Hi,
There is a new insn on my target, which has a nested if_then_else and
set -1, 0 and 1 according to a comparison.
[(set (match_operand:SI 0 "gpc_reg_operand" "=r")
(if_then_else:SI (lt (match_operand:CC 1 "cc_reg_operand" "y")
(const_int 0))
(const_int -1)
(if_then_else (gt (match_dup 1)
(const_int 0))
(const_int 1)
(const_int 0))))]
In ifcvt pass, it probably contains a comparison, a branch, a setcc
and a constant set.
8: r122:CC=cmp(r120:DI#0,r121:DI#0)
9: pc={(r122:CC<0)?L29:pc}
14: r118:SI=r122:CC>0
29: L29:
5: r118:SI=0xffffffffffffffff
This patch adds the new conversion into ifcvt and convert this kind of
branch into a nested if-then-else insn if the target supports such
pattern.
HAVE_ternary_conditional_set indicates if the target has such nested
if-then-else insn. It's set in genconfig. noce_try_ternary_cset will be
executed to detect suitable pattern and convert it to the nested
if-then-else insn if HAVE_ternary_conditional_set is set. The hook
TARGET_NOCE_TERNARY_CSET_P detects target specific pattern and output
conditions and setting integers for the nested if-then-else.
Bootstrapped and tested on powerpc64-linux BE/LE and x86 with no
regressions. Is this okay for trunk? Any recommendations? Thanks a lot.
ChangeLog
2022-11-23 Haochen Gui <guih...@linux.ibm.com>
gcc/
* doc/tm.texi: Regenerate.
* doc/tm.texi.in (TARGET_NOCE_TERNARY_CSET_P): Document new hook.
* genconfig.cc (have_ternary_cset_flag): New.
(walk_insn_part): Detect nested if-then-else with const_int setting
and set have_ternary_cset_flag.
(HAVE_ternary_conditional_set): Define.
* ifcvt.cc (noce_emit_ternary_cset): New function to emit nested
if-then-else insns.
(noce_try_ternary_cset): Detect ternary conditional set and emit the
insn.
(noce_process_if_block): Try to do ternary condition set convertion
when a target supports ternary conditional set insn.
* target.def (noce_ternary_cset_p): New hook.
* targhooks.cc (default_noce_ternary_cset_p): New function.
* targhooks.h (default_noce_ternary_cset_p): New declare.
patch.diff
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index 92bda1a7e14..9823eccbe68 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -7094,6 +7094,15 @@ the @code{POLY_VALUE_MIN}, @code{POLY_VALUE_MAX} and
implementation returns the lowest possible value of @var{val}.
@end deftypefn
+@deftypefn {Target Hook} bool TARGET_NOCE_TERNARY_CSET_P (struct noce_if_info
*@var{if_info}, rtx *@var{outer_cond}, rtx *@var{inner_cond}, int *@var{int1},
int *@var{int2}, int *@var{int3})
+This hook returns true if the if-then-else-join blocks describled in
+@code{if_info} can be converted to a ternary conditional set implemented by
+a nested if-then-else insn. The @code{int1}, @code{int2} and @code{int3}
+are three possible results of the nested if-then-else insn.
+@code{outer_cond} and @code{inner_cond} are the conditions for outer and
+if-then-else.
