From c19f47bf5e8fe3dbd10206a52d0e6e348f803933 Mon Sep 17 00:00:00 2001 From: Aurelien Jarno Date: Thu, 4 Jun 2015 21:47:08 +0200 Subject: [PATCH] tcg: fix dead computation for repeated input arguments When the same temp is used twice or more as an input argument to a TCG instruction, the dead computation code doesn't recognize the second use as a dead temp. This is because the temp is marked as live in the same loop where dead inputs are checked. The fix is to split the loop in two parts. This avoid emitting a move and using a register for the movcond instruction when used as "move if true" on x86-64. This might bring more improvements on RISC TCG targets which don't have outputs aliased to inputs. Reviewed-by: Richard Henderson Signed-off-by: Aurelien Jarno Message-Id: <1433447228-29425-3-git-send-email-aurelien@aurel32.net> Signed-off-by: Richard Henderson --- tcg/tcg.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/tcg/tcg.c b/tcg/tcg.c index 4a6eb26d0a..7e088b1f28 100644 --- a/tcg/tcg.c +++ b/tcg/tcg.c @@ -1387,16 +1387,20 @@ static void tcg_liveness_analysis(TCGContext *s) memset(dead_temps, 1, s->nb_globals); } - /* input args are live */ + /* record arguments that die in this helper */ for (i = nb_oargs; i < nb_iargs + nb_oargs; i++) { arg = args[i]; if (arg != TCG_CALL_DUMMY_ARG) { if (dead_temps[arg]) { dead_args |= (1 << i); } - dead_temps[arg] = 0; } } + /* input arguments are live for preceeding opcodes */ + for (i = nb_oargs; i < nb_oargs + nb_iargs; i++) { + arg = args[i]; + dead_temps[arg] = 0; + } s->op_dead_args[oi] = dead_args; s->op_sync_args[oi] = sync_args; } @@ -1531,12 +1535,16 @@ static void tcg_liveness_analysis(TCGContext *s) memset(mem_temps, 1, s->nb_globals); } - /* input args are live */ + /* record arguments that die in this opcode */ for (i = nb_oargs; i < nb_oargs + nb_iargs; i++) { arg = args[i]; if (dead_temps[arg]) { dead_args |= (1 << i); } + } + /* input arguments are live for preceeding opcodes */ + for (i = nb_oargs; i < nb_oargs + nb_iargs; i++) { + arg = args[i]; dead_temps[arg] = 0; } s->op_dead_args[oi] = dead_args;