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Re: [PATCH] Make CSE path following use the CFG


> It's just a function call, you know.

Yes, but absolutely useless, i.e. with no algorithmic function whatsoever.  
Moreover this makes the code more complex.  Note that I already spotted it.

> I had a longer comment and I was asked to remove that.

+            The old CSE path following code would use MAX(2*nsets,500)
+            but now that we know exactly how many insns (and hence sets)
+            we will see in the path, it seemed like a good idea to just
+            use max_qty = 2 * nsets.  Interestingly, we end up writing
+            past the end of qty_table with that value for max_qty.  In
+            other words, this was a latent bug in cse.c present since 
+            at least 1992.
+            Oh well, we just take a bigger max_qty now to play safe.  */

This didn't explain the heuristics either.  Where does

max_qty = ebb_data.nsets * MAX_RECOG_OPERANDS;

come from?

> Yikes!  I even tested Ada with a previous version of the patch. 
> Grrrrrrr....
>
> My guess is that it's another behind-the-back change of a may-trap
> insn into a non-trapping insn.  You can use the debug counter to find
> out at which cse_main invocation the problem appears, and then go
> through the changes to all BB_END insns (or move the counter inside
> cse_insn).

OK, thanks for the tip.

-- 
Eric Botcazou


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