[PATCH] aarch64: prefer using csinv, csneg in zero extend contexts

Given the C code:

unsigned long long inv(unsigned a, unsigned b, unsigned c)
{
  return a ? b : ~c;
}

Prior to this patch, AArch64 GCC at -O2 generates:

inv:
        cmp     w0, 0
        mvn     w2, w2
        csel    w0, w1, w2, ne
        ret

and after applying the patch, we get:

inv:
        cmp     w0, 0
        csinv   w0, w1, w2, ne
        ret

The new pattern also catches the optimization for the symmetric case where the
body of foo reads a ? ~b : c.

Similarly, with the following code:

unsigned long long neg(unsigned a, unsigned b, unsigned c)
{
  return a ? b : -c;
}

GCC at -O2 previously gave:

neg:
        cmp     w0, 0
        neg     w2, w2
        csel    w0, w1, w2, ne

but now gives:

neg:
        cmp     w0, 0
        csneg   w0, w1, w2, ne
        ret

with the corresponding code for the symmetric case as above.

2020-05-11  Alex Coplan  <alex.coplan@arm.com>

gcc/
	* config/aarch64/aarch64.c (aarch64_if_then_else_costs): Add case
	to correctly calculate cost for new pattern (*csinv3_uxtw_insn3).
	* config/aarch64/aarch64.md (*csinv3_utxw_insn1): New.
	(*csinv3_uxtw_insn2): New.
	(*csinv3_uxtw_insn3): New.
	* config/aarch64/iterators.md (neg_not_cs): New.

gcc/testsuite/
	* gcc.target/aarch64/csinv-neg.c: New test.

6 files changed, 165 insertions, 0 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 0a98c7441e1..c4856f422a3 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,12 @@
+2020-05-11  Alex Coplan  <alex.coplan@arm.com>
+
+	* config/aarch64/aarch64.c (aarch64_if_then_else_costs): Add case
+	to correctly calculate cost for new pattern (*csinv3_uxtw_insn3).
+	* config/aarch64/aarch64.md (*csinv3_utxw_insn1): New.
+	(*csinv3_uxtw_insn2): New.
+	(*csinv3_uxtw_insn3): New.
+	* config/aarch64/iterators.md (neg_not_cs): New.
+
 2020-05-11  Uroš Bizjak  <ubizjak@gmail.com>
 
 	PR target/95046
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index e92c7e69fcb..434e095cb66 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -11695,6 +11695,13 @@ aarch64_if_then_else_costs (rtx op0, rtx op1, rtx op2, int *cost, bool speed)
 	  op1 = XEXP (op1, 0);
 	  op2 = XEXP (op2, 0);
 	}
+      else if (GET_CODE (op1) == ZERO_EXTEND && op2 == const0_rtx)
+	{
+	  inner = XEXP (op1, 0);
+	  if (GET_CODE (inner) == NEG || GET_CODE (inner) == NOT)
+	    /* CSINV/NEG with zero extend + const 0 (*csinv3_uxtw_insn3).  */
+	    op1 = XEXP (inner, 0);
+	}
 
       *cost += rtx_cost (op1, VOIDmode, IF_THEN_ELSE, 1, speed);
       *cost += rtx_cost (op2, VOIDmode, IF_THEN_ELSE, 2, speed);
diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md
index ff15505d455..b2cfd015530 100644
--- a/gcc/config/aarch64/aarch64.md
+++ b/gcc/config/aarch64/aarch64.md
@@ -4391,6 +4391,44 @@
   [(set_attr "type" "csel")]
 )
 
+(define_insn "*csinv3_uxtw_insn1"
+  [(set (match_operand:DI 0 "register_operand" "=r")
+	(if_then_else:DI
+	  (match_operand 1 "aarch64_comparison_operation" "")
+	  (zero_extend:DI
+	    (match_operand:SI 2 "register_operand" "r"))
+	  (zero_extend:DI
+	    (NEG_NOT:SI (match_operand:SI 3 "register_operand" "r")))))]
+  ""
+  "cs<neg_not_cs>\\t%w0, %w2, %w3, %m1"
+  [(set_attr "type" "csel")]
+)
+
+(define_insn "*csinv3_uxtw_insn2"
+  [(set (match_operand:DI 0 "register_operand" "=r")
+	(if_then_else:DI
+	  (match_operand 1 "aarch64_comparison_operation" "")
+	  (zero_extend:DI
+	    (NEG_NOT:SI (match_operand:SI 2 "register_operand" "r")))
+	  (zero_extend:DI
+	    (match_operand:SI 3 "register_operand" "r"))))]
+  ""
+  "cs<neg_not_cs>\\t%w0, %w3, %w2, %M1"
+  [(set_attr "type" "csel")]
+)
+
+(define_insn "*csinv3_uxtw_insn3"
+  [(set (match_operand:DI 0 "register_operand" "=r")
+	(if_then_else:DI
+	  (match_operand 1 "aarch64_comparison_operation" "")
+	  (zero_extend:DI
+	    (NEG_NOT:SI (match_operand:SI 2 "register_operand" "r")))
+	  (const_int 0)))]
+  ""
+  "cs<neg_not_cs>\\t%w0, wzr, %w2, %M1"
+  [(set_attr "type" "csel")]
+)
+
 ;; If X can be loaded by a single CNT[BHWD] instruction,
 ;;
 ;;    A = UMAX (B, X)
diff --git a/gcc/config/aarch64/iterators.md b/gcc/config/aarch64/iterators.md
index 8e434389e59..a568cf21b99 100644
--- a/gcc/config/aarch64/iterators.md
+++ b/gcc/config/aarch64/iterators.md
@@ -1932,6 +1932,9 @@
 ;; Operation names for negate and bitwise complement.
 (define_code_attr neg_not_op [(neg "neg") (not "not")])
 
+;; csinv, csneg insn suffixes.
+(define_code_attr neg_not_cs [(neg "neg") (not "inv")])
+
 ;; Similar, but when the second operand is inverted.
 (define_code_attr nlogical [(and "bic") (ior "orn") (xor "eon")])
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index dace5ae17c5..ac40f2ef474 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2020-05-11  Alex Coplan  <alex.coplan@arm.com>
+
+	* gcc.target/aarch64/csinv-neg.c: New test.
+
 2020-05-11  Kelvin Nilsen  <kelvin@gcc.gnu.org>
 
 	* gcc.target/powerpc/dg-future-0.c: New.
diff --git a/gcc/testsuite/gcc.target/aarch64/csinv-neg.c b/gcc/testsuite/gcc.target/aarch64/csinv-neg.c
new file mode 100644
index 00000000000..cc64b4094d7
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/csinv-neg.c
@@ -0,0 +1,104 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+/*
+** inv1:
+**	cmp	w0, 0
+**	csinv	w0, w1, w2, ne
+**	ret
+*/
+unsigned long long
+inv1(unsigned a, unsigned b, unsigned c)
+{
+  return a ? b : ~c;
+}
+
+/*
+** inv1_local:
+**	cmp	w0, 0
+**	csinv	w0, w1, w2, ne
+**	ret
+*/
+unsigned long long
+inv1_local(unsigned a, unsigned b, unsigned c)
+{
+  unsigned d = ~c;
+  return a ? b : d;
+}
+
+/*
+** inv_zero1:
+**	cmp	w0, 0
+**	csinv	w0, wzr, w1, ne
+**	ret
+*/
+unsigned long long
+inv_zero1(unsigned a, unsigned b)
+{
+  return a ? 0 : ~b;
+}
+
+/*
+** inv_zero2:
+**	cmp	w0, 0
+**	csinv	w0, wzr, w1, eq
+**	ret
+*/
+unsigned long long
+inv_zero2(unsigned a, unsigned b)
+{
+  return a ? ~b : 0;
+}
+
+
+/*
+** inv2:
+**	cmp	w0, 0
+**	csinv	w0, w2, w1, eq
+**	ret
+*/
+unsigned long long
+inv2(unsigned a, unsigned b, unsigned c)
+{
+  return a ? ~b : c;
+}
+
+/*
+** inv2_local:
+**	cmp	w0, 0
+**	csinv	w0, w2, w1, eq
+**	ret
+*/
+unsigned long long
+inv2_local(unsigned a, unsigned b, unsigned c)
+{
+  unsigned d = ~b;
+  return a ? d : c;
+}
+
+/*
+** neg1:
+**	cmp	w0, 0
+**	csneg	w0, w1, w2, ne
+**	ret
+*/
+unsigned long long
+neg1(unsigned a, unsigned b, unsigned c)
+{
+  return a ? b : -c;
+}
+
+
+/*
+** neg2:
+**	cmp	w0, 0
+**	csneg	w0, w2, w1, eq
+**	ret
+*/
+unsigned long long
+neg2(unsigned a, unsigned b, unsigned c)
+{
+  return a ? -b : c;
+}
+
+/* { dg-final { check-function-bodies "**" "" "" } } */