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[Ada] Improve performance of conversion from String to Long_Float

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Once it is sure that the result will be infinity, stop computation and return
the result. This ensure that the function call duration is bounded. Before that
change on some cases the computation was taking more than a few seconds.

2018-05-25  Nicolas Roche  <roche@adacore.com>

gcc/ada/

	* libgnat/s-valrea.adb (Scan_Real): Abort computation once it is sure
	that the result will be either -infinite or +infinite.

From-SVN: r260743
This commit is contained in:
Nicolas Roche 2018-05-25 09:05:34 +00:00 committed by Pierre-Marie de Rodat
parent 38806cd3da
commit 529e1a3f52
2 changed files with 13 additions and 5 deletions
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5
gcc/ada/ChangeLog
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@ -1,3 +1,8 @@
2018-05-25 Nicolas Roche <roche@adacore.com>
* libgnat/s-valrea.adb (Scan_Real): Abort computation once it is sure
that the result will be either -infinite or +infinite.
2018-05-25 Patrick Bernardi <bernardi@adacore.com>
* libgnat/s-parame.ads, libgnat/s-parame__vxworks.ads,

13
gcc/ada/libgnat/s-valrea.adb
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@ -342,7 +342,7 @@ package body System.Val_Real is
-- For base 10, use power of ten table, repeatedly if necessary
elsif Scale > 0 then
while Scale > Maxpow loop
while Scale > Maxpow and then Uval'Valid loop
Uval := Uval * Powten (Maxpow);
Scale := Scale - Maxpow;
end loop;
@ -350,18 +350,21 @@ package body System.Val_Real is
-- Note that we still know that Scale > 0, since the loop
-- above leaves Scale in the range 1 .. Maxpow.
Uval := Uval * Powten (Scale);
if Uval'Valid then
Uval := Uval * Powten (Scale);
end if;
elsif Scale < 0 then
while (-Scale) > Maxpow loop
while (-Scale) > Maxpow and then Uval'Valid loop
Uval := Uval / Powten (Maxpow);
Scale := Scale + Maxpow;
end loop;
-- Note that we still know that Scale < 0, since the loop
-- above leaves Scale in the range -Maxpow .. -1.
Uval := Uval / Powten (-Scale);
if Uval'Valid then
Uval := Uval / Powten (-Scale);
end if;
end if;
-- Here is where we check for a bad based number