Patchwork IVOPT improvement patch

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Submitter H.J. Lu
Date July 30, 2010, 3:45 p.m.
Message ID <AANLkTikX01vs8_taOwuEnULBkXaRhr1rQHQR4KUMXuM7@mail.gmail.com>
Download mbox | patch
Permalink /patch/60364/
State New