@@ -282,8 +282,20 @@ static bool
combine_set_extension (ext_cand *cand, rtx curr_insn, rtx *orig_set)
{
rtx orig_src = SET_SRC (*orig_set);
- rtx new_reg = gen_rtx_REG (cand->mode, REGNO (SET_DEST (*orig_set)));
rtx new_set;
+ rtx cand_pat = PATTERN (cand->insn);
+
+ /* If the extension's source/destination registers are not the same
+ then we need to change the original load to reference the destination
+ of the extension. Then we need to emit a copy from that destination
+ to the original destination of the load. */
+ rtx new_reg;
+ bool copy_needed
+ = (REGNO (SET_DEST (cand_pat)) != REGNO (XEXP (SET_SRC (cand_pat), 0)));
+ if (copy_needed)
+ new_reg = gen_rtx_REG (cand->mode, REGNO (SET_DEST (cand_pat)));
+ else
+ new_reg = gen_rtx_REG (cand->mode, REGNO (SET_DEST (*orig_set)));
/* Merge constants by directly moving the constant into the register under
some conditions. Recall that RTL constants are sign-extended. */
@@ -342,7 +354,8 @@ combine_set_extension (ext_cand *cand, rtx curr_insn, rtx *orig_set)
if (dump_file)
{
fprintf (dump_file,
- "Tentatively merged extension with definition:\n");
+ "Tentatively merged extension with definition %s:\n",
+ (copy_needed) ? "(copy needed)" : "");
print_rtl_single (dump_file, curr_insn);
}
return true;
@@ -662,6 +675,53 @@ combine_reaching_defs (ext_cand *cand, const_rtx set_pat, ext_state *state)
if (!outcome)
return false;
+ /* If the destination operand of the extension is a different
+ register than the source operand, then additional restrictions
+ are needed. */
+ if ((REGNO (SET_DEST (PATTERN (cand->insn)))
+ != REGNO (XEXP (SET_SRC (PATTERN (cand->insn)), 0))))
+ {
+ /* In theory we could handle more than one reaching def, it
+ just makes the code to update the insn stream more complex. */
+ if (state->defs_list.length () != 1)
+ return false;
+
+ /* We require the candidate not already be modified. This may
+ be overly conservative. */
+ if (state->modified[INSN_UID (cand->insn)].kind != EXT_MODIFIED_NONE)
+ return false;
+
+ /* There's only one reaching def. */
+ rtx def_insn = state->defs_list[0];
+
+ /* The defining statementmust not have been modified either. */
+ if (state->modified[INSN_UID (def_insn)].kind != EXT_MODIFIED_NONE)
+ return false;
+
+ /* The defining statement and candidate insn must be in the same block.
+ This is merely to keep the test for safety and updating the insn
+ stream simple. */
+ if (BLOCK_FOR_INSN (cand->insn) != BLOCK_FOR_INSN (def_insn))
+ return false;
+
+ /* If there is an overlap between the destination of DEF_INSN and
+ CAND->insn, then this transformation is not safe. Note we have
+ to test in the widened mode. */
+ rtx tmp_reg = gen_rtx_REG (GET_MODE (SET_DEST (PATTERN (cand->insn))),
+ REGNO (SET_DEST (PATTERN (def_insn))));
+ if (reg_overlap_mentioned_p (tmp_reg, SET_DEST (PATTERN (cand->insn))))
+ return false;
+
+ /* The destination register of the extension insn must not be
+ used or set between the def_insn and cand->insn exclusive. */
+ if (reg_used_between_p (SET_DEST (PATTERN (cand->insn)),
+ def_insn, cand->insn)
+ || reg_set_between_p (SET_DEST (PATTERN (cand->insn)),
+ def_insn, cand->insn))
+ return false;
+ }
+
+
/* If cand->insn has been already modified, update cand->mode to a wider
mode if possible, or punt. */
if (state->modified[INSN_UID (cand->insn)].kind != EXT_MODIFIED_NONE)
@@ -778,8 +838,7 @@ add_removable_extension (const_rtx expr, rtx insn,
if (REG_P (dest)
&& (code == SIGN_EXTEND || code == ZERO_EXTEND)
- && REG_P (XEXP (src, 0))
- && REGNO (dest) == REGNO (XEXP (src, 0)))
+ && REG_P (XEXP (src, 0)))
{
struct df_link *defs, *def;
ext_cand *cand;
@@ -863,6 +922,7 @@ find_and_remove_re (void)
int num_re_opportunities = 0, num_realized = 0, i;
vec<ext_cand> reinsn_list;
auto_vec<rtx> reinsn_del_list;
+ auto_vec<rtx> reinsn_copy_list;
ext_state state;
/* Construct DU chain to get all reaching definitions of each
@@ -899,11 +959,41 @@ find_and_remove_re (void)
if (dump_file)
fprintf (dump_file, "Eliminated the extension.\n");
num_realized++;
- reinsn_del_list.safe_push (curr_cand->insn);
+ if (REGNO (SET_DEST (PATTERN (curr_cand->insn)))
+ != REGNO (XEXP (SET_SRC (PATTERN (curr_cand->insn)), 0)))
+ {
+ reinsn_copy_list.safe_push (curr_cand->insn);
+ reinsn_copy_list.safe_push (state.defs_list[0]);
+ }
+ reinsn_del_list.safe_push (curr_cand->insn);
state.modified[INSN_UID (curr_cand->insn)].deleted = 1;
}
}
+ /* The copy list contains pairs of insns which describe copies we
+ need to insert into the INSN stream.
+
+ The first insn in each pair is the extension insn, from which
+ we derive the source and destination of the copy.
+
+ The second insn in each pair is the memory reference where the
+ extension will ultimately happen. We emit the new copy
+ immediately after this insn.
+
+ It may first appear that the arguments for the copy are reversed.
+ Remember that the memory reference will be changed to refer to the
+ destination of the extention. So we're actually emitting a copy
+ from the new destination to the old destination. */
+ for (unsigned int i = 0; i < reinsn_copy_list.length (); i += 2)
+ {
+ rtx curr_insn = reinsn_copy_list[i];
+ rtx pat = PATTERN (curr_insn);
+ rtx new_reg = gen_rtx_REG (GET_MODE (SET_DEST (pat)),
+ REGNO (XEXP (SET_SRC (pat), 0)));
+ rtx set = gen_rtx_SET (VOIDmode, new_reg, SET_DEST (pat));
+ emit_insn_after (set, reinsn_copy_list[i + 1]);
+ }
+
/* Delete all useless extensions here in one sweep. */
FOR_EACH_VEC_ELT (reinsn_del_list, i, curr_insn)
delete_insn (curr_insn);
new file mode 100644
@@ -0,0 +1,25 @@
+/* { dg-do compile { target {! ia32 } } } */
+/* { dg-options "-O2 -fdump-rtl-ree" } */
+
+
+#include <stdint.h>
+
+typedef (*inst_t)(int64_t rdi, int64_t rsi, int64_t rdx);
+
+int16_t code[256];
+inst_t dispatch[256];
+
+void an_inst(int64_t rdi, int64_t rsi, int64_t rdx) {
+ rdx = code[rdx];
+ uint8_t inst = (uint8_t) rdx;
+ rdx >>= 8;
+ dispatch[inst](rdi, rsi, rdx);
+}
+
+int main(void) {
+ return 0;
+}
+
+/* { dg-final { scan-rtl-dump "copy needed" "ree" } } */
+/* { dg-final { cleanup-rtl-dump "ree" } } */
+