From 3d7355450f018898e50c4a5c9c1951c93b8224ae Mon Sep 17 00:00:00 2001
From: Navid Rahimi <navidrahimi@microsoft.com>
Date: Mon, 8 Nov 2021 13:57:19 -0800
Subject: [PATCH] PR tree-optimization/102232

	* match.pd (x * (1 + y / x) - y) -> (x - y % x): New optimization.
	* gcc.dg/tree-ssa/pr102232.c: testcase for this optimization.
---
 gcc/match.pd                             |  6 +++
 gcc/testsuite/gcc.dg/tree-ssa/pr102232.c | 52 ++++++++++++++++++++++++
 2 files changed, 58 insertions(+)
 create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr102232.c

diff --git a/gcc/match.pd b/gcc/match.pd
index 71cf6f9df0a..c91fff46936 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -608,6 +608,12 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
  (if (INTEGRAL_TYPE_P (type) || VECTOR_INTEGER_TYPE_P (type))
   (convert (trunc_mod @0 @1))))
 
+/* x * (1 + y / x) - y -> x - y % x */
+(simplify
+ (minus (mult:cs @0 (plus:s (trunc_div:s @1 @0) integer_onep)) @1)
+ (if (INTEGRAL_TYPE_P (type))
+  (minus @0 (trunc_mod @1 @0))))
+
 /* Optimize TRUNC_MOD_EXPR by a power of two into a BIT_AND_EXPR,
    i.e. "X % C" into "X & (C - 1)", if X and C are positive.
    Also optimize A % (C << N)  where C is a power of 2,
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr102232.c b/gcc/testsuite/gcc.dg/tree-ssa/pr102232.c
new file mode 100644
index 00000000000..62bca6922ab
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr102232.c
@@ -0,0 +1,52 @@
+/* PR tree-optimization/102232 */
+/* { dg-do run } */
+/* { dg-options "-O -fdump-tree-optimized" } */
+
+int __attribute__ ((noipa)) foo (int a, int b)
+{
+  return b * (1 + a / b) - a;
+}
+
+int
+main (void)
+{
+  // few randomly generated test cases
+  if (foo (71856034, 238) != 212)
+    {
+      __builtin_abort ();
+    }
+  if (foo (71856034, 10909) != 1549)
+    {
+      __builtin_abort ();
+    }
+  if (foo (20350, 1744) != 578)
+    {
+      __builtin_abort ();
+    }
+  if (foo (444813, 88563) != 86565)
+    {
+      __builtin_abort ();
+    }
+  if (foo (112237, 63004) != 13771)
+    {
+      __builtin_abort ();
+    }
+  if (foo (68268386, 787116) != 210706)
+    {
+      __builtin_abort ();
+    }
+  if (foo (-444813, 88563) != 90561)
+    {
+      __builtin_abort ();
+    }
+  if (foo (-68268386, 787116) != 1363526)
+    {
+      __builtin_abort ();
+    }
+
+  return 0;
+}
+
+/* Verify that multiplication and division has been removed.  */
+/* { dg-final { scan-tree-dump-not " \\* " "optimized" } } */
+/* { dg-final { scan-tree-dump-not " / " "optimized" } } */
\ No newline at end of file
-- 
2.25.1