From: Doug Kwan <dougkwan@google.com>
Date: Thu, 22 Dec 2011 19:36:46 +0000 (+0000)
Subject: backport: [multiple changes]
X-Git-Tag: releases/gcc-4.6.3~232
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=38854abd48e66ac1819063b0513db184be9e560f;p=thirdparty%2Fgcc.git

backport: [multiple changes]

2011-12-22  Doug Kwan  <dougkwan@google.com>

	Backport from mainline
	2011-03-23  Julian Brown  <julian@codesourcery.com>

	* expr.c (expand_expr_real_1): Only use BLKmode for volatile
	accesses which are not naturally aligned.

	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.

2011-12-22  Doug Kwan  <dougkwan@google.com>

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

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

From-SVN: r182635
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 9135dcfeea6b..02d2aa5916ad 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,16 @@
+2011-12-22  Doug Kwan  <dougkwan@google.com>
+
+	Backport from mainline
+	2011-03-23  Julian Brown  <julian@codesourcery.com>
+
+	* expr.c (expand_expr_real_1): Only use BLKmode for volatile
+	accesses which are not naturally aligned.
+
+	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.
+
 2011-12-21  Richard Earnshaw  <rearnsha@arm.com>
 
 	PR target/51643
diff --git a/gcc/expr.c b/gcc/expr.c
index c4a00aa3f780..6bf9f2489dab 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -9189,8 +9189,16 @@ 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.  */
-	    || (volatilep && flag_strict_volatile_bitfields > 0)
+	       access.  Do this in following two situations:
+	       1. the access is not already naturally
+	       aligned, otherwise "normal" (non-bitfield) volatile fields
+	       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 
+		    || (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 86ca26fccf47..24bdfd049288 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,10 @@
+2011-12-22  Doug Kwan  <dougkwan@google.com>
+
+	Backport from mainline
+	2011-11-20  Joey Ye  <joey.ye@arm.com>
+
+	* gcc.dg/volatile-bitfields-1.c: New.
+
 2011-12-21  Richard Earnshaw  <rearnsha@arm.com>
 
 	PR target/51643
diff --git a/gcc/testsuite/gcc.dg/volatile-bitfields-1.c b/gcc/testsuite/gcc.dg/volatile-bitfields-1.c
new file mode 100644
index 000000000000..6adda27fea4c
--- /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;
+}