diff options
Diffstat (limited to 'gcc/regmove.c')
| -rw-r--r-- | gcc/regmove.c | 34 |
1 files changed, 26 insertions, 8 deletions
diff --git a/gcc/regmove.c b/gcc/regmove.c index 81a3520a4fe..800859582c7 100644 --- a/gcc/regmove.c +++ b/gcc/regmove.c @@ -62,7 +62,7 @@ static int find_matches PROTO((rtx, struct match *)); static int fixup_match_1 PROTO((rtx, rtx, rtx, rtx, rtx, int, int, int, FILE *)) ; static int reg_is_remote_constant_p PROTO((rtx, rtx, rtx)); -static int stable_but_for_p PROTO((rtx, rtx, rtx)); +static int stable_and_no_regs_but_for_p PROTO((rtx, rtx, rtx)); static int regclass_compatible_p PROTO((int, int)); static int loop_depth; @@ -1663,6 +1663,12 @@ fixup_match_1 (insn, set, src, src_subreg, dst, backward, operand_number, rtx src_note = find_reg_note (insn, REG_DEAD, src), dst_note; int length, s_length, true_loop_depth; + /* If SRC is marked as unchanging, we may not change it. + ??? Maybe we could get better code by removing the unchanging bit + instead, and changing it back if we don't succeed? */ + if (RTX_UNCHANGING_P (src)) + return 0; + if (! src_note) { /* Look for (set (regX) (op regA constX)) @@ -1679,7 +1685,7 @@ fixup_match_1 (insn, set, src, src_subreg, dst, backward, operand_number, && XEXP (SET_SRC (set), 0) == src && GET_CODE (XEXP (SET_SRC (set), 1)) == CONST_INT) insn_const = INTVAL (XEXP (SET_SRC (set), 1)); - else if (! stable_but_for_p (SET_SRC (set), src, dst)) + else if (! stable_and_no_regs_but_for_p (SET_SRC (set), src, dst)) return 0; else /* We might find a src_note while scanning. */ @@ -2089,10 +2095,16 @@ fixup_match_1 (insn, set, src, src_subreg, dst, backward, operand_number, } -/* return nonzero if X is stable but for mentioning SRC or mentioning / - changing DST . If in doubt, presume it is unstable. */ +/* return nonzero if X is stable and mentions no regsiters but for + mentioning SRC or mentioning / changing DST . If in doubt, presume + it is unstable. + The rationale is that we want to check if we can move an insn easily + while just paying attention to SRC and DST. A register is considered + stable if it has the RTX_UNCHANGING_P bit set, but that would still + leave the burden to update REG_DEAD / REG_UNUSED notes, so we don't + want any registers but SRC and DST. */ static int -stable_but_for_p (x, src, dst) +stable_and_no_regs_but_for_p (x, src, dst) rtx x, src, dst; { RTX_CODE code = GET_CODE (x); @@ -2103,13 +2115,19 @@ stable_but_for_p (x, src, dst) int i; char *fmt = GET_RTX_FORMAT (code); for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--) - if (fmt[i] == 'e' && ! stable_but_for_p (XEXP (x, i), src, dst)) + if (fmt[i] == 'e' + && ! stable_and_no_regs_but_for_p (XEXP (x, i), src, dst)) return 0; return 1; } case 'o': - if (x == src || x == dst) - return 1; + if (code == REG) + return x == src || x == dst; + /* If this is a MEM, look inside - there might be a register hidden in + the address of an unchanging MEM. */ + if (code == MEM + && ! stable_and_no_regs_but_for_p (XEXP (x, 0), src, dst)) + return 0; /* fall through */ default: return ! rtx_unstable_p (x); |