diff options
Diffstat (limited to 'gcc/optabs.c')
| -rw-r--r-- | gcc/optabs.c | 80 |
1 files changed, 80 insertions, 0 deletions
diff --git a/gcc/optabs.c b/gcc/optabs.c index 5afd935..bf15d4f 100644 --- a/gcc/optabs.c +++ b/gcc/optabs.c @@ -122,6 +122,8 @@ static void prepare_float_lib_cmp (rtx *, rtx *, enum rtx_code *, enum machine_mode *, int *); static rtx widen_clz (enum machine_mode, rtx, rtx); static rtx expand_parity (enum machine_mode, rtx, rtx); +static rtx expand_ffs (enum machine_mode, rtx, rtx); +static rtx expand_ctz (enum machine_mode, rtx, rtx); static enum rtx_code get_rtx_code (enum tree_code, bool); static rtx vector_compare_rtx (tree, bool, enum insn_code); @@ -2561,6 +2563,68 @@ expand_parity (enum machine_mode mode, rtx op0, rtx target) return 0; } +/* Try calculating ffs(x) using clz(x). Since the ffs builtin promises + to return zero for a zero value and clz may have an undefined value + in that case, only do this if we know clz returns the right thing so + that we don't have to generate a test and branch. */ +static rtx +expand_ffs (enum machine_mode mode, rtx op0, rtx target) +{ + HOST_WIDE_INT val; + if (clz_optab->handlers[(int) mode].insn_code != CODE_FOR_nothing + && CLZ_DEFINED_VALUE_AT_ZERO (mode, val) == 2 + && val == GET_MODE_BITSIZE (mode)) + { + rtx last = get_last_insn (); + rtx temp; + + temp = expand_unop (mode, neg_optab, op0, NULL_RTX, true); + if (temp) + temp = expand_binop (mode, and_optab, op0, temp, NULL_RTX, + true, OPTAB_DIRECT); + if (temp) + temp = expand_unop (mode, clz_optab, temp, NULL_RTX, true); + if (temp) + temp = expand_binop (mode, sub_optab, + GEN_INT (GET_MODE_BITSIZE (mode)), + temp, + target, true, OPTAB_DIRECT); + if (temp == 0) + delete_insns_since (last); + return temp; + } + return 0; +} + +/* We can compute ctz(x) using clz(x) with a similar recipe. Here the ctz + builtin has an undefined result on zero, just like clz, so we don't have + to do that check. */ +static rtx +expand_ctz (enum machine_mode mode, rtx op0, rtx target) +{ + if (clz_optab->handlers[(int) mode].insn_code != CODE_FOR_nothing) + { + rtx last = get_last_insn (); + rtx temp; + + temp = expand_unop (mode, neg_optab, op0, NULL_RTX, true); + if (temp) + temp = expand_binop (mode, and_optab, op0, temp, NULL_RTX, + true, OPTAB_DIRECT); + if (temp) + temp = expand_unop (mode, clz_optab, temp, NULL_RTX, true); + if (temp) + temp = expand_binop (mode, xor_optab, temp, + GEN_INT (GET_MODE_BITSIZE (mode) - 1), + target, + true, OPTAB_DIRECT); + if (temp == 0) + delete_insns_since (last); + return temp; + } + return 0; +} + /* Extract the OMODE lowpart from VAL, which has IMODE. Under certain conditions, VAL may already be a SUBREG against which we cannot generate a further SUBREG. In this case, we expect forcing the value into a @@ -2886,6 +2950,22 @@ expand_unop (enum machine_mode mode, optab unoptab, rtx op0, rtx target, return temp; } + /* Try implementing ffs (x) in terms of clz (x). */ + if (unoptab == ffs_optab) + { + temp = expand_ffs (mode, op0, target); + if (temp) + return temp; + } + + /* Try implementing ctz (x) in terms of clz (x). */ + if (unoptab == ctz_optab) + { + temp = expand_ctz (mode, op0, target); + if (temp) + return temp; + } + try_libcall: /* Now try a library call in this mode. */ if (optab_handler (unoptab, mode)->libfunc) |