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<div class="moz-cite-prefix">On 8/3/18 2:53 PM, Artem Dergachev
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:e2f781a6-7438-dc97-5e8e-d9bae2045437@gmail.com">
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The terminator for [B3] is not the binary operator; it's the whole
if-statement. I guess it's kind of generic if-statement logic
here. It wouldn't make that much sense to change the terminator
here to 'b' if in all other places it's still the if-statement.
And i think we don't really want to rewrite AST to create an 'if
(b)' statement only to use it as a terminator, that'd be pretty
weird.<br>
<br>
But it might make sense if we change the behavior in all other
places to avoid using the if-statement as a terminator. I'm not
sure how much information would be lost in this case; it might
work if we simply say in all places "here's the condition
expression, compute it, then jump to this or that block depending
on the value" and simply never store control flow statements in
the CFG. We might as well separate "terminator condition
expression" from "terminator control flow statement", not sure if
i'm making any sense right now.<br>
</blockquote>
<br>
On second thought, it's exactly how it works right now, if we
declare that the "terminator condition expression" is just the last
expression in the block. I.e., for [B4] the condition is 'a' and the
terminator is '||', for [B3] the condition is 'b' and the terminator
is 'if'. <br>
<br>
<blockquote type="cite"
cite="mid:e2f781a6-7438-dc97-5e8e-d9bae2045437@gmail.com"> <br>
The logic in the Analyzer to act upon this part of CFG is pretty
weird, cf. ExprEngine::VisitLogicalExpr(). It definitely needs a
cleanup, probably with the help of a more easy-to-read CFG.<br>
<br>
<br>
<div class="moz-cite-prefix">On 8/3/18 2:35 PM, Gábor Horváth via
cfe-dev wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAPRL4a17NYGTSMtZ9zvFx42KJa56uk3FtktRVMGBE9PQJSagiQ@mail.gmail.com">
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<div>Hi!</div>
<div><br>
</div>
<div>I found the terminator condition for binary operators a
bit unintuitive in the CFG. I was wondering if I am missing
something or it is a possible improvement.</div>
<div><br>
</div>
<div>Let's consider the following simple code snippet:</div>
<div><br>
</div>
<div><span style="font-family:monospace,monospace"><font
size="2">void g(bool a, bool b) {<br>
if (a || b) {<br>
body();<br>
} else {<br>
body2();<br>
}<br>
}</font></span></div>
<div><br>
</div>
<div>We get the following CFG:</div>
<div><br>
</div>
<div><span style="font-family:monospace,monospace"><font
size="2"> [B1]<br>
1: body2<br>
2: [B1.1] (ImplicitCastExpr, FunctionToPointerDecay,
void (*)(void))<br>
3: [B1.2]()<br>
Preds (1): B3<br>
Succs (1): B0<br>
<br>
[B2]<br>
1: body<br>
2: [B2.1] (ImplicitCastExpr, FunctionToPointerDecay,
void (*)(void))<br>
3: [B2.2]()<br>
Preds (2): B3 B4<br>
Succs (1): B0<br>
<br>
[B3]<br>
1: b<br>
2: [B3.1] (ImplicitCastExpr, LValueToRValue, _Bool)<br>
T: if [B4.2] || [B3.2]<br>
Preds (1): B4<br>
Succs (2): B2 B1<br>
<br>
[B4]<br>
1: a<br>
2: [B4.1] (ImplicitCastExpr, LValueToRValue, _Bool)<br>
T: [B4.2] || ...<br>
Preds (1): B5<br>
Succs (2): B2 B3</font></span><br>
</div>
<div><br>
</div>
<div>The terminator condition for <span
style="font-family:monospace,monospace">[B4]</span> is (a
cast above) <span style="font-family:monospace,monospace">a</span>.
This is pretty intuitive. This value will determine which
branch do we take when we leave the basic block.</div>
<div><br>
</div>
<div>The terminator condition for <span
style="font-family:monospace,monospace">[B3]</span>,
however, is the whole binary or expression. I would expect
it to be the right hand side of the logical or. What do you
think? What is the reason that we have the whole expression
here?</div>
<div><br>
</div>
<div>Regards,</div>
<div>Gabor<br>
</div>
<div><br>
</div>
</div>
<br>
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