Using statement nodes restricts the set of valid SetOp operations,
because you can't SetOp across representation. Rewrite various
code to avoid crossing those as-yet-unintroduced boundaries.
In particular, code like
x, y := v.(T)
x, y := f()
x, y := m[k]
x, y := <-c
starts out with Op = OAS2, and then it turns into a specific Op
OAS2DOTTYPE, OAS2FUNC, OAS2MAPR, OAS2RECV, and then
later in walk is lowered to an OAS2 again.
In the middle, the specific forms move the right-hand side from
n.Rlist().First() to n.Right(), and then the conversion to OAS2 moves
it back. This is unnecessary and makes it hard for these all to
share an underlying Node implementation.
This CL changes these specific forms to leave the right-hand side
in n.Rlist().First().
Similarly, OSELRECV2 is really just a temporary form of OAS2.
This CL changes it to use same fields too.
Finally, this CL fixes the printing of OAS2 nodes in ir/fmt.go,
which formerly printed n.Right() instead of n.Rlist().
This results in a (correct!) update to cmd/compile/internal/logopt's
expected output: ~R0 = <N> becomes ~R0 = &y.b.
Passes buildall w/ toolstash -cmp.
Change-Id: I164aa2e17dc55bfb292024de53d7d250192ad64a
Reviewed-on: https://go-review.googlesource.com/c/go/+/274105
Trust: Russ Cox <rsc@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Now that we have specific types for ONAME and ODCLFUNC nodes
(*Name and *Func), use them throughout the compiler to be more
precise about what data is being operated on.
This is a somewhat large CL, but once you start applying the types
in a few places, you end up needing to apply them to many other
places to keep everything type-checking. A lot of code also melts
away as types are added.
Passes buildall w/ toolstash -cmp.
Change-Id: I21dd9b945d701c470332bac5394fca744a5b232d
Reviewed-on: https://go-review.googlesource.com/c/go/+/274097
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
The plan is to introduce a Node interface that replaces the old *Node pointer-to-struct.
The previous CL defined an interface INode modeling a *Node.
This CL:
- Changes all references outside internal/ir to use INode,
along with many references inside internal/ir as well.
- Renames Node to node.
- Renames INode to Node
So now ir.Node is an interface implemented by *ir.node, which is otherwise inaccessible,
and the code outside package ir is now (clearly) using only the interface.
The usual rule is never to redefine an existing name with a new meaning,
so that old code that hasn't been updated gets a "unknown name" error
instead of more mysterious errors or silent misbehavior. That rule would
caution against replacing Node-the-struct with Node-the-interface,
as in this CL, because code that says *Node would now be using a pointer
to an interface. But this CL is being landed at the same time as another that
moves Node from gc to ir. So the net effect is to replace *gc.Node with ir.Node,
which does follow the rule: any lingering references to gc.Node will be told
it's gone, not silently start using pointers to interfaces. So the rule is followed
by the CL sequence, just not this specific CL.
Overall, the loss of inlining caused by using interfaces cuts the compiler speed
by about 6%, a not insignificant amount. However, as we convert the representation
to concrete structs that are not the giant Node over the next weeks, that speed
should come back as more of the compiler starts operating directly on concrete types
and the memory taken up by the graph of Nodes drops due to the more precise
structs. Honestly, I was expecting worse.
% benchstat bench.old bench.new
name old time/op new time/op delta
Template 168ms ± 4% 182ms ± 2% +8.34% (p=0.000 n=9+9)
Unicode 72.2ms ±10% 82.5ms ± 6% +14.38% (p=0.000 n=9+9)
GoTypes 563ms ± 8% 598ms ± 2% +6.14% (p=0.006 n=9+9)
Compiler 2.89s ± 4% 3.04s ± 2% +5.37% (p=0.000 n=10+9)
SSA 6.45s ± 4% 7.25s ± 5% +12.41% (p=0.000 n=9+10)
Flate 105ms ± 2% 115ms ± 1% +9.66% (p=0.000 n=10+8)
GoParser 144ms ±10% 152ms ± 2% +5.79% (p=0.011 n=9+8)
Reflect 345ms ± 9% 370ms ± 4% +7.28% (p=0.001 n=10+9)
Tar 149ms ± 9% 161ms ± 5% +8.05% (p=0.001 n=10+9)
XML 190ms ± 3% 209ms ± 2% +9.54% (p=0.000 n=9+8)
LinkCompiler 327ms ± 2% 325ms ± 2% ~ (p=0.382 n=8+8)
ExternalLinkCompiler 1.77s ± 4% 1.73s ± 6% ~ (p=0.113 n=9+10)
LinkWithoutDebugCompiler 214ms ± 4% 211ms ± 2% ~ (p=0.360 n=10+8)
StdCmd 14.8s ± 3% 15.9s ± 1% +6.98% (p=0.000 n=10+9)
[Geo mean] 480ms 510ms +6.31%
name old user-time/op new user-time/op delta
Template 223ms ± 3% 237ms ± 3% +6.16% (p=0.000 n=9+10)
Unicode 103ms ± 6% 113ms ± 3% +9.53% (p=0.000 n=9+9)
GoTypes 758ms ± 8% 800ms ± 2% +5.55% (p=0.003 n=10+9)
Compiler 3.95s ± 2% 4.12s ± 2% +4.34% (p=0.000 n=10+9)
SSA 9.43s ± 1% 9.74s ± 4% +3.25% (p=0.000 n=8+10)
Flate 132ms ± 2% 141ms ± 2% +6.89% (p=0.000 n=9+9)
GoParser 177ms ± 9% 183ms ± 4% ~ (p=0.050 n=9+9)
Reflect 467ms ±10% 495ms ± 7% +6.17% (p=0.029 n=10+10)
Tar 183ms ± 9% 197ms ± 5% +7.92% (p=0.001 n=10+10)
XML 249ms ± 5% 268ms ± 4% +7.82% (p=0.000 n=10+9)
LinkCompiler 544ms ± 5% 544ms ± 6% ~ (p=0.863 n=9+9)
ExternalLinkCompiler 1.79s ± 4% 1.75s ± 6% ~ (p=0.075 n=10+10)
LinkWithoutDebugCompiler 248ms ± 6% 246ms ± 2% ~ (p=0.965 n=10+8)
[Geo mean] 483ms 504ms +4.41%
[git-generate]
cd src/cmd/compile/internal/ir
: # We need to do the conversion in multiple steps, so we introduce
: # a temporary type alias that will start out meaning the pointer-to-struct
: # and then change to mean the interface.
