[gcc r13-4620] middle-end: simplify complex if expressions where comparisons are inverse of one another.

[Tamar Christina <tnfchris@gcc.gnu.org>]

https://gcc.gnu.org/g:4d9db4bdd458a4b526f59e4bc5bbd549d3861cea

commit r13-4620-g4d9db4bdd458a4b526f59e4bc5bbd549d3861cea
Author: Tamar Christina <tamar.christina@arm.com>
Date:   Mon Dec 12 15:21:39 2022 +0000

    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.

Diff:
---
 gcc/match.pd                                    | 55 ++++++++++++++
 gcc/testsuite/gcc.target/aarch64/if-compare_1.c | 47 ++++++++++++
 gcc/testsuite/gcc.target/aarch64/if-compare_2.c | 96 +++++++++++++++++++++++++
 3 files changed, 198 insertions(+)

diff --git a/gcc/match.pd b/gcc/match.pd
index fdba5833beb..c48fe2d6bf2 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 00000000000..53bbd779a30
--- /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 00000000000..14988abac45
--- /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;
+}