[PR51570] minimize ENTRY_VALUEs in debug location lists

[Alexandre Oliva]

gcc.dg/guality/pr45003-*.c have regressed with reordering of the
exploration of the loc expansion space, in a way that didn't always
privilege expansions without ENTRY_VALUEs over ones with it.

This patch fixes it, by ensuring that we'll only ever use ENTRY_VALUEs
if we can't help it given a maximum expression depth (complexity,
actually), and, if we can't help it, we'll go for an option that uses
the fewest ENTRY_VALUEs.

Regstrap time is about the same, as expected, assuming the 2% lower
regstrap time is not statistically significant.

Regstrapped on trunk on x86_64-linux-gnu and i686-linux-gnu.  It
restored pr45003-[23].c to XPASS, without any regressions.  pr45003-1.c
is unchanged by this patch by itself, but in combination with another
patch I'm posting soon that caused it to regress, this patch also avoids
the regression.

Ok to install?

-------------- next part --------------
A non-text attachment was scrubbed...
Name: vta-expand-depth-minimize-entryval-pr51570.patch
Type: text/x-diff
Size: 7967 bytes
Desc: not available
URL: <http://gcc.gnu.org/pipermail/gcc-patches/attachments/20120409/7fec7cbf/attachment.bin>
-------------- next part --------------


-- 
Alexandre Oliva, freedom fighter    http://FSFLA.org/~lxoliva/
You must be the change you wish to see in the world. -- Gandhi
Be Free! -- http://FSFLA.org/   FSF Latin America board member
Free Software Evangelist      Red Hat Brazil Compiler Engineer