From 62473daf8169a04a07409f344d938bc51a4536c3 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= Date: Thu, 25 Jun 2015 13:21:14 +0200 Subject: 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. --- erts/emulator/beam/beam_emu.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'erts/emulator/beam/beam_emu.c') 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); \ -- cgit v1.2.3