Be more clear about the two conditions that we care about:
1) a block that performs a nil check (OpIsNonNil), which may be removed
2) a block that is the non-nil sucessor for an OpIsNonNil block

Now we only care about removing nilchecks for two scenarios:
- a type 1 block is dominated by a type 2 block for the same value
- a block is both type 1 and type 2 for the same value

Fixes math/big.

Change-Id: I50018a4014830461ddfe2a2daf588468e4a8f0b4
Reviewed-on: https://go-review.googlesource.com/14325Reviewed-by: Keith Randall <khr@golang.org>

Now that the standard library tests
are all passing, add the
test directory tests.

These contain a number of edge case tests
that are of particular interest for compilers.

Some kinds of tests are not well-suited
for a new backend, such as errorcheck tests.
To start, use SSA only for run and runoutput.

There are three failing tests now.
Just mark them as such for now,
so that we can prevent regressions.

This code will all be unwound once SSA
codegen matures and becomes the default.

Change-Id: Ic51e6d0cc1cd48ef1e2fe2c9a743bf0cce275200
Reviewed-on: https://go-review.googlesource.com/14344Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Change-Id: I1271c015e602cd7ec92bf24f019dd8839b3180fc
Reviewed-on: https://go-review.googlesource.com/14346Reviewed-by: Keith Randall <khr@golang.org>

Change-Id: I17c83f6552367d42d48c1ec62fbb494f010fd866
Reviewed-on: https://go-review.googlesource.com/14343
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Change-Id: I32953c4e1d82795bacba9eb94d65cd2e26bfeb87
Reviewed-on: https://go-review.googlesource.com/14339Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>

Change-Id: Ifb6b2ad6078ad084b73c0e785e748e92139684e2
Reviewed-on: https://go-review.googlesource.com/14338Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

They are already handled by the frontend, we just need to
skip them when we see them in ssa.

Change-Id: I309d91552f96a761f8d429a2cab3a47d200ca9e5
Reviewed-on: https://go-review.googlesource.com/14341Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

CL 14337 made SSA support fixedbugs/issue9604b.go.
That test contains > 40k blocks.
This made the O(n^2) dom algorithm fail to terminate
in a reasonable length of time, breaking the build.

For the moment, cap the number of blocks
to fix the build.

This will be reverted when a more efficient
dom algorithm is put in place,
which will be soon.

Change-Id: Ia66c2629481d29d06655ec54d1deff076b0422c6
Reviewed-on: https://go-review.googlesource.com/14342Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

Change-Id: Iaf282211a717e38b05e5d2661d400d465decad50
Reviewed-on: https://go-review.googlesource.com/14337Reviewed-by: Keith Randall <khr@golang.org>

TODO: for now, just function calls.  Do method and interface calls.

Change-Id: Ib262dfa31cb753996cde899beaad4dc2e66705ac
Reviewed-on: https://go-review.googlesource.com/14035Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

Todd Neal has made all the stdlib tests pass.
Now the trybots and build dashboard can
help us keep them passing.

All of this code will be unwound bit by bit
as SSA matures and then becomes the default.

Change-Id: I52ac7e72a87d329ccce974d6671c054374828d11
Reviewed-on: https://go-review.googlesource.com/14294Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

This change is all about leveraging the gc bitmap generation
that is already done by the current compiler.  We rearrange how
stack allocation is done so that we generate a variable declaration
for each spill.  We also reorganize how args/locals are recorded
during SSA.  Then we can use the existing allocauto/defframe to
allocate the stack frame and liveness to make the gc bitmaps.

With this change, stack copying works correctly and we no longer
need hacks in runtime/stack*.go to make tests work.  GC is close
to working, it just needs write barriers.

Change-Id: I990fb4e3fbe98850c6be35c3185a1c85d9e1a6ba
Reviewed-on: https://go-review.googlesource.com/13894Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

Change to table-driven instead of branchy code; leads to
net reduction in lines, easier to understand what happens,
easier to modify code if we want option to exclude generation
of branchy cases.

Doesn't appear to scale for 8x8 case of integer types.

