expr.c (expand_expr_real_1): Correctly handle strict volatile bitfield loads smaller...

2011-11-20  Joey Ye  <joey.ye@arm.com>

	* expr.c (expand_expr_real_1): Correctly handle strict volatile
	bitfield loads smaller than mode size.

testsuite:

	* gcc.dg/volatile-bitfields-1.c: New.

From-SVN: r181549

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 6a14c5419ce4598a0b839ec1c29acd806c0337ba..590dba822e27cd520893bdb7e5ab0f07b6b24728 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2011-11-20  Joey Ye  <joey.ye@arm.com>
+
+       * expr.c (expand_expr_real_1): Correctly handle strict volatile
+       bitfield loads smaller than mode size.
+
 2011-11-20  Richard Henderson  <rth@redhat.com>
 
        * config/mips/mips.c (mips_init_libfuncs): Call init_sync_libfuncs.

diff --git a/gcc/expr.c b/gcc/expr.c
index 84cfe5c23ee230ed15846f39f1cf9034ad4b14a0..8d3a0f671a8a0f4372ca4eb9f7b091ad40b41e88 100644 (file)
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -9740,11 +9740,16 @@ expand_expr_real_1 (tree exp, rtx target, enum machine_mode tmode,
                && modifier != EXPAND_CONST_ADDRESS
                && modifier != EXPAND_INITIALIZER)
            /* If the field is volatile, we always want an aligned
-              access.  Only do this if the access is not already naturally
+              access.  Do this in following two situations:
+              1. the access is not already naturally
               aligned, otherwise "normal" (non-bitfield) volatile fields
-              become non-addressable.  */
+              become non-addressable.
+              2. the bitsize is narrower than the access size. Need
+              to extract bitfields from the access.  */
            || (volatilep && flag_strict_volatile_bitfields > 0
-               && (bitpos % GET_MODE_ALIGNMENT (mode) != 0))
+               && (bitpos % GET_MODE_ALIGNMENT (mode) != 0 
+                   || (mode1 != BLKmode
+                       && bitsize < GET_MODE_SIZE (mode1) * BITS_PER_UNIT)))
            /* If the field isn't aligned enough to fetch as a memref,
               fetch it as a bit field.  */
            || (mode1 != BLKmode

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 58a3ff0aaf680e1b7e73afa2e7f589581889eb48..5c1fb0077d6d69ff7d18282488d06168c88e7a97 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2011-11-20  Joey Ye  <joey.ye@arm.com>
+
+       * gcc.dg/volatile-bitfields-1.c: New.
+
 2011-11-20  Jason Merrill  <jason@redhat.com>
 
        PR c++/48322

diff --git a/gcc/testsuite/gcc.dg/volatile-bitfields-1.c b/gcc/testsuite/gcc.dg/volatile-bitfields-1.c
new file mode 100644 (file)
index 0000000..6adda27
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/volatile-bitfields-1.c
@@ -0,0 +1,23 @@
+/* { dg-options "-fstrict-volatile-bitfields" } */
+/* { dg-do run } */
+
+extern int puts(const char *);
+extern void abort(void) __attribute__((noreturn));
+
+typedef struct {
+  volatile unsigned short a:8, b:8;
+} BitStruct;
+
+BitStruct bits = {1, 2};
+
+void check(int i, int j)
+{
+  if (i != 1 || j != 2) puts("FAIL"), abort();
+}
+
+int main ()
+{
+  check(bits.a, bits.b);
+
+  return 0;
+}