------- Comment #5 from matz at gcc dot gnu dot org 2009-12-19 01:19 ------- To explain: the miscompilation is a result of the cloner (when cloning for the find() call) creating a new tree for a local static variable (the 'm' in main). After inlining we have:
if ( &mD.2293._M_tD.2062._M_implD.2039._M_headerD.2043 != &mD.2303._M_tD.2062._M_implD.2039._M_headerD.2043) note the different UIDs for 'm'. fold will say true to the unequality, as references to static vars are unequal if the base VAR_DECL is different. The reason for all this is because the LTO reader/writer of jump_functions create the new tree already. The input for the LTO writer contains the same tree node for the decl in main and the jump_function (val.constant), but as it uses a different output_block (hence unshared cache) it can't find the tree and emits a new copy. For whatever reason richis patch makes this work, but I can't see why it does ... ;-/ -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42401
