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authorBjörn Gustavsson <[email protected]>2010-12-08 15:27:37 +0100
committerBjörn Gustavsson <[email protected]>2011-01-17 15:23:46 +0100
commit74d7bd100b742a803c8de82c9c997308cf871038 (patch)
tree8230b273d29b0c2f60950c9c7a0db747d217d18d /erts/emulator
parentb166f8975387d7ef07409e841d45c2cd74c2282e (diff)
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Optimize addition of a small integer to a variable
Introduce a new i_increment/4 to optimize the addition of a register and a small integer. This instruction saves two instruction words compared to the standard instructions (an i_fetch/2 instruction followed by a i_plus/3 instruction) and will also be slightly faster.
Diffstat (limited to 'erts/emulator')
-rw-r--r--erts/emulator/beam/beam_emu.c46
-rw-r--r--erts/emulator/beam/beam_load.c46
-rw-r--r--erts/emulator/beam/ops.tab20
-rw-r--r--erts/emulator/test/beam_literals_SUITE.erl37
4 files changed, 146 insertions, 3 deletions
diff --git a/erts/emulator/beam/beam_emu.c b/erts/emulator/beam/beam_emu.c
index afba17f7bd..741ba8fb93 100644
--- a/erts/emulator/beam/beam_emu.c
+++ b/erts/emulator/beam/beam_emu.c
@@ -1276,6 +1276,52 @@ void process_main(void)
#define STORE_ARITH_RESULT(res) StoreBifResult(2, (res));
#define ARITH_FUNC(name) erts_gc_##name
+ {
+ Eterm increment_reg_val;
+ Eterm increment_val;
+ Uint live;
+ Eterm result;
+
+ OpCase(i_increment_yIId):
+ increment_reg_val = yb(Arg(0));
+ goto do_increment;
+
+ OpCase(i_increment_xIId):
+ increment_reg_val = xb(Arg(0));
+ goto do_increment;
+
+ OpCase(i_increment_rIId):
+ increment_reg_val = r(0);
+ I--;
+
+ do_increment:
+ increment_val = Arg(1);
+ if (is_small(increment_reg_val)) {
+ Sint i = signed_val(increment_reg_val) + increment_val;
+ ASSERT(MY_IS_SSMALL(i) == IS_SSMALL(i));
+ if (MY_IS_SSMALL(i)) {
+ result = make_small(i);
+ store_result:
+ StoreBifResult(3, result);
+ }
+ }
+
+ live = Arg(2);
+ SWAPOUT;
+ reg[0] = r(0);
+ reg[live] = increment_reg_val;
+ reg[live+1] = make_small(increment_val);
+ result = erts_gc_mixed_plus(c_p, reg, live);
+ r(0) = reg[0];
+ SWAPIN;
+ ERTS_HOLE_CHECK(c_p);
+ if (is_value(result)) {
+ goto store_result;
+ }
+ ASSERT(c_p->freason != BADMATCH || is_value(c_p->fvalue));
+ goto find_func_info;
+ }
+
OpCase(i_plus_jId):
{
Eterm result;
diff --git a/erts/emulator/beam/beam_load.c b/erts/emulator/beam/beam_load.c
index 2d57c8a218..e6448931eb 100644
--- a/erts/emulator/beam/beam_load.c
+++ b/erts/emulator/beam/beam_load.c
@@ -2787,6 +2787,52 @@ gen_skip_bits2(LoaderState* stp, GenOpArg Fail, GenOpArg Ms,
return op;
}
+static GenOp*
+gen_increment(LoaderState* stp, GenOpArg Reg, GenOpArg Integer,
+ GenOpArg Live, GenOpArg Dst)
+{
+ GenOp* op;
+
+ NEW_GENOP(stp, op);
+ op->op = genop_i_increment_4;
+ op->arity = 4;
+ op->next = NULL;
+ op->a[0] = Reg;
+ op->a[1].type = TAG_u;
+ op->a[1].val = Integer.val;
+ op->a[2] = Live;
+ op->a[3] = Dst;
+ return op;
+}
+
+static GenOp*
+gen_increment_from_minus(LoaderState* stp, GenOpArg Reg, GenOpArg Integer,
+ GenOpArg Live, GenOpArg Dst)
+{
+ GenOp* op;
+
+ NEW_GENOP(stp, op);
+ op->op = genop_i_increment_4;
+ op->arity = 4;
+ op->next = NULL;
+ op->a[0] = Reg;
+ op->a[1].type = TAG_u;
+ op->a[1].val = -Integer.val;
+ op->a[2] = Live;
+ op->a[3] = Dst;
+ return op;
+}
+
+/*
+ * Test whether the negation of the given number is small.
