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<div class="moz-cite-prefix">On 7/14/13 5:56 PM, Andrew Trick wrote:<br>
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cite="mid:344919F0-3ED1-4EED-865D-8AC273821A3B@apple.com"
type="cite">
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<div>On Jul 12, 2013, at 3:49 PM, Shuxin Yang <<a
moz-do-not-send="true" href="mailto:shuxin.llvm@gmail.com">shuxin.llvm@gmail.com</a>>
wrote:</div>
<br class="Apple-interchange-newline">
<blockquote type="cite"><span style="font-family: Helvetica;
font-size: 12px; font-style: normal; font-variant: normal;
font-weight: normal; letter-spacing: normal; line-height:
normal; orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;">3.2 Compile partitions
independently</span><br style="font-family: Helvetica;
font-size: 12px; font-style: normal; font-variant: normal;
font-weight: normal; letter-spacing: normal; line-height:
normal; orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px;">
<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;">--------------------------------------</span><br
style="font-family: Helvetica; font-size: 12px; font-style:
normal; font-variant: normal; font-weight: normal;
letter-spacing: normal; line-height: normal; orphans: auto;
text-align: start; text-indent: 0px; text-transform: none;
white-space: normal; widows: auto; word-spacing: 0px;
-webkit-text-stroke-width: 0px;">
<br style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px;">
<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;"> There are two camps:
one camp advocate compiling partitions via multi-process,</span><br
style="font-family: Helvetica; font-size: 12px; font-style:
normal; font-variant: normal; font-weight: normal;
letter-spacing: normal; line-height: normal; orphans: auto;
text-align: start; text-indent: 0px; text-transform: none;
white-space: normal; widows: auto; word-spacing: 0px;
-webkit-text-stroke-width: 0px;">
<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;">the other one favor
multi-thread.</span><br style="font-family: Helvetica;
font-size: 12px; font-style: normal; font-variant: normal;
font-weight: normal; letter-spacing: normal; line-height:
normal; orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px;">
<br style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px;">
<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;"> Inside Apple compiler
teams, I'm the only one belong to the 1st comp. I think</span><br
style="font-family: Helvetica; font-size: 12px; font-style:
normal; font-variant: normal; font-weight: normal;
letter-spacing: normal; line-height: normal; orphans: auto;
text-align: start; text-indent: 0px; text-transform: none;
white-space: normal; widows: auto; word-spacing: 0px;
-webkit-text-stroke-width: 0px;">
<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;">while multi-proc sounds
bit red-neck, it has its advantage for this purpose, and</span><br
style="font-family: Helvetica; font-size: 12px; font-style:
normal; font-variant: normal; font-weight: normal;
letter-spacing: normal; line-height: normal; orphans: auto;
text-align: start; text-indent: 0px; text-transform: none;
white-space: normal; widows: auto; word-spacing: 0px;
-webkit-text-stroke-width: 0px;">
<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;">while multi-thread is
certainly more eye-popping, it has its advantage</span><br
style="font-family: Helvetica; font-size: 12px; font-style:
normal; font-variant: normal; font-weight: normal;
letter-spacing: normal; line-height: normal; orphans: auto;
text-align: start; text-indent: 0px; text-transform: none;
white-space: normal; widows: auto; word-spacing: 0px;
-webkit-text-stroke-width: 0px;">
<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;">as well.</span><br
style="font-family: Helvetica; font-size: 12px; font-style:
normal; font-variant: normal; font-weight: normal;
letter-spacing: normal; line-height: normal; orphans: auto;
text-align: start; text-indent: 0px; text-transform: none;
white-space: normal; widows: auto; word-spacing: 0px;
-webkit-text-stroke-width: 0px;">
<br style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px;">
<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;"> The advantage of
multi-proc are:</span><br style="font-family: Helvetica;
font-size: 12px; font-style: normal; font-variant: normal;
font-weight: normal; letter-spacing: normal; line-height:
normal; orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px;">
<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;"> 1) easier to implement,
the process run in its own address space.</span><br
style="font-family: Helvetica; font-size: 12px; font-style:
