/Parse both MOLoad and MOStore when they occur together.
Summary:
They're not always mutually exclusive. read-modify-write atomics are both
at the same time. One example of this is the SWP instructions on AArch64.
Another example is GlobalISel's G_ATOMICRMW_* generic instructions which
will be added in a later patch.

Reviewers: arphaman, aemerson

Reviewed By: aemerson

Subscribers: aemerson, javed.absar, kristof.beyls, llvm-commits

Differential Revision: https://reviews.llvm.org/D40157

llvm-svn: 319202
2017-11-28 18:57:02 +00:00
Francis Visoiu Mistrih 9d419d3b0c [CodeGen] Rename functions PrintReg* to printReg*
LLVM Coding Standards:
  Function names should be verb phrases (as they represent actions), and
  command-like function should be imperative. The name should be camel
  case, and start with a lower case letter (e.g. openFile() or isFoo()).

Differential Revision: https://reviews.llvm.org/D40416

llvm-svn: 319168
2017-11-28 12:42:37 +00:00
David Blaikie b3bde2ea50 Fix a bunch more layering of CodeGen headers that are in Target
All these headers already depend on CodeGen headers so moving them into
CodeGen fixes the layering (since CodeGen depends on Target, not the
other way around).

llvm-svn: 318490
2017-11-17 01:07:10 +00:00
David Blaikie 3f833edc7c Target/TargetInstrInfo.h -> CodeGen/TargetInstrInfo.h to match layering
This header includes CodeGen headers, and is not, itself, included by
any Target headers, so move it into CodeGen to match the layering of its
implementation.

llvm-svn: 317647
2017-11-08 01:01:31 +00:00
Bjorn Pettersson a42ed3e361 [MIRPrinter] Use %subreg.xxx syntax for subregister index operands
Summary:
Print %subreg.<subregidxname> instead of just the subregister
index when printing immediate operands corresponding to subreg
indices in INSERT_SUBREG, EXTRACT_SUBREG, SUBREG_TO_REG and
REG_SEQUENCE.

Reviewers: qcolombet, MatzeB

Reviewed By: MatzeB

Subscribers: nhaehnle, javed.absar, llvm-commits

Differential Revision: https://reviews.llvm.org/D39696

llvm-svn: 317513
2017-11-06 21:46:06 +00:00
Francis Visoiu Mistrih 66d2c269dc [AsmPrinterDwarf] Add support for .cfi_restore directive
As of today we only use .cfi_offset to specify the offset of a CSR, but
we never use .cfi_restore when the CSR is restored.

If we want to perform a more advanced type of shrink-wrapping, we need
to use .cfi_restore in order to switch the CFI state between blocks.

This patch only aims at adding support for the directive.

Differential Revision: https://reviews.llvm.org/D36114

llvm-svn: 317199
2017-11-02 12:00:58 +00:00
Justin Bogner 6c452834a1 MIR: Print the register class or bank in vreg defs
This updates the MIRPrinter to include the regclass when printing
virtual register defs, which is already valid syntax for the
parser. That is, given 64 bit %0 and %1 in a "gpr" regbank,

  %1(s64) = COPY %0(s64)

would now be written as

  %1:gpr(s64) = COPY %0(s64)

While this change alone introduces a bit of redundancy with the
registers block, it allows us to update the tests to be more concise
and understandable and brings us closer to being able to remove the
registers block completely.

Note: We generally only print the class in defs, but there is one
exception. If there are uses without any defs whatsoever, we'll print
the class on all uses. I'm not completely convinced this comes up in
meaningful machine IR, but for now the MIRParser and MachineVerifier
both accept that kind of stuff, so we don't want to have a situation
where we can print something we can't parse.

llvm-svn: 316479
2017-10-24 18:04:54 +00:00
Krzysztof Parzyszek 72518eaa6f Add iterator range MachineRegisterInfo::liveins(), adopt users, NFC
llvm-svn: 315927
2017-10-16 19:08:41 +00:00
Justin Bogner fdf9bf4f16 CodeGen: Minor cleanups to use MachineInstr::getMF. NFC
Since r315388 we have a shorter way to say this, so we'll replace
MI->getParent()->getParent() with MI->getMF() in a few places.

llvm-svn: 315390
2017-10-10 23:50:49 +00:00
Matthias Braun 5c3e8a450e MIR: Serialize CaleeSavedInfo Restored flag
llvm-svn: 314449
2017-09-28 18:52:14 +00:00
Quentin Colombet d652aeb144 [MIRPrinter] Print empty successor lists when they cannot be guessed
This re-applies commit r313685, this time with the proper updates to
the test cases.

Original commit message:
Unreachable blocks in the machine instr representation are these
weird empty blocks with no successors.
The MIR printer used to not print empty lists of successors. However,
the MIR parser now treats non-printed list of successors as "please
guess it for me". As a result, the parser tries to guess the list of
successors and given the block is empty, just assumes it falls through
the next block (if any).

For instance, the following test case used to fail the verifier.
The MIR printer would print

         entry
        /      \
   true (def)   false (no list of successors)
       |
 split.true (use)

The MIR parser would understand this:

         entry
        /      \
   true (def)   false
       |        /  <-- invalid edge
 split.true (use)

Because of the invalid edge, we get the "def does not
dominate all uses" error.

The fix consists in printing empty successor lists, so that the parser
knows what to do for unreachable blocks.

rdar://problem/34022159

llvm-svn: 313696
2017-09-19 23:34:12 +00:00