Fix runtime error: left shift of negative value (PR, ipa/78555).

From 61a6b5e0c973bd77341a1053609c7ad331691a9e Mon Sep 17 00:00:00 2001
From: marxin <mliska@suse.cz>
Date: Wed, 30 Nov 2016 15:24:48 +0100
Subject: [PATCH] Fix runtime error: left shift of negative value (PR
 ipa/78555).

gcc/ChangeLog:

2016-11-30  Martin Liska  <mliska@suse.cz>

	PR ipa/78555
	* sreal.c (sreal::to_int): Make absolute value before shifting.
	(sreal::operator/): Likewise.
	(sreal_verify_negative_division): New test.
	(void sreal_c_tests): Call the new test.
	* sreal.h (sreal::normalize_up): Use new SREAL_ABS and
	SREAL_SIGN macros.
	(sreal::normalize_down): Likewise.
---
 gcc/sreal.c | 20 +++++++++++++++++---
 gcc/sreal.h |  9 +++++----
 2 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/gcc/sreal.c b/gcc/sreal.c
index 9c43b4e..52e530d 100644
--- a/gcc/sreal.c
+++ b/gcc/sreal.c
@@ -102,14 +102,14 @@  sreal::shift_right (int s)
 int64_t
 sreal::to_int () const
 {
-  int64_t sign = m_sig < 0 ? -1 : 1;
+  int64_t sign = SREAL_SIGN (m_sig);
 
   if (m_exp <= -SREAL_BITS)
     return 0;
   if (m_exp >= SREAL_PART_BITS)
     return sign * INTTYPE_MAXIMUM (int64_t);
   if (m_exp > 0)
-    return m_sig << m_exp;
+    return sign * (SREAL_ABS (m_sig) << m_exp);
   if (m_exp < 0)
     return m_sig >> -m_exp;
   return m_sig;
@@ -229,7 +229,8 @@  sreal::operator/ (const sreal &other) const
 {
   gcc_checking_assert (other.m_sig != 0);
   sreal r;
-  r.m_sig = (m_sig << SREAL_PART_BITS) / other.m_sig;
+  r.m_sig
+    = SREAL_SIGN (m_sig) * (SREAL_ABS (m_sig) << SREAL_PART_BITS) / other.m_sig;
   r.m_exp = m_exp - other.m_exp - SREAL_PART_BITS;
   r.normalize ();
   return r;
@@ -334,6 +335,18 @@  sreal_verify_shifting (void)
     verify_shifting (values[i]);
 }
 
+/* Verify division by (of) a negative value.  */
+
+static void
+sreal_verify_negative_division (void)
+{
+  ASSERT_EQ (sreal (1) / sreal (1), sreal (1));
+  ASSERT_EQ (sreal (-1) / sreal (-1), sreal (1));
+  ASSERT_EQ (sreal (-1234567) / sreal (-1234567), sreal (1));
+  ASSERT_EQ (sreal (-1234567) / sreal (1234567), sreal (-1));
+  ASSERT_EQ (sreal (1234567) / sreal (-1234567), sreal (-1));
+}
+
 /* Run all of the selftests within this file.  */
 
 void sreal_c_tests ()
@@ -341,6 +354,7 @@  void sreal_c_tests ()
   sreal_verify_basics ();
   sreal_verify_arithmetics ();
   sreal_verify_shifting ();
+  sreal_verify_negative_division ();
 }
 
 } // namespace selftest
diff --git a/gcc/sreal.h b/gcc/sreal.h
index ce9cdbb..21f14b0 100644
--- a/gcc/sreal.h
+++ b/gcc/sreal.h
@@ -31,6 +31,9 @@  along with GCC; see the file COPYING3.  If not see
 
 #define SREAL_BITS SREAL_PART_BITS
 
+#define SREAL_SIGN(v) (v < 0 ? -1: 1)
+#define SREAL_ABS(v) (v < 0 ? -v: v)
+
 /* Structure for holding a simple real number.  */
 class sreal
 {
@@ -193,7 +196,6 @@  inline sreal operator>> (const sreal &a, int exp)
 inline void
 sreal::normalize_up ()
 {
-  int64_t s = m_sig < 0 ? -1 : 1;
   unsigned HOST_WIDE_INT sig = absu_hwi (m_sig);
   int shift = SREAL_PART_BITS - 2 - floor_log2 (sig);
 
@@ -208,7 +210,7 @@  sreal::normalize_up ()
       m_exp = -SREAL_MAX_EXP;
       sig = 0;
     }
-  if (s == -1)
+  if (SREAL_SIGN (m_sig) == -1)
     m_sig = -sig;
   else
     m_sig = sig;
@@ -221,7 +223,6 @@  sreal::normalize_up ()
 inline void
 sreal::normalize_down ()
 {
-  int64_t s = m_sig < 0 ? -1 : 1;
   int last_bit;
   unsigned HOST_WIDE_INT sig = absu_hwi (m_sig);
   int shift = floor_log2 (sig) - SREAL_PART_BITS + 2;
@@ -246,7 +247,7 @@  sreal::normalize_down ()
       m_exp = SREAL_MAX_EXP;
       sig = SREAL_MAX_SIG;
     }
-  if (s == -1)
+  if (SREAL_SIGN (m_sig) == -1)
     m_sig = -sig;
   else
     m_sig = sig;
-- 
2.10.2