------- Additional Comments From steven at gcc dot gnu dot org 2005-03-19
18:58 -------
Actually you can get this from any trivial "implicit set"-like
code, for example:
int b;
void foo (int a) {
if (a)
a = 3;
b = a;
}
The out-of-ssa pass turns that into
foo (aD.1461)
{
intD.0 a.0D.1468;
# BLOCK 0
# PRED: ENTRY [100.0%] (fallthru,exec)
if (aD.1461 != 0) goto <L3>; else goto <L2>;
# SUCC: 3 [67.0%] (true,exec) 1 [33.0%] (false,exec)
# BLOCK 3
# PRED: 0 [67.0%] (true,exec)
<L3>:;
a.0D.1468 = 3;
goto <bb 2> (<L1>);
# SUCC: 2 [100.0%] (fallthru)
# BLOCK 1
# PRED: 0 [33.0%] (false,exec)
<L2>:;
a.0D.1468 = 0;
# SUCC: 2 [100.0%] (fallthru)
# BLOCK 2
# PRED: 1 [100.0%] (fallthru) 3 [100.0%] (fallthru)
<L1>:;
# bD.1460_4 = V_MUST_DEF <bD.1460_3>;
bD.1460 = a.0D.1468;
return;
# SUCC: EXIT [100.0%]
}
We do not get rid of the "a.0 = 0" set until the first RTL if conversion
pass.
(Also note the useless live range splitting of a!)
This is IMHO a little more important than the normal enhancement request,
so I'm making this a "normal" bug. Andrew, any comments on this bug???
--
What |Removed |Added
----------------------------------------------------------------------------
CC| |amacleod at redhat dot com
Severity|enhancement |normal
Known to fail| |4.0.0 4.1.0
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14627
