diff options
Diffstat (limited to 'gcc/flow.c')
| -rw-r--r-- | gcc/flow.c | 108 |
1 files changed, 108 insertions, 0 deletions
@@ -306,6 +306,8 @@ static void mark_set_regs PARAMS ((struct propagate_block_info *, static void mark_set_1 PARAMS ((struct propagate_block_info *, enum rtx_code, rtx, rtx, rtx, int)); +static int find_regno_partial PARAMS ((rtx *, void *)); + #ifdef HAVE_conditional_execution static int mark_regno_cond_dead PARAMS ((struct propagate_block_info *, int, rtx)); @@ -1290,6 +1292,112 @@ calculate_global_regs_live (blocks_in, blocks_out, flags) free (queue); } + + +/* This structure is used to pass parameters to an from the + the function find_regno_partial(). It is used to pass in the + register number we are looking, as well as to return any rtx + we find. */ + +typedef struct { + unsigned regno_to_find; + rtx retval; +} find_regno_partial_param; + + +/* Find the rtx for the reg numbers specified in 'data' if it is + part of an expression which only uses part of the register. Return + it in the structure passed in. */ +static int +find_regno_partial (ptr, data) + rtx *ptr; + void *data; +{ + find_regno_partial_param *param = (find_regno_partial_param *)data; + unsigned reg = param->regno_to_find; + param->retval = NULL_RTX; + + if (*ptr == NULL_RTX) + return 0; + + switch (GET_CODE (*ptr)) + { + case ZERO_EXTRACT: + case SIGN_EXTRACT: + case STRICT_LOW_PART: + if (GET_CODE (XEXP (*ptr, 0)) == REG && REGNO (XEXP (*ptr, 0)) == reg) + { + param->retval = *ptr; + return 1; + } + break; + + case SUBREG: + if (GET_CODE (SUBREG_REG (*ptr)) == REG + && REGNO (SUBREG_REG (*ptr)) == reg) + { + param->retval = *ptr; + return 1; + } + break; + } + + return 0; +} + +/* Process all immediate successors of the entry block looking for pseudo + registers which are live on entry. Find all of those whose first + instance is a partial register reference of some kind, and initialize + them to 0 after the entry block. This will prevent bit sets within + registers whose value is unknown, and may contain some kind of sticky + bits we don't want. */ + +int +initialize_uninitialized_subregs () +{ + rtx insn; + edge e; + int reg, did_something = 0; + find_regno_partial_param param; + + for (e = ENTRY_BLOCK_PTR->succ; e; e = e->succ_next) + { + basic_block bb = e->dest; + regset map = bb->global_live_at_start; + EXECUTE_IF_SET_IN_REG_SET (map, + FIRST_PSEUDO_REGISTER, reg, + { + int uid = REGNO_FIRST_UID (reg); + rtx i; + + /* Find an insn which mentions the register we are looking for. + Its preferable to have an instance of the register's rtl since + there may be various flags set which we need to duplicate. + If we can't find it, its probably an automatic whose initial + value doesnt matter, or hopefully something we dont care about. */ + for (i = get_insns (); i && INSN_UID (i) != uid; i = NEXT_INSN (i)) + ; + if (i != NULL_RTX) + { + /* Found the insn, now get the REG rtx, if we can. */ + param.regno_to_find = reg; + for_each_rtx (&i, find_regno_partial, ¶m); + if (param.retval != NULL_RTX) + { + insn = gen_move_insn (param.retval, + CONST0_RTX (GET_MODE (param.retval))); + insert_insn_on_edge (insn, e); + did_something = 1; + } + } + }); + } + + if (did_something) + commit_edge_insertions (); + return did_something; +} + /* Subroutines of life analysis. */ |