https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66790
--- Comment #22 from Eric Botcazou <ebotcazou at gcc dot gnu.org> --- > A native English speaker would say that this could be written better. I > would suggest the term "on at least one path" and this is what a MAY problem > is generally defined as. Thanks. Here's a proposed amended wording: Index: df-problems.c =================================================================== --- df-problems.c (revision 227819) +++ df-problems.c (working copy) @@ -1309,22 +1309,23 @@ df_lr_verify_transfer_functions (void) /*---------------------------------------------------------------------------- - LIVE AND MUST-INITIALIZED REGISTERS. + LIVE AND MAY-INITIALIZED REGISTERS. This problem first computes the IN and OUT bitvectors for the - must-initialized registers problems, which is a forward problem. - It gives the set of registers for which we MUST have an available - definition on any path from the entry block to the entry/exit of - a basic block. Sets generate a definition, while clobbers kill + may-initialized registers problems, which is a forward problem. + It gives the set of registers for which we MAY have an available + definition, i.e. for which there is an available definition on + at least one path from the entry block to the entry/exit of a + basic block. Sets generate a definition, while clobbers kill a definition. In and out bitvectors are built for each basic block and are indexed by regnum (see df.h for details). In and out bitvectors in struct - df_live_bb_info actually refers to the must-initialized problem; + df_live_bb_info actually refers to the may-initialized problem; Then, the in and out sets for the LIVE problem itself are computed. These are the logical AND of the IN and OUT sets from the LR problem - and the must-initialized problem. + and the may-initialized problem. ----------------------------------------------------------------------------*/ /* Private data used to verify the solution for this problem. */ @@ -1531,7 +1532,7 @@ df_live_confluence_n (edge e) } -/* Transfer function for the forwards must-initialized problem. */ +/* Transfer function for the forwards may-initialized problem. */ static bool df_live_transfer_function (int bb_index) @@ -1555,7 +1556,7 @@ df_live_transfer_function (int bb_index) } -/* And the LR info with the must-initialized registers, to produce the LIVE info. */ +/* And the LR info with the may-initialized registers, to produce the LIVE info. */ static void df_live_finalize (bitmap all_blocks)