xtensa: Optimize '(x & CST1_POW2) != 0 ? CST2_POW2 : 0'

This patch decreses one machine instruction from "single bit extraction
with shifting" operation, and tries to eliminate the conditional
branch if CST2_POW2 doesn't fit into signed 12 bits with the help
of ifcvt optimization.

    /* example #1 */
    int test0(int x) {
      return (x & 1048576) != 0 ? 1024 : 0;
    }
    extern int foo(void);
    int test1(void) {
      return (foo() & 1048576) != 0 ? 16777216 : 0;
    }

    ;; before
    test0:
	movi	a9, 0x400
	srai	a2, a2, 10
	and	a2, a2, a9
	ret.n
    test1:
	addi	sp, sp, -16
	s32i.n	a0, sp, 12
	call0	foo
	extui	a2, a2, 20, 1
	slli	a2, a2, 20
	beqz.n	a2, .L2
	movi.n	a2, 1
	slli	a2, a2, 24
    .L2:
	l32i.n	a0, sp, 12
	addi	sp, sp, 16
	ret.n

    ;; after
    test0:
	extui	a2, a2, 20, 1
	slli	a2, a2, 10
	ret.n
    test1:
	addi	sp, sp, -16
	s32i.n	a0, sp, 12
	call0	foo
	l32i.n	a0, sp, 12
	extui	a2, a2, 20, 1
	slli	a2, a2, 24
	addi	sp, sp, 16
	ret.n

In addition, if the left shift amount ('exact_log2(CST2_POW2)') is
between 1 through 3 and a either addition or subtraction with another
register follows, emit a ADDX[248] or SUBX[248] machine instruction
instead of separate left shift and add/subtract ones.

    /* example #2 */
    int test2(int x, int y) {
      return ((x & 1048576) != 0 ? 4 : 0) + y;
    }
    int test3(int x, int y) {
      return ((x & 2) != 0 ? 8 : 0) - y;
    }

    ;; before
    test2:
	movi.n	a9, 4
	srai	a2, a2, 18
	and	a2, a2, a9
	add.n	a2, a2, a3
	ret.n
    test3:
	movi.n	a9, 8
	slli	a2, a2, 2
	and	a2, a2, a9
	sub	a2, a2, a3
	ret.n

    ;; after
    test2:
	extui	a2, a2, 20, 1
	addx4	a2, a2, a3
	ret.n
    test3:
	extui	a2, a2, 1, 1
	subx8	a2, a2, a3
	ret.n

gcc/ChangeLog:

	* config/xtensa/predicates.md (addsub_operator): New.
	* config/xtensa/xtensa.md (*extzvsi-1bit_ashlsi3,
	*extzvsi-1bit_addsubx): New insn_and_split patterns.
	* config/xtensa/xtensa.cc (xtensa_rtx_costs):
	Add a special case about ifcvt 'noce_try_cmove()' to handle
	constant loads that do not fit into signed 12 bits in the
	patterns added above.

diff --git a/gcc/config/xtensa/predicates.md b/gcc/config/xtensa/predicates.md
index 2dac193373a1a4e6311119658cda0426f63b719e..5faf1be8c15990729b4e8d9d8fc31b800d8f4588 100644 (file)
--- a/gcc/config/xtensa/predicates.md
+++ b/gcc/config/xtensa/predicates.md
@@ -191,6 +191,9 @@
 (define_predicate "logical_shift_operator"
   (match_code "ashift,lshiftrt"))
 
+(define_predicate "addsub_operator"
+  (match_code "plus,minus"))
+
 (define_predicate "xtensa_cstoresi_operator"
   (match_code "eq,ne,gt,ge,lt,le"))
 

diff --git a/gcc/config/xtensa/xtensa.cc b/gcc/config/xtensa/xtensa.cc
index bb1444c44b6a70f239c54631eb47b00f069859a5..e3af78cd2284627729994e4900d2253ad8393a72 100644 (file)
--- a/gcc/config/xtensa/xtensa.cc
+++ b/gcc/config/xtensa/xtensa.cc
@@ -4355,7 +4355,8 @@ xtensa_rtx_costs (rtx x, machine_mode mode, int outer_code,
       switch (outer_code)
        {
        case SET:
-         if (xtensa_simm12b (INTVAL (x)))
+         if (xtensa_simm12b (INTVAL (x))
+             || (current_pass && current_pass->tv_id == TV_IFCVT))
            {
              *total = speed ? COSTS_N_INSNS (1) : 0;
              return true;