rf '
mv Node OldNode
add node.go \
type Node = *OldNode
'
: # It should work to do this ex in ir, but it misses test files, due to a bug in rf.
: # Run the command in gc to handle gc's tests, and then again in ssa for ssa's tests.
cd ../gc
rf '
ex . ../arm ../riscv64 ../arm64 ../mips64 ../ppc64 ../mips ../wasm {
import "cmd/compile/internal/ir"
*ir.OldNode -> ir.Node
}
'
cd ../ssa
rf '
ex {
import "cmd/compile/internal/ir"
*ir.OldNode -> ir.Node
}
'
: # Back in ir, finish conversion clumsily with sed,
: # because type checking and circular aliases do not mix.
cd ../ir
sed -i '' '
/type Node = \*OldNode/d
s/\*OldNode/Node/g
s/^func (n Node)/func (n *OldNode)/
s/OldNode/node/g
s/type INode interface/type Node interface/
s/var _ INode = (Node)(nil)/var _ Node = (*node)(nil)/
' *.go
gofmt -w *.go
sed -i '' '
s/{Func{}, 136, 248}/{Func{}, 152, 280}/
s/{Name{}, 32, 56}/{Name{}, 44, 80}/
s/{Param{}, 24, 48}/{Param{}, 44, 88}/
s/{node{}, 76, 128}/{node{}, 88, 152}/
' sizeof_test.go
cd ../ssa
sed -i '' '
s/{LocalSlot{}, 28, 40}/{LocalSlot{}, 32, 48}/
' sizeof_test.go
cd ../gc
sed -i '' 's/\*ir.Node/ir.Node/' mkbuiltin.go
cd ../../../..
go install std cmd
cd cmd/compile
go test -u || go test -u
Change-Id: I196bbe3b648e4701662e4a2bada40bf155e2a553
Reviewed-on: https://go-review.googlesource.com/c/go/+/272935
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
If we want to break up package gc at all, we will need to move
the compiler IR it defines into a separate package that can be
imported by packages that gc itself imports. This CL does that.
It also removes the TINT8 etc aliases so that all code is clear
about which package things are coming from.
This CL is automatically generated by the script below.
See the comments in the script for details about the changes.
[git-generate]
cd src/cmd/compile/internal/gc
rf '
