Hi,
I'm investigating the following ICE building the Blackfin compiler from trunk:
/home/shender/gnu-upstream/toolchain/gcc-4.7/libgfortran/generated/eoshift1_4.c:
In function ÃâËeoshift1Ãââ:
/home/shender/gnu-upstream/toolchain/gcc-4.7/libgfortran/generated/eoshift1_4.c:250:1:
error: unable to find a register to spill in class ÃâËCCREGSÃââ
/home/shender/gnu-upstream/toolchain/gcc-4.7/libgfortran/generated/eoshift1_4.c:250:1:
error: this is the insn:
(insn 546 540 479 46 (set (reg:BI 455)
(le:BI (reg/v:SI 6 R6 [orig:122 size ] [122])
(const_int 0 [0])))
/home/shender/gnu-upstream/toolchain/gcc-4.7/libgfortran/generated/eoshift1_4.c:212
119 {compare_le}
(nil))
/home/shender/gnu-upstream/toolchain/gcc-4.7/libgfortran/generated/eoshift1_4.c:250:1:
internal compiler error: in spill_failure, at reload1.c:2123
The problem occurs when the ce2 pass does an IF-CASE-2 transformation, moving
an instruction which sets the condition code register into a block between
another instruction which sets the condition code register and its conditional
jump.
e.g.
block 44:
set cc = x;
if cc jump;
...
block 49:
set cc = y;
block 51:
if cc jump;
gets transformed into...
block 44:
set cc = x;
set cc = y;
if cc jump;
...
block 51:
if cc jump;
When we reach cc=y in
reload1.c:reload()->select_reload_regs()->find_reload_regs(), find_reg() fails
and we call spill_failure(), which doesn't return. However, right after the
call to spill_failure, we set the failure flag, which is checked for right
after select_reload_regs returns. I'm a little confused as to what the
intention of this code was. It seems like the idea was to note the
spill_failure and then try and fix it by jumping to the "failed:" label, but
obviously this never happens due to the call to spill_failure. A spill failure
like this looks very fixable and I would expect the previously live register
(cc=x) to be spilled. Is there a reason this isn't attempted here?
Thanks,
Stu