+ */
+static int
+negation_is_small(LoaderState* stp, GenOpArg Int)
+{
+ return Int.type == TAG_i && IS_SSMALL(-Int.val);
+}
+
+
static int
smp(LoaderState* stp)
{
diff --git a/erts/emulator/beam/ops.tab b/erts/emulator/beam/ops.tab
index 6db55e1402..029d7b512c 100644
--- a/erts/emulator/beam/ops.tab
+++ b/erts/emulator/beam/ops.tab
@@ -1371,7 +1371,21 @@ apply I
apply_last I P
#
-# New GCing arithmetic instructions.
+# Optimize addition and subtraction of small literals using
+# the i_increment/4 instruction (in bodies, not in guards).
+#
+
+gc_bif2 p Live u$bif:erlang:splus/2 Int=i Reg=d Dst => \
+ gen_increment(Reg, Int, Live, Dst)
+gc_bif2 p Live u$bif:erlang:splus/2 Reg=d Int=i Dst => \
+ gen_increment(Reg, Int, Live, Dst)
+
+gc_bif2 p Live u$bif:erlang:sminus/2 Reg=d Int=i Dst | \
+ negation_is_small(Int) => \
+ gen_increment_from_minus(Reg, Int, Live, Dst)
+
+#
+# GCing arithmetic instructions.
#
gc_bif2 Fail I u$bif:erlang:splus/2 S1 S2 Dst=d => i_fetch S1 S2 | i_plus Fail I Dst
@@ -1394,6 +1408,10 @@ gc_bif1 Fail I u$bif:erlang:bnot/1 Src Dst=d => i_int_bnot Fail Src I Dst
gc_bif1 Fail I u$bif:erlang:sminus/1 Src Dst=d => i_fetch i Src | i_minus Fail I Dst
gc_bif1 Fail I u$bif:erlang:splus/1 Src Dst=d => i_fetch i Src | i_plus Fail I Dst
+i_increment r I I d
+i_increment x I I d
+i_increment y I I d
+
i_plus j I d
i_minus j I d
i_times j I d
diff --git a/erts/emulator/test/beam_literals_SUITE.erl b/erts/emulator/test/beam_literals_SUITE.erl
index f56d7ac1c5..1eda939cf8 100644
--- a/erts/emulator/test/beam_literals_SUITE.erl
+++ b/erts/emulator/test/beam_literals_SUITE.erl
@@ -23,7 +23,8 @@
matching_bigs/1, matching_more_bigs/1,
matching_bigs_and_smalls/1, badmatch/1, case_clause/1,
receiving/1, literal_type_tests/1,
- put_list/1, fconv/1, literal_case_expression/1]).
+ put_list/1, fconv/1, literal_case_expression/1,
+ increment/1]).
-include("test_server.hrl").
@@ -32,7 +33,7 @@ all(suite) ->
matching_bigs, matching_more_bigs,
matching_bigs_and_smalls, badmatch, case_clause,
receiving, literal_type_tests,
- put_list, fconv, literal_case_expression].
+ put_list, fconv, literal_case_expression, increment].
putting(doc) -> "Test creating lists and tuples containing big number literals.";
putting(Config) when is_list(Config) ->
@@ -419,6 +420,38 @@ literal_case_expression(Config) when is_list(Config) ->
?line code:purge(Mod),
ok.
+%% Test the i_increment instruction.
+increment(Config) when is_list(Config) ->
+ %% In the 32-bit emulator, Neg32 can be represented as a small,
+ %% but -Neg32 cannot. Therefore the i_increment instruction must
+ %% not be used in the subtraction that follows (since i_increment
+ %% cannot handle a bignum literal).
+ Neg32 = -(1 bsl 27),
+ Big32 = id(1 bsl 32),
+ Result32 = (1 bsl 32) + (1 bsl 27),
+ ?line Result32 = Big32 + (1 bsl 27),
+ ?line Result32 = Big32 - Neg32,
+
+ %% Same thing, but for the 64-bit emulator.
+ Neg64 = -(1 bsl 59),
+ Big64 = id(1 bsl 64),
+ Result64 = (1 bsl 64) + (1 bsl 59),
+ ?line Result64 = Big64 + (1 bsl 59),
+ ?line Result64 = Big64 - Neg64,
+
+ %% Test error handling for the i_increment instruction.
+ Bad = id(bad),
+ ?line {'EXIT',{badarith,_}} = (catch Bad + 42),
+
+ %% Small operands, but a big result.
+ Res32 = 1 bsl 27,
+ Small32 = id(Res32-1),
+ ?line Res32 = Small32 + 1,
+ Res64 = 1 bsl 59,
+ Small64 = id(Res64-1),
+ ?line Res64 = Small64 + 1,
+ ok.
+
%% Help functions.
chksum(Term) ->