| Message ID | 87obqpnj9i.fsf@schwinge.name |
|---|---|
| State | Rejected, archived |
| Headers | show |
On 18/04/12 16:37, Thomas Schwinge wrote: > Hi! > > As it's been some time: this was the discussion about > -fstrict-volatile-bitfields (as enabled by default on SH, for example) > breaking some testsuite bits due to missed optimizations (even for > bitfields that are not volatile). > > On Tue, 21 Feb 2012 09:40:07 +0000, Richard Earnshaw <rearnsha@arm.com> wrote: >> On 20/02/12 17:51, Bernd Schmidt wrote: >>> On 02/20/2012 06:39 PM, Richard Earnshaw wrote: >>>> I'm not sure why it should be. Can't a user write >>>> >>>> #ifdef __cplusplus >>>> #define BOOL bool >>>> #else >>>> #define bool _Bool >>>> #endif >>>> >>>> struct x { >>>> volatile BOOL a : 1; >>>> volatile BOOL b : 1; >>>> volatile unsigned char c : 6; >>>> volatile BOOL d : 1; >>>> } y; >>>> >>>> ? >>>> >>>> If you've got strict volatile bitfields, then the concept here is that >>>> the access uses the declared type for accessing the member. Since in >>>> the ABI bool has a defined size, then it should access the member using >>>> that size. >>>> >>>> On ARM, sizeof bool is 1, so I'd take the above to mean that accessing >>>> y.a to mean a read of a, b and c, but not d. >>> >>> What are your thoughts on the argument about enums? >> >> Similar. A particular enumeration type has a defined size, so accesses >> should use that size. > > In that case, would it be appropriate to apply the following? > > gcc/testsuite/ > * gcc.dg/tree-ssa/20030922-1.c: Compile with > -fno-strict-volatile-bitfields. > * gcc.dg/tree-ssa/foldconst-3.c: Likewise. > * gcc.dg/tree-ssa/vrp15.c: Likewise. > None of these have any volatile bitfields, so the option should be a no-op.
On 04/18/2012 06:14 PM, Richard Earnshaw wrote: > On 18/04/12 16:37, Thomas Schwinge wrote: >> gcc/testsuite/ >> * gcc.dg/tree-ssa/20030922-1.c: Compile with >> -fno-strict-volatile-bitfields. >> * gcc.dg/tree-ssa/foldconst-3.c: Likewise. >> * gcc.dg/tree-ssa/vrp15.c: Likewise. >> > > None of these have any volatile bitfields, so the option should be a no-op. The problem is that we have to treat normal bitfields differently as well, since a variable may later be declared as volatile. Bernd
Index: gcc/testsuite/gcc.dg/tree-ssa/20030922-1.c =================================================================== --- gcc/testsuite/gcc.dg/tree-ssa/20030922-1.c (revision 355696) +++ gcc/testsuite/gcc.dg/tree-ssa/20030922-1.c (working copy) @@ -1,5 +1,5 @@ /* { dg-do compile } */ -/* { dg-options "-O1 -fdump-tree-dom2" } */ +/* { dg-options "-O1 -fno-strict-volatile-bitfields -fdump-tree-dom2" } */ extern void abort (void); Index: gcc/testsuite/gcc.dg/tree-ssa/foldconst-3.c =================================================================== --- gcc/testsuite/gcc.dg/tree-ssa/foldconst-3.c (revision 355696) +++ gcc/testsuite/gcc.dg/tree-ssa/foldconst-3.c (working copy) @@ -1,5 +1,5 @@ /* { dg-do compile } */ -/* { dg-options "-O2 -fdump-tree-optimized -fno-short-enums" } */ +/* { dg-options "-O2 -fno-strict-volatile-bitfields -fdump-tree-optimized -fno-short-enums" } */ typedef const union tree_node *const_tree; typedef struct { Index: gcc/testsuite/gcc.dg/tree-ssa/vrp15.c =================================================================== --- gcc/testsuite/gcc.dg/tree-ssa/vrp15.c (revision 355696) +++ gcc/testsuite/gcc.dg/tree-ssa/vrp15.c (working copy) @@ -1,5 +1,5 @@ /* { dg-do compile } */ -/* { dg-options "-O2 -fdump-tree-vrp1" } */ +/* { dg-options "-O2 -fno-strict-volatile-bitfields -fdump-tree-vrp1" } */ extern void abort (void) __attribute__ ((__noreturn__));