@@ -1512,6 +1512,79 @@ replace_uses (struct invariant *inv, rtx reg, bool in_group)
return 1;
}
And the new patch:
+/* Whether invariant INV setting REG can be moved out of LOOP, at the end of
+ the block preceding its header. */
+
+static bool
+can_move_invariant_reg (struct loop *loop, struct invariant *inv, rtx reg)
+{
+ df_ref def, use;
+ unsigned int dest_regno, defs_in_loop_count = 0;
+ rtx_insn *insn = inv->insn;
+ basic_block bb = BLOCK_FOR_INSN (inv->insn);
+
+ /* We ignore hard register and memory access for cost and complexity reasons.
+ Hard register are few at this stage and expensive to consider as they
+ require building a separate data flow. Memory access would require using
+ df_simulate_* and can_move_insns_across functions and is more complex. */
+ if (!REG_P (reg) || HARD_REGISTER_P (reg))
+ return false;
+
+ /* Check whether the set is always executed. We could omit this condition if
+ we know that the register is unused outside of the loop, but it does not
+ seem worth finding out. */
+ if (!inv->always_executed)
+ return false;
+
+ /* Check that all uses reached by the def in insn would still be reached
+ it. */
+ dest_regno = REGNO (reg);
+ for (use = DF_REG_USE_CHAIN (dest_regno); use; use = DF_REF_NEXT_REG (use))
+ {
+ rtx_insn *use_insn;
+ basic_block use_bb;
+
+ use_insn = DF_REF_INSN (use);
+ use_bb = BLOCK_FOR_INSN (use_insn);
+
+ /* Ignore instruction considered for moving. */
+ if (use_insn == insn)
+ continue;
+
+ /* Don't consider uses outside loop. */
+ if (!flow_bb_inside_loop_p (loop, use_bb))
+ continue;
+
+ /* Don't move if a use is not dominated by def in insn. */
+ if (use_bb == bb && DF_INSN_LUID (insn) >= DF_INSN_LUID (use_insn))
+ return false;
+ if (!dominated_by_p (CDI_DOMINATORS, use_bb, bb))
+ return false;
+ }
+
+ /* Check for other defs. Any other def in the loop might reach a use
+ currently reached by the def in insn. */
+ for (def = DF_REG_DEF_CHAIN (dest_regno); def; def = DF_REF_NEXT_REG (def))
+ {
+ basic_block def_bb = DF_REF_BB (def);
+
+ /* Defs in exit block cannot reach a use they weren't already. */
+ if (single_succ_p (def_bb))
+ {
+ basic_block def_bb_succ;
+
+ def_bb_succ = single_succ (def_bb);
+ if (!flow_bb_inside_loop_p (loop, def_bb_succ))
+ continue;
+ }
+
+ if (++defs_in_loop_count > 1)
+ return false;
+ }
+
+ return true;
+}
+
/* Move invariant INVNO out of the LOOP. Returns true if this succeeds, false
otherwise. */
@@ -1545,11 +1618,8 @@ move_invariant_reg (struct loop *loop, unsigned invno)
}
}
- /* Move the set out of the loop. If the set is always executed (we could
- omit this condition if we know that the register is unused outside of
- the loop, but it does not seem worth finding out) and it has no uses
- that would not be dominated by it, we may just move it (TODO).
- Otherwise we need to create a temporary register. */
+ /* If possible, just move the set out of the loop. Otherwise, we
+ need to create a temporary register. */
set = single_set (inv->insn);
reg = dest = SET_DEST (set);
if (GET_CODE (reg) == SUBREG)
@@ -1557,19 +1627,25 @@ move_invariant_reg (struct loop *loop, unsigned invno)
if (REG_P (reg))
regno = REGNO (reg);
- reg = gen_reg_rtx_and_attrs (dest);
+ if (!can_move_invariant_reg (loop, inv, reg))
+ {
+ reg = gen_reg_rtx_and_attrs (dest);
- /* Try replacing the destination by a new pseudoregister. */
- validate_change (inv->insn, &SET_DEST (set), reg, true);
+ /* Try replacing the destination by a new pseudoregister. */
+ validate_change (inv->insn, &SET_DEST (set), reg, true);
- /* As well as all the dominated uses. */
- replace_uses (inv, reg, true);
+ /* As well as all the dominated uses. */
+ replace_uses (inv, reg, true);
- /* And validate all the changes. */
- if (!apply_change_group ())
- goto fail;
+ /* And validate all the changes. */
+ if (!apply_change_group ())
+ goto fail;
- emit_insn_after (gen_move_insn (dest, reg), inv->insn);
+ emit_insn_after (gen_move_insn (dest, reg), inv->insn);
+ }
+ else if (dump_file)
+ fprintf (dump_file, "Invariant %d moved without introducing a new "
+ "temporary register\n", invno);
reorder_insns (inv->insn, inv->insn, BB_END (preheader));
/* If there is a REG_EQUAL note on the insn we just moved, and the
new file mode 100644
@@ -0,0 +1,24 @@
+/* { dg-do compile } */
+/* { dg-options "-O1 -fdump-rtl-loop2_invariant" } */
+
+void
+f (int *a, int *b)
+{
+ int i;
+
+ for (i = 0; i < 100; i++)
+ {
+ int d = 42;
+
+ a[i] = d;
+ if (i % 2)
+ d = i;
+ b[i] = d;
+ }
+}
+
+/* Load of 42 is moved out of the loop, introducing a new pseudo register. */
+/* { dg-final { scan-rtl-dump-times "Decided" 1 "loop2_invariant" } } */
+/* { dg-final { scan-rtl-dump-not "without introducing a new temporary register" "loop2_invariant" } } */
+/* { dg-final { cleanup-rtl-dump "loop2_invariant" } } */
+
new file mode 100644
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-O1 -fdump-rtl-loop2_invariant" } */
+
+void
+f (double *a)
+{
+ int i;
+ for (i = 0; i < 100; i++)
+ a[i] = 18.4242;
+}
+
+/* Load of x is moved out of the loop. */
+/* { dg-final { scan-rtl-dump "Decided" "loop2_invariant" } } */
+/* { dg-final { scan-rtl-dump "without introducing a new temporary register" "loop2_invariant" } } */
+/* { dg-final { cleanup-rtl-dump "loop2_invariant" } } */
+