This removes the need for Om1's postLower() code which did its own ad-hoc register allocation.  And it actually speeds up Om1 translation significantly.

This mode of register allocation only allocates for infinite-weight Variables, while respecting live ranges of pre-colored Variables.

BUG= none
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/733643005

Seems to be part of the non-sfi link now:
https://codereview.chromium.org/686723003/diff/180001/pnacl/driver/pnacl-translate.py

Otherwise I get:
x86-32-linux/lib/unsandboxed_irt.o:(.rodata+0x68): undefined reference to `nacl_secure_random'

BUG=none
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/726093002

Even after earlier simplifications, FakeKill was still handled somewhat inefficiently for the register allocator.  For x86-32, any function containing call instructions would result in about 11 pre-colored Variables, each with an identical and relatively complex live range consisting of points.  They would start out on the UnhandledPrecolored list, then all move to the Inactive list, where they would be repeatedly compared against each register allocation candidate via overlapsRange().

We improve this by keeping around a single copy of that live range and directly masking out the Free[] register set when that live range overlaps the current candidate's live range.  This saves ~10 overlaps() calculations per candidate while FakeKills are still pending.

Also, slightly rearrange the initialization of the Unhandled etc. sets into a separate init routine, which will make it easier to reuse the register allocator in other situations such as Om1 post-lowering.

BUG= none
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/720343003

This is purely for convenience of personal testing/debugging.

To demonstrate its correctness in this CL, -build-on-read=0 is removed
from the two .ll lit tests that explicitly use it, and also from the
crosstest.py script.  The lit test wrapper run-llvm2ice.py is left
unchanged to be safe.

BUG= none
R=kschimpf@google.com

Review URL: https://codereview.chromium.org/732583002

Instead, separately compute it during prolog generation via another
pass over the Cfg.

This may slow down translation by ~1%, but it greatly simplifies the
management of this flag/property.

The higher motivation is to pull this management out of register
allocation to make it easier to extend register allocation for other
uses.

BUG= none
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/692633004

Use LLVM's intrusive list ADT template to implement instruction lists.  This embeds prev/next pointers into the instruction, and as such, iterators essentially double as instruction pointers.  This means stripping off one level of indirection when dereferencing, and also the range-based for loop can't be used.

The performance difference in translation time seems to be 1-2%.

I tried to also do this for the much less used PhiList and AssignList, but ran into SFINAE problems.

BUG= none
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/709533002

This CL allows one to time Subzero's bitcode parsing without IR generation
(other than types, function declarations, and uninitialized global variables)
for performance testing.

BUG=None
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/696383004

Eventually, I wanted to have a flag "UseELFWriter" like:
https://codereview.chromium.org/678533005/diff/120001/src/IceCfg.cpp

Where the emit OStream would not have text, and only have
binary. This refactor hopefully means fewer places to
check for a flag to disable the text version of IAS,
and be able to write binary. Otherwise, there are some
text labels for branches that are still being dumped out.

BUG=none
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/700263003

Currently NodeList is defined as std::vector<CfgNode*>, but in the future it may be desirable to change it to something like std::list<CfgNode*> so that it is easier to split edges and insert the new nodes at the right locations, rather than re-sorting them in a separate pass.

This gets us closer by using foo.front() instead of foo[0].  There are still a couple more places using the [] operator, but the changes would be more intrusive.

Also, a few instances of ".size()==0" are changed to the possibly more efficient ".empty()".

BUG= none
R=jvoung@chromium.org, kschimpf@google.com

Review URL: https://codereview.chromium.org/704753007

There is one in IceDefs.h and one in IceGlobalInits.h. Can we just use one?

BUG=none (mini cleanup)
R=kschimpf@google.com, stichnot@chromium.org

Review URL: https://codereview.chromium.org/695563006

More consistently use auto while doing llvm::dyn_cast/cast in the emit
and emitIAS routines.

BUG=none
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/699923002

Also deletes a few entirely trivial test files.

These tests were useful in the early days of Subzero, but now mostly just clutter things up.

BUG= none
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/705513002

The FakeKill instruction is always used for killing scratch registers, and a fair amount of effort is spent building new copies of the same scratch register list each time (i.e., for each lowered call instruction).  As such, we can create one master list of scratch registers and share it among all FakeKill instructions.

