In order to improve the line numbering for debuggers,
it's necessary to trace lines through compilation.
This makes it (much) easier to follow.

The format of the last column of the ssa.html output was
also changed to reduce the spamminess of the file name,
which is usually the same and makes it far harder to read
instructions and line numbers, and to make it wider and also
able to break words when wrapping (long path names still
can push off the end otherwise; side-to-side scrolling was
tried but was more annoying than the occasional wrapped
line).

Sample output now, where [...] is elision for sake of making
the CL character-counter happy -- and the (##) line numbers
are rendered in italics and a smaller font (11 point) under
control of a CSS class "line-number".

genssa
      # /Users/drchase/[...]/ssa/testdata/hist.go
      00000 (35) TEXT	"".main(SB)
      00001 (35) FUNCDATA	$0, gclocals·7be4bb[...]1e8b(SB)
      00002 (35) FUNCDATA	$1, gclocals·9ab98a[...]4568(SB)
v920  00003 (36) LEAQ	""..autotmp_31-640(SP), DI
v858  00004 (36) XORPS	X0, X0
v6    00005 (36) LEAQ	-48(DI), DI
v6    00006 (36) DUFFZERO	$277
v576  00007 (36) LEAQ	""..autotmp_31-640(SP), AX
v10   00008 (36) TESTB	AX, (AX)
b1    00009 (36) JMP	10

and from an earlier phase:

b18: ← b17
v242 (47) = Copy <mem> v238
v243 (47) = VarKill <mem> {.autotmp_16} v242
v244 (48) = Addr <**bufio.Scanner> {scanner} v2
v245 (48) = Load <*bufio.Scanner> v244 v243
[...]
v279 (49) = Store <mem> {int64} v277 v276 v278
v280 (49) = Addr <*error> {.autotmp_18} v2
v281 (49) = Load <error> v280 v279
v282 (49) = Addr <*error> {err} v2
v283 (49) = VarDef <mem> {err} v279
v284 (49) = Store <mem> {error} v282 v281 v283
v285 (47) = VarKill <mem> {.autotmp_18} v284
v286 (47) = VarKill <mem> {.autotmp_17} v285
v287 (50) = Addr <*error> {err} v2
v288 (50) = Load <error> v287 v286
v289 (50) = NeqInter <bool> v288 v51
If v289 → b21 b22 (line 50)

Change-Id: I3f46310918f965761f59e6f03ea53067237c28a8
Reviewed-on: https://go-review.googlesource.com/69591
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>