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Josh Bleecher Snyder 0bc94a8864 cmd/compile: when inlining ==, don’t take the address of the values 
This CL reworks walkcompare for clarity and concision.
It also makes one significant functional change.
(The functional change is hard to separate cleanly
from the cleanup, so I just did them together.)
When inlining and unrolling an equality comparison
for a small struct or array, compare the elements like:

a[0] == b[0] && a[1] == b[1]

rather than

pa := &a
pb := &b
pa[0] == pb[0] && pa[1] == pb[1]

The result is the same, but taking the address
and working through the indirect
forces the backends to generate less efficient code.

This is only an improvement with the SSA backend.
However, every port but s390x now has a working
SSA backend, and switching to the SSA backend
by default everywhere is a priority for Go 1.8.
It thus seems reasonable to start to prioritize
SSA performance over the old backend.

Updates #15303


Sample code:

type T struct {
	a, b int8
}

func g(a T) bool {
	return a == T{1, 2}
}


SSA before:

"".g t=1 size=80 args=0x10 locals=0x8
	0x0000 00000 (badeq.go:7)	TEXT	"".g(SB), $8-16
	0x0000 00000 (badeq.go:7)	SUBQ	$8, SP
	0x0004 00004 (badeq.go:7)	FUNCDATA	$0, gclocals·23e8278e2b69a3a75fa59b23c49ed6ad(SB)
	0x0004 00004 (badeq.go:7)	FUNCDATA	$1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
	0x0004 00004 (badeq.go:8)	MOVBLZX	"".a+16(FP), AX
	0x0009 00009 (badeq.go:8)	MOVB	AL, "".autotmp_0+6(SP)
	0x000d 00013 (badeq.go:8)	MOVBLZX	"".a+17(FP), AX
	0x0012 00018 (badeq.go:8)	MOVB	AL, "".autotmp_0+7(SP)
	0x0016 00022 (badeq.go:8)	MOVB	$0, "".autotmp_1+4(SP)
	0x001b 00027 (badeq.go:8)	MOVB	$1, "".autotmp_1+4(SP)
	0x0020 00032 (badeq.go:8)	MOVB	$2, "".autotmp_1+5(SP)
	0x0025 00037 (badeq.go:8)	MOVBLZX	"".autotmp_0+6(SP), AX
	0x002a 00042 (badeq.go:8)	MOVBLZX	"".autotmp_1+4(SP), CX
	0x002f 00047 (badeq.go:8)	CMPB	AL, CL
	0x0031 00049 (badeq.go:8)	JNE	70
	0x0033 00051 (badeq.go:8)	MOVBLZX	"".autotmp_0+7(SP), AX
	0x0038 00056 (badeq.go:8)	CMPB	AL, $2
	0x003a 00058 (badeq.go:8)	SETEQ	AL
	0x003d 00061 (badeq.go:8)	MOVB	AL, "".~r1+24(FP)
	0x0041 00065 (badeq.go:8)	ADDQ	$8, SP
	0x0045 00069 (badeq.go:8)	RET
	0x0046 00070 (badeq.go:8)	MOVB	$0, AL
	0x0048 00072 (badeq.go:8)	JMP	61

SSA after:

"".g t=1 size=32 args=0x10 locals=0x0
	0x0000 00000 (badeq.go:7)	TEXT	"".g(SB), $0-16
	0x0000 00000 (badeq.go:7)	NOP
	0x0000 00000 (badeq.go:7)	NOP
	0x0000 00000 (badeq.go:7)	FUNCDATA	$0, gclocals·23e8278e2b69a3a75fa59b23c49ed6ad(SB)
	0x0000 00000 (badeq.go:7)	FUNCDATA	$1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
	0x0000 00000 (badeq.go:8)	MOVBLZX	"".a+8(FP), AX
	0x0005 00005 (badeq.go:8)	CMPB	AL, $1
	0x0007 00007 (badeq.go:8)	JNE	25
	0x0009 00009 (badeq.go:8)	MOVBLZX	"".a+9(FP), CX
	0x000e 00014 (badeq.go:8)	CMPB	CL, $2
	0x0011 00017 (badeq.go:8)	SETEQ	AL
	0x0014 00020 (badeq.go:8)	MOVB	AL, "".~r1+16(FP)
	0x0018 00024 (badeq.go:8)	RET
	0x0019 00025 (badeq.go:8)	MOVB	$0, AL
	0x001b 00027 (badeq.go:8)	JMP	20


