Make tcg_constant_folding do copy and constant propagation. It is a
preparational work before actual constant folding.
Signed-off-by: Kirill Batuzov <batuz...@ispras.ru>
---
tcg/optimize.c | 123 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 123 insertions(+), 0 deletions(-)
diff --git a/tcg/optimize.c b/tcg/optimize.c
index cf31d18..a761c51 100644
--- a/tcg/optimize.c
+++ b/tcg/optimize.c
@@ -31,22 +31,139 @@
#include "qemu-common.h"
#include "tcg-op.h"
+typedef enum {
+ TCG_TEMP_UNDEF = 0,
+ TCG_TEMP_CONST,
+ TCG_TEMP_COPY,
+ TCG_TEMP_ANY
+} tcg_temp_state;
+
+static int mov_to_movi(int op)
+{
+ switch (op) {
+ case INDEX_op_mov_i32: return INDEX_op_movi_i32;
+#if TCG_TARGET_REG_BITS == 64
+ case INDEX_op_mov_i64: return INDEX_op_movi_i64;
+#endif
+ default:
+ fprintf(stderr, "Unrecognized operation %d in mov_to_movi.\n", op);
+ tcg_abort();
+ }
+}
+
+/* Reset TEMP's state to TCG_TEMP_ANY. If TEMP was a representative of some
+ class of equivalent temp's, a new representative should be chosen in this
+ class. */
+static void reset_temp(tcg_temp_state *state, tcg_target_ulong *vals,
+ TCGArg temp, int nb_temps, int nb_globals)
+{
+ int i;
+ TCGArg new_base;
+ new_base = (TCGArg)-1;
+ for (i = nb_globals; i < nb_temps; i++) {
+ if (state[i] == TCG_TEMP_COPY && vals[i] == temp) {
+ if (new_base == ((TCGArg)-1)) {
+ new_base = (TCGArg)i;
+ state[i] = TCG_TEMP_ANY;
+ } else {
+ vals[i] = new_base;
+ }
+ }
+ }
+ for (i = 0; i < nb_globals; i++) {
+ if (state[i] == TCG_TEMP_COPY && vals[i] == temp) {
+ if (new_base == ((TCGArg)-1)) {
+ state[i] = TCG_TEMP_ANY;
+ } else {
+ vals[i] = new_base;
+ }
+ }
+ }
+ state[temp] = TCG_TEMP_ANY;
+}
+
+/* Propagate constants and copies, fold constant expressions. */
static TCGArg *tcg_constant_folding(TCGContext *s, uint16_t *tcg_opc_ptr,
TCGArg *args, TCGOpDef *tcg_op_defs)
{
int i, nb_ops, op_index, op, nb_temps, nb_globals;
const TCGOpDef *def;
TCGArg *gen_args;
+ /* Array VALS has an element for each temp.
+ If this temp holds a constant then its value is kept in VALS' element.
+ If this temp is a copy of other ones then this equivalence class'
+ representative is kept in VALS' element.
+ If this temp is neither copy nor constant then corresponding VALS'
+ element is unused. */
+ static tcg_target_ulong vals[TCG_MAX_TEMPS];
+ static tcg_temp_state state[TCG_MAX_TEMPS];
nb_temps = s->nb_temps;
nb_globals = s->nb_globals;
+ memset(state, 0, nb_temps * sizeof(tcg_temp_state));
nb_ops = tcg_opc_ptr - gen_opc_buf;
gen_args = args;
for (op_index = 0; op_index < nb_ops; op_index++) {
op = gen_opc_buf[op_index];
def = &tcg_op_defs[op];
+ /* Do copy propagation */
+ if (op != INDEX_op_call) {
+ for (i = def->nb_oargs; i < def->nb_oargs + def->nb_iargs; i++) {
+ if (state[args[i]] == TCG_TEMP_COPY
+ && !(def->args_ct[i].ct & TCG_CT_IALIAS)
+ && (def->args_ct[i].ct & TCG_CT_REG)) {
+ args[i] = vals[args[i]];
+ }
+ }
+ }
+
+ /* Propagate constants through copy operations and do constant
+ folding. Constants will be substituted to arguments by register
+ allocator where needed and possible. Also detect copies. */
switch (op) {
+ case INDEX_op_mov_i32:
+#if TCG_TARGET_REG_BITS == 64
+ case INDEX_op_mov_i64:
+#endif
+ if ((state[args[1]] == TCG_TEMP_COPY
+ && vals[args[1]] == args[0])
+ || args[0] == args[1]) {
+ args += 2;
+ gen_opc_buf[op_index] = INDEX_op_nop;
+ break;
+ }
+ if (state[args[1]] != TCG_TEMP_CONST) {
+ reset_temp(state, vals, args[0], nb_temps, nb_globals);
+ if (args[1] >= s->nb_globals) {
+ state[args[0]] = TCG_TEMP_COPY;
+ vals[args[0]] = args[1];
+ }
+ gen_args[0] = args[0];
+ gen_args[1] = args[1];
+ gen_args += 2;
+ args += 2;
+ break;
+ } else {
+ /* Source argument is constant. Rewrite the operation and
+ let movi case handle it. */
+ op = mov_to_movi(op);
+ gen_opc_buf[op_index] = op;
+ args[1] = vals[args[1]];
+ /* fallthrough */
+ }
+ case INDEX_op_movi_i32:
+#if TCG_TARGET_REG_BITS == 64
+ case INDEX_op_movi_i64:
+#endif
+ reset_temp(state, vals, args[0], nb_temps, nb_globals);
+ state[args[0]] = TCG_TEMP_CONST;
+ vals[args[0]] = args[1];
+ gen_args[0] = args[0];
+ gen_args[1] = args[1];
+ gen_args += 2;
+ args += 2;
+ break;
case INDEX_op_call:
case INDEX_op_jmp:
case INDEX_op_br:
@@ -55,6 +172,7 @@ static TCGArg *tcg_constant_folding(TCGContext *s, uint16_t
*tcg_opc_ptr,
#if TCG_TARGET_REG_BITS == 64
case INDEX_op_brcond_i64:
#endif
+ memset(state, 0, nb_temps * sizeof(tcg_temp_state));
i = (op == INDEX_op_call) ?
(args[0] >> 16) + (args[0] & 0xffff) + 3 :
def->nb_args;
@@ -66,6 +184,11 @@ static TCGArg *tcg_constant_folding(TCGContext *s, uint16_t
*tcg_opc_ptr,
}
break;
default:
+ /* Default case: we do know nothing about operation so no
+ propagation is done. We only trash output args. */
+ for (i = 0; i < def->nb_oargs; i++) {
+ reset_temp(state, vals, args[i], nb_temps, nb_globals);
+ }
for (i = 0; i < def->nb_args; i++) {
gen_args[i] = args[i];
}
--
1.7.4.1
