Currently we only ever call emit_conditional_move with the comparison
(as well as its comparands) we got from the jump. Thus, backends are
going to emit a CC comparison for every conditional move that is being
generated instead of re-using the existing CC.
This, combined with emitting temporaries for each conditional move,
causes sky-high costs for conditional moves.
This patch allows to re-use a CC so the costing situation is improved a
bit.
---
gcc/ifcvt.c | 16 +++--
gcc/optabs.c | 163 ++++++++++++++++++++++++++++++++++-----------------
gcc/optabs.h | 1 +
3 files changed, 121 insertions(+), 59 deletions(-)
diff --git a/gcc/ifcvt.c b/gcc/ifcvt.c
index ac0c142c9fe..c5b8641e2aa 100644
--- a/gcc/ifcvt.c
+++ b/gcc/ifcvt.c
@@ -771,7 +771,7 @@ static int noce_try_addcc (struct noce_if_info *);
static int noce_try_store_flag_constants (struct noce_if_info *);
static int noce_try_store_flag_mask (struct noce_if_info *);
static rtx noce_emit_cmove (struct noce_if_info *, rtx, enum rtx_code, rtx,
- rtx, rtx, rtx);
+ rtx, rtx, rtx, rtx = NULL, rtx = NULL);
static int noce_try_cmove (struct noce_if_info *);
static int noce_try_cmove_arith (struct noce_if_info *);
static rtx noce_get_alt_condition (struct noce_if_info *, rtx, rtx_insn **);
@@ -1710,7 +1710,8 @@ noce_try_store_flag_mask (struct noce_if_info *if_info)
static rtx
noce_emit_cmove (struct noce_if_info *if_info, rtx x, enum rtx_code code,
- rtx cmp_a, rtx cmp_b, rtx vfalse, rtx vtrue)
+ rtx cmp_a, rtx cmp_b, rtx vfalse, rtx vtrue, rtx cc_cmp,
+ rtx rev_cc_cmp)
{
rtx target ATTRIBUTE_UNUSED;
int unsignedp ATTRIBUTE_UNUSED;
@@ -1756,9 +1757,14 @@ noce_emit_cmove (struct noce_if_info *if_info, rtx x,
enum rtx_code code,
unsignedp = (code == LTU || code == GEU
|| code == LEU || code == GTU);
- target = emit_conditional_move (x, code, cmp_a, cmp_b, VOIDmode,
- vtrue, vfalse, GET_MODE (x),
- unsignedp);
+ if (cc_cmp != NULL_RTX && rev_cc_cmp != NULL_RTX)
+ target = emit_conditional_move (x, cc_cmp, rev_cc_cmp,
+ vtrue, vfalse, GET_MODE (x));
+ else
+ target = emit_conditional_move (x, code, cmp_a, cmp_b, VOIDmode,
+ vtrue, vfalse, GET_MODE (x),
+ unsignedp);
+
if (target)
return target;
diff --git a/gcc/optabs.c b/gcc/optabs.c
index 62a6bdb4c59..6bf486b9b50 100644
--- a/gcc/optabs.c
+++ b/gcc/optabs.c
@@ -52,6 +52,8 @@ static void prepare_float_lib_cmp (rtx, rtx, enum rtx_code,
rtx *,
static rtx expand_unop_direct (machine_mode, optab, rtx, rtx, int);
static void emit_libcall_block_1 (rtx_insn *, rtx, rtx, rtx, bool);
+static rtx emit_conditional_move (rtx, rtx, rtx, rtx, machine_mode);
+
/* Debug facility for use in GDB. */
void debug_optab_libfuncs (void);
@@ -4747,7 +4749,6 @@ emit_conditional_move (rtx target, enum rtx_code code,
rtx op0, rtx op1,
machine_mode mode, int unsignedp)
{
rtx comparison;
- rtx_insn *last;
enum insn_code icode;
enum rtx_code reversed;
@@ -4774,6 +4775,7 @@ emit_conditional_move (rtx target, enum rtx_code code,
rtx op0, rtx op1,
/* get_condition will prefer to generate LT and GT even if the old
