On Wed, Sep 05, 2012 at 02:10:03PM -0700, Andrew Pinski wrote:
> The problem here is the strlen optimization tries to remove a null
> character store as we already have done it but it does it for a
> volatile store which is not a valid thing to do.
> This patch fixes the problem by ignoring statements which have
> volatile operands.
That should be caught by the !TREE_SIDE_EFFECTS (lhs) check a few lines
later. Isn't the bug instead that remap_gimple_op_r copies over
TREE_THIS_VOLATILE flag, but doesn't copy over TREE_SIDE_EFFECTS?
> * tree-ssa-strlen.c (strlen_optimize_stmt): Don't look at statements
> which have volatile operands.
>
> testsuite/ChangeLog:
> * gcc.dg/tree-ssa/strlen-1.c: New testcase.
> Index: gcc/tree-ssa-strlen.c
> ===================================================================
> --- gcc/tree-ssa-strlen.c (revision 190993)
> +++ gcc/tree-ssa-strlen.c (working copy)
> @@ -1782,7 +1782,8 @@ strlen_optimize_stmt (gimple_stmt_iterat
> break;
> }
> }
> - else if (is_gimple_assign (stmt))
> + else if (is_gimple_assign (stmt)
> + && !gimple_has_volatile_ops (stmt))
> {
> tree lhs = gimple_assign_lhs (stmt);
>
> Index: gcc/testsuite/gcc.dg/tree-ssa/strlen-1.c
> ===================================================================
> --- gcc/testsuite/gcc.dg/tree-ssa/strlen-1.c (revision 0)
> +++ gcc/testsuite/gcc.dg/tree-ssa/strlen-1.c (revision 0)
> @@ -0,0 +1,17 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-optimized" } */
> +extern const unsigned long base;
> +static inline void wreg(unsigned char val, unsigned long addr)
> __attribute__((always_inline));
> +static inline void wreg(unsigned char val, unsigned long addr)
> +{
> + *((volatile unsigned char *) (__SIZE_TYPE__) (base + addr)) = val;
> +}
> +void wreg_twice(void)
> +{
> + wreg(0, 42);
> + wreg(0, 42);
> +}
> +
> +/* We should not remove the second null character store to (base+42)
> address. */
> +/* { dg-final { scan-tree-dump-times " ={v} 0;" 2 "optimized" } } */
> +/* { dg-final { cleanup-tree-dump "optimized" } } */
Jakub
