On Tue, Nov 1, 2016 at 11:29 PM, Aaron Sawdey
<acsaw...@linux.vnet.ibm.com> wrote:
> This patch adds code to expand_builtin_strncmp so it also attempts
> expansion via cmpstrnsi in the case where c_strlen() returns NULL for
> both string arguments, meaning that neither one is a constant.
@@ -3929,61 +3929,85 @@
unsigned int arg1_align = get_pointer_alignment (arg1) / BITS_PER_UNIT;
unsigned int arg2_align = get_pointer_alignment (arg2) / BITS_PER_UNIT;
+ /* If we don't have POINTER_TYPE, call the function. */
+ if (arg1_align == 0 || arg2_align == 0)
+ return NULL_RTX;
+
hm? we cann validate_arglist at the beginning...
+ if (!len1 && !len2)
+ {
+ /* If neither arg1 nor arg2 are constant strings. */
+ /* Stabilize the arguments in case gen_cmpstrnsi fails. */
+ arg1 = builtin_save_expr (arg1);
+ arg2 = builtin_save_expr (arg2);
we no longer need the stabilization dance since we expand from GIMPLE.
+ /* Use save_expr here because cmpstrnsi may modify arg3
+ and builtin_save_expr() doesn't force the save to happen. */
+ len = save_expr (arg3);
+ len = fold_convert_loc (loc, sizetype, len);
cmpstrnsi may certainly not modify trees in-place. If it does it
needs to be fixed.
+ /* If both arguments have side effects, we cannot optimize. */
+ if (TREE_SIDE_EFFECTS (len))
+ return NULL_RTX;
this can't happen anymore
btw, due to the re-indention a context diff would be _much_ easier to review.
So the real "meat" of your change is
/* If both arguments have side effects, we cannot optimize. */
- if (!len || TREE_SIDE_EFFECTS (len))
+ if (TREE_SIDE_EFFECTS (len))
return NULL_RTX;
and falling back to arg3 as len if !len1 && !len2.
Plus
+ /* Set MEM_SIZE as appropriate. This will only happen in
+ the case where incoming arg3 is constant and arg1/arg2 are not. */
+ if (CONST_INT_P (arg3_rtx))
+ {
+ set_mem_size (arg1_rtx, INTVAL (arg3_rtx));
+ set_mem_size (arg2_rtx, INTVAL (arg3_rtx));
+ }
where I don't really see why you need it or how it is even correct (arg1 might
terminate with a '\0' before arg3).
It would be nice to simplify the patch to simply do
if (!len1 && !len2)
len = arg3;
else if (!len1)
...
Richard.
> --
> Aaron Sawdey, Ph.D. acsaw...@linux.vnet.ibm.com
> 050-2/C113 (507) 253-7520 home: 507/263-0782
> IBM Linux Technology Center - PPC Toolchain
