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author | Alexander Monakov <amonakov@ispras.ru> | 2020-02-14 20:14:36 +0300 |
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committer | Alexander Monakov <amonakov@ispras.ru> | 2020-02-14 20:22:36 +0300 |
commit | d8305a03b4f0bb081dd9c88917cc8c48def22a80 (patch) | |
tree | cb1eb11e78e31963e2d7e79195a9170a281aa2aa /gcc/rtlanal.c | |
parent | 519a33f954fd71cb8b74053e168e23a1cb00d30b (diff) | |
download | gcc-d8305a03b4f0bb081dd9c88917cc8c48def22a80.zip gcc-d8305a03b4f0bb081dd9c88917cc8c48def22a80.tar.gz gcc-d8305a03b4f0bb081dd9c88917cc8c48def22a80.tar.bz2 |
rtlanal: optimize costly division in rtx_cost
There's a costly signed 64-bit division in rtx_cost on x86 as well as
any other target where UNITS_PER_WORD expands to TARGET_64BIT ? 8 : 4.
It's also evident that rtx_cost does redundant work for a SET.
Obviously the variable named 'factor' rarely exceeds 1, so in the
majority of cases it can be computed with a well-predictable branch
rather than a division.
This patch makes rtx_cost do the division only in case mode is wider
than UNITS_PER_WORD, and also moves a test for a SET up front to avoid
redundancy.
No functional change.
* rtlanal.c (rtx_cost): Handle a SET up front. Avoid division if
the mode is not wider than UNITS_PER_WORD.
Diffstat (limited to 'gcc/rtlanal.c')
-rw-r--r-- | gcc/rtlanal.c | 21 |
1 files changed, 9 insertions, 12 deletions
diff --git a/gcc/rtlanal.c b/gcc/rtlanal.c index 9a7afcc..c7ab86e 100644 --- a/gcc/rtlanal.c +++ b/gcc/rtlanal.c @@ -4207,18 +4207,23 @@ rtx_cost (rtx x, machine_mode mode, enum rtx_code outer_code, const char *fmt; int total; int factor; + unsigned mode_size; if (x == 0) return 0; - if (GET_MODE (x) != VOIDmode) + if (GET_CODE (x) == SET) + /* A SET doesn't have a mode, so let's look at the SET_DEST to get + the mode for the factor. */ + mode = GET_MODE (SET_DEST (x)); + else if (GET_MODE (x) != VOIDmode) mode = GET_MODE (x); + mode_size = estimated_poly_value (GET_MODE_SIZE (mode)); + /* A size N times larger than UNITS_PER_WORD likely needs N times as many insns, taking N times as long. */ - factor = estimated_poly_value (GET_MODE_SIZE (mode)) / UNITS_PER_WORD; - if (factor == 0) - factor = 1; + factor = mode_size > UNITS_PER_WORD ? mode_size / UNITS_PER_WORD : 1; /* Compute the default costs of certain things. Note that targetm.rtx_costs can override the defaults. */ @@ -4243,14 +4248,6 @@ rtx_cost (rtx x, machine_mode mode, enum rtx_code outer_code, /* Used in combine.c as a marker. */ total = 0; break; - case SET: - /* A SET doesn't have a mode, so let's look at the SET_DEST to get - the mode for the factor. */ - mode = GET_MODE (SET_DEST (x)); - factor = estimated_poly_value (GET_MODE_SIZE (mode)) / UNITS_PER_WORD; - if (factor == 0) - factor = 1; - /* FALLTHRU */ default: total = factor * COSTS_N_INSNS (1); } |