Hello, Matthias noticed the following ICE when attempting to build the SPU compiler from the Linaro GCC 4.5 sources:
../../../../src-spu/libgcc/../gcc/libgcc2.c: In function '__fixunssfdi': ../../../../src-spu/libgcc/../gcc/libgcc2.c:1344:1: internal compiler error: in spu_expand_mov, at config/spu/spu.c:4575 It turns out that this is due to the new "extension elimination" pass that was recently added in Linaro GCC, as port from the CodeSourcery compiler. This patch has also been proposed, but not yet included upstream. The problem is that this patch seems to frequently introduce instructions that *set* a sub-word lowpart subreg of a register. Now such instructions, according to the docs, are probably valid RTL, but since the effect of the instruction onto the highpart of the register is deliberately left unspecified, they tend to be very infrequently used. Probably because of this, there seem to be parts of the compiler that simply don't handle such instructions correctly. This has been already noticed in the case of the RTL loop optimizers (see discussion here http://gcc.gnu.org/ml/gcc/2010-11/msg00552.html). The failure in the SPU back-end is another instance of the same problem. SPU needs special code to handle subregs (since a "lowpart" SImode subreg of a DImode register is not actually valid on the SPU, because SImode values live in bytes 0..3 while DImode values live in bytes 0..7 of the otherwise big-endian 16-byte SPU registers), and this code simply aborts when given an assignment to a sub-word lowpart subreg. Now, I guess there's two ways forward: either the outcome of the ongoing discussions on gcc-patches is that it is in fact not a good idea to generate such sets, and the EE pass is subsequently rewritten to avoid them; or else, if those instructions are considered valid, I'll have to extend the SPU move expander to handle them. Thoughts? Matthias, if you need a quick workaround for now, I guess you could disable the new pass for SPU by adding a line "flag_ee = 0;" to spu_override_options. Mit freundlichen Gruessen / Best Regards Ulrich Weigand -- Dr. Ulrich Weigand | Phone: +49-7031/16-3727 STSM, GNU compiler and toolchain for Linux on System z and Cell/B.E. IBM Deutschland Research & Development GmbH Vorsitzender des Aufsichtsrats: Martin Jetter | Geschäftsführung: Dirk Wittkopp Sitz der Gesellschaft: Böblingen | Registergericht: Amtsgericht Stuttgart, HRB 243294 _______________________________________________ linaro-toolchain mailing list linaro-toolchain@lists.linaro.org http://lists.linaro.org/mailman/listinfo/linaro-toolchain