normal; font-variant: normal; font-weight: normal;
letter-spacing: normal; line-height: normal; orphans: auto;
text-align: start; text-indent: 0px; text-transform: none;
white-space: normal; widows: auto; word-spacing: 0px;
-webkit-text-stroke-width: 0px;">
<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;"> We don't need to worry
about they can interfere with each other.</span><br
style="font-family: Helvetica; font-size: 12px; font-style:
normal; font-variant: normal; font-weight: normal;
letter-spacing: normal; line-height: normal; orphans: auto;
text-align: start; text-indent: 0px; text-transform: none;
white-space: normal; widows: auto; word-spacing: 0px;
-webkit-text-stroke-width: 0px;">
<br style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px;">
<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;"> 2)huge, or not
unlimited, address space.</span><br style="font-family:
Helvetica; font-size: 12px; font-style: normal;
font-variant: normal; font-weight: normal; letter-spacing:
normal; line-height: normal; orphans: auto; text-align:
start; text-indent: 0px; text-transform: none; white-space:
normal; widows: auto; word-spacing: 0px;
-webkit-text-stroke-width: 0px;">
<br style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px;">
<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;"> The disadvantage is
that it's expensive. But I guess the cost is</span><br
style="font-family: Helvetica; font-size: 12px; font-style:
normal; font-variant: normal; font-weight: normal;
letter-spacing: normal; line-height: normal; orphans: auto;
text-align: start; text-indent: 0px; text-transform: none;
white-space: normal; widows: auto; word-spacing: 0px;
-webkit-text-stroke-width: 0px;">
<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;"> almost negligible
compared to the overall IPO compilation.</span><br
style="font-family: Helvetica; font-size: 12px; font-style:
normal; font-variant: normal; font-weight: normal;
letter-spacing: normal; line-height: normal; orphans: auto;
text-align: start; text-indent: 0px; text-transform: none;
white-space: normal; widows: auto; word-spacing: 0px;
-webkit-text-stroke-width: 0px;">
<br style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px;">
<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;"> The advantage of
multi-threads I can imagine are:</span><br
style="font-family: Helvetica; font-size: 12px; font-style:
normal; font-variant: normal; font-weight: normal;
letter-spacing: normal; line-height: normal; orphans: auto;
text-align: start; text-indent: 0px; text-transform: none;
white-space: normal; widows: auto; word-spacing: 0px;
-webkit-text-stroke-width: 0px;">
<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;"> 1) sound fancy</span><br
style="font-family: Helvetica; font-size: 12px; font-style:
normal; font-variant: normal; font-weight: normal;
letter-spacing: normal; line-height: normal; orphans: auto;
text-align: start; text-indent: 0px; text-transform: none;
white-space: normal; widows: auto; word-spacing: 0px;
-webkit-text-stroke-width: 0px;">
<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;"> 2) it is light-weight</span><br
style="font-family: Helvetica; font-size: 12px; font-style:
normal; font-variant: normal; font-weight: normal;
letter-spacing: normal; line-height: normal; orphans: auto;
text-align: start; text-indent: 0px; text-transform: none;
white-space: normal; widows: auto; word-spacing: 0px;
-webkit-text-stroke-width: 0px;">
<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;"> 3) inter-thread
communication is easier than IPC.</span><br
style="font-family: Helvetica; font-size: 12px; font-style:
normal; font-variant: normal; font-weight: normal;
letter-spacing: normal; line-height: normal; orphans: auto;
text-align: start; text-indent: 0px; text-transform: none;
white-space: normal; widows: auto; word-spacing: 0px;
-webkit-text-stroke-width: 0px;">
<br style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px;">
<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;"> Its disadvantage are:</span><br
style="font-family: Helvetica; font-size: 12px; font-style:
normal; font-variant: normal; font-weight: normal;
letter-spacing: normal; line-height: normal; orphans: auto;
text-align: start; text-indent: 0px; text-transform: none;
white-space: normal; widows: auto; word-spacing: 0px;
-webkit-text-stroke-width: 0px;">
<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;"> 1). Oftentime we will
come across race-condition, and it took</span><br
style="font-family: Helvetica; font-size: 12px; font-style:
normal; font-variant: normal; font-weight: normal;
letter-spacing: normal; line-height: normal; orphans: auto;
