gcc-2.95.3 internal error on head/MachOp.hs

[Donald Bruce Stewart]

dons:
> A start on the gcc-2.95.3 issue provoked by MachOp.hs in the head, on
> the openbsd nightly builds. I haven't solved this, but I thought I'd put
> out some info, in case someone else can spot it, or has some hints...

And we have a minimal test case :) Maybe this will help.

        module M where

        f :: DT -> Bool
        f a = case a of -- any less cases and we don't trigger it
                A -> True
                C -> True
                D -> True
                E -> True
                F -> True
                J -> True
                M -> True
                N -> True
                _other -> False

        -- any less constructors and we don't trigger it
        data DT = A | B | C | D | E | F | G | H | I | J 
                | K | L | M | N | O | P | Q | R 

Which provokes, using the stage1 compiler from the head:

        manzano$ ~/head/i386-unknown-openbsd/ghc/compiler/ghc-inplace -c -keep-tmp-files -fvia-C T.hs
        /tmp/ghc10780.hc: In function `s1Eo_ret':
        /tmp/ghc10780.hc:859: Internal compiler error in `build_insn_chain', at global.c:1756
        Please submit a full bug report.
        See <URL:http://www.gnu.org/software/gcc/bugs.html> for instructions.

And the .hc function that gcc aborts in (full .hc at
http://www.cse.unsw.edu.au/~dons/ghc10780.hc):

        static StgWord s1Eo_info[] = {
                0x0, 0x24
        };

        EI_(GHCziBase_False_closure);
        EI_(GHCziBase_True_closure);
        IF_(s1Eo_ret) {
                W_ _c1Ey;
                FB_
                _c1Ey = (W_)((*((StgWord16*)((*R1.p) + (-0x2)))));
                if (_c1Ey < 0x5) goto _c1EH;
                if (_c1Ey < 0xc) goto _c1EI;
                if (_c1Ey < 0xd) goto _c1EJ;
                if (_c1Ey != 0xd) goto _c1EK;
                R1.p = (P_)(W_)GHCziBase_True_closure;
                Sp=Sp+1;
                JMP_(*((P_)((*Sp) + (-0x14))));
            _c1EK:
                R1.p = (P_)(W_)GHCziBase_False_closure;
                Sp=Sp+1;
                JMP_(*((P_)((*Sp) + (-0x10))));
            _c1EL:
                R1.p = (P_)(W_)GHCziBase_True_closure;
                Sp=Sp+1;
                JMP_(*((P_)((*Sp) + (-0x14))));
            _c1EM:
                R1.p = (P_)(W_)GHCziBase_True_closure;
                Sp=Sp+1;
                JMP_(*((P_)((*Sp) + (-0x14))));
            _c1EN:
                R1.p = (P_)(W_)GHCziBase_True_closure;
                Sp=Sp+1;
                JMP_(*((P_)((*Sp) + (-0x14))));
            _c1EO:
                R1.p = (P_)(W_)GHCziBase_True_closure;
                Sp=Sp+1;
                JMP_(*((P_)((*Sp) + (-0x14))));
            _c1EP:
                if (_c1Ey != 0x5) goto _c1EK;
                R1.p = (P_)(W_)GHCziBase_True_closure;
                Sp=Sp+1;
                JMP_(*((P_)((*Sp) + (-0x14))));
            _c1EJ:
                R1.p = (P_)(W_)GHCziBase_True_closure;
                Sp=Sp+1;
                JMP_(*((P_)((*Sp) + (-0x14))));
            _c1EI:
                if (_c1Ey < 0x9) goto _c1EP;
                if (_c1Ey != 0x9) goto _c1EK;
                R1.p = (P_)(W_)GHCziBase_True_closure;
                Sp=Sp+1;
                JMP_(*((P_)((*Sp) + (-0x14))));
            _c1EH:
                switch (_c1Ey) {
                    case 0x0: goto _c1EL;
                    case 0x1: goto _c1EK;
                    case 0x2: goto _c1EM;
                    case 0x3: goto _c1EN;
                    case 0x4: goto _c1EO;
                }
                FE_
        }