Change-Id: Ib40104b149d30bb329c5782f6cac45c75743e768
Reviewed-on: https://go-review.googlesource.com/14163Reviewed-by: Keith Randall <khr@golang.org>

Also, improve HTML formatting.

Change-Id: I07e2482a30862e2091707f260a2c43d6e9a85d97
Reviewed-on: https://go-review.googlesource.com/14333Reviewed-by: Todd Neal <todd@tneal.org>

Change-Id: I9c84f5ca18745fb2358494c6944bf7ddd05cf8f0
Reviewed-on: https://go-review.googlesource.com/14332Reviewed-by: Todd Neal <todd@tneal.org>

Rewite user nil checks as OpIsNonNil so our nil check elimination pass
can take advantage and remove redundant checks.

With make.bash this removes 10% more nilchecks (34110 vs 31088).

Change-Id: Ifb01d1b6d2d759f5e2a5aaa0470e1d5a2a680212
Reviewed-on: https://go-review.googlesource.com/14321Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

SSA uses this opcode, the old compiler doesn't.

Change-Id: Ic3dde6216496b4b89d570584d34cb0971fdf379d
Reviewed-on: https://go-review.googlesource.com/14330Reviewed-by: Minux Ma <minux@golang.org>

Add timing/allocation information to each compiler pass for both the
console and html output.

Change-Id: I75833003b806a09b4fb1bbf63983258612cdb7b0
Reviewed-on: https://go-review.googlesource.com/14277Reviewed-by: Keith Randall <khr@golang.org>

Store floats in AuxInt to reduce allocations.

Change-Id: I101e6322530b4a0b2ea3591593ad022c992e8df8
Reviewed-on: https://go-review.googlesource.com/14320Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Keith Randall <khr@golang.org>

Store bools in AuxInt to reduce allocations.

Change-Id: Ibd26db67fca5e1e2803f53d7ef094897968b704b
Reviewed-on: https://go-review.googlesource.com/14276Reviewed-by: Keith Randall <khr@golang.org>

Fallthrough return needs to be a return block before jumping
to the exit block.

Change-Id: I994de2064da5c326c9cade2c33cbb15bdbce5acb
Reviewed-on: https://go-review.googlesource.com/14256Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

It is confusing to have exceptional edges jump back into
real code.  Distinguish return blocks, which execute acutal
code, and the exit block, which is a merge point for the regular
and exceptional return flow.

Prevent critical edge insertion from adding blocks on edges
into the exit block.  These added blocks serve no purpose and
add a bunch of dead jumps to the assembly output.  Furthermore,
live variable analysis is confused by these jumps.

Change-Id: Ifd69e6c00e90338ed147e7cb351b5100dc0364df
Reviewed-on: https://go-review.googlesource.com/14254Reviewed-by: David Chase <drchase@google.com>

Change-Id: I6ea0a3482d8813b8555b16fe6c377cad33554619
Reviewed-on: https://go-review.googlesource.com/14247Reviewed-by: David Chase <drchase@google.com>

cse was incorrectly classifying -0.0 and 0.0 as equivalent. This lead
to invalid code as ssa uses PXOR -0.0, reg to negate a floating point.

Fixes math.

Change-Id: Id7eb10c71749eaed897f29b02c33891cf5820acf
Reviewed-on: https://go-review.googlesource.com/14205Reviewed-by: Keith Randall <khr@golang.org>

complex128 was being treated as a complex64

Fixes math/cmplx.

Change-Id: I2996915b4cb6b94198d41cf08a30bd8531b9fec5
Reviewed-on: https://go-review.googlesource.com/14206Reviewed-by: Keith Randall <khr@golang.org>

liblink was rewriting xor by a negative zero (used by SSA
for negation) as XORPS reg,reg.

Fixes strconv.

Change-Id: I627a0a7366618e6b07ba8f0ad0db0e102340c5e3
Reviewed-on: https://go-review.googlesource.com/14200Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Keith Randall <khr@golang.org>

Modified to use the truncating conversion.

Fixes reflect.

