From: Jakub Jelinek <jakub@redhat.com>
Date: Thu, 7 Jul 2016 21:50:41 +0000 (+0200)
Subject: backport: re PR rtl-optimization/70429 (Wrong code with -O1.)
X-Git-Tag: releases/gcc-4.9.4~89
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=65084d607d438623476efbc7eaf06b3f3bf2ad0f;p=thirdparty%2Fgcc.git

backport: re PR rtl-optimization/70429 (Wrong code with -O1.)

	Backported from mainline
	2016-03-29  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/70429
	* combine.c (simplify_shift_const_1): For ASHIFTRT don't optimize
	(cst1 >> count) >> cst2 into (cst1 >> cst2) >> count if
	mode != result_mode.

	* gcc.c-torture/execute/pr70429.c: New test.

From-SVN: r238141
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 52b69c8f3ea2..1dbd3df30629 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,6 +1,13 @@
 2016-07-07  Jakub Jelinek  <jakub@redhat.com>
 
 	Backported from mainline
+	2016-03-29  Jakub Jelinek  <jakub@redhat.com>
+
+	PR rtl-optimization/70429
+	* combine.c (simplify_shift_const_1): For ASHIFTRT don't optimize
+	(cst1 >> count) >> cst2 into (cst1 >> cst2) >> count if
+	mode != result_mode.
+
 	2016-03-15  Jakub Jelinek  <jakub@redhat.com>
 
 	PR rtl-optimization/70222
diff --git a/gcc/combine.c b/gcc/combine.c
index c48d9b11e47b..d2f00d1b7e7d 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -10182,6 +10182,11 @@ simplify_shift_const_1 (enum rtx_code code, enum machine_mode result_mode,
 				       >> orig_count, result_mode,
 				       &complement_p))
 		break;
+	      /* For ((int) (cstLL >> count)) >> cst2 just give up.  Queuing
+		 up outer sign extension (often left and right shift) is
+		 hardly more efficient than the original.  See PR70429.  */
+	      if (code == ASHIFTRT && mode != result_mode)
+		break;
 
 	      rtx new_rtx = simplify_const_binary_operation (code, mode,
 							     XEXP (varop, 0),
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index dac1b34b1b3b..888311c89cf0 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,6 +1,11 @@
 2016-07-07  Jakub Jelinek  <jakub@redhat.com>
 
 	Backported from mainline
+	2016-03-29  Jakub Jelinek  <jakub@redhat.com>
+
+	PR rtl-optimization/70429
+	* gcc.c-torture/execute/pr70429.c: New test.
+
 	2016-03-15  Jakub Jelinek  <jakub@redhat.com>
 
 	PR rtl-optimization/70222
diff --git a/gcc/testsuite/gcc.c-torture/execute/pr70429.c b/gcc/testsuite/gcc.c-torture/execute/pr70429.c
new file mode 100644
index 000000000000..6b08c8ead084
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr70429.c
@@ -0,0 +1,17 @@
+/* PR rtl-optimization/70429 */
+
+__attribute__((noinline, noclone)) int
+foo (int a)
+{
+  return (int) (0x14ff6e2207db5d1fLL >> a) >> 4;
+}
+
+int
+main ()
+{
+  if (sizeof (int) != 4 || sizeof (long long) != 8 || __CHAR_BIT__ != 8)
+    return 0;
+  if (foo (1) != 0x3edae8 || foo (2) != -132158092)
+    __builtin_abort ();
+  return 0;
+}