middle-end: simplify complex if expressions where comparisons are inverse of one another.

This optimizes the following sequence

  ((a < b) & c) | ((a >= b) & d)

into

  (a < b ? c : d) & 1

for scalar and on vector we can omit the & 1.

Also recognizes

  (-(a < b) & c) | (-(a >= b) & d)

into

  a < b ? c : d

This changes the code generation from

zoo2:
	cmp     w0, w1
	cset    w0, lt
	cset    w1, ge
	and     w0, w0, w2
	and     w1, w1, w3
	orr     w0, w0, w1
	ret

into

	cmp	w0, w1
	csel	w0, w2, w3, lt
	and	w0, w0, 1
	ret

and significantly reduces the number of selects we have to do in the vector
code.

gcc/ChangeLog:

	* match.pd: Add new rule.

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/if-compare_1.c: New test.
	* gcc.target/aarch64/if-compare_2.c: New test.

3 files changed, 198 insertions, 0 deletions

diff --git a/gcc/match.pd b/gcc/match.pd
index fdba583..c48fe2d 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -1906,6 +1906,61 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
  (if (INTEGRAL_TYPE_P (type))
   (bit_and @0 @1)))
 
+(for cmp (tcc_comparison)
+     icmp (inverted_tcc_comparison)
+ /* Fold (((a < b) & c) | ((a >= b) & d)) into (a < b ? c : d) & 1.  */
+ (simplify
+  (bit_ior
+   (bit_and:c (convert? (cmp@0  @01 @02)) @3)
+   (bit_and:c (convert? (icmp@4 @01 @02)) @5))
+    (if (INTEGRAL_TYPE_P (type)
+	 /* The scalar version has to be canonicalized after vectorization
+	    because it makes unconditional loads conditional ones, which
+	    means we lose vectorization because the loads may trap.  */
+	 && canonicalize_math_after_vectorization_p ())
+     (bit_and (cond @0 @3 @5) { build_one_cst (type); })))
+
+ /* Fold ((-(a < b) & c) | (-(a >= b) & d)) into a < b ? c : d.  This is
+    canonicalized further and we recognize the conditional form:
+    (a < b ? c : 0) | (a >= b ? d : 0) into a < b ? c : d.  */
+ (simplify
+  (bit_ior
+   (cond (cmp@0  @01 @02) @3 zerop)
+   (cond (icmp@4 @01 @02) @5 zerop))
+    (if (INTEGRAL_TYPE_P (type)
+	 /* The scalar version has to be canonicalized after vectorization
+	    because it makes unconditional loads conditional ones, which
+	    means we lose vectorization because the loads may trap.  */
+	 && canonicalize_math_after_vectorization_p ())
+    (cond @0 @3 @5)))
+
+ /* Vector Fold (((a < b) & c) | ((a >= b) & d)) into a < b ? c : d. 
+    and ((~(a < b) & c) | (~(a >= b) & d)) into a < b ? c : d.  */
+ (simplify
+  (bit_ior
+   (bit_and:c (vec_cond:s (cmp@0 @6 @7) @4 @5) @2)
+   (bit_and:c (vec_cond:s (icmp@1 @6 @7) @4 @5) @3))
+    (if (integer_zerop (@5))
+     (switch
+      (if (integer_onep (@4))
+       (bit_and (vec_cond @0 @2 @3) @4))
+	(if (integer_minus_onep (@4))
+	 (vec_cond @0 @2 @3)))
+    (if (integer_zerop (@4))
+     (switch
+      (if (integer_onep (@5))
+       (bit_and (vec_cond @0 @3 @2) @5))
+      (if (integer_minus_onep (@5))
+       (vec_cond @0 @3 @2))))))
+
+ /* Scalar Vectorized Fold ((-(a < b) & c) | (-(a >= b) & d))
+    into a < b ? d : c.  */
+ (simplify
+  (bit_ior
+   (vec_cond:s (cmp@0 @4 @5) @2 integer_zerop)
+   (vec_cond:s (icmp@1 @4 @5) @3 integer_zerop))
+    (vec_cond @0 @2 @3)))
+
 /* Transform X & -Y into X * Y when Y is { 0 or 1 }.  */
 (simplify
  (bit_and:c (convert? (negate zero_one_valued_p@0)) @1)
diff --git a/gcc/testsuite/gcc.target/aarch64/if-compare_1.c b/gcc/testsuite/gcc.target/aarch64/if-compare_1.c