text-align: start; text-indent: 0px; text-transform: none;
white-space: normal; widows: auto; word-spacing: 0px;
-webkit-text-stroke-width: 0px;">
<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;"> awful long time to
figure it out. While the code is supposed</span><br
style="font-family: Helvetica; font-size: 12px; font-style:
normal; font-variant: normal; font-weight: normal;
letter-spacing: normal; line-height: normal; orphans: auto;
text-align: start; text-indent: 0px; text-transform: none;
white-space: normal; widows: auto; word-spacing: 0px;
-webkit-text-stroke-width: 0px;">
<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;"> to be mult-thread
safe, we might miss some tricky case.</span><br
style="font-family: Helvetica; font-size: 12px; font-style:
normal; font-variant: normal; font-weight: normal;
letter-spacing: normal; line-height: normal; orphans: auto;
text-align: start; text-indent: 0px; text-transform: none;
white-space: normal; widows: auto; word-spacing: 0px;
-webkit-text-stroke-width: 0px;">
<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;"> Trouble-shooting
race condition is a nightmare.</span><br style="font-family:
Helvetica; font-size: 12px; font-style: normal;
font-variant: normal; font-weight: normal; letter-spacing:
normal; line-height: normal; orphans: auto; text-align:
start; text-indent: 0px; text-transform: none; white-space:
normal; widows: auto; word-spacing: 0px;
-webkit-text-stroke-width: 0px;">
<br style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px;">
<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;"> 2) Small address space.
This is big problem if we the compiler</span><br
style="font-family: Helvetica; font-size: 12px; font-style:
normal; font-variant: normal; font-weight: normal;
letter-spacing: normal; line-height: normal; orphans: auto;
text-align: start; text-indent: 0px; text-transform: none;
white-space: normal; widows: auto; word-spacing: 0px;
-webkit-text-stroke-width: 0px;">
<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;"> is built 32-bit . In
that case, the compiler is not able to bring</span><br
style="font-family: Helvetica; font-size: 12px; font-style:
normal; font-variant: normal; font-weight: normal;
letter-spacing: normal; line-height: normal; orphans: auto;
text-align: start; text-indent: 0px; text-transform: none;
white-space: normal; widows: auto; word-spacing: 0px;
-webkit-text-stroke-width: 0px;">
<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;"> lots of stuff in
memory even if the HW dose</span><br style="font-family:
Helvetica; font-size: 12px; font-style: normal;
font-variant: normal; font-weight: normal; letter-spacing:
normal; line-height: normal; orphans: auto; text-align:
start; text-indent: 0px; text-transform: none; white-space:
normal; widows: auto; word-spacing: 0px;
-webkit-text-stroke-width: 0px;">
<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;"> provide ample mem.</span><br
style="font-family: Helvetica; font-size: 12px; font-style:
normal; font-variant: normal; font-weight: normal;
letter-spacing: normal; line-height: normal; orphans: auto;
text-align: start; text-indent: 0px; text-transform: none;
white-space: normal; widows: auto; word-spacing: 0px;
-webkit-text-stroke-width: 0px;">
<br style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
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<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;"> 3) The thread-safe
run-time lib is more expensive.</span><br
style="font-family: Helvetica; font-size: 12px; font-style:
normal; font-variant: normal; font-weight: normal;
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<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;"> I once linked a
compiler using -lpthread (I dose not have to) on a</span><br
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normal; font-variant: normal; font-weight: normal;
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<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;"> UNIX platform, and
saw the compiler slow down by about 1/3.</span><br
style="font-family: Helvetica; font-size: 12px; font-style:
normal; font-variant: normal; font-weight: normal;
letter-spacing: normal; line-height: normal; orphans: auto;
text-align: start; text-indent: 0px; text-transform: none;
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-webkit-text-stroke-width: 0px;">
<br style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px;">
<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;"> I'm not able to
convince the folks in other camp, neither are they</span><br
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normal; font-variant: normal; font-weight: normal;
