From b166f8975387d7ef07409e841d45c2cd74c2282e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Tue, 7 Dec 2010 16:04:05 +0100
Subject: Introduce a special instruction for select_val with two values

The new instruction will save one word (because no size operand
is needed), and is slightly faster.

Handle select_tuple_arity in the same way.
---
 erts/emulator/beam/beam_emu.c  | 47 ++++++++++++++++++++++++++++++++++++++++++
 erts/emulator/beam/beam_load.c | 27 ++++++++++++++++++++++++
 erts/emulator/beam/ops.tab     |  9 ++++++++
 3 files changed, 83 insertions(+)

(limited to 'erts/emulator/beam')

diff --git a/erts/emulator/beam/beam_emu.c b/erts/emulator/beam/beam_emu.c
index ea813ef09f..afba17f7bd 100644
--- a/erts/emulator/beam/beam_emu.c
+++ b/erts/emulator/beam/beam_emu.c
@@ -1882,6 +1882,53 @@ void process_main(void)
      NextPF(0, next);
  }
 
+
+ {
+     Eterm select_val2;
+
+ OpCase(i_select_tuple_arity2_yfAfAf):
+     select_val2 = yb(Arg(0));
+     goto do_select_tuple_arity2;
+
+ OpCase(i_select_tuple_arity2_xfAfAf):
+     select_val2 = xb(Arg(0));
+     goto do_select_tuple_arity2;
+
+ OpCase(i_select_tuple_arity2_rfAfAf):
+     select_val2 = r(0);
+     I--;
+
+ do_select_tuple_arity2:
+     if (is_not_tuple(select_val2)) {
+	 goto select_val2_fail;
+     }
+     select_val2 = *tuple_val(select_val2);
+     goto do_select_val2;
+
+ OpCase(i_select_val2_yfcfcf):
+     select_val2 = yb(Arg(0));
+     goto do_select_val2;
+
+ OpCase(i_select_val2_xfcfcf):
+     select_val2 = xb(Arg(0));
+     goto do_select_val2;
+
+ OpCase(i_select_val2_rfcfcf):
+     select_val2 = r(0);
+     I--;
+
+ do_select_val2:
+     if (select_val2 == Arg(2)) {
+	 I += 2;
+     } else if (select_val2 == Arg(4)) {
+	 I += 4;
+     }
+
+ select_val2_fail:
+     SET_I((BeamInstr *) Arg(1));
+     Goto(*I);
+ }
+
  {
      Eterm select_val;
 
diff --git a/erts/emulator/beam/beam_load.c b/erts/emulator/beam/beam_load.c
index 02aef95a52..2d57c8a218 100644
--- a/erts/emulator/beam/beam_load.c
+++ b/erts/emulator/beam/beam_load.c
@@ -2978,6 +2978,21 @@ gen_select_tuple_arity(LoaderState* stp, GenOpArg S, GenOpArg Fail,
 	ASSERT(op->a[i].val < op->a[i+2].val);
     }
 #endif
+
+    /*
+     * Use a special-cased instruction if there are only two values.
+     */
+    if (size == 2) {
+	op->op = genop_i_select_tuple_arity2_6;
+	op->arity--;
+	op->a[2].type = TAG_u;
+	op->a[2].val = arityval(op->a[3].val);
+	op->a[3] = op->a[4];
+	op->a[4].type = TAG_u;
+	op->a[4].val = arityval(op->a[5].val);
+	op->a[5] = op->a[6];
+    }
+
     return op;
 }
 
@@ -3228,6 +3243,18 @@ gen_select_val(LoaderState* stp, GenOpArg S, GenOpArg Fail,
     }
 #endif
 
+    /*
+     * Use a special-cased instruction if there are only two values.
+     */
+    if (size == 2) {
+	op->op = genop_i_select_val2_6;
+	op->arity--;
+	op->a[2] = op->a[3];
+	op->a[3] = op->a[4];
+	op->a[4] = op->a[5];
+	op->a[5] = op->a[6];
+    }
+
     return op;
 }
 
diff --git a/erts/emulator/beam/ops.tab b/erts/emulator/beam/ops.tab
index 04e2e72b0d..6db55e1402 100644
--- a/erts/emulator/beam/ops.tab
+++ b/erts/emulator/beam/ops.tab
@@ -160,6 +160,15 @@ select_tuple_arity S=d Fail=f Size=u Rest=* => \
 i_select_val r f I
 i_select_val x f I
 i_select_val y f I
+
+i_select_val2 r f c f c f
+i_select_val2 x f c f c f
+i_select_val2 y f c f c f
+
+i_select_tuple_arity2 r f A f A f
+i_select_tuple_arity2 x f A f A f
+i_select_tuple_arity2 y f A f A f
+
 i_select_tuple_arity r f I
 i_select_tuple_arity x f I
 i_select_tuple_arity y f I
-- 
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