From 6d449531a60b56ed0f4aeb640aa9e46e4ec35208 Mon Sep 17 00:00:00 2001
From: Andrew Pinski <apinski@marvell.com>
Date: Thu, 20 Jul 2023 17:36:29 -0700
Subject: [PATCH] MATCH: Add Max<Max<a,b>,a> -> Max<a,b> simplifcation

This adds a simple match pattern to simplify
`max<max<a,b>,a>` to `max<a,b>`.  Reassociation handles
this already (r0-77700-ge969dbde29bfd396259357) but
seems like we should be able to handle this even before
reassociation.

This fixes part of PR tree-optimization/80574 but more
work is needed fix it the rest of the way. The original
testcase there is fixed but the RTL level is what fixes
it the rest of the way.

OK? Bootstrapped and tested on x86_64-linux-gnu.

gcc/ChangeLog:

	* match.pd (minmax<minmax<a,b>,a>->minmax<a,b>): New
	transformation.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/reassoc-12.c: Disable all of
	the passes that enables match-and-simplify.
	* gcc.dg/tree-ssa/minmax-23.c: New test.
---
 gcc/match.pd                               |  6 +++++-
 gcc/testsuite/gcc.dg/tree-ssa/minmax-23.c  | 22 ++++++++++++++++++++++
 gcc/testsuite/gcc.dg/tree-ssa/reassoc-12.c |  3 ++-
 3 files changed, 29 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/minmax-23.c

diff --git a/gcc/match.pd b/gcc/match.pd
index 4dfe92623f7..bfd15d6cd4a 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -3503,7 +3503,11 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
 (for minmax (min max)
  (simplify
   (minmax @0 @0)
-  @0))
+  @0)
+/* max(max(x,y),x) -> max(x,y)  */
+ (simplify
+  (minmax:c (minmax:c@2 @0 @1) @0)
+  @2))
 /* For fmin() and fmax(), skip folding when both are sNaN.  */
 (for minmax (FMIN_ALL FMAX_ALL)
  (simplify
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/minmax-23.c b/gcc/testsuite/gcc.dg/tree-ssa/minmax-23.c
new file mode 100644
index 00000000000..0b7e51bb97e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/minmax-23.c
@@ -0,0 +1,22 @@
+/* { dg-do compile } */
+/* { dg-options "-O1 -fno-tree-reassoc -fdump-tree-optimized" } */
+
+
+#define MAX(a,b) (a)>=(b) ? (a) : (b)
+
+#define MIN(a,b) (a)<=(b) ? (a) : (b)
+
+int test1(int a, int b)
+{
+  int d = MAX(a,b);
+  return MAX(a,d);
+}
+int test2(int a, int b)
+{
+  int d = MIN(a,b);
+  return MIN(a,d);
+}
+
+/* We should be optimize these two functions even without reassociation. */
+/* { dg-final { scan-tree-dump-times "MAX_EXPR " 1 "optimized"} } */
+/* { dg-final { scan-tree-dump-times "MIN_EXPR " 1 "optimized"} } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/reassoc-12.c b/gcc/testsuite/gcc.dg/tree-ssa/reassoc-12.c
index 9a138ebcf70..2238147de19 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/reassoc-12.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/reassoc-12.c
@@ -1,5 +1,6 @@
 /* { dg-do compile } */ 
-/* { dg-options "-O2 -fdump-tree-reassoc1-details" } */
+/* Match-and-simplify can handle now MAX<MAX<a,b>,a>->MAX<a,b>, disable all of the passes that uses that. */
+/* { dg-options "-O1 -fdump-tree-reassoc1-details -fno-tree-ccp -fno-tree-ccp -fno-tree-forwprop -fno-tree-fre" } */
 int f(int a, int b)
 {
   /* MAX_EXPR <a, a> should cause it to be equivalent to a.  */
-- 
2.11.4.GIT