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The Go programming language
84f291b1bd
Input code like
0000 (x.go:2) TEXT main+0(SB),$36-0
0001 (x.go:3) MOVL $5,i+-8(SP)
0002 (x.go:3) MOVL $0,i+-4(SP)
0003 (x.go:4) MOVL $1,BX
0004 (x.go:4) MOVL i+-8(SP),AX
0005 (x.go:4) MOVL i+-4(SP),DX
0006 (x.go:4) MOVL AX,autotmp_0000+-20(SP)
0007 (x.go:4) MOVL DX,autotmp_0000+-16(SP)
0008 (x.go:4) MOVL autotmp_0000+-20(SP),CX
0009 (x.go:4) CMPL autotmp_0000+-16(SP),$0
0010 (x.go:4) JNE ,13
0011 (x.go:4) CMPL CX,$32
0012 (x.go:4) JCS ,14
0013 (x.go:4) MOVL $0,BX
0014 (x.go:4) SHLL CX,BX
0015 (x.go:4) MOVL BX,x+-12(SP)
0016 (x.go:5) MOVL x+-12(SP),AX
0017 (x.go:5) CDQ ,
0018 (x.go:5) MOVL AX,autotmp_0001+-28(SP)
0019 (x.go:5) MOVL DX,autotmp_0001+-24(SP)
0020 (x.go:5) MOVL autotmp_0001+-28(SP),AX
0021 (x.go:5) MOVL autotmp_0001+-24(SP),DX
0022 (x.go:5) MOVL AX,(SP)
0023 (x.go:5) MOVL DX,4(SP)
0024 (x.go:5) CALL ,runtime.printint+0(SB)
0025 (x.go:5) CALL ,runtime.printnl+0(SB)
0026 (x.go:6) RET ,
is problematic because the liveness range for
autotmp_0000 (0006-0009) is nested completely
inside a span where BX holds a live value (0003-0015).
Because the register allocator only looks at 0006-0009
to see which registers are used, it misses the fact that
BX is unavailable and uses it anyway.
The n->pun = anyregalloc() check in tempname is
a workaround for this bug, but I hit it again because
I did the tempname call before allocating BX, even
though I then used the temporary after storing in BX.
This should fix the real bug, and then we can remove
the workaround in tempname.
The code creates pseudo-variables for each register
and includes that information in the liveness propagation.
Then the regu fields can be populated using that more
complete information. With that approach, BX is marked
as in use on every line in the whole span 0003-0015,
so that the decision about autotmp_0000
(using only 0006-0009) still has all the information
it needs.
This is not specific to the 386, but it only happens in
generated code of the form
load R1
...
load var into R2
...
store R2 back into var
...
use R1
and for the most part the other compilers generate
the loads for a given compiled line before any of
the stores. Even so, this may not be the case everywhere,
so the change is worth making in all three.
R=ken2, ken, ken
CC=golang-dev
https://golang.org/cl/4529106
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This is the source code repository for the Go programming language.
For documentation about how to install and use Go,
visit http://golang.org/ or load doc/install.html in your web browser.
After installing Go, you can view a nicely formatted
doc/install.html by running godoc --http=:6060
and then visiting http://localhost:6060/doc/install.html.
Unless otherwise noted, the Go source files are distributed
under the BSD-style license found in the LICENSE file.
--
Binary Distribution Notes
If you have just untarred a binary Go distribution, you need to set
the environment variable $GOROOT to the full path of the go
directory (the one containing this README). You can omit the
variable if you unpack it into /usr/local/go, or if you rebuild
from sources by running all.bash (see doc/install.html).
You should also add the Go binary directory $GOROOT/bin
to your shell's path.
For example, if you extracted the tar file into $HOME/go, you might
put the following in your .profile:
export GOROOT=$HOME/go
export PATH=$PATH:$GOROOT/bin
See doc/install.html for more details.