Change-Id: I47bf3200abc2d2c662939a2a2351e2ff84168f4a
Reviewed-on: https://go-review.googlesource.com/14167Reviewed-by: David Chase <drchase@google.com>

It does a XOR internally and clobbers flags.

Change-Id: Id6ef9219c4e6c3a2b5fc79c8d52bcfa30c148617
Reviewed-on: https://go-review.googlesource.com/14165Reviewed-by: Keith Randall <khr@golang.org>

They do an AND or an OR internally, so they clobber flags.

Fixes #12441

Change-Id: I6c843bd268496bc13fc7e3c561d76619e961e8ad
Reviewed-on: https://go-review.googlesource.com/14180Reviewed-by: Todd Neal <todd@tneal.org>

liblink rewrites MOV $0, reg into XOR reg, reg. Make MOVxconst clobber
flags so we don't generate invalid code in the unlikely case that it
matters.  In testing, this change leads to no additional regenerated
flags due to a scheduling fix in CL14042.

Change-Id: I7bc1cfee94ef83beb2f97c31ec6a97e19872fb89
Reviewed-on: https://go-review.googlesource.com/14043Reviewed-by: Keith Randall <khr@golang.org>

Still to do:
details, more testing corner cases. (e.g. negative zero)
Includes small cleanups for previous CL.

Note: complex division is currently done in the runtime,
so the division code here is apparently not yet necessary
and also not tested.  Seems likely better to open code
division and expose the widening/narrowing to optimization.

Complex64 multiplication and division is done in wide
format to avoid cancellation errors; for division, this
also happens to be compatible with pre-SSA practice
(which uses a single complex128 division function).

It would-be-nice to widen for complex128 multiplication
intermediates as well, but that is trickier to implement
without a handy wider-precision format.

Change-Id: I595a4300f68868fb7641852a54674c6b2b78855e
Reviewed-on: https://go-review.googlesource.com/14028Reviewed-by: Keith Randall <khr@golang.org>

Specifying types in rewrites for all subexpressions gets verbose
quickly.  Allow opcodes to specify a default type which is used when
none is supplied explicitly.

Provide default types for a few easy opcodes.  There are probably more
we can do, but this is a good start.

Change-Id: Iedc2a1a423cc3e2d4472640433982f9aa76a9f18
Reviewed-on: https://go-review.googlesource.com/14128Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

Change-Id: Ib0ea4b9c245f3d551e0f703826caa6b444b56a2d
Reviewed-on: https://go-review.googlesource.com/14136Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

To reduce the number of spills, give any non-phi values whose argument
is the control the same priority as the control.

With mask.bash, this reduces regenerated flags from 603 to 240.

Change-Id: I26883d69e80357c56b343428fb528102b3f26e7a
Reviewed-on: https://go-review.googlesource.com/14042Reviewed-by: Keith Randall <khr@golang.org>

Change-Id: Ic7be8fa3a89e46a93df181df3163ec1bf7e96a23
Reviewed-on: https://go-review.googlesource.com/14076Reviewed-by: Minux Ma <minux@golang.org>

Change-Id: Ice206f7e94af4a148d9dd9a7570f5ed21722bedc
Reviewed-on: https://go-review.googlesource.com/14075Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

Change-Id: Ia5483d23fe0b5dd0b6cfe2099e9b475184742716
Reviewed-on: https://go-review.googlesource.com/14074Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

Change-Id: I8fd3727763c812297967c8069847833fc8516ff2
Reviewed-on: https://go-review.googlesource.com/14073Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

Instead of trying to delete dead code as soon as we find it, just
mark it as dead using a PlainAndDead block kind.  The deadcode pass
will do the real removal.

This way is somewhat more efficient because we don't need to mess
with successor and predecessor lists of all the dead blocks.

Fixes #12347

Change-Id: Ia42d6b5f9cdb3215a51737b3eb117c00bd439b13
Reviewed-on: https://go-review.googlesource.com/14033Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

This also fixes the encoding/gob TestTopLevelNilPointer failure.

Change-Id: I9b29a6fddffd51af305c685f3a8e2a0594bfeeab
Reviewed-on: https://go-review.googlesource.com/14032Reviewed-by: Keith Randall <khr@golang.org>