Change-Id: I120185d58012b7bbcdb1ec01225b5b08d0855d86
Reviewed-on: https://go-review.googlesource.com/22277
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
 		2016-08-25 17:51:10 +00:00
..
bench all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
bugs all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
chan all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
ddd2.dir all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
dwarf
…
fixedbugs cmd/compile: when inlining ==, don’t take the address of the values 2016-08-25 17:51:10 +00:00
import2.dir all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
import4.dir test: adjust gccgo expected import errors 2015-10-07 14:37:44 +00:00
interface cmd/compile: inline x, ok := y.(T) where T is a scalar 2016-08-17 01:12:01 +00:00
intrinsic.dir cmd/compile: clean up ctz ops 2016-08-23 23:45:12 +00:00
ken all: fix spelling mistakes 2016-04-03 17:03:15 +00:00
method4.dir
…
safe
…
stress all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
syntax cmd/compile/internal/syntax: match old parser errors and line numbers 2016-08-19 01:10:21 +00:00
uintptrescapes.dir cmd/compile, syscall: add //go:uintptrescapes comment, and use it 2016-07-06 20:48:41 +00:00
64bit.go
…
235.go
…
alg.go test: add test that required algs get generated 2016-04-24 21:36:52 +00:00
alias.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
alias1.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
append.go
…
args.go
…
assign.go
…
assign1.go
…
atomicload.go cmd/compile: keep value use counts in SSA 2016-03-17 04:20:02 +00:00
bigalg.go
…
bigmap.go
…
blank.go
…
blank1.go cmd/compile: don't allow blank method declarations on builtins 2015-12-02 18:26:38 +00:00
bom.go
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bombad.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
bounds.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
chancap.go
…
chanlinear.go
…
char_lit.go
…
char_lit1.go
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checkbce.go cmd/compile: optimize integer "in range" expressions 2016-08-25 03:49:16 +00:00
clearfat.go
…
closedchan.go
…
closure.go
…
closure1.go
…
closure2.go
…
cmp.go
…
cmp6.go
…
cmplx.go
…
cmplxdivide.c all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
cmplxdivide.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
cmplxdivide1.go
…
complit.go
…
complit1.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
compos.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
const.go
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const1.go
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const2.go
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const3.go
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const4.go
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const5.go
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const6.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
convT2X.go
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convert.go
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convert1.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
convert3.go
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convlit.go
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convlit1.go
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copy.go
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crlf.go
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ddd.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
ddd1.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
ddd2.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
decl.go
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declbad.go
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defer.go
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deferfin.go
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deferprint.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
deferprint.out
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divide.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
divmod.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
empty.go
…
env.go
…
eof.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
eof1.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
errchk cmd/vet: make checking example names in _test packages more robust 2016-06-28 22:09:00 +00:00
escape.go
…
escape2.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
escape2n.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
escape3.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
escape4.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
escape5.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
escape_array.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
escape_because.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
escape_calls.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
escape_closure.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
escape_field.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
escape_iface.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
escape_indir.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
escape_level.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
escape_map.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
escape_param.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
escape_slice.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
escape_struct_param1.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
escape_struct_param2.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
escape_struct_return.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
fibo.go
…
finprofiled.go runtime: fix finalization and profiling of tiny allocations 2015-11-03 18:57:18 +00:00
float_lit.go
…
float_lit2.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
float_lit3.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
floatcmp.go
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for.go
…
func.go
…
func1.go
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func2.go
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func3.go
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func4.go
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func5.go
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func6.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
func7.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
func8.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
funcdup.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
funcdup2.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
gc.go
…
gc1.go
…
gc2.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
gcstring.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
goprint.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
goprint.out
…
goto.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
heapsampling.go test: really force heap profile update in heapsampling.go 2015-11-12 18:32:13 +00:00
helloworld.go
…
helloworld.out
…
if.go
…
import.go
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import1.go
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import2.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
import4.go
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import5.go