# These names were never fully qualified
# when the types package was added.
# Do it now, to avoid confusion about where they live.
inline -rm \
Txxx \
TINT8 \
TUINT8 \
TINT16 \
TUINT16 \
TINT32 \
TUINT32 \
TINT64 \
TUINT64 \
TINT \
TUINT \
TUINTPTR \
TCOMPLEX64 \
TCOMPLEX128 \
TFLOAT32 \
TFLOAT64 \
TBOOL \
TPTR \
TFUNC \
TSLICE \
TARRAY \
TSTRUCT \
TCHAN \
TMAP \
TINTER \
TFORW \
TANY \
TSTRING \
TUNSAFEPTR \
TIDEAL \
TNIL \
TBLANK \
TFUNCARGS \
TCHANARGS \
NTYPE \
BADWIDTH
# esc.go and escape.go do not need to be split.
# Append esc.go onto the end of escape.go.
mv esc.go escape.go
# Pull out the type format installation from func Main,
# so it can be carried into package ir.
mv Main:/Sconv.=/-0,/TypeLinkSym/-1 InstallTypeFormats
# Names that need to be exported for use by code left in gc.
mv Isconst IsConst
mv asNode AsNode
mv asNodes AsNodes
mv asTypesNode AsTypesNode
mv basicnames BasicTypeNames
mv builtinpkg BuiltinPkg
mv consttype ConstType
mv dumplist DumpList
mv fdumplist FDumpList
mv fmtMode FmtMode
mv goopnames OpNames
mv inspect Inspect
mv inspectList InspectList
mv localpkg LocalPkg
mv nblank BlankNode
mv numImport NumImport
mv opprec OpPrec
mv origSym OrigSym
mv stmtwithinit StmtWithInit
mv dump DumpAny
mv fdump FDumpAny
mv nod Nod
mv nodl NodAt
mv newname NewName
mv newnamel NewNameAt
mv assertRepresents AssertValidTypeForConst
mv represents ValidTypeForConst
mv nodlit NewLiteral
# Types and fields that need to be exported for use by gc.
mv nowritebarrierrecCallSym SymAndPos
mv SymAndPos.lineno SymAndPos.Pos
mv SymAndPos.target SymAndPos.Sym
mv Func.lsym Func.LSym
mv Func.setWBPos Func.SetWBPos
mv Func.numReturns Func.NumReturns
mv Func.numDefers Func.NumDefers
mv Func.nwbrCalls Func.NWBRCalls
# initLSym is an algorithm left behind in gc,
# not an operation on Func itself.
mv Func.initLSym initLSym
mv nodeQueue NodeQueue
mv NodeQueue.empty NodeQueue.Empty
mv NodeQueue.popLeft NodeQueue.PopLeft
mv NodeQueue.pushRight NodeQueue.PushRight
# Many methods on Node are actually algorithms that
# would apply to any node implementation.
# Those become plain functions.
mv Node.funcname FuncName
mv Node.isBlank IsBlank
mv Node.isGoConst isGoConst
mv Node.isNil IsNil
mv Node.isParamHeapCopy isParamHeapCopy
mv Node.isParamStackCopy isParamStackCopy
mv Node.isSimpleName isSimpleName
mv Node.mayBeShared MayBeShared
mv Node.pkgFuncName PkgFuncName
mv Node.backingArrayPtrLen backingArrayPtrLen
mv Node.isterminating isTermNode
mv Node.labeledControl labeledControl
mv Nodes.isterminating isTermNodes
mv Nodes.sigerr fmtSignature
mv Node.MethodName methodExprName
mv Node.MethodFunc methodExprFunc
mv Node.IsMethod IsMethod
# Every node will need to implement RawCopy;
# Copy and SepCopy algorithms will use it.
mv Node.rawcopy Node.RawCopy
mv Node.copy Copy
mv Node.sepcopy SepCopy
# Extract Node.Format method body into func FmtNode,
# but leave method wrapper behind.
mv Node.Format:0,$ FmtNode
# Formatting helpers that will apply to all node implementations.
mv Node.Line Line
mv Node.exprfmt exprFmt
mv Node.jconv jconvFmt
mv Node.modeString modeString
mv Node.nconv nconvFmt
mv Node.nodedump nodeDumpFmt
mv Node.nodefmt nodeFmt
mv Node.stmtfmt stmtFmt
# Constant support needed for code moving to ir.
mv okforconst OKForConst
mv vconv FmtConst
mv int64Val Int64Val
mv float64Val Float64Val
mv Node.ValueInterface ConstValue
# Organize code into files.
mv LocalPkg BuiltinPkg ir.go
mv NumImport InstallTypeFormats Line fmt.go
mv syntax.go Nod NodAt NewNameAt Class Pxxx PragmaFlag Nointerface SymAndPos \
AsNode AsTypesNode BlankNode OrigSym \
Node.SliceBounds Node.SetSliceBounds Op.IsSlice3 \
IsConst Node.Int64Val Node.CanInt64 Node.Uint64Val Node.BoolVal Node.StringVal \
Node.RawCopy SepCopy Copy \
IsNil IsBlank IsMethod \
Node.Typ Node.StorageClass node.go
mv ConstType ConstValue Int64Val Float64Val AssertValidTypeForConst ValidTypeForConst NewLiteral idealType OKForConst val.go
# Move files to new ir package.
mv bitset.go class_string.go dump.go fmt.go \
ir.go node.go op_string.go val.go \
sizeof_test.go cmd/compile/internal/ir
'
: # fix mkbuiltin.go to generate the changes made to builtin.go during rf
sed -i '' '
s/\[T/[types.T/g
s/\*Node/*ir.Node/g
/internal\/types/c \
fmt.Fprintln(&b, `import (`) \
fmt.Fprintln(&b, ` "cmd/compile/internal/ir"`) \
fmt.Fprintln(&b, ` "cmd/compile/internal/types"`) \
fmt.Fprintln(&b, `)`)
' mkbuiltin.go
gofmt -w mkbuiltin.go
: # update cmd/dist to add internal/ir
cd ../../../dist
sed -i '' '/compile.internal.gc/a\
"cmd/compile/internal/ir",
' buildtool.go
gofmt -w buildtool.go
: # update cmd/compile TestFormats
cd ../..
go install std cmd
cd cmd/compile
go test -u || go test # first one updates but fails; second passes
Change-Id: I5f7caf6b20629b51970279e81231a3574d5b51db
Reviewed-on: https://go-review.googlesource.com/c/go/+/273008
Trust: Russ Cox <rsc@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Move Flag, Debug, Ctxt, Exit, and error messages to
new package cmd/compile/internal/base.
These are the core functionality that everything in gc uses
and which otherwise prevent splitting any other code
out of gc into different packages.
A minor milestone: the compiler source code
no longer contains the string "yy".
[git-generate]
cd src/cmd/compile/internal/gc
rf '
mv atExit AtExit
mv Ctxt atExitFuncs AtExit Exit base.go
mv lineno Pos
mv linestr FmtPos
mv flusherrors FlushErrors
mv yyerror Errorf
mv yyerrorl ErrorfAt
mv yyerrorv ErrorfVers
mv noder.yyerrorpos noder.errorAt
mv Warnl WarnfAt
mv errorexit ErrorExit
mv base.go debug.go flag.go print.go cmd/compile/internal/base
'
: # update comments
sed -i '' 's/yyerrorl/ErrorfAt/g; s/yyerror/Errorf/g' *.go
: # bootstrap.go is not built by default so invisible to rf
sed -i '' 's/Fatalf/base.Fatalf/' bootstrap.go
goimports -w bootstrap.go
: # update cmd/dist to add internal/base
cd ../../../dist
sed -i '' '/internal.amd64/a\
"cmd/compile/internal/base",
' buildtool.go
gofmt -w buildtool.go
Change-Id: I59903c7084222d6eaee38823fd222159ba24a31a
Reviewed-on: https://go-review.googlesource.com/c/go/+/272250
Trust: Russ Cox <rsc@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
gc debug flags are currently stored in a 256-long array, that is then
addressed using the ASCII numeric value of the flag itself (a quirk
inherited from the old C compiler). It is also a little wasteful,
since we only define 16 flags, and the other 240 array elements are
always empty.