letter-spacing: normal; line-height: normal; orphans: auto;
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<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;">able to convince me. I
decide to implement both. Fortunately, this</span><br
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normal; font-variant: normal; font-weight: normal;
letter-spacing: normal; line-height: normal; orphans: auto;
text-align: start; text-indent: 0px; text-transform: none;
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<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;">part is not difficult, it
seems to be rather easy to crank out one within short</span><br
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normal; font-variant: normal; font-weight: normal;
letter-spacing: normal; line-height: normal; orphans: auto;
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<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;">period of time. It would
be interesting to compare them side-by-side,</span><br
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normal; font-variant: normal; font-weight: normal;
letter-spacing: normal; line-height: normal; orphans: auto;
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<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;">and see which camp
lose:-). On the other hand, if we run into race-condition</span><br
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normal; font-variant: normal; font-weight: normal;
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<span style="font-family: Helvetica; font-size: 12px;
font-style: normal; font-variant: normal; font-weight:
normal; letter-spacing: normal; line-height: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px; float:
none; display: inline !important;">problem, we choose
multi-proc version as a fall-back.</span><br
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normal; font-variant: normal; font-weight: normal;
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</blockquote>
<div dir="auto"><br>
</div>
<div dir="auto">While I am a self-proclaimed multi-process
red-neck, in this case I would prefer to see a multi-threaded
implementation because I want to verify that LLVMContext can
be used as advertised. I'm sure some extra care will be needed
to report failures/diagnostics, but we should start with the
assumption that this approach is not significantly harder than
multi-process because that's how we advertise the design.</div>
<div dir="auto"><br>
</div>
<div dir="auto">If any of the multi-threaded disadvantages you
point out are real, I would like to find out about it.</div>
<div dir="auto"><br>
</div>
<div dir="auto">1. Race Conditions: We should be able to verify
that the thread-parallel vs. sequential or multi-process
compilation generate the same result. If they diverge, we
would like to know about the bug so it can be
fixed--independent of LTO.</div>
<div dir="auto"><br>
</div>
<div dir="auto">2. Small Address Space with LTO. We don't need
to design around this hypothetical case.</div>
<div dir="auto"><br>
</div>
<div dir="auto">3. Expensive thread-safe runtime lib. We should
not speculate that platforms that we, as the LLVM community,
care about have this problem. Let's assume that our platforms
are well implemented unless we have data to the contrary.
(Personally, I would even love to use TLS in the compiler to
vastly simplify API design in the backend, but I am not going
to be popular for saying so).</div>
<div dir="auto"><br>
</div>
<div dir="auto">We should be able to decompose each step of
compilation for debugging.</div>
</div>
</blockquote>
Yes, of course, we should be able to save the IR before and after
each major steps, and when <br>
trouble-shooting, we should be able to focus on one smaller
partition. Once the problem of<br>
of the partition is fixed, we can manually link all the partition
and other libs into final <br>
executable/dyn-lib. <br>
<br>
This is one important reasons for partitioning. <br>
<br>
<blockquote
cite="mid:344919F0-3ED1-4EED-865D-8AC273821A3B@apple.com"
type="cite">
<div>
<div dir="auto"> So the multi-process "implementation" should
just be a degenerate form of threading with a bit of driver
magic if you want to automate it.</div>
<div><br>
</div>
<br>
</div>
</blockquote>
Yes! That is why I'd like implement both.<br>
<br>
There is one difference though, with multi-proc implementation, we
need to pass the /path/to/{llc/opt} to the libLTO.{so|dylib}, such <br>
that it can invoke these tools from right place. While in
multi-thread implementation, we don't need this info. <br>
<br>
<br>
<br>
<br>
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