I added several comments to the regopt-related structures when
porting it to 9g.  Synchronize those comments back in to the
other compilers.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/175720043

This adds registerization support to 9g equivalent to what the
other compilers have.

LGTM=rsc
R=rsc, dave
CC=golang-codereviews
https://golang.org/cl/174980043

None of the other compilers have a tag for this enum.
Cleaning all of this up to use proper types will happen after
the conversion.

LGTM=minux, rsc
R=rsc, minux
CC=golang-codereviews
https://golang.org/cl/166690043

Previously, the 6g and 8g registerizers scanned for used
registers beyond the end of a region being considered for
registerization.  This ancient artifact was copied from the C
compilers, where it was probably necessary to track implicitly
used registers.  In the Go compilers it's harmless (because it
can only over-restrict the set of available registers), but no
longer necessary because the Go compilers correctly track
register use/set information.  The consequences of this extra
scan were (at least) that 1) we would not consider allocating
the AX register if there was a deferproc call in the future
because deferproc uses AX as a return register, so we see the
use of AX, but don't track that AX is set by the CALL, and 2)
we could not consider allocating the DX register if there was
a MUL in the future because MUL implicitly sets DX and (thanks
to an abuse of copyu in this code) we would also consider DX
used.

This commit fixes these problems by nuking this code.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/174110043

LGTM=dave, rsc
R=rsc, dave
CC=golang-codereviews
https://golang.org/cl/169460043

For D_OREG addresses, store the used registers in regindex
instead of reguse because they're really part of addressing.

Add implicit register use/set for DUFFZERO/DUFFCOPY.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/174050044

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/174970043

Replace a bit-wise AND with a logical one.  This happened to
work before because bany returns 0 or 1, but the intent here
is clearly logical (and this makes 5g match with 6g and 8g).

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/172850043

For OITAB nodes, 5g's naddr was setting the wrong etype and
failing to set the width of the resulting Addr.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/171220043

9g's naddr was missing assignments to a->width in several
cases, so the optimizer was getting bogus width information.
Add them.

This correct width information also lets us enable the width
check in gins for MOV*.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/167310043

The etype of references to strings was being incorrectly set
to TINT32 on all platforms.  Change it to TSTRING.  It seems
this doesn't matter for compilation, since x86 uses LEA
instructions to load string addresses and arm and power64
disassemble the string into its constituent pieces (with the
correct types), but it helps when debugging.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/170100043

Previously, mkvar treated, for example, 0(AX) the same as AX.
As a result, a move to an indirect address would be marked as
*setting* the register, rather than just using it, resulting
in unnecessary register moves.  Fix this by not producing
variables for indirect addresses.

LGTM=rsc
R=rsc, dave
CC=golang-codereviews
https://golang.org/cl/164610043

So far all of our architectures have had at most 32 registers,
so we've been able to use entry 0 in the Bits uint32 array
directly as a register mask.  Power64 has 64 registers, so
this converts Bits to a uint64 array so we can continue to use
entry 0 directly as a register mask on Power64.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/169060043

On power64x, this one line in live.go reports that t is live
because of missing optimization passes.  This isn't what this
test is trying to test, so shuffle bad40 so that it still
accomplishes the intent of the test without also depending on
optimization.

LGTM=rsc
R=rsc, dave
CC=golang-codereviews
https://golang.org/cl/167110043

The remaining failures in this test are because of incomplete
optimization support on power64x.  Tracked in issue 9058.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/168130043

Print PC stored in target Prog* of branch instructions when
available instead of the offset stored in the branch
instruction.  The offset tends to be wrong after code
transformations, so previously this led to confusing listings.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/168980043

Previously, nilopt was disabled on power64x because it threw
away "seemly random segments of code."  Indeed, excise on
power64x failed to preserve the link field, so it excised not
only the requested instruction but all following instructions
in the function.  Fix excise to retain the link field while
otherwise zeroing the instruction.

This makes nilopt safe on power64x.  It still fails
nilptr3.go's tests for removal of repeated nil checks because
those depend on also optimizing away repeated loads, which
doesn't currently happen on power64x.