This change makes Debug a struct, which also provides static checking
that we're not referencing flags that does not exist.
Change-Id: I2f0dfef2529325514b3398cf78635543cdf48fe0
Reviewed-on: https://go-review.googlesource.com/c/go/+/263539
Trust: Alberto Donizetti <alb.donizetti@gmail.com>
Run-TryBot: Alberto Donizetti <alb.donizetti@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
On a negative answer, the assignop and convertop functions write the
reason why to a string pointer passed as an argument, likely a C-ism
leftover since the compiler's machine assisted translation to Go.
This change makes why a return parameter.
It also fixes a few places where the assignop/convertop result was
compared to 0. While OXXX's value may be zero now, using the named
constant is more robust.
Change-Id: Id9147ed4c1b97d658d30a2f778f876b7867006b4
Reviewed-on: https://go-review.googlesource.com/c/go/+/261857
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Trust: Alberto Donizetti <alb.donizetti@gmail.com>
Right now we just prevent such types from being on the heap. This CL
makes it so they cannot appear on the stack either. The distinction
between heap and stack is pretty vague at the language level (e.g. it
is affected by -N), and we don't need the flexibility anyway.
Once go:notinheap types cannot be in either place, we don't need to
consider pointers to such types to be pointers, at least according to
the garbage collector and stack copying. (This is the big win of this
CL, in my opinion.)
The distinction between HasPointers and HasHeapPointer no longer
exists. There is only HasPointers.
This CL is cleanup before possible use of go:notinheap to fix#40954.
Update #13386
Change-Id: Ibd895aadf001c0385078a6d4809c3f374991231a
Reviewed-on: https://go-review.googlesource.com/c/go/+/249917
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
More ergonomic that way. Also change Haspointers to HasPointers
while we are here.
Change-Id: I45bedc294c1a8c2bd01dc14bd04615ae77555375
Reviewed-on: https://go-review.googlesource.com/c/go/+/249959
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
This CL changes cmd/compile to use Node.Right instead of
Node.Rlist for OAS2FUNC/OAS2RECV/OAS2MAPR/OAS2DOTTYPE nodes.
Fixes#32293
Change-Id: I4c9d9100be2d98d15e016797f934f64d385f5faa
Reviewed-on: https://go-review.googlesource.com/c/go/+/197817
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
The spec carefully and consistently uses "key" and "element"
as map terminology. The implementation, not so much.
This change attempts to make the implementation consistently
hew to the spec's terminology. Beyond consistency, this has
the advantage of avoid some confusion and naming collisions,
since v and value are very generic and commonly used terms.
I believe that I found all everything, but there are a lot of
non-obvious places for these to hide, and grepping for them is hard.
Hopefully this change changes enough of them that we will start using
elem going forward. Any remaining hidden cases can be removed ad hoc
as they are discovered.
The only externally-facing part of this change is in package reflect,
where there is a minor doc change and a function parameter name change.
Updates #27167
Change-Id: I2f2d78f16c360dc39007b9966d5c2046a29d3701
Reviewed-on: https://go-review.googlesource.com/c/go/+/174523
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Currently,
for i := range a {
a[i] = nil
}
will compile to have write barriers even if a is a slice of pointers
to go:notinheap types. This happens because the optimization that
transforms this into a memclr only asks it a's element type has
pointers, and not if it specifically has heap pointers.
Fix this by changing arrayClear to use HasHeapPointer instead of
types.Haspointers. We probably shouldn't have both of these functions,
since a pointer to a notinheap type is effectively a uintptr, but
that's not going to change in this CL.
Change-Id: I284b85bdec6ae1e641f894e8f577989facdb0cf1
Reviewed-on: https://go-review.googlesource.com/c/152723
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
There are two places where the compiler generates memclrHasPointers
calls. These are effectively write barriers, but the compiler doesn't
currently record them as such in the function. As a result code like
for i := range a {
a[i] = nil
}
inserts a write barrier for the assignment to a[i], but the compiler
doesn't report this. Hence, it's not reported in the -d=wb output, and
it's not checked against //go:nowritebarrier annotations.
Change-Id: I40299ebc9824f05cf516cba494d4c086b80ffb53
Reviewed-on: https://go-review.googlesource.com/c/152722
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
This change does a bulk rename of several identifiers in the compiler.
See #27167 and https://docs.google.com/document/d/19_ExiylD9MRfeAjKIfEsMU1_RGhuxB9sA0b5Zv7byVI/
for context and for discussion of these particular renames.
Commands run to generate this change:
gorename -from '"cmd/compile/internal/gc".OPROC' -to OGO
gorename -from '"cmd/compile/internal/gc".OCOM' -to OBITNOT
gorename -from '"cmd/compile/internal/gc".OMINUS' -to ONEG
gorename -from '"cmd/compile/internal/gc".OIND' -to ODEREF
gorename -from '"cmd/compile/internal/gc".OARRAYBYTESTR' -to OBYTES2STR
gorename -from '"cmd/compile/internal/gc".OARRAYBYTESTRTMP' -to OBYTES2STRTMP
gorename -from '"cmd/compile/internal/gc".OARRAYRUNESTR' -to ORUNES2STR
gorename -from '"cmd/compile/internal/gc".OSTRARRAYBYTE' -to OSTR2BYTES
gorename -from '"cmd/compile/internal/gc".OSTRARRAYBYTETMP' -to OSTR2BYTESTMP
gorename -from '"cmd/compile/internal/gc".OSTRARRAYRUNE' -to OSTR2RUNES
gorename -from '"cmd/compile/internal/gc".Etop' -to ctxStmt
gorename -from '"cmd/compile/internal/gc".Erv' -to ctxExpr
gorename -from '"cmd/compile/internal/gc".Ecall' -to ctxCallee
gorename -from '"cmd/compile/internal/gc".Efnstruct' -to ctxMultiOK
gorename -from '"cmd/compile/internal/gc".Easgn' -to ctxAssign
gorename -from '"cmd/compile/internal/gc".Ecomplit' -to ctxCompLit
Not altered: parameters and local variables (mostly in typecheck.go) named top,
which should probably now be called ctx (and which should probably have a named type).