+@end deftypefn
+
@node Scheduling
@section Adjusting the Instruction Scheduler
diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index 112462310b1..1d6f28cc50a 100644
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -4631,6 +4631,8 @@ Define this macro if a non-short-circuit operation
produced by
@hook TARGET_ESTIMATED_POLY_VALUE
+@hook TARGET_NOCE_TERNARY_CSET_P
+
@node Scheduling
@section Adjusting the Instruction Scheduler
diff --git a/gcc/genconfig.cc b/gcc/genconfig.cc
index b7c6b48eec6..902c832cf5a 100644
--- a/gcc/genconfig.cc
+++ b/gcc/genconfig.cc
@@ -33,6 +33,7 @@ static int max_recog_operands; /* Largest operand number
seen. */
static int max_dup_operands; /* Largest number of match_dup in any insn. */
static int max_clobbers_per_insn;
static int have_cmove_flag;
+static int have_ternary_cset_flag;
static int have_cond_exec_flag;
static int have_lo_sum_flag;
static int have_rotate_flag;
@@ -136,6 +137,12 @@ walk_insn_part (rtx part, int recog_p, int non_pc_set_src)
&& GET_CODE (XEXP (part, 1)) == MATCH_OPERAND
&& GET_CODE (XEXP (part, 2)) == MATCH_OPERAND)
have_cmove_flag = 1;
+ else if (recog_p && non_pc_set_src
+ && GET_CODE (XEXP (part, 1)) == CONST_INT
+ && GET_CODE (XEXP (part, 2)) == IF_THEN_ELSE
+ && GET_CODE (XEXP (XEXP (part, 2), 1)) == CONST_INT
+ && GET_CODE (XEXP (XEXP (part, 2), 2)) == CONST_INT)
+ have_ternary_cset_flag = 1;
break;
case COND_EXEC:
@@ -328,6 +335,11 @@ main (int argc, const char **argv)
else
printf ("#define HAVE_conditional_move 0\n");
+ if (have_ternary_cset_flag)
+ printf ("#define HAVE_ternary_conditional_set 1\n");
+ else
+ printf ("#define HAVE_ternary_conditional_set 0\n");
+
if (have_cond_exec_flag)
printf ("#define HAVE_conditional_execution 1\n");
else
diff --git a/gcc/ifcvt.cc b/gcc/ifcvt.cc
index eb8efb89a89..774dff21719 100644
--- a/gcc/ifcvt.cc
+++ b/gcc/ifcvt.cc
@@ -1830,6 +1830,42 @@ noce_emit_cmove (struct noce_if_info *if_info, rtx x,
enum rtx_code code,
return NULL_RTX;
}
+/* Emit a nested if-then-else insn. */
+
+static rtx
+noce_emit_ternary_cset (rtx x, rtx outer_cond, rtx inner_cond,
+ int a, int b, int c)
+{
+ rtx target;
+ machine_mode mode;
+ machine_mode orig_mode = GET_MODE (x);
+
+ FOR_EACH_MODE_FROM (mode, orig_mode)
+ {
+ rtx inner_if_then_else = gen_rtx_IF_THEN_ELSE (mode, inner_cond,
+ GEN_INT (b), GEN_INT (c));
+ rtx outer_if_then_else = gen_rtx_IF_THEN_ELSE (mode, outer_cond,
+ GEN_INT (a),
+ inner_if_then_else);
+ target = (mode == orig_mode) ? x : gen_reg_rtx (mode);
+ rtx set = gen_rtx_SET (target, outer_if_then_else);
+ start_sequence ();
+ rtx_insn *insn = emit_insn (set);
+
+ if (recog_memoized (insn) >= 0)
+ {
+ rtx_insn *seq = get_insns ();
+ end_sequence ();
+ emit_insn (seq);
+
+ return target;
+ }
+ }
+
+ end_sequence ();
+ return NULL_RTX;
+}
+
/* Try only simple constants and registers here. More complex cases
are handled in noce_try_cmove_arith after noce_try_store_flag_arith
has had a go at it. */
@@ -2987,6 +3023,43 @@ noce_try_bitop (struct noce_if_info *if_info)
return TRUE;
}
+/* Try to find pattern "a < b ? -1 : (a > b ? 1 : 0);" and convert it to
+ a nested if-then-else insn. */
+
+static int
+noce_try_ternary_cset (struct noce_if_info *if_info)
+{
+ rtx outer_cond = NULL_RTX, inner_cond = NULL_RTX;
+ int int1 = 0, int2 = 0, int3 = 0;
+
+ if (targetm.noce_ternary_cset_p (if_info, &outer_cond, &inner_cond,
+ &int1, &int2, &int3))
+ {
+ start_sequence ();
+ rtx target = noce_emit_ternary_cset (if_info->x, outer_cond, inner_cond,
+ int1, int2, int3);
+ if (target)
+ {
+ rtx_insn *ifcvt_seq;
+
+ if (target != if_info->x)
+ noce_emit_move_insn (if_info->x, target);
+
+ ifcvt_seq = end_ifcvt_sequence (if_info);
+ if (!ifcvt_seq)
+ return false;
+
+ emit_insn_before_setloc (ifcvt_seq, if_info->jump,
+ INSN_LOCATION (if_info->insn_a));
+ if_info->transform_name = "noce_try_ternary_cset";
+ return true;
+ }
+
+ end_sequence ();
+ }
+
+ return false;
+}
/* Similar to get_condition, only the resulting condition must be
valid at JUMP, instead of at EARLIEST.
