diff options
Diffstat (limited to 'gcc/flow.c')
| -rw-r--r-- | gcc/flow.c | 43 |
1 files changed, 25 insertions, 18 deletions
@@ -1853,13 +1853,15 @@ insn_dead_p (x, needed, call_ok) regset needed; int call_ok; { - register RTX_CODE code = GET_CODE (x); + enum rtx_code code = GET_CODE (x); + /* If setting something that's a reg or part of one, see if that register's altered value will be live. */ if (code == SET) { - register rtx r = SET_DEST (x); + rtx r = SET_DEST (x); + /* A SET that is a subroutine call cannot be dead. */ if (! call_ok && GET_CODE (SET_SRC (x)) == CALL) return 0; @@ -1873,15 +1875,13 @@ insn_dead_p (x, needed, call_ok) && rtx_equal_p (r, last_mem_set)) return 1; - while (GET_CODE (r) == SUBREG - || GET_CODE (r) == STRICT_LOW_PART - || GET_CODE (r) == ZERO_EXTRACT - || GET_CODE (r) == SIGN_EXTRACT) + while (GET_CODE (r) == SUBREG || GET_CODE (r) == STRICT_LOW_PART + || GET_CODE (r) == ZERO_EXTRACT) r = SUBREG_REG (r); if (GET_CODE (r) == REG) { - register int regno = REGNO (r); + int regno = REGNO (r); /* Don't delete insns to set global regs. */ if ((regno < FIRST_PSEUDO_REGISTER && global_regs[regno]) @@ -1913,26 +1913,33 @@ insn_dead_p (x, needed, call_ok) return 1; } } + /* If performing several activities, insn is dead if each activity is individually dead. Also, CLOBBERs and USEs can be ignored; a CLOBBER or USE that's inside a PARALLEL doesn't make the insn worth keeping. */ else if (code == PARALLEL) { - register int i = XVECLEN (x, 0); + int i = XVECLEN (x, 0); + for (i--; i >= 0; i--) - { - rtx elt = XVECEXP (x, 0, i); - if (!insn_dead_p (elt, needed, call_ok) - && GET_CODE (elt) != CLOBBER - && GET_CODE (elt) != USE) - return 0; - } + if (GET_CODE (XVECEXP (x, 0, i)) != CLOBBER + && GET_CODE (XVECEXP (x, 0, i)) != USE + && ! insn_dead_p (XVECEXP (x, 0, i), needed, call_ok)) + return 0; + return 1; } - /* We do not check CLOBBER or USE here. - An insn consisting of just a CLOBBER or just a USE - should not be deleted. */ + + /* A CLOBBER of a pseudo-register that is dead serves no purpose. That + is not necessarily true for hard registers. */ + else if (code == CLOBBER && GET_CODE (XEXP (x, 0)) == REG + && REGNO (XEXP (x, 0)) >= FIRST_PSEUDO_REGISTER + && ! REGNO_REG_SET_P (needed, REGNO (XEXP (x, 0)))) + return 1; + + /* We do not check other CLOBBER or USE here. An insn consisting of just + a CLOBBER or just a USE should not be deleted. */ return 0; } |