Also not altered: Field called Top in gc.Func.
gorename -from '"cmd/compile/internal/gc".Node.Isddd' -to IsDDD
gorename -from '"cmd/compile/internal/gc".Node.SetIsddd' -to SetIsDDD
gorename -from '"cmd/compile/internal/gc".nodeIsddd' -to nodeIsDDD
gorename -from '"cmd/compile/internal/types".Field.Isddd' -to IsDDD
gorename -from '"cmd/compile/internal/types".Field.SetIsddd' -to SetIsDDD
gorename -from '"cmd/compile/internal/types".fieldIsddd' -to fieldIsDDD
Not altered: function gc.hasddd, params and local variables called isddd
Also not altered: fmt.go prints nodes using "isddd(%v)".
cd cmd/compile/internal/gc; go generate
I then manually found impacted comments using exact string match
and fixed them up by hand. The comment changes were trivial.
Passes toolstash-check.
Fixes#27167. If this experiment is deemed a success,
we will open a new tracking issue for renames to do
at the end of the 1.13 cycles.
Change-Id: I2dc541533d2ab0d06cb3d31d65df205ecfb151e8
Reviewed-on: https://go-review.googlesource.com/c/150140
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Like the conv helper function but for creating OCONVNOP nodes
instead of OCONV nodes.
passes toolstash -cmp
Change-Id: Ib93ffe66590ebaa2b4fa552c81f1a2902e789d8e
Reviewed-on: https://go-review.googlesource.com/112597
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Currently, range loops over slices and arrays are compiled roughly
like:
for i, x := range s { b }
⇓
for i, _n, _p := 0, len(s), &s[0]; i < _n; i, _p = i+1, _p + unsafe.Sizeof(s[0]) { b }
⇓
i, _n, _p := 0, len(s), &s[0]
goto cond
body:
{ b }
i, _p = i+1, _p + unsafe.Sizeof(s[0])
cond:
if i < _n { goto body } else { goto end }
end:
The problem with this lowering is that _p may temporarily point past
the end of the allocation the moment before the loop terminates. Right
now this isn't a problem because there's never a safe-point during
this brief moment.
We're about to introduce safe-points everywhere, so this bad pointer
is going to be a problem. We could mark the increment as an unsafe
block, but this inhibits reordering opportunities and could result in
infrequent safe-points if the body is short.
Instead, this CL fixes this by changing how we compile range loops to
never produce this past-the-end pointer. It changes the lowering to
roughly:
i, _n, _p := 0, len(s), &s[0]
if i < _n { goto body } else { goto end }
top:
_p += unsafe.Sizeof(s[0])
body:
{ b }
i++
if i < _n { goto top } else { goto end }
end:
Notably, the increment is split into two parts: we increment the index
before checking the condition, but increment the pointer only *after*
the condition check has succeeded.
The implementation builds on the OFORUNTIL construct that was
introduced during the loop preemption experiments, since OFORUNTIL
places the increment and condition after the loop body. To support the
extra "late increment" step, we further define OFORUNTIL's "List"
field to contain the late increment statements. This makes all of this
a relatively small change.
This depends on the improvements to the prove pass in CL 102603. With
the current lowering, bounds-check elimination knows that i < _n in
the body because the body block is dominated by the cond block. In the
new lowering, deriving this fact requires detecting that i < _n on
*both* paths into body and hence is true in body. CL 102603 made prove
able to detect this.