diff --git a/gcc/config/xtensa/xtensa.md b/gcc/config/xtensa/xtensa.md
index 3521fa33b47dd8670a5bbb35a7e292b2870cbc2f..c75fde1023af5bfe1f2212782a0cab3216d7bbf6 100644 (file)
--- a/gcc/config/xtensa/xtensa.md
+++ b/gcc/config/xtensa/xtensa.md
@@ -997,6 +997,89 @@
    (set_attr "mode"    "SI")
    (set_attr "length"  "3")])
 
+(define_insn_and_split "*extzvsi-1bit_ashlsi3"
+  [(set (match_operand:SI 0 "register_operand" "=a")
+       (and:SI (match_operator:SI 4 "logical_shift_operator"
+                       [(match_operand:SI 1 "register_operand" "r")
+                        (match_operand:SI 2 "const_int_operand" "i")])
+               (match_operand:SI 3 "const_int_operand" "i")))]
+  "exact_log2 (INTVAL (operands[3])) > 0"
+  "#"
+  "&& 1"
+  [(set (match_dup 0)
+       (zero_extract:SI (match_dup 1)
+                        (const_int 1)
+                        (match_dup 2)))
+   (set (match_dup 0)
+       (ashift:SI (match_dup 0)
+                  (match_dup 3)))]
+{
+  int pos = INTVAL (operands[2]),
+      shift = floor_log2 (INTVAL (operands[3]));
+  switch (GET_CODE (operands[4]))
+    {
+    case ASHIFT:
+      pos = shift - pos;
+      break;
+    case LSHIFTRT:
+      pos = shift + pos;
+      break;
+    default:
+      gcc_unreachable ();
+    }
+  if (BITS_BIG_ENDIAN)
+    pos = (32 - (1 + pos)) & 0x1f;
+  operands[2] = GEN_INT (pos);
+  operands[3] = GEN_INT (shift);
+}
+  [(set_attr "type"    "arith")
+   (set_attr "mode"    "SI")
+   (set_attr "length"  "6")])
+
+(define_insn_and_split "*extzvsi-1bit_addsubx"
+  [(set (match_operand:SI 0 "register_operand" "=a")
+       (match_operator:SI 5 "addsub_operator"
+               [(and:SI (match_operator:SI 6 "logical_shift_operator"
+                               [(match_operand:SI 1 "register_operand" "r")
+                                (match_operand:SI 3 "const_int_operand" "i")])
+                        (match_operand:SI 4 "const_int_operand" "i"))
+                (match_operand:SI 2 "register_operand" "r")]))]
+  "TARGET_ADDX
+   && IN_RANGE (exact_log2 (INTVAL (operands[4])), 1, 3)"
+  "#"
+  "&& 1"
+  [(set (match_dup 0)
+       (zero_extract:SI (match_dup 1)
+                        (const_int 1)
+                        (match_dup 3)))
+   (set (match_dup 0)
+       (match_op_dup 5
+               [(ashift:SI (match_dup 0)
+                           (match_dup 4))
+                (match_dup 2)]))]
+{
+  int pos = INTVAL (operands[3]),
+      shift = floor_log2 (INTVAL (operands[4]));
+  switch (GET_CODE (operands[6]))
+    {
+    case ASHIFT:
+      pos = shift - pos;
+      break;
+    case LSHIFTRT:
+      pos = shift + pos;
+      break;
+    default:
+      gcc_unreachable ();
+    }
+  if (BITS_BIG_ENDIAN)
+    pos = (32 - (1 + pos)) & 0x1f;
+  operands[3] = GEN_INT (pos);
+  operands[4] = GEN_INT (shift);
+}
+  [(set_attr "type"    "arith")
+   (set_attr "mode"    "SI")
+   (set_attr "length"  "6")])
+
 \f
 ;; Conversions.