[AArch64][1/3] Expand signed mod by power of 2 using CSNEG

	* config/aarch64/aarch64.md (mod<mode>3): New define_expand.
	(*neg<mode>2_compare0): Rename to...
	(neg<mode>2_compare0): ... This.
	* config/aarch64/aarch64.c (aarch64_rtx_costs, MOD case):
	Move check for speed inside the if-then-elses.  Reflect
	CSNEG sequence in MOD by power of 2 case.

From-SVN: r227585

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 542abcf..25ecf5a 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,12 @@
+2015-09-09  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
+
+       * config/aarch64/aarch64.md (mod<mode>3): New define_expand.
+       (*neg<mode>2_compare0): Rename to...
+       (neg<mode>2_compare0): ... This.
+       * config/aarch64/aarch64.c (aarch64_rtx_costs, MOD case):
+       Move check for speed inside the if-then-elses.  Reflect
+       CSNEG sequence in MOD by power of 2 case.
+
 2015-09-09  Alan Modra  <amodra@gmail.com>
 
        PR target/67378

diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index feb7b28..b2a481b 100644 (file)
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -6769,6 +6769,25 @@ cost_plus:
       return true;
 
     case MOD:
+    /* We can expand signed mod by power of 2 using a NEGS, two parallel
+       ANDs and a CSNEG.  Assume here that CSNEG is the same as the cost of
+       an unconditional negate.  This case should only ever be reached through
+       the set_smod_pow2_cheap check in expmed.c.  */
+      if (CONST_INT_P (XEXP (x, 1))
+         && exact_log2 (INTVAL (XEXP (x, 1))) > 0
+         && (mode == SImode || mode == DImode))
+       {
+         /* We expand to 4 instructions.  Reset the baseline.  */
+         *cost = COSTS_N_INSNS (4);
+
+         if (speed)
+           *cost += 2 * extra_cost->alu.logical
+                    + 2 * extra_cost->alu.arith;
+
+         return true;
+       }
+
+    /* Fall-through.  */
     case UMOD:
       if (speed)
        {

diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md
index 2522982..594bef0 100644 (file)
--- a/gcc/config/aarch64/aarch64.md
+++ b/gcc/config/aarch64/aarch64.md
@@ -313,6 +313,62 @@
   }
 )
 
+;; Expansion of signed mod by a power of 2 using CSNEG.
+;; For x0 % n where n is a power of 2 produce:
+;; negs   x1, x0
+;; and    x0, x0, #(n - 1)
+;; and    x1, x1, #(n - 1)
+;; csneg  x0, x0, x1, mi
+
+(define_expand "mod<mode>3"
+  [(match_operand:GPI 0 "register_operand" "")
+   (match_operand:GPI 1 "register_operand" "")
+   (match_operand:GPI 2 "const_int_operand" "")]
+  ""
+  {
+    HOST_WIDE_INT val = INTVAL (operands[2]);
+
+    if (val <= 0
+       || exact_log2 (val) <= 0
+       || !aarch64_bitmask_imm (val - 1, <MODE>mode))
+      FAIL;
+
+    rtx mask = GEN_INT (val - 1);
+
+    /* In the special case of x0 % 2 we can do the even shorter:
+       cmp    x0, xzr
+       and    x0, x0, 1
+       cneg   x0, x0, lt.  */
+    if (val == 2)
+      {
+       rtx masked = gen_reg_rtx (<MODE>mode);
+       rtx ccreg = aarch64_gen_compare_reg (LT, operands[1], const0_rtx);
+       emit_insn (gen_and<mode>3 (masked, operands[1], mask));
+       rtx x = gen_rtx_LT (VOIDmode, ccreg, const0_rtx);
+       emit_insn (gen_csneg3<mode>_insn (operands[0], x, masked, masked));
+       DONE;
+      }
+
+    rtx neg_op = gen_reg_rtx (<MODE>mode);
+    rtx_insn *insn = emit_insn (gen_neg<mode>2_compare0 (neg_op, operands[1]));
+
+    /* Extract the condition register and mode.  */
+    rtx cmp = XVECEXP (PATTERN (insn), 0, 0);
+    rtx cc_reg = SET_DEST (cmp);
+    rtx cond = gen_rtx_GE (VOIDmode, cc_reg, const0_rtx);
+
+    rtx masked_pos = gen_reg_rtx (<MODE>mode);
+    emit_insn (gen_and<mode>3 (masked_pos, operands[1], mask));
+
+    rtx masked_neg = gen_reg_rtx (<MODE>mode);
+    emit_insn (gen_and<mode>3 (masked_neg, neg_op, mask));
+
+    emit_insn (gen_csneg3<mode>_insn (operands[0], cond,
+                                      masked_neg, masked_pos));
+    DONE;
+  }
+)
+
 (define_insn "*condjump"
   [(set (pc) (if_then_else (match_operator 0 "aarch64_comparison_operator"
                            [(match_operand 1 "cc_register" "") (const_int 0)])
@@ -2457,7 +2513,7 @@
   [(set_attr "type" "adc_reg")]
 )
 
-(define_insn "*neg<mode>2_compare0"
+(define_insn "neg<mode>2_compare0"
   [(set (reg:CC_NZ CC_REGNUM)
        (compare:CC_NZ (neg:GPI (match_operand:GPI 1 "register_operand" "r"))
                       (const_int 0)))