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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>
<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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