From patchwork Sat Feb 19 20:55:08 2011
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Subject: [PR, tree-optimization/46620,
 4.4] skip padding in bitfield SRA grouping
Date: Sat, 19 Feb 2011 10:55:08 -0000
From: Alexandre Oliva <aoliva@redhat.com>
X-Patchwork-Id: 83715
Message-Id: <oraahr218z.fsf@livre.localdomain>
To: Richard Guenther <richard.guenther@gmail.com>
Cc: gcc-patches@gcc.gnu.org

On Feb 16, 2011, Richard Guenther <richard.guenther@gmail.com> wrote:

> On Wed, Feb 16, 2011 at 11:04 AM, Alexandre Oliva <aoliva@redhat.com> wrote:
>> Before the latest SRA rewrite, we had a pass that attempted to group
>> multiple bitfields into single variables.  It attempted to extend these
>> variables to cover padding bits, but there was a bug that got it
>> confused when it found padding bits before the range it intended to
>> cover.
>> 
>> This patch changes the tests so that the tentatively-extended range will
>> always shrink towards the range of interest, instead of getting stuck at
>> a padding range.
>> 
>> Regstrapped on x86_64-linux-gnu.  Ok to install?

> Please add a runtime testcase for such wrong-code bugs.  Ok with
> that, please also install the testcase on the 4.5 branch and trunk.

Here's the patch that adds the testcase, reduced to a single source file
from the two source files in the bug report.


for  gcc/testsuite/ChangeLog
from  Alexandre Oliva  <aoliva@redhat.com>

	PR tree-optimization/46620
	* gcc.dg/pr46620.c: New.

Index: gcc/testsuite/gcc.dg/pr46620.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ gcc/testsuite/gcc.dg/pr46620.c	2011-02-19 18:52:23.116761084 -0200
@@ -0,0 +1,76 @@
+/* PR tree-optimization/46620 */
+/* SRA bitfield grouping used to lose track at padding bitfields in
+   the middle of a word.  */
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+
+#include <stdlib.h>
+
+struct PCT
+{
+  unsigned char	pi1	: 4;
+  unsigned char	pi2	: 3;
+  unsigned char	pif	: 5;
+
+  unsigned char	sl	: 2;
+  unsigned char	uc	: 1;
+  unsigned char	st	: 1;
+
+  unsigned char	p	: 1;
+  unsigned char	cs	: 1;
+  unsigned char	ss	: 1;
+
+  unsigned char	pc	: 3;
+  unsigned char	dmv	: 4;
+  unsigned char	cv	: 4;
+};
+
+struct rt
+{
+  struct rt*		d;
+  void (*edo)(void * const);
+  short			lId;
+  char          dac;
+};
+
+struct pedr
+{
+  struct rt re;
+  struct PCT pc;
+  unsigned char mid;
+} ;
+
+void __attribute__((__noinline__))
+rei(struct rt* const me, unsigned short anId, void *ad )
+{
+  asm volatile ("");
+}
+
+void __attribute__((__noinline__))
+pedrdo(void * const p)
+{
+  asm volatile ("");
+}
+
+void __attribute__((__noinline__))
+pedri (struct pedr* const  me, struct PCT ppc, unsigned char pmid)
+{
+  rei(&(me->re), 0x7604, 0);
+  me->pc = ppc;
+  me->mid = pmid;
+  (me)->re.edo = pedrdo;
+}
+
+int main()
+{
+  struct PCT ps;
+  struct pedr pm;
+
+  pm.pc.dmv = 0;
+  ps.dmv = 1;
+  pedri(&pm, ps, 32);
+
+  if (pm.pc.dmv != 1)
+    abort ();
+  exit (0);
+}