aboutsummaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
authorBjörn Gustavsson <[email protected]>2015-06-25 13:21:14 +0200
committerBjörn Gustavsson <[email protected]>2015-07-03 14:34:58 +0200
commit62473daf8169a04a07409f344d938bc51a4536c3 (patch)
tree153bf43a5833103f6d368de318288aad692fcedf
parent3dc2bee53b4d36f41821a6ab512cf01c958c11f9 (diff)
downloadotp-62473daf8169a04a07409f344d938bc51a4536c3.tar.gz
otp-62473daf8169a04a07409f344d938bc51a4536c3.tar.bz2
otp-62473daf8169a04a07409f344d938bc51a4536c3.zip
Introduce swap_temp/3 and swap/2
Sequences of three move instructionst that effectively swap the contents of two registers are fairly common. We can replace them with a swap_temp/3 instruction. The third operand is the temporary register to be used for swapping, since the temporary register may actually be used. If swap_temp/3 instruction is followed by a call, the temporary register will often (but not always) be killed by the call. If it is killed, we can replace the swap_temp/3 instruction with a slightly cheaper swap/2 instruction.
-rw-r--r--erts/emulator/beam/beam_emu.c14
-rw-r--r--erts/emulator/beam/beam_load.c6
-rw-r--r--erts/emulator/beam/ops.tab28
3 files changed, 48 insertions, 0 deletions
diff --git a/erts/emulator/beam/beam_emu.c b/erts/emulator/beam/beam_emu.c
index 2c10e7ae7c..4e6e7aa48a 100644
--- a/erts/emulator/beam/beam_emu.c
+++ b/erts/emulator/beam/beam_emu.c
@@ -545,6 +545,20 @@ void** beam_ops;
HTOP += 2; \
} while (0)
+#define Swap(R1, R2) \
+ do { \
+ Eterm V = R1; \
+ R1 = R2; \
+ R2 = V; \
+ } while (0)
+
+#define SwapTemp(R1, R2, Tmp) \
+ do { \
+ Eterm V = R1; \
+ R1 = R2; \
+ R2 = Tmp = V; \
+ } while (0)
+
#define Move(Src, Dst, Store) \
do { \
Eterm term = (Src); \
diff --git a/erts/emulator/beam/beam_load.c b/erts/emulator/beam/beam_load.c
index 871c2b1f55..1e3690fcd6 100644
--- a/erts/emulator/beam/beam_load.c
+++ b/erts/emulator/beam/beam_load.c
@@ -2702,6 +2702,12 @@ same_label(LoaderState* stp, GenOpArg Target, GenOpArg Label)
Target.val == Label.val;
}
+static int
+is_killed(LoaderState* stp, GenOpArg Reg, GenOpArg Live)
+{
+ return Reg.type == TAG_x && Live.type == TAG_u &&
+ Live.val <= Reg.val;
+}
/*
* Generate an instruction for element/2.
diff --git a/erts/emulator/beam/ops.tab b/erts/emulator/beam/ops.tab
index 97525c3b72..386de0a658 100644
--- a/erts/emulator/beam/ops.tab
+++ b/erts/emulator/beam/ops.tab
@@ -303,6 +303,34 @@ move_window3 x x x y
move_window4 x x x x y
move_window5 x x x x x y
+# Swap registers.
+move R1=x Tmp=x | move R2=xy R1 | move Tmp R2 => swap_temp R1 R2 Tmp
+
+swap_temp R1 R2 Tmp | line Loc | apply Live | is_killed(Tmp, Live) => \
+ swap R1 R2 | line Loc | apply Live
+
+swap_temp R1 R2 Tmp | line Loc | call Live Addr | is_killed(Tmp, Live) => \
+ swap R1 R2 | line Loc | call Live Addr
+swap_temp R1 R2 Tmp | call_only Live Addr | \
+ is_killed(Tmp, Live) => swap R1 R2 | call_only Live Addr
+swap_temp R1 R2 Tmp | call_last Live Addr D | \
+ is_killed(Tmp, Live) => swap R1 R2 | call_last Live Addr D
+
+swap_temp R1 R2 Tmp | line Loc | call_ext Live Addr | is_killed(Tmp, Live) => \
+ swap R1 R2 | line Loc | call_ext Live Addr
+swap_temp R1 R2 Tmp | line Loc | call_ext_only Live Addr | \
+ is_killed(Tmp, Live) => swap R1 R2 | line Loc | call_ext_only Live Addr
+swap_temp R1 R2 Tmp | line Loc | call_ext_last Live Addr D | \
+ is_killed(Tmp, Live) => swap R1 R2 | line Loc | call_ext_last Live Addr D
+
+%macro: swap_temp SwapTemp -pack
+swap_temp x x x
+swap_temp x y x
+
+%macro: swap Swap -pack
+swap x x
+swap x y
+
move Src=x D1=x | move Src=x D2=x => move_dup Src D1 D2
move Src=x SD=x | move SD=x D=x => move_dup Src SD D
move Src=x D1=x | move Src=x D2=y => move_dup Src D1 D2