@@ -3963,6 +4036,9 @@ noce_process_if_block (struct noce_if_info *if_info)
if (HAVE_conditional_move
&& noce_try_cmove (if_info))
goto success;
+ if (HAVE_ternary_conditional_set
+ && noce_try_ternary_cset (if_info))
+ goto success;
if (! targetm.have_conditional_execution ())
{
if (noce_try_addcc (if_info))
diff --git a/gcc/target.def b/gcc/target.def
index 2a7fa68f83d..1b983bf852e 100644
--- a/gcc/target.def
+++ b/gcc/target.def
@@ -3907,6 +3907,20 @@ candidate as a replacement for the if-convertible
sequence described in\n\
bool, (rtx_insn *seq, struct noce_if_info *if_info),
default_noce_conversion_profitable_p)
+/* Return true if the if-then-else-join blocks can be converted to a nested\n\
+if-then-else insn. */
+DEFHOOK
+(noce_ternary_cset_p,
+ "This hook returns true if the if-then-else-join blocks describled in\n\
+@code{if_info} can be converted to a ternary conditional set implemented by\n\
+a nested if-then-else insn. The @code{int1}, @code{int2} and @code{int3}\n\
+are three possible results of the nested if-then-else insn.\n\
+@code{outer_cond} and @code{inner_cond} are the conditions for outer and\n\
+if-then-else.",
+bool, (struct noce_if_info *if_info, rtx *outer_cond, rtx *inner_cond,
+ int *int1, int *int2, int *int3),
+default_noce_ternary_cset_p)
+
/* Return true if new_addr should be preferred over the existing address used
by
memref in insn. */
DEFHOOK
diff --git a/gcc/targhooks.cc b/gcc/targhooks.cc
index b15ae19bcb6..179324e3f0b 100644
--- a/gcc/targhooks.cc
+++ b/gcc/targhooks.cc
@@ -2673,4 +2673,17 @@ default_gcov_type_size (void)
return TYPE_PRECISION (long_long_integer_type_node) > 32 ? 64 : 32;
}
+/* The default implementation of TARGET_NOCE_TERNARY_CSET_P. */
+
+bool
+default_noce_ternary_cset_p (struct noce_if_info *if_info ATTRIBUTE_UNUSED,
+ rtx *outer_cond ATTRIBUTE_UNUSED,
+ rtx *inner_cond ATTRIBUTE_UNUSED,
+ int *int1 ATTRIBUTE_UNUSED,
+ int *int2 ATTRIBUTE_UNUSED,
+ int *int3 ATTRIBUTE_UNUSED)
+{
+ return false;
+}
+
#include "gt-targhooks.h"
diff --git a/gcc/targhooks.h b/gcc/targhooks.h
index ecce55ebe79..a58bc8ef6a6 100644
--- a/gcc/targhooks.h
+++ b/gcc/targhooks.h
@@ -296,5 +296,7 @@ extern rtx default_memtag_extract_tag (rtx, rtx);
extern rtx default_memtag_untagged_pointer (rtx, rtx);
extern HOST_WIDE_INT default_gcov_type_size (void);
+extern bool default_noce_ternary_cset_p (struct noce_if_info *, rtx *, rtx *,
+ int *, int *, int *);
#endif /* GCC_TARGHOOKS_H */