Also, in all situations where an instruction's Srcs[] were considered for liveness, we had to either explicitly ignore an InstFakeKill instruction, or treat it specially.  Now that InstFakeKill lacks any Srcs[] (or Dest), it doesn't need to be specially ignored, and the code is simplified.

In addition, the text asm emitter no longer clutters the output with FakeKill comments (and FakeUse as well).

BUG= none
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/691693003

BUG= none
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/701673002

The integrated assembler assumed there is at most one fixup per instruction.  For x86, there could actually be two fixups, for any instruction that allows memory and immediate operands at the same time.  Using the now-default -build-on-read flag, it happens in spec2k - the smallest function I found where this happens is 176.gcc and perm_tree_cons.

This changes the textual emission of integrated assembler code to allow for multiple consecutive fixups in a single instruction.

BUG= none
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/693393002

Build a pure-Subzero binary when neither --include nor --exclude is specified.

A pure-Subzero binary is built without flags:
  -externalize
  -ffunction-sections
  -fdata-sections
which is good because that configuration is closer to what real usage will be, and will get more testing during development.

BUG= none
R=kschimpf@google.com

Review URL: https://codereview.chromium.org/693393003

Adds timers to each bitcode block parser in Subzero, to get a reading
on how much time is used by the bitcode parser.

BUG=None
R=jvoung@chromium.org, stichnot@chromium.org

Review URL: https://codereview.chromium.org/688543003

They are no longer needed now that we aren't using the buggy llvm-mc parser for Intel syntax.

This also gets all spec2k components to work with -build-on-read.

Also, adds an emit-time check that infinite-weight Variables actually got a physical register.

BUG= none
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/696153002

The main motivation is that -build-on-read introduces Intel-style asm output like:
  mov al, byte ptr [flags]
and llvm-mc misinterprets the global symbol "flags" as the flags register.  Further workarounds will likely cost more effort than switching over to AT&T syntax.

Most of the lit tests don't need changing, since the asm text is generated by assembling and disassembling the llvm2ice asm output.

There some LEAHACK TODOs that can be fixed, but that would change some of the instructions, so that can be a separate CL.

The Operand emit() routines really ought to be moved entirely into the target-specific source files.

BUG= none
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/695993004

The -asm-verbose flag adds comments to the text asm output about register availability.  Specifically, it prints the registers in use at the beginning and end of each block, and it prints which registers' live ranges end at each instruction.

This is extremely helpful when studying the output to find opportunities to improve the code quality.

BUG= none
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/682983004

The 32-bit validator is now consistent with the 64-bit
validator w.r.t. 16-bit shld/shrd and accepts it. We didn't
really use the 16-bit form in Subzero though, only the 32-bit
one for 64-bit ops, I think.

BUG=none
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/696753003

When compiling using toolchain_build_pnacl.py, we get errors of form:

  Don't use default labels in fully covered switches over enumerations

I tried different combinations of -Wno-covered-switch-default and
-Wno-error=covered-switch-default, but was not able to stop this
error from being generated. Hence, taking the simplier route of
removing -Werror from Makefile.

(see www.llvm.org/docs/CodingStandards.html for more details)

BUG=None
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/686103006

Delays Phi lowering until after register allocation.  This lets the Phi assignment order take register allocation into account and avoid creating false dependencies.

All edges that lead to Phi instructions are split, and the new node gets mov instructions in the correct topological order, using available physical registers as needed.

This lowering style is controllable under -O2 using -phi-edge-split (enabled by default).

The result is faster translation time (due to fewer temporaries leading to faster liveness analysis and register allocation) as well as better code quality (due to better register allocation and fewer phi-based assignments).

BUG= none
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/680733002

The file ifatts.py no longer exists.

BUG= none
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/687403002

BUG=
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/689433002

BUG=None
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/689753002

indices are used.

Also introduces a "error" instruction method for inserting an instruction
placeholder when an instruction is erroneous, and the type of generated
value is known.

BUG=
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/686913003

Adds conditionality to lit tests in two ways:

1) Allows the use of "; REQUIRES: XXX" lines in lit tests. In this
case, the tests defined by the file are only run if all REQUIRES are
met.

