Move definition of can-be-constant-propagated to a central location #2221
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tautschnig
requested review from
kroening,
peterschrammel and
smowton
as code owners
| } | ||
| else if(expr.id()==ID_with) | ||
| { | ||
| // this is bad |
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This is probably not your code, but it would be good to give an idea of 'what didn't work here' in place of a commented piece of code.
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Indeed, let me try to dig this up.
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(But it might take a while to do so.)
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Throughout the back-end there are hints that the array theory used to do Strange Things. At one point I (tried to) patch a rewrite that converted with to ITE.
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#3095 for further discussion.
| { | ||
| if(expr.id()==ID_mult) | ||
| { | ||
| // propagate stuff with sizeof in it |
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Why is this only the case for multiply?
(Again, I realise that this is not new code.)
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#3095 for further discussion.
| } | ||
| else if(expr.id()==ID_with) | ||
| { | ||
| // this is bad |
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Throughout the back-end there are hints that the array theory used to do Strange Things. At one point I (tried to) patch a rewrite that converted with to ITE.
| return is_constant(expr.op0()); | ||
| } | ||
| else if( | ||
| expr.id() == ID_plus || expr.id() == ID_mult || expr.id() == ID_array || |
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What about divide, floating-point ops, etc. Do we have any exprt's that cannot be constant folded if all arguments are constant? If we do; should we?
I realise that constant folding and expression forwarding in symex is more involved than just "is it constant" but...
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#3095 for further discussion.
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@kroening Would you be able to respond to some of the questions above? |
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Passed Diffblue compatibility checks (cbmc commit: 8d24d2f).
Build URL: https://travis-ci.com/diffblue/test-gen/builds/86785268
This is re-usable, for example for the constant-propagation data-flow analysis.
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Passed Diffblue compatibility checks (cbmc commit: be11b36).
Build URL: https://travis-ci.com/diffblue/test-gen/builds/86839351
This is re-usable, for example for the constant-propagation data-flow analysis.
This is factored out from #2132.