From abef36919f741c8e4f7380b2c2ffbc6ad97c2b6b Mon Sep 17 00:00:00 2001
From: Eugene Rozenfeld <Eugene.Rozenfeld@microsoft.com>
Date: Tue, 1 Dec 2020 16:26:59 -0700
Subject: [PATCH] Optimize max/min pattern with comparison

gcc/
	PR tree-optimization/96708
	* match.pd: New pattern for comparing X with MAX (X, Y)
	or MIN (X, y).

gcc/testsuite
	* gcc.dg/pr96708-negative.c: New test.
	* gcc.dg/pr96708-positive.c: New test.
---
 gcc/match.pd                            | 10 ++++++
 gcc/testsuite/gcc.dg/pr96708-negative.c | 48 +++++++++++++++++++++++++
 gcc/testsuite/gcc.dg/pr96708-positive.c | 48 +++++++++++++++++++++++++
 3 files changed, 106 insertions(+)
 create mode 100644 gcc/testsuite/gcc.dg/pr96708-negative.c
 create mode 100644 gcc/testsuite/gcc.dg/pr96708-positive.c

diff --git a/gcc/match.pd b/gcc/match.pd
index 6cf16c67009..68201ff2e07 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -2883,6 +2883,16 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
   (cmp (minmax @0 INTEGER_CST@1) INTEGER_CST@2)
   (comb (cmp @0 @2) (cmp @1 @2))))
 
+/* X <= MAX(X, Y) -> true
+   X > MAX(X, Y) -> false 
+   X >= MIN(X, Y) -> true
+   X < MIN(X, Y) -> false */
+(for minmax (min     min     max     max     )
+     cmp    (ge      lt      le      gt      )
+ (simplify
+  (cmp @0 (minmax:c @0 @1))
+  { constant_boolean_node (cmp == GE_EXPR || cmp == LE_EXPR, type); } ))
+
 /* Undo fancy way of writing max/min or other ?: expressions,
    like a - ((a - b) & -(a < b)), in this case into (a < b) ? b : a.
    People normally use ?: and that is what we actually try to optimize.  */
diff --git a/gcc/testsuite/gcc.dg/pr96708-negative.c b/gcc/testsuite/gcc.dg/pr96708-negative.c
new file mode 100644
index 00000000000..91964d3b971
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr96708-negative.c
@@ -0,0 +1,48 @@
+/* { dg-do run } */
+/* { dg-options "-O -fdump-tree-optimized" } */
+
+#include <stdbool.h>
+
+bool __attribute__ ((noinline))
+test1 (int a, int b)
+{
+    int tmp = (a < b) ? b : a;
+    return tmp <= a;
+}
+
+bool __attribute__ ((noinline))
+test2 (int a, int b)
+{
+    int tmp = (a < b) ? b : a;
+    return tmp > a;
+}
+
+bool __attribute__ ((noinline))
+test3 (int a, int b)
+{
+    int tmp = (a > b) ? b : a;
+    return tmp >= a;
+}
+
+bool __attribute__ ((noinline))
+test4 (int a, int b)
+{
+    int tmp = (a > b) ? b : a;
+    return tmp < a;
+}
+
+int main()
+{
+    if (test1 (1, 2) || !test1 (2, 1) || 
+        !test2 (1, 2) || test2 (2, 1) ||
+        !test3 (1, 2) || test3 (2, 1) ||
+        test4 (1, 2) || !test4 (2, 1)) {
+        __builtin_abort();	
+    }
+    return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "MAX_EXPR" 2 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "MIN_EXPR" 2 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "return 0;" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-not { "return 1;" } "optimized" } } */
diff --git a/gcc/testsuite/gcc.dg/pr96708-positive.c b/gcc/testsuite/gcc.dg/pr96708-positive.c
new file mode 100644
index 00000000000..65af85344b6
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr96708-positive.c
@@ -0,0 +1,48 @@
+/* { dg-do run } */
+/* { dg-options "-O -fdump-tree-optimized" } */
+
+#include <stdbool.h>
+
+bool __attribute__ ((noinline))
+test1(int a, int b)
+{
+    int tmp = (a < b) ? b : a;
+    return tmp >= a;
+}
+
+bool __attribute__ ((noinline))
+test2(int a, int b)
+{
+    int tmp = (a < b) ? b : a;
+    return tmp < a;
+}
+
+bool __attribute__ ((noinline))
+test3(int a, int b)
+{
+    int tmp = (a > b) ? b : a;
+    return tmp <= a;
+}
+
+bool __attribute__ ((noinline))
+test4(int a, int b)
+{
+    int tmp = (a > b) ? b : a;
+    return tmp > a;
+}
+
+int main()
+{
+    if (!test1 (1, 2) || !test1 (2, 1) || 
+        test2 (1, 2) || test2 (2, 1) ||
+        !test3 (1, 2) || !test3 (2, 1) ||
+        test4 (1, 2) || test4 (2, 1)) {
+        __builtin_abort();	
+    }
+    return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "return 0;" 3 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "return 1;" 2 "optimized" } } */
+/* { dg-final { scan-tree-dump-not { "MAX_EXPR" } "optimized" } } */
+/* { dg-final { scan-tree-dump-not { "MIN_EXPR" } "optimized" } } */
-- 
2.30.2