LGTM=dave, rsc
R=rsc, dave
CC=golang-codereviews
https://golang.org/cl/168120043

Trivial merge except for src/runtime/asm_power64x.s and
src/runtime/signal_power64x.c

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/168950044

LGTM=r, rsc
R=r, rsc, adg
CC=golang-codereviews
https://golang.org/cl/168890043

LGTM=rsc, austin
R=austin, rsc, bradfitz
CC=golang-codereviews
https://golang.org/cl/164300043

On heavily loaded build servers, a 5 second timeout is too aggressive,
which causes this test to fail spuriously.

LGTM=iant
R=iant
CC=golang-codereviews, sqweek
https://golang.org/cl/170850043

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/164410043

The GC info masks for slices and strings were changed in
commit caab29a25f68, but the reference masks used by
gcinfo_test for power64x hadn't caught up.  Now they're
identical to amd64, so this CL fixes this test by combining
the reference masks for these platforms.

LGTM=rsc
R=rsc, dave
CC=golang-codereviews
https://golang.org/cl/162620044

reflect/asm_power64x.s was missing changes made to other
platforms for stack maps.  This CL ports those changes.  With
this fix, the reflect test passes on power64x.

LGTM=rsc
R=rsc, dave
CC=golang-codereviews
https://golang.org/cl/170870043

fastrand1 depends on testing the high bit of its uint32 state.
For efficiency, all of the architectures implement this as a
sign bit test.  However, on power64, fastrand1 was using a
64-bit sign test on the zero-extended 32-bit state.  This
always failed, causing fastrand1 to have very short periods
and often decay to 0 and get stuck.

Fix this by using a 32-bit signed compare instead of a 64-bit
compare.  This fixes various tests for the randomization of
select of map iteration.

LGTM=rsc
R=rsc, dave
CC=golang-codereviews
https://golang.org/cl/166990043

LGTM=bradfitz
R=bradfitz
CC=golang-codereviews
https://golang.org/cl/168860044

Using -test.cpu=1,1 made it crash before.

Fixes #9024

LGTM=iant
R=adg, iant
CC=golang-codereviews
https://golang.org/cl/169860043

LGTM=iant
R=golang-codereviews, iant, bradfitz
CC=golang-codereviews
https://golang.org/cl/163690043

LGTM=bradfitz
R=adg, bradfitz
CC=golang-codereviews
https://golang.org/cl/162580043

All three cases of clearfat were wrong on power64x.

The cases that handle 1032 bytes and up and 32 bytes and up
both use MOVDU (one directly generated in a loop and the other
via duffzero), which leaves the pointer register pointing at
the *last written* address.  The generated code was not
accounting for this, so the byte fill loop was re-zeroing the
last zeroed dword, rather than the bytes following the last
zeroed dword.  Fix this by simply adding an additional 8 byte
offset to the byte zeroing loop.

The case that handled under 32 bytes was also wrong.  It
didn't update the pointer register at all, so the byte zeroing
loop was simply re-zeroing the beginning of region.  Again,
the fix is to add an offset to the byte zeroing loop to
account for this.

LGTM=dave, bradfitz
R=rsc, dave, bradfitz
CC=golang-codereviews
https://golang.org/cl/168870043

Fixes #9029

LGTM=adg, r
R=r, adg
CC=golang-codereviews
https://golang.org/cl/161630044

Apparently I had already moved on to fixing another problem
when I submitted CL 169790043.

LGTM=dave
R=rsc, dave
CC=golang-codereviews
https://golang.org/cl/165210043

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/170770043

TBR=iant
R=iant
CC=golang-codereviews
https://golang.org/cl/155560045

LGTM=iant
R=golang-codereviews, iant
CC=adg, golang-codereviews
https://golang.org/cl/165170043

No real problems found.  Just lots of argument names that
didn't quite match up.

LGTM=rsc
R=rsc, dave
CC=golang-codereviews
https://golang.org/cl/169790043

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/169800043

+ Regression test.

Fixes #9026.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/162490043

LGTM=bradfitz
R=rsc, bradfitz
CC=golang-codereviews
https://golang.org/cl/162500043

This adds a test to runtime·check to ensure CAS of large
unsigned 32-bit numbers does not accidentally sign-extend its
arguments.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/162490044