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Re: IVOPT improvement patch


On Fri, Jul 30, 2010 at 9:58 AM, Xinliang David Li <davidxl@google.com> wrote:
> There is a problem in this patch -- when i wraps to zero and terminate
> the loop, the maxoffset computed will be zero which is wrong.
>
> My previous patch won't have this problem.

Your patch changed the start offset.  Here is the updated patch.


H.J.
>
> David
>
> On Fri, Jul 30, 2010 at 9:49 AM, Xinliang David Li <davidxl@google.com> wrote:
>> This looks fine to me -- Zdenek or other reviewers --- is this one ok?
>>
>> Thanks,
>>
>> David
>>
>> On Fri, Jul 30, 2010 at 8:45 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>>> On Thu, Jul 29, 2010 at 6:04 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
>>>> It looks strange:
>>>>
>>>> + ? ? ?width = (GET_MODE_BITSIZE (address_mode) < ?HOST_BITS_PER_WIDE_INT - 1)
>>>> + ? ? ? ? ?? GET_MODE_BITSIZE (address_mode) : HOST_BITS_PER_WIDE_INT - 1;
>>>> ? ? ? addr = gen_rtx_fmt_ee (PLUS, address_mode, reg1, NULL_RTX);
>>>> - ? ? ?for (i = start; i <= 1 << 20; i <<= 1)
>>>> + ? ? ?for (i = 1; i < width; i++)
>>>> ? ? ? ?{
>>>> - ? ? ? ? XEXP (addr, 1) = gen_int_mode (i, address_mode);
>>>> + ? ? ? ? ?HOST_WIDE_INT offset = (1ll << i);
>>>> + ? ? ? ? XEXP (addr, 1) = gen_int_mode (offset, address_mode);
>>>> ? ? ? ? ?if (!memory_address_addr_space_p (mem_mode, addr, as))
>>>> ? ? ? ? ? ?break;
>>>> ? ? ? ?}
>>>>
>>>> HOST_WIDE_INT may be long or long long. "1ll" isn't always correct.
>>>> I think width can be >= 31. Depending on HOST_WIDE_INT,
>>>>
>>>> HOST_WIDE_INT offset = -(1ll << i);
>>>>
>>>> may have different values. The whole function looks odd to me.
>>>>
>>>>
>>>
>>> Here is a different approach to check address overflow.
>>>
>>>
>>> --
>>> H.J.
>>> --
>>> 2010-07-29 ?H.J. Lu ?<hongjiu.lu@intel.com>
>>>
>>> ? ? ? ?PR bootstrap/45119
>>> ? ? ? ?* tree-ssa-loop-ivopts.c (get_address_cost): Re-apply revision
>>> ? ? ? ?162652. ?Check address overflow.
>>>
>>
>



-- 
H.J.
2010-07-29  H.J. Lu  <hongjiu.lu@intel.com>

	PR bootstrap/45119
	* tree-ssa-loop-ivopts.c (get_address_cost): Re-apply revision
	162652.  Check address overflow.

diff --git a/gcc/tree-ssa-loop-ivopts.c b/gcc/tree-ssa-loop-ivopts.c
index 1d65b4a..e9016c3 100644
--- a/gcc/tree-ssa-loop-ivopts.c
+++ b/gcc/tree-ssa-loop-ivopts.c
@@ -3242,8 +3242,8 @@ get_address_cost (bool symbol_present, bool var_present,
     {
       HOST_WIDE_INT i;
       HOST_WIDE_INT start = BIGGEST_ALIGNMENT / BITS_PER_UNIT;
-      HOST_WIDE_INT rat, off;
-      int old_cse_not_expected;
+      HOST_WIDE_INT rat, off, max_off, last_off;
+      int old_cse_not_expected, width;
       unsigned sym_p, var_p, off_p, rat_p, add_c;
       rtx seq, addr, base;
       rtx reg0, reg1;
@@ -3252,33 +3252,40 @@ get_address_cost (bool symbol_present, bool var_present,
 
       reg1 = gen_raw_REG (address_mode, LAST_VIRTUAL_REGISTER + 1);
 
+      width = (GET_MODE_BITSIZE (address_mode) < HOST_BITS_PER_WIDE_INT - 1)
+          ? GET_MODE_BITSIZE (address_mode) : HOST_BITS_PER_WIDE_INT - 1;
+      max_off = (HOST_WIDE_INT) 1 << width;
       addr = gen_rtx_fmt_ee (PLUS, address_mode, reg1, NULL_RTX);
-      for (i = start; i <= 1 << 20; i <<= 1)
+      last_off = start;
+      for (i = start; i && i <= max_off; i <<= 1)
 	{
 	  XEXP (addr, 1) = gen_int_mode (i, address_mode);
 	  if (!memory_address_addr_space_p (mem_mode, addr, as))
 	    break;
+	  last_off = i;
 	}
-      data->max_offset = i == start ? 0 : i >> 1;
+      data->max_offset = last_off;
       off = data->max_offset;
 
-      for (i = start; i <= 1 << 20; i <<= 1)
+      last_off = -start;
+      for (i = start; i && i <= max_off; i <<= 1)
 	{
 	  XEXP (addr, 1) = gen_int_mode (-i, address_mode);
 	  if (!memory_address_addr_space_p (mem_mode, addr, as))
 	    break;
+	  last_off = -i;
 	}
-      data->min_offset = i == start ? 0 : -(i >> 1);
+      data->min_offset = last_off;
 
       if (dump_file && (dump_flags & TDF_DETAILS))
 	{
 	  fprintf (dump_file, "get_address_cost:\n");
-	  fprintf (dump_file, "  min offset %s %d\n",
+	  fprintf (dump_file, "  min offset %s " HOST_WIDE_INT_PRINT_DEC "\n",
 		   GET_MODE_NAME (mem_mode),
-		   (int) data->min_offset);
-	  fprintf (dump_file, "  max offset %s %d\n",
+		   data->min_offset);
+	  fprintf (dump_file, "  max offset %s " HOST_WIDE_INT_PRINT_DEC "\n",
 		   GET_MODE_NAME (mem_mode),
-		   (int) data->max_offset);
+		   data->max_offset);
 	}
 
       rat = 1;

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