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Reload finds invalid class
- From: Ian Dall <ian at beware dot dropbear dot id dot au>
- To: gcc-help <gcc at gcc dot gnu dot org>
- Date: Sat, 14 Dec 2002 00:06:04 +1030
- Subject: Reload finds invalid class
I think I have found a problem in reload.c:find_valid_class(), which
only shows up for small register classes.
The particular example I have is it is called with m1=SImode, n=1,
dest_regno=18 and I have a sub-class of floating point registers
with a size of just one.
The one register floating point class is found even though it is a)
too small and b) not OK for SImode.
In the following code:
for (regno = 0; regno < FIRST_PSEUDO_REGISTER && ! bad; regno++)
if (TEST_HARD_REG_BIT (reg_class_contents[class], regno)
&& TEST_HARD_REG_BIT (reg_class_contents[class], regno + n)
&& ! HARD_REGNO_MODE_OK (regno + n, m1))
bad = 1;
HARD_REGNO_MODE_OK (regno + n, m1) will be evaluated at least once, so
long as the class is at size of at least (n + 1), but if the class is
smaller than that, it will be never checked if it is OK for mode.
I think inserting and extra test:
if (reg_class_size[class] < (n + 1))
continue;
solves the problem.
Is my analysis correct? If so I will submit a patch.
Ian