expmed.c (strict_volatile_bitfield_p): Check that the access will not cross a MODESIZE boundary.

gcc:
2015-04-01  Bernd Edlinger  <bernd.edlinger@hotmail.de>

        * expmed.c (strict_volatile_bitfield_p): Check that the access will
        not cross a MODESIZE boundary.
        (store_bit_field, extract_bit_field): Added assertions in the
        strict volatile bitfields code path.

testsuite:
2015-04-01  Bernd Edlinger  <bernd.edlinger@hotmail.de>

        * gcc.dg/pr23623.c: Added aligned attribute.
        * gcc.dg/20141029-1.c: Likewise.
        * gcc.dg/20150306-1.c: New test.

From-SVN: r221809

6 files changed, 57 insertions, 13 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 11a79db..47c0f22 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2015-04-01  Bernd Edlinger  <bernd.edlinger@hotmail.de>
+
+	* expmed.c (strict_volatile_bitfield_p): Check that the access will
+	not cross a MODESIZE boundary.
+	(store_bit_field, extract_bit_field): Added assertions in the
+	strict volatile bitfields code path.
+
 2015-04-01  Max Ostapenko  <m.ostapenko@partner.samsung.com>
 
 	PR target/65624
diff --git a/gcc/expmed.c b/gcc/expmed.c
index e0b2619..6327629 100644
--- a/gcc/expmed.c
+++ b/gcc/expmed.c
@@ -472,9 +472,13 @@ strict_volatile_bitfield_p (rtx op0, unsigned HOST_WIDE_INT bitsize,
     return false;
 
   /* Check for cases of unaligned fields that must be split.  */
-  if (bitnum % BITS_PER_UNIT + bitsize > modesize
-      || (STRICT_ALIGNMENT
-	  && bitnum % GET_MODE_ALIGNMENT (fieldmode) + bitsize > modesize))
+  if (bitnum % modesize + bitsize > modesize)
+    return false;
+
+  /* The memory must be sufficiently aligned for a MODESIZE access.
+     This condition guarantees, that the memory access will not
+     touch anything after the end of the structure.  */
+  if (MEM_ALIGN (op0) < modesize)
     return false;
 
   /* Check for cases where the C++ memory model applies.  */
@@ -973,13 +977,15 @@ store_bit_field (rtx str_rtx, unsigned HOST_WIDE_INT bitsize,
   if (strict_volatile_bitfield_p (str_rtx, bitsize, bitnum, fieldmode,
 				  bitregion_start, bitregion_end))
     {
-      /* Storing any naturally aligned field can be done with a simple
-	 store.  For targets that support fast unaligned memory, any
-	 naturally sized, unit aligned field can be done directly.  */
+      /* Storing of a full word can be done with a simple store.
+	 We know here that the field can be accessed with one single
+	 instruction.  For targets that support unaligned memory,
+	 an unaligned access may be necessary.  */
       if (bitsize == GET_MODE_BITSIZE (fieldmode))
 	{
 	  str_rtx = adjust_bitfield_address (str_rtx, fieldmode,
 					     bitnum / BITS_PER_UNIT);
+	  gcc_assert (bitnum % BITS_PER_UNIT == 0);
 	  emit_move_insn (str_rtx, value);
 	}
       else
@@ -988,6 +994,7 @@ store_bit_field (rtx str_rtx, unsigned HOST_WIDE_INT bitsize,
 
 	  str_rtx = narrow_bit_field_mem (str_rtx, fieldmode, bitsize, bitnum,
 					  &bitnum);
+	  gcc_assert (bitnum + bitsize <= GET_MODE_BITSIZE (fieldmode));
 	  temp = copy_to_reg (str_rtx);
 	  if (!store_bit_field_1 (temp, bitsize, bitnum, 0, 0,
 				  fieldmode, value, true))
@@ -1790,17 +1797,21 @@ extract_bit_field (rtx str_rtx, unsigned HOST_WIDE_INT bitsize,
 
   if (strict_volatile_bitfield_p (str_rtx, bitsize, bitnum, mode1, 0, 0))
     {
-      /* Extraction of a full MODE1 value can be done with a load as long as
-	 the field is on a byte boundary and is sufficiently aligned.  */
-      if (bitsize == GET_MODE_BITSIZE(mode1))
+      /* Extraction of a full MODE1 value can be done with a simple load.
+	 We know here that the field can be accessed with one single
+	 instruction.  For targets that support unaligned memory,
+	 an unaligned access may be necessary.  */
+      if (bitsize == GET_MODE_BITSIZE (mode1))
 	{
 	  rtx result = adjust_bitfield_address (str_rtx, mode1,
 						bitnum / BITS_PER_UNIT);
+	  gcc_assert (bitnum % BITS_PER_UNIT == 0);
 	  return convert_extracted_bit_field (result, mode, tmode, unsignedp);
 	}
 
       str_rtx = narrow_bit_field_mem (str_rtx, mode1, bitsize, bitnum,
 				      &bitnum);
+      gcc_assert (bitnum + bitsize <= GET_MODE_BITSIZE (mode1));
       str_rtx = copy_to_reg (str_rtx);
     }
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 399f9cc..9f8e0b7 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2015-04-01  Bernd Edlinger  <bernd.edlinger@hotmail.de>
+
+	* gcc.dg/pr23623.c: Added aligned attribute.
+	* gcc.dg/20141029-1.c: Likewise.
+	* gcc.dg/20150306-1.c: New test.
+
 2015-04-01  Marek Polacek  <polacek@redhat.com>
 
 	PR c++/65554
diff --git a/gcc/testsuite/gcc.dg/20141029-1.c b/gcc/testsuite/gcc.dg/20141029-1.c
index b25af57..1d18a1b 100644
--- a/gcc/testsuite/gcc.dg/20141029-1.c
+++ b/gcc/testsuite/gcc.dg/20141029-1.c
@@ -14,7 +14,7 @@ struct system_periph {
       unsigned short  :8;
     } BIT;
   } ALL;
-};
+} __attribute__((aligned(2)));
 
 void
 foo()
diff --git a/gcc/testsuite/gcc.dg/20150306-1.c b/gcc/testsuite/gcc.dg/20150306-1.c
new file mode 100644
index 0000000..55caf3b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/20150306-1.c
@@ -0,0 +1,20 @@
+/* { dg-do run } */
+/* { dg-require-effective-target size32plus } */
+/* { dg-options "-fstrict-volatile-bitfields" } */
+
+struct s
+{
+  char x : 8;
+  unsigned int y : 31;
+} __attribute__((packed));
+
+volatile struct s global;
+
+int
+main ()
+{
+  global.y = 0x7FFFFFFF;
+  if (global.y != 0x7FFFFFFF)
+    __builtin_abort ();
+  return 0;
+}
diff --git a/gcc/testsuite/gcc.dg/pr23623.c b/gcc/testsuite/gcc.dg/pr23623.c
index 7ba1470..e076b60 100644
--- a/gcc/testsuite/gcc.dg/pr23623.c
+++ b/gcc/testsuite/gcc.dg/pr23623.c
@@ -10,19 +10,19 @@ extern struct
 {
   unsigned int b : 1;
   unsigned int : 31;
-} bf1;
+} __attribute__((aligned(4))) bf1;
 
 extern volatile struct
 {
   unsigned int b : 1;
   unsigned int : 31;
-} bf2;
+} __attribute__((aligned(4))) bf2;
 
 extern struct
 {
   volatile unsigned int b : 1;
   volatile unsigned int : 31;
-} bf3;
+} __attribute__((aligned(4))) bf3;
 
 void writeb(void)
 {