The code size effect of this is minimal. The cmd/go binary on
linux/amd64 increases by 0.17%. Performance-wise, this actually
appears to be a net win, though it's mostly noise:
name old time/op new time/op delta
BinaryTree17-12 2.80s ± 0% 2.61s ± 1% -6.88% (p=0.000 n=20+18)
Fannkuch11-12 2.41s ± 0% 2.42s ± 0% +0.05% (p=0.005 n=20+20)
FmtFprintfEmpty-12 41.6ns ± 5% 41.4ns ± 6% ~ (p=0.765 n=20+19)
FmtFprintfString-12 69.4ns ± 3% 69.3ns ± 1% ~ (p=0.084 n=19+17)
FmtFprintfInt-12 76.1ns ± 1% 77.3ns ± 1% +1.57% (p=0.000 n=19+19)
FmtFprintfIntInt-12 122ns ± 2% 123ns ± 3% +0.95% (p=0.015 n=20+20)
FmtFprintfPrefixedInt-12 153ns ± 2% 151ns ± 3% -1.27% (p=0.013 n=20+20)
FmtFprintfFloat-12 215ns ± 0% 216ns ± 0% +0.47% (p=0.000 n=20+16)
FmtManyArgs-12 486ns ± 1% 498ns ± 0% +2.40% (p=0.000 n=20+17)
GobDecode-12 6.43ms ± 0% 6.50ms ± 0% +1.08% (p=0.000 n=18+19)
GobEncode-12 5.43ms ± 1% 5.47ms ± 0% +0.76% (p=0.000 n=20+20)
Gzip-12 218ms ± 1% 218ms ± 1% ~ (p=0.883 n=20+20)
Gunzip-12 38.8ms ± 0% 38.9ms ± 0% ~ (p=0.644 n=19+19)
HTTPClientServer-12 76.2µs ± 1% 76.4µs ± 2% ~ (p=0.218 n=20+20)
JSONEncode-12 12.2ms ± 0% 12.3ms ± 1% +0.45% (p=0.000 n=19+19)
JSONDecode-12 54.2ms ± 1% 53.3ms ± 0% -1.67% (p=0.000 n=20+20)
Mandelbrot200-12 3.71ms ± 0% 3.71ms ± 0% ~ (p=0.143 n=19+20)
GoParse-12 3.22ms ± 0% 3.19ms ± 1% -0.72% (p=0.000 n=20+20)
RegexpMatchEasy0_32-12 76.7ns ± 1% 75.8ns ± 1% -1.19% (p=0.000 n=20+17)
RegexpMatchEasy0_1K-12 245ns ± 1% 243ns ± 0% -0.72% (p=0.000 n=18+17)
RegexpMatchEasy1_32-12 71.9ns ± 0% 71.7ns ± 1% -0.39% (p=0.006 n=12+18)
RegexpMatchEasy1_1K-12 358ns ± 1% 354ns ± 1% -1.13% (p=0.000 n=20+19)
RegexpMatchMedium_32-12 105ns ± 2% 105ns ± 1% -0.63% (p=0.007 n=19+20)
RegexpMatchMedium_1K-12 31.9µs ± 1% 31.9µs ± 1% ~ (p=1.000 n=17+17)
RegexpMatchHard_32-12 1.51µs ± 1% 1.52µs ± 2% +0.46% (p=0.042 n=18+18)
RegexpMatchHard_1K-12 45.3µs ± 1% 45.5µs ± 2% +0.44% (p=0.029 n=18+19)
Revcomp-12 388ms ± 1% 385ms ± 0% -0.57% (p=0.000 n=19+18)
Template-12 63.0ms ± 1% 63.3ms ± 0% +0.50% (p=0.000 n=19+20)
TimeParse-12 309ns ± 1% 307ns ± 0% -0.62% (p=0.000 n=20+20)
TimeFormat-12 328ns ± 0% 333ns ± 0% +1.35% (p=0.000 n=19+19)
[Geo mean] 47.0µs 46.9µs -0.20%
(https://perf.golang.org/search?q=upload:20180326.1)
For #10958.
For #24543.
Change-Id: Icbd52e711fdbe7938a1fea3e6baca1104b53ac3a
Reviewed-on: https://go-review.googlesource.com/102604
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: David Chase <drchase@google.com>
replace map clears of the form:
for k := range m {
delete(m, k)
}
(where m is map with key type that is reflexive for ==)
with a new runtime function that clears the maps backing
array with a memclr and reinitializes the hmap struct.
Map key types that for example contain floats are not
replaced by this optimization since NaN keys cannot
be deleted from maps using delete.
name old time/op new time/op delta
GoMapClear/Reflexive/1 92.2ns ± 1% 47.1ns ± 2% -48.89% (p=0.000 n=9+9)
GoMapClear/Reflexive/10 108ns ± 1% 48ns ± 2% -55.68% (p=0.000 n=10+10)
GoMapClear/Reflexive/100 303ns ± 2% 110ns ± 3% -63.56% (p=0.000 n=10+10)
GoMapClear/Reflexive/1000 3.58µs ± 3% 1.23µs ± 2% -65.49% (p=0.000 n=9+10)
GoMapClear/Reflexive/10000 28.2µs ± 3% 10.3µs ± 2% -63.55% (p=0.000 n=9+10)
GoMapClear/NonReflexive/1 121ns ± 2% 124ns ± 7% ~ (p=0.097 n=10+10)
GoMapClear/NonReflexive/10 137ns ± 2% 139ns ± 3% +1.53% (p=0.033 n=10+10)
GoMapClear/NonReflexive/100 331ns ± 3% 334ns ± 2% ~ (p=0.342 n=10+10)
GoMapClear/NonReflexive/1000 3.64µs ± 3% 3.64µs ± 2% ~ (p=0.887 n=9+10)
GoMapClear/NonReflexive/10000 28.1µs ± 2% 28.4µs ± 3% ~ (p=0.247 n=10+10)
Fixes#20138
Change-Id: I181332a8ef434a4f0d89659f492d8711db3f3213
Reviewed-on: https://go-review.googlesource.com/110055
Reviewed-by: Keith Randall <khr@golang.org>
Rename memclrrange to signify that it does not handle
all types of range clears.
Simplify checks to detect the range clear idiom for
arrays and slices.
Add tests to verify the optimization for the slice
range clear idiom is being applied by the compiler.
Change-Id: I5c3b7c9a479699ebdb4c407fde692f30f377860c
Reviewed-on: https://go-review.googlesource.com/110477
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This reduces the API surface of Type slightly (for #25056), but also
makes it more consistent with the reflect and go/types APIs.
Passes toolstash-check.
Change-Id: Ief9a8eb461ae6e88895f347e2a1b7b8a62423222
Reviewed-on: https://go-review.googlesource.com/109138
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Focus on "isfoo" funcs that take a *Node, and conver them to isFoo
methods instead. This makes for more idiomatic Go code, and also more
readable func names.
Found candidates with grep, and applied most changes with sed. The funcs
chosen were isgoconst, isnil, and isblank. All had the same signature,
func(*Node) bool.
