On Tue, Sep 10, 2013 at 12:38 PM, Jakub Jelinek <ja...@redhat.com> wrote:
> Hi!
>
> If two instructions are rtl_equal_p, and cross-jumping decides to cross-jump
> them together, merge_memattrs takes care of clearing various MEM_ATTRS
> or setting alignment to minimum, size to maximum etc.
> But, it didn't handle flags on the MEMs.
>
> The following patch fixes that. MEM_KEEP_ALIAS_SET_P from quick skimming
> seems to be used only during expansion and thus can be ignored IMHO.
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk/4.8?
Ok.
Thanks,
Richard.
> BTW, I wonder about REG_ATTRS and REG_POINTER, REG_USERVAR_P,
> REG_FUNCTION_VALUE_P, is it fine to keep them as is
Definitely REG_EXPR is used to check for signedness of a register, but I suppose
that is cleared. I don't see how REG_POINTER can be merged at all, not sure
of the others - they don't seem to have a "conservative correct" value either.
> (as in, can rtx_equal_p
> for REG only compares REGNO and mode, nothing else, not sure if we could
> end up with differences in any of those during cross-jumping and whether
> it could affect code generation).
If REGNO is the same then all of the attributes are, too, no?
Richard.
> 2013-09-10 Jakub Jelinek <ja...@redhat.com>
>
> PR rtl-optimization/58365
> * cfgcleanup.c (merge_memattrs): Also clear MEM_READONLY_P
> resp. MEM_NOTRAP_P if they differ, or set MEM_VOLATILE_P if
> it differs.
>
> * gcc.c-torture/execute/pr58365.c: New test.
>
> --- gcc/cfgcleanup.c.jj 2013-09-09 11:32:42.000000000 +0200
> +++ gcc/cfgcleanup.c 2013-09-10 09:13:43.783165931 +0200
> @@ -925,6 +925,24 @@ merge_memattrs (rtx x, rtx y)
> set_mem_align (y, MEM_ALIGN (x));
> }
> }
> + if (code == MEM)
> + {
> + if (MEM_READONLY_P (x) != MEM_READONLY_P (y))
> + {
> + MEM_READONLY_P (x) = 0;
> + MEM_READONLY_P (y) = 0;
> + }
> + if (MEM_NOTRAP_P (x) != MEM_NOTRAP_P (y))
> + {
> + MEM_NOTRAP_P (x) = 0;
> + MEM_NOTRAP_P (y) = 0;
> + }
> + if (MEM_VOLATILE_P (x) != MEM_VOLATILE_P (y))
> + {
> + MEM_VOLATILE_P (x) = 1;
> + MEM_VOLATILE_P (y) = 1;
> + }
> + }
>
> fmt = GET_RTX_FORMAT (code);
> for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
> --- gcc/testsuite/gcc.c-torture/execute/pr58365.c.jj 2013-09-10
> 09:20:01.761164460 +0200
> +++ gcc/testsuite/gcc.c-torture/execute/pr58365.c 2013-09-10
> 09:19:18.000000000 +0200
> @@ -0,0 +1,35 @@
> +/* PR rtl-optimization/58365 */
> +
> +extern void abort (void);
> +
> +struct S
> +{
> + volatile int a;
> + int b, c, d, e;
> +} f;
> +static struct S g, h;
> +int i = 1;
> +
> +char
> +foo (void)
> +{
> + return i;
> +}
> +
> +static struct S
> +bar (void)
> +{
> + if (foo ())
> + return f;
> + return g;
> +}
> +
> +int
> +main ()
> +{
> + h = bar ();
> + f.b = 1;
> + if (h.b != 0)
> + abort ();
> + return 0;
> +}
>
> Jakub