comparison was against zero, so undo that canonicalization here since
comparisons against zero are cheaper. */
+
if (code == LT && op1 == const1_rtx)
code = LE, op1 = const0_rtx;
else if (code == GT && op1 == constm1_rtx)
@@ -4782,17 +4784,29 @@ emit_conditional_move (rtx target, enum rtx_code code,
rtx op0, rtx op1,
if (cmode == VOIDmode)
cmode = GET_MODE (op0);
- enum rtx_code orig_code = code;
+ /* If the first source operand is constant and the second is not, swap
+ it into the second. In that case we also need to reverse the
+ comparison. It is possible, though, that the conditional move
+ will not expand with operands in this order, so we might also need
+ to revert to the original comparison and operand order. */
+
+ rtx rev_comparison = NULL_RTX;
bool swapped = false;
- if (swap_commutative_operands_p (op2, op3)
- && ((reversed = reversed_comparison_code_parts (code, op0, op1, NULL))
- != UNKNOWN))
+
+ code = unsignedp ? unsigned_condition (code) : code;
+ comparison = simplify_gen_relational (code, VOIDmode, cmode, op0, op1);
+
+ if ((reversed = reversed_comparison_code_parts (code, op0, op1, NULL))
+ != UNKNOWN)
{
- std::swap (op2, op3);
- code = reversed;
- swapped = true;
+ reversed = unsignedp ? unsigned_condition (reversed) : reversed;
+ rev_comparison = simplify_gen_relational (reversed, VOIDmode, cmode,
+ op0, op1);
}
+ if (swap_commutative_operands_p (op2, op3) && reversed != UNKNOWN)
+ swapped = true;
+
if (mode == VOIDmode)
mode = GET_MODE (op2);
@@ -4804,58 +4818,99 @@ emit_conditional_move (rtx target, enum rtx_code code,
rtx op0, rtx op1,
if (!target)
target = gen_reg_rtx (mode);
- for (int pass = 0; ; pass++)
+ if (comparison && COMPARISON_P (comparison))
+ prepare_cmp_insn (XEXP (comparison, 0), XEXP (comparison, 1),
+ GET_CODE (comparison), NULL_RTX, unsignedp, OPTAB_WIDEN,
+ &comparison, &cmode);
+ else
+ return NULL_RTX;
+
+ if (rev_comparison && COMPARISON_P (rev_comparison))
+ prepare_cmp_insn (XEXP (rev_comparison, 0), XEXP (rev_comparison, 1),
+ GET_CODE (rev_comparison), NULL_RTX,
+ unsignedp, OPTAB_WIDEN, &rev_comparison, &cmode);
+
+ if (!swapped)
+ return emit_conditional_move (target, comparison, rev_comparison,
+ op2, op3, mode);
+ else
+ return emit_conditional_move (target, rev_comparison, comparison,
+ op3, op2, mode);
+}
+
+/* Helper function for emitting a conditional move. Given a COMPARISON
+ and a reversed REV_COMPARISON it will try to expand a conditional move
+ with COMPARISON first and try with REV_COMPARISON if that fails. */
+
+rtx
+emit_conditional_move (rtx target, rtx comparison, rtx rev_comparison,
+ rtx op2, rtx op3, machine_mode mode)
+{
+
+ rtx res = emit_conditional_move (target, comparison, op2, op3, mode);
+
+ if (res != NULL_RTX)
+ return res;
+
+ return emit_conditional_move (target, rev_comparison, op3, op2, mode);
+}
+
+/* Helper for emitting a conditional move. */
+
+static rtx
+emit_conditional_move (rtx target, rtx comparison,
+ rtx op2, rtx op3, machine_mode mode)
+{
+ rtx_insn *last;
+ enum insn_code icode;
+