While at it, camelCase the isliteral and iszero function names. Don't
move these to methods, as they are only used in the backend part of gc,
which might one day be split into a separate package.
Passes toolstash -cmp on std cmd.
Change-Id: I4df081b12d36c46c253167c8841c5a841f1c5a16
Reviewed-on: https://go-review.googlesource.com/105555
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
This experiment has gone stale. It causes a type-checking failure
because the condition of the OIF produced by range loop lowering has
type "untyped bool". Fix this by typechecking the whole OIF statement,
not just its condition.
This doesn't quite fix the whole experiment, but it gets further.
Something about preemption point insertion is causing failures like
"internal compiler error: likeliness prediction 1 for block b10 with 1
successors" in cmd/compile/internal/gc.
Change-Id: I7d80d618d7c91c338bf5f2a8dc174d582a479df3
Reviewed-on: https://go-review.googlesource.com/102157
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
We already require expressions to have already been typechecked before
reaching walk. Moreover, all untyped expressions should have been
converted to their default type by walk.
However, in practice, we've been somewhat sloppy and inconsistent
about ensuring this. In particular, a lot of AST rewrites ended up
leaving untyped bool expressions scattered around. These likely aren't
harmful in practice, but it seems worth cleaning up.
The two most common cases addressed by this CL are:
1) When generating OIF and OFOR nodes, we would often typecheck the
conditional expression, but not apply defaultlit to force it to the
expression's default type.
2) When rewriting string comparisons into more fundamental primitives,
we were simply overwriting r.Type with the desired type, which didn't
propagate the type to nested subexpressions. These are fixed by
utilizing finishcompare, which correctly handles this (and is already
used by other comparison lowering rewrites).
Lastly, walkexpr is extended to assert that it's not called on untyped
expressions.
Fixes#23834.
Change-Id: Icbd29648a293555e4015d3b06a95a24ccbd3f790
Reviewed-on: https://go-review.googlesource.com/98337
Reviewed-by: Robert Griesemer <gri@golang.org>
Split typecheckrange into two, separating the bigger chunk of code that
takes care of the range expression. It had to sometimes exit early,
which was done via a goto in the larger func. This lets us simplify many
declarations and the flow of the code. While at it, also replace the
toomany int with a bool.
In the case of walkselect, split it into two funcs too since using a
defer for all the trailing work would be a bit much. It also lets us
simplify the declarations and the flow of the code, since now
walkselectcases has a narrower scope and straightforward signature.
Also replace the gotos in typecheckaste with a lineno defer.
Passes toolstash -cmp on std cmd.
Change-Id: Iacfaa0a34c987c44f180a792c473558785cf6823
Reviewed-on: https://go-review.googlesource.com/72374
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
These are likely from the time when gc was written in C. There is no
need for any of these to be passed pointers, as the previous values are
not kept in any way, and the pointers are never nil. Others were left
untouched as they fell into one of these useful cases.
While at it, also turn some 0/1 integers into booleans.
Passes toolstash -cmp on std cmd.
Change-Id: Id3a9c9e84ef89536c4dc69a7fdbacd0fd7a76a9b
Reviewed-on: https://go-review.googlesource.com/72990
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Focused on ranges, selects and switches for this one.
While at it, simplify some vars in typecheckselect.
Updates #19683.
Change-Id: Ib6aabe0f6826cb1930483aeb4bb2de1ff8052d9e
Reviewed-on: https://go-review.googlesource.com/69690
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Refactor walkrange to treat "for _ = range a" as "for range a".
This avoids generating some later discarded nodes in the compiler.
Passes toolstash -cmp.
Change-Id: Ifb2e1ca3b8519cbb67e8ad5aad514af9d18f1ec4
Reviewed-on: https://go-review.googlesource.com/61017
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Previously the type was first set to uint8 and then corrected
later in walkrange.
Change-Id: I9e4b597710e8a5fad39dde035df85676bc8d2874
Reviewed-on: https://go-review.googlesource.com/61032
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Loops of the form "for i,e := range" needed to have their
condition rotated to the "bottom" for the preemptible loops
GOEXPERIMENT, but this caused a performance regression
because it degraded bounds check removal. For now, make
the loop rotation/guarding conditional on the experiment.
Fixes#20711.
Updates #10958.
Change-Id: Icfba14cb3b13a910c349df8f84838cf4d9d20cf6
Reviewed-on: https://go-review.googlesource.com/46410
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
- created new package cmd/compile/internal/types
- moved Pkg, Sym, Type to new package
- to break cycles, for now we need the (ugly) types/utils.go
file which contains a handful of functions that must be installed
early by the gc frontend
- to break cycles, for now we need two functions to convert between
*gc.Node and *types.Node (the latter is a dummy type)
- adjusted the gc's code to use the new package and the conversion
functions as needed
- made several Pkg, Sym, and Type methods functions as needed
- renamed constructors typ, typPtr, typArray, etc. to types.New,
types.NewPtr, types.NewArray, etc.
Passes toolstash-check -all.
Change-Id: I8adfa5e85c731645d0a7fd2030375ed6ebf54b72
Reviewed-on: https://go-review.googlesource.com/39855
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
This makes the overall naming and use of the functions
to create a Type more consistent.
Passes toolstash -cmp.
Change-Id: Ie0d40b42cc32b5ecf5f20502675a225038ea40e4
Reviewed-on: https://go-review.googlesource.com/38354
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
After benchmarking with a compiler modified to have better
spill location, it became clear that this method of checking
was actually faster on (at least) two different architectures
(ppc64 and amd64) and it also provides more timely interruption
of loops.
