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Nadav:<br>
<br>
I don't think this is right approach for engineering. <br>
The time-complexity of re-analyzing addr_taken for each single alias
query depends on <br>
1. how many global variable<br>
2. how many occurrence of these global variables.<br>
3. how many queries the compiler have.<br>
<br>
3) depends on compiler. You never know what we will have in the
following few years. <br>
1 and 2 depends on the program. You never know what kind of program
you will run into. <br>
How can we use what we have today the extrapolate the future
ignoring the highly <br>
unpredictable complexity.<br>
<br>
It's interesting that recently, many EE magazine (circuit cellar,
Elector, EE times) are <br>
discussing buggy SW kill people. I remember some posts complaining
that some buggy program<br>
have amazingly large # of global variables. I can find one post in
Chinese website: <br>
<br>
<a class="moz-txt-link-freetext" href="http://forum.xitek.com/thread-1226816-5-1-1.html">http://forum.xitek.com/thread-1226816-5-1-1.html</a><br>
<br>
The 1st post says, "a program has 11000 global variables"!<br>
<br>
As to "Can you provide this data"? My answer is no, and I will
not to implement the analysis <br>
which perform on-the-fly analysis unless I'm convinced that saving
addr_taken bit to llvm::GlobalVariable <br>
is fundamentally flawed. <br>
<br>
Shuxin<br>
<br>
<br>
<br>
<br>
<br>
<div class="moz-cite-prefix">On 10/30/13 9:20 AM, Nadav Rotem wrote:<br>
</div>
<blockquote
cite="mid:5A2E41D8-C57B-4E7A-85E3-11748700BADA@apple.com"
type="cite">
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<br>
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<div>On Oct 29, 2013, at 4:39 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;"> That said, I don't
think it is still inexpensive if we re-analyze the</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;"> addr-taken again and
again *ON THE FLY". It is really difficult to</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;"> predict compile-time
impact. You never know how many global variables</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;"> in a program, and you
never know how extensive they are used.</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;"> Poorly-written program
tends to have lots of global-vars.</span></blockquote>
</div>
<br>
<div>Actually, it is not that difficult to predict the effect on
compile time. All you need to do is implement the analysis “on
the fly” and measure the compile time. Can you provide this
data ? Compile time measurements can help us make a decision. </div>
</blockquote>
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