+ if (comparison == NULL_RTX || !COMPARISON_P (comparison))
+ return NULL_RTX;
+
+ /* If the two source operands are identical, that's just a move. */
+ if (rtx_equal_p (op2, op3))
{
- code = unsignedp ? unsigned_condition (code) : code;
- comparison = simplify_gen_relational (code, VOIDmode, cmode, op0, op1);
+ if (!target)
+ target = gen_reg_rtx (mode);
- /* We can get const0_rtx or const_true_rtx in some circumstances. Just
- punt and let the caller figure out how best to deal with this
- situation. */
- if (COMPARISON_P (comparison))
- {
- saved_pending_stack_adjust save;
- save_pending_stack_adjust (&save);
- last = get_last_insn ();
- do_pending_stack_adjust ();
- machine_mode cmpmode = cmode;
- prepare_cmp_insn (XEXP (comparison, 0), XEXP (comparison, 1),
- GET_CODE (comparison), NULL_RTX, unsignedp,
- OPTAB_WIDEN, &comparison, &cmpmode);
- if (comparison)
- {
- class expand_operand ops[4];
+ emit_move_insn (target, op3);
+ return target;
+ }
- create_output_operand (&ops[0], target, mode);
- create_fixed_operand (&ops[1], comparison);
- create_input_operand (&ops[2], op2, mode);
- create_input_operand (&ops[3], op3, mode);
- if (maybe_expand_insn (icode, 4, ops))
- {
- if (ops[0].value != target)
- convert_move (target, ops[0].value, false);
- return target;
- }
- }
- delete_insns_since (last);
- restore_pending_stack_adjust (&save);
- }
+ if (mode == VOIDmode)
+ mode = GET_MODE (op2);
- if (pass == 1)
- return NULL_RTX;
+ icode = direct_optab_handler (movcc_optab, mode);
- /* If the preferred op2/op3 order is not usable, retry with other
- operand order, perhaps it will expand successfully. */
- if (swapped)
- code = orig_code;
- else if ((reversed = reversed_comparison_code_parts (orig_code, op0, op1,
- NULL))
- != UNKNOWN)
- code = reversed;
- else
- return NULL_RTX;
- std::swap (op2, op3);
+ if (icode == CODE_FOR_nothing)
+ return NULL_RTX;
+
+ if (!target)
+ target = gen_reg_rtx (mode);
+
+ saved_pending_stack_adjust save;
+ save_pending_stack_adjust (&save);
+ last = get_last_insn ();
+ do_pending_stack_adjust ();
+
+ class expand_operand ops[4];
+
+ create_output_operand (&ops[0], target, mode);
+ create_fixed_operand (&ops[1], comparison);
+ create_input_operand (&ops[2], op2, mode);
+ create_input_operand (&ops[3], op3, mode);
+
+ if (maybe_expand_insn (icode, 4, ops))
+ {
+ if (ops[0].value != target)
+ convert_move (target, ops[0].value, false);
+ return target;
}
+
+ delete_insns_since (last);
+ restore_pending_stack_adjust (&save);
+
+ return NULL_RTX;
}
diff --git a/gcc/optabs.h b/gcc/optabs.h
index 3bbceff92d9..f853b93f37f 100644
--- a/gcc/optabs.h
+++ b/gcc/optabs.h
@@ -281,6 +281,7 @@ extern void emit_indirect_jump (rtx);
/* Emit a conditional move operation. */
rtx emit_conditional_move (rtx, enum rtx_code, rtx, rtx, machine_mode,
rtx, rtx, machine_mode, int);
+rtx emit_conditional_move (rtx, rtx, rtx, rtx, rtx, machine_mode);
/* Emit a conditional negate or bitwise complement operation. */
rtx emit_conditional_neg_or_complement (rtx, rtx_code, machine_mode, rtx,
--
2.31.1