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index.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
index0.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
index1.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
index2.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
indirect.go
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indirect1.go
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init.go
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init1.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
initcomma.go
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initialize.go
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initializerr.go
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initloop.go
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inline.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
int_lit.go
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intcvt.go
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intrinsic.go cmd/compile: added some intrinsics to SSA back end 2016-03-28 16:29:59 +00:00
iota.go
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label.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
label1.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
linkmain.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
linkmain_run.go test: fix linkmain test 2015-12-17 23:36:13 +00:00
linkobj.go cmd/compile: add -linkobj flag to allow writing object file in two parts 2016-05-09 17:31:45 +00:00
linkx.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
linkx_run.go test: print output on link -X failure 2016-04-20 17:37:35 +00:00
literal.go
…
live.go cmd/compile: ppc64le working, not optimized enough 2016-08-18 16:34:47 +00:00
live1.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
live2.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
live_ssa.go [dev.ssa] cmd/compile, etc.: more ARM64 optimizations, and enable SSA by default 2016-08-15 03:37:34 +00:00
live_syscall.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
loopbce.go cmd/compile: bce when max and limit are consts 2016-04-11 16:01:22 +00:00
mallocfin.go
…
map.go
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map1.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
maplinear.go
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method.go
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method1.go cmd/compile: ignore receiver parameters in Eqtype 2016-03-17 00:38:15 +00:00
method2.go
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method3.go
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method4.go
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method5.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
named.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
named1.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
nil.go
…
nilcheck.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
nilptr.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
nilptr2.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
nilptr3.go test: add test for CL 26831 2016-08-17 14:50:34 +00:00
nilptr3_ssa.go test: add test for CL 26831 2016-08-17 14:50:34 +00:00
nilptr4.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
nosplit.go cmd/compile: ppc64le working, not optimized enough 2016-08-18 16:34:47 +00:00
nul1.go cmd/compile/internal/syntax: match old parser errors and line numbers 2016-08-19 01:10:21 +00:00
opt_branchlikely.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
parentype.go
…
peano.go
…
phiopt.go cmd/compile: introduce bool operations. 2016-04-25 20:43:04 +00:00
print.go
…
print.out
…
printbig.go
…
printbig.out
…
prove.go cmd/compile: transform some Phis into Or8. 2016-04-19 22:04:30 +00:00
range.go
…
recover.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
recover1.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
recover2.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
recover3.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
recover4.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
reflectmethod1.go cmd/compile: track reflect.Type.Method in deadcode 2016-03-11 21:19:20 +00:00
reflectmethod2.go cmd/compile: track reflect.Type.Method in deadcode 2016-03-11 21:19:20 +00:00
reflectmethod3.go cmd/compile: track reflect.Type.Method in deadcode 2016-03-11 21:19:20 +00:00
reflectmethod4.go cmd/link: treat reflect.Value.Method like Call 2016-03-11 22:07:02 +00:00
rename.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
rename1.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
reorder.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
reorder2.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
return.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
rotate.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
rotate0.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
rotate1.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
rotate2.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
rotate3.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
run.go test: remove unused variable 2016-08-16 21:46:54 +00:00
rune.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
runtime.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
shift1.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
shift2.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
sieve.go
…
sigchld.go
…
sigchld.out
…
simassign.go
…
sinit.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
sinit_run.go
…
sizeof.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
slice3.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
slice3err.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
slicecap.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
sliceopt.go cmd/compile: ppc64le working, not optimized enough 2016-08-18 16:34:47 +00:00
solitaire.go
…
stack.go
…
strength.go cmd/compile: generalize strength reduction of mulq 2016-03-30 22:27:13 +00:00
string_lit.go
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stringrange.go
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struct0.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
switch.go
…
switch2.go cmd/compile/internal/syntax: match old parser errors and line numbers 2016-08-19 01:10:21 +00:00
switch3.go
…
switch4.go
…
switch5.go cmd/compile: use a map to track const switch cases 2016-08-23 05:28:33 +00:00
switch6.go cmd/compile: set correct line number for multiple defaults in switch error 2016-08-22 19:56:06 +00:00
tinyfin.go runtime: fix finalization and profiling of tiny allocations 2015-11-03 18:57:18 +00:00
torture.go
…
turing.go
…
typecheck.go
…
typecheckloop.go
…
typeswitch.go
…
typeswitch1.go
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typeswitch2.go
…
typeswitch3.go
…
uintptrescapes.go cmd/compile, syscall: add //go:uintptrescapes comment, and use it 2016-07-06 20:48:41 +00:00
uintptrescapes2.go cmd/compile, syscall: add //go:uintptrescapes comment, and use it 2016-07-06 20:48:41 +00:00
undef.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
utf.go
…
varerr.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
varinit.go
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writebarrier.go all: make copyright headers consistent with one space after period 2016-05-02 13:43:18 +00:00
zerodivide.go
…