This change adds a modified FOR loop node "FORUNTIL" that
checks after executing the loop body instead of before (i.e.,
always at least once). This ensures that a pointer past the
end of a slice or array is not made visible to the garbage
collector.
Without the rescheduling checks inserted, the restructured
loop from this change apparently provides a 1% geomean
improvement on PPC64 running the go1 benchmarks; the
improvement on AMD64 is only 0.12%.
Inserting the rescheduling check exposed some peculiar bug
with the ssa test code for s390x; this was updated based on
initial code actually generated for GOARCH=s390x to use
appropriate OpArg, OpAddr, and OpVarDef.
NaCl is disabled in testing.
Change-Id: Ieafaa9a61d2a583ad00968110ef3e7a441abca50
Reviewed-on: https://go-review.googlesource.com/36206
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
runtime.memclr* functions have signatures
func memclrNoHeapPointers(ptr unsafe.Pointer, n uintptr)
func memclrHasPointers(ptr unsafe.Pointer, n uintptr)
Update compiler's copy. Also teach gc/mkbuiltin.go to handle
unsafe.Pointer. The import statement and its support is not
really necessary, but just to make it look like real Go code.
Fixes#19185.
Change-Id: I251d02571fde2716d4727e31e04d56ec04b6f22a
Reviewed-on: https://go-review.googlesource.com/37257
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Add Set3 function to complement existing Set1 and Set2 functions.
Consistently use Set1, Set2 and Set3 for []*Node instead of Set where applicable.
Add SetFirst and SetSecond for setting elements of []*Node to mirror
First and Second for accessing elements in []*Node.
Replace uses of Index by First and Second and
SetIndex with SetFirst and SetSecond where applicable.
Passes toolstash -cmp.
Change-Id: I8255aae768cf245c8f93eec2e9efa05b8112b4e5
Reviewed-on: https://go-review.googlesource.com/37430
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
If a slice's backing store has pointers, we need to lower clears of
that slice to memclrHasPointers instead of memclrNoHeapPointers.
Updates #17503.
Change-Id: I20750e4bf57f7b8862f3d898bfb32d964b91d07b
Reviewed-on: https://go-review.googlesource.com/31450
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Since barrier-less memclr is only safe in very narrow circumstances,
this commit renames memclr to avoid accidentally calling memclr on
typed memory. This can cause subtle, non-deterministic bugs, so it's
worth some effort to prevent. In the near term, this will also prevent
bugs creeping in from any concurrent CLs that add calls to memclr; if
this happens, whichever patch hits master second will fail to compile.
This also adds the other new memclr variants to the compiler's
builtin.go to minimize the churn on that binary blob. We'll use these
in future commits.
Updates #17503.
Change-Id: I00eead049f5bd35ca107ea525966831f3d1ed9ca
Reviewed-on: https://go-review.googlesource.com/31369
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Copies utf8 constants and EncodeRune implementation from unicode/utf8.
Adds a new decoderune implementation that is used by the compiler
in code generated for ranging over strings. It does not handle
ASCII runes since these are handled directly before calls to decoderune.
The DecodeRuneInString implementation from unicode/utf8 is not used
since it uses a lookup table that would increase the use of cpu caches.
Adds more tests that check decoding of valid and invalid utf8 sequences.
name old time/op new time/op delta
RuneIterate/range2/ASCII-4 7.45ns ± 2% 7.45ns ± 1% ~ (p=0.634 n=16+16)
RuneIterate/range2/Japanese-4 53.5ns ± 1% 49.2ns ± 2% -8.03% (p=0.000 n=20+20)
RuneIterate/range2/MixedLength-4 46.3ns ± 1% 41.0ns ± 2% -11.57% (p=0.000 n=20+20)
new:
"".decoderune t=1 size=423 args=0x28 locals=0x0
old:
"".charntorune t=1 size=666 args=0x28 locals=0x0
Change-Id: I1df1fdb385bb9ea5e5e71b8818ea2bf5ce62de52
Reviewed-on: https://go-review.googlesource.com/28490
Run-TryBot: Martin Möhrmann <martisch@uos.de>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Follow up to CL 29134. Generated with gofmt -r 'Nod -> nod', plus
three manual adjustments to the comments in syntax/parser.go
Change-Id: I02920f7ab10c70b6e850457b42d5fe35f1f3821a
Reviewed-on: https://go-review.googlesource.com/29136
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
After the removal of the old backend many types are no longer referenced
outside internal/gc. Make these functions private so that tools like
honnef.co/go/unused can spot when they become dead code. In doing so
this CL identified several previously public helpers which are no longer
used, so removes them.
This should be the last of the public functions.
Change-Id: I7e9c4e72f86f391b428b9dddb6f0d516529706c3
Reviewed-on: https://go-review.googlesource.com/29134
Run-TryBot: Dave Cheney <dave@cheney.net>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
After the removal of the old backend many types are no longer referenced
outside internal/gc. Make these functions private so that tools like
honnef.co/go/unused can spot when they become dead code. In doing so
this CL identified several previously public helpers which are no longer
used, so removes them.
Change-Id: Idc2d485f493206de9d661bd3cb0ecb4684177b32
Reviewed-on: https://go-review.googlesource.com/29133
Run-TryBot: Dave Cheney <dave@cheney.net>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
- also consistently use %v instead of %s when we have a (gc) Formatter
- rewrite done automatically using Formats test in -u (update) mode
- manual update of format strings that were not single string constants
- updated fmt.go, fmt_test.go accordingly
- fmt_test: permit "%T" always
Change-Id: I8f0704286aba5704600ad0c4a4484005b79b905d
Reviewed-on: https://go-review.googlesource.com/28954
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