2) Allows the conditional running of RUN commands, based on build
flags. This comes in two subforms. There are predefined %ifX commands
that run the command defined by remaining arguments, if the
corresponding %X2i command is applicable. Alternatively, one can use
%if with explicit '--att' arguments to define what conditions should
be checked.

In any case, unlike REQUIRES, the %if commands RUN all the time, but
simply generate empty output, rather then output defined by the
following command, if the condition is not met. These latter tests are
useful when the same input is to be tested under different conditions,
since the REQUIRES form does not allow this.

Note that m2i, p2i, l2i, and lc2i are also conditionally controlled,
so that they do nothing if the build did not construct the appropriate
Subzero translator.

This CL replaces https://codereview.chromium.org/644143002

BUG=None
R=jvoung@chromium.org, stichnot@chromium.org

Review URL: https://codereview.chromium.org/659513005

The (final) newline is emitted by the caller of emit(), instead of
by all the emit() implementations.  This sets the stage for being
able to add useful comments to the textual asm, such as annotating
which registers became free after the instruction.

BUG= none
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/681783002

The only functional change (though not actually visible at this point) is that redundant assignment elimination is moved into a separate pass.

BUG= none
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/672393003

Currently not testing fixups of forward branches and
instead streaming a ".byte (foo - (. + 1))" or
".long (foo - (. + 4))". It should be supported once
emitIAS() delays writing things out until after the
function is fully emitted (and therefore forward labels
have all been bound).

BUG=none
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/673543002

Previously, llvm would emit naclcall instead of call to get the effect
of bundle-align-to-end, but now it just emits plain calls and aligns
plain calls like NaCl binutils would do. Adjust a few Subzero tests.
See: https://codereview.chromium.org/647443005/

Currently leaving the nop checks loose in case the integrated assembler
has some intermediate stage where it emits the bytes of a call
in a "raw" manner (without padding).

BUG=none
R=kschimpf@google.com

Review URL: https://codereview.chromium.org/671193003

1. Decorate the list of live-in and live-out variables with register assignments in the dump() output.  This helps one to assess register pressure.

2. Fix a bug where the DisableInternal flag wasn't being honored for function definitions.

3. Add a -translate-only=<symbol> to limit translation to a single function or global variable.  This makes it easier to focus on debugging a single function.

4. Change the -no-phi-edge-split option to -phi-edge-split and invert the meaning, to better not avoid the non double negatives.

BUG= none
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/673783002

Helps make it work with p2i instead of lc2i. This affected the
address mode optimizations, so some of the test expectations
have changed.

BUG=none
(happened to notice it while trying to test some things manually)

R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/671443003

The definition of ExternName4 in crosstest/test_global_main.cpp was
not defined as a pointer, but was in crosstest/test_global.cpp. As
a result, that name was not linked properly.

BUG=None
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/651673003

Fixes bug in the representation of relocation names (in either global
initializers or as constant expressions in code) so that they
understand when the name is externally defined. This allows us to test
this property using command line arguments, and fixes relocation tests
in cross compilations (where externnally referenced names shouldn't be
name mangled).

BUG=
R=jvoung@chromium.org, stichnot@chromium.org

Review URL: https://codereview.chromium.org/667763002

Similar to https://codereview.chromium.org/656123003/, but cover some of
the assembler files which were avoided to avoid conflicts.

BUG=none
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/643903006

We can't do direct calls via the .long sym hack, since that is
normally for an absolute relocation, but calls are expecting
relative relocations (except for reg/mem forms).

Nop-out the InstFake emitIAS methods. Remove the generic dispatcher
that redirects emitIAS() to emit(), since only branches and labels
are left.

BUG=none
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/647193003

Force dest to be the full 32-bit reg instead of sometimes being
a 16-bit reg. This is to save on a operand size prefix (and
avoid passing the DestTy down to the dispatchers).

BUG=none
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/647223004

Currently, O2 calls VariablesMetadata::init() 4 times:

- Twice for liveness analysis, where only multi-block use information is needed for dealing with sparse bit vectors.

- Once for address mode inference, where single-definition information is needed.

- Once for register allocation, where all information is needed, including the set of all definitions which is needed for determining AllowOverlap.

So we limit the amount of data we gather based on the actual need.

BUG= none
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/650613003