ICE building compiler

[Henderson, Stuart]

Hi,
I'm investigating an ICE building the Blackfin compiler from trunk.

/home/shender/gnu-upstream/toolchain/gcc-4.7/libgfortran/generated/eoshift1_4.c: In function ‘eoshift1’:
/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 ‘CCREGS’
/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 the reload pass the CC reg is already in use from cc=x, find_reg fails to find an alternative and we bomb out.

This seems like something IF-CASE-2 could do a lot, so is it supposed to avoid such scenarios?  or should reload handle the situation by finding the previous use of CC and spilling it to memory?

Any pointers would be appreciated.

Thanks,
Stu