http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51933
--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-01-21 18:40:23 UTC --- That unfortunately slightly pessimizes it. E.g. on i686-linux bootstrap on: ../../gcc/config/i386/i386.c ix86_memory_move_cost ../../gcc/config/i386/i386.c ix86_register_move_cost ../../../../libgfortran/io/write.c write_float ../../../libgfortran/io/write.c write_float s-regpat.adb system__regpat__dump_until /usr/src/gcc/gcc/testsuite/gcc.target/i386/avx-vpackuswb-1.c do_test /usr/src/gcc/gcc/testsuite/gcc.target/i386/sse2-packuswb-1.c do_test /usr/src/gcc/libstdc++-v3/testsuite/ext/rope/1.cc _S_tree_concat /usr/src/gcc/libstdc++-v3/testsuite/ext/rope/2.cc _S_tree_concat /usr/src/gcc/libstdc++-v3/testsuite/ext/rope/3.cc _S_tree_concat /usr/src/gcc/libstdc++-v3/testsuite/ext/rope/44963.cc _S_tree_concat /usr/src/gcc/libstdc++-v3/testsuite/ext/rope/4.cc _S_tree_concat /usr/src/gcc/libstdc++-v3/testsuite/ext/rope/pthread7-rope.cc _S_tree_concat and on x86_64-linux bootstrap sans regtest: ../../gcc/ada/par.adb par__prag__process_restrictions_or_restriction_warnings ../../gcc/config/i386/i386.c ix86_memory_move_cost ../../gcc/config/i386/i386.c ix86_register_move_cost ../../gcc/java/jcf-parse.c rewrite_reflection_indexes ../../../libgfortran/io/write.c write_float s-regpat.adb system__regpat__dump_until The problem is if the def insn satisfies is_cond_copy_insn, then it can be in a wider mode, yet all definitions could still be in a narrower mode. So, perhaps we'd need to have a recursive function that for is_cond_copy_insn defs calls get_defs on both args and recurses, checking mode of real definitions only. Not sure if we'd need also this is_insn_visited array for it to avoid recursing infinitely. BTW, for 4.8, I guess a couple of ree.c cleanups will be needed, e.g. several functions allocate and free way too many heap allocated vectors, I guess if we allocate them in the caller (or caller's caller) and just pass addresses of those vectors around, we could just VEC_truncate the vectors and avoid the permanent malloc/free.
