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tcg: Improve move ops in liveness_pass_2 

If the output of the move is dead, then the last use is in
the store.  If we propagate the input to the store, then we
can remove the move opcode entirely.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson 2020-04-23 12:27:53 -07:00
parent cea94ba36d
commit 61f15c487f
1 changed files with 56 additions and 22 deletions
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34
tcg/tcg.c
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@ -2982,6 +2982,39 @@ static bool liveness_pass_2(TCGContext *s)
}
/* Outputs become available. */
if (opc == INDEX_op_mov_i32 || opc == INDEX_op_mov_i64) {
arg_ts = arg_temp(op->args[0]);
dir_ts = arg_ts->state_ptr;
if (dir_ts) {
op->args[0] = temp_arg(dir_ts);
changes = true;
/* The output is now live and modified. */
arg_ts->state = 0;
if (NEED_SYNC_ARG(0)) {
TCGOpcode sopc = (arg_ts->type == TCG_TYPE_I32
? INDEX_op_st_i32
: INDEX_op_st_i64);
TCGOp *sop = tcg_op_insert_after(s, op, sopc);
TCGTemp *out_ts = dir_ts;
if (IS_DEAD_ARG(0)) {
out_ts = arg_temp(op->args[1]);
arg_ts->state = TS_DEAD;
tcg_op_remove(s, op);
} else {
arg_ts->state = TS_MEM;
}
sop->args[0] = temp_arg(out_ts);
sop->args[1] = temp_arg(arg_ts->mem_base);
sop->args[2] = arg_ts->mem_offset;
} else {
tcg_debug_assert(!IS_DEAD_ARG(0));
}
}
} else {
for (i = 0; i < nb_oargs; i++) {
arg_ts = arg_temp(op->args[i]);
dir_ts = arg_ts->state_ptr;
@ -3013,6 +3046,7 @@ static bool liveness_pass_2(TCGContext *s)
}
}
}
}
return changes;
}