new file mode 100644
index 0000000..53bbd77
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/if-compare_1.c
@@ -0,0 +1,47 @@
+/* { dg-do run } */
+/* { dg-additional-options "-O -save-temps" } */
+/* { dg-final { check-function-bodies "**" "" "" { target { le } } } } */
+
+extern void abort ();
+
+/*
+**zoo1:
+**	cmp	w0, w1
+**	csel	w0, w2, w3, lt
+**	and	w0, w0, 1
+**	ret
+*/
+__attribute((noipa, noinline))
+int zoo1 (int a, int b, int c, int d)
+{
+   return ((a < b) & c) | ((a >= b) & d);
+}
+
+/*
+**zoo2:
+**	cmp	w0, w1
+**	csel	w0, w2, w3, lt
+**	ret
+*/
+__attribute((noipa, noinline))
+int zoo2 (int a, int b, int c, int d)
+{
+   return (-(a < b) & c) | (-(a >= b) & d);
+}
+
+int main ()
+{
+  if (zoo1 (-3, 3, 5, 8) != 1)
+    abort ();
+
+  if (zoo1 (3, -3, 5, 8) != 0)
+    abort ();
+
+  if (zoo2 (-3, 3, 5, 8) != 5)
+    abort ();
+
+  if (zoo2 (3, -3, 5, 8) != 8)
+    abort ();
+
+  return 0;
+}
diff --git a/gcc/testsuite/gcc.target/aarch64/if-compare_2.c b/gcc/testsuite/gcc.target/aarch64/if-compare_2.c
new file mode 100644
index 0000000..14988ab
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/if-compare_2.c
@@ -0,0 +1,96 @@
+/* { dg-do run } */
+/* { dg-additional-options "-O3 -std=c99 -save-temps" } */
+/* { dg-final { check-function-bodies "**" "" "" { target { le } } } } */
+
+#pragma GCC target "+nosve"
+
+#include <string.h>
+
+typedef int v4si __attribute__ ((vector_size (16)));
+
+/*
+**foo1:
+**	cmgt	v0.4s, v1.4s, v0.4s
+**	bsl	v0.16b, v2.16b, v3.16b
+**	ret
+*/
+v4si foo1 (v4si a, v4si b, v4si c, v4si d) {
+    return ((a < b) & c) | ((a >= b) & d);
+}
+
+/*
+**foo2:
+**	cmgt	v0.4s, v1.4s, v0.4s
+**	bsl	v0.16b, v3.16b, v2.16b
+**	ret
+*/
+v4si foo2 (v4si a, v4si b, v4si c, v4si d) {
+    return (~(a < b) & c) | (~(a >= b) & d);
+}
+
+
+/**
+**bar1:
+**...
+**	cmge	v[0-9]+.4s, v[0-9]+.4s, v[0-9]+.4s
+**	bsl	v[0-9]+.16b, v[0-9]+.16b, v[0-9]+.16b
+**	and	v[0-9]+.16b, v[0-9]+.16b, v[0-9]+.16b
+**...
+*/
+void bar1 (int * restrict a, int * restrict b, int * restrict c,
+	  int * restrict d, int * restrict res, int n)
+{
+  for (int i = 0; i < (n & -4); i++)
+    res[i] = ((a[i] < b[i]) & c[i]) | ((a[i] >= b[i]) & d[i]);
+}
+
+/**
+**bar2:
+**...
+**	cmge	v[0-9]+.4s, v[0-9]+.4s, v[0-9]+.4s
+**	bsl	v[0-9]+.16b, v[0-9]+.16b, v[0-9]+.16b
+**...
+*/
+void bar2 (int * restrict a, int * restrict b, int * restrict c,
+	  int * restrict d, int * restrict res, int n)
+{
+  for (int i = 0; i < (n & -4); i++)
+    res[i] = (-(a[i] < b[i]) & c[i]) | (-(a[i] >= b[i]) & d[i]);
+}
+
+extern void abort ();
+
+int main ()
+{
+
+  v4si a = { -3, -3, -3, -3 };
+  v4si b = { 3, 3, 3, 3 };
+  v4si c = { 5, 5, 5, 5 };
+  v4si d = { 8, 8, 8, 8 };
+
+  v4si res1 = foo1 (a, b, c, d);
+  if (memcmp (&res1, &c, 16UL) != 0)
+    abort ();
+
+  v4si res2 = foo2 (a, b, c, d);
+  if (memcmp (&res2, &d, 16UL) != 0)
+   abort ();
+
+  int ar[4] = { -3, -3, -3, -3 };
+  int br[4] = { 3, 3, 3, 3 };
+  int cr[4] = { 5, 5, 5, 5 };
+  int dr[4] = { 8, 8, 8, 8 };
+
+  int exp1[4] = { 1, 1, 1, 1 };
+  int res3[4];
+  bar1 ((int*)&ar, (int*)&br, (int*)&cr, (int*)&dr, (int*)&res3, 4);
+  if (memcmp (&res3, &exp1, 16UL) != 0)
+    abort ();
+
+  int res4[4];
+  bar2 ((int*)&ar, (int*)&br, (int*)&cr, (int*)&dr, (int*)&res4, 4);
+  if (memcmp (&res4, &cr, 16UL) != 0)
+    abort ();
+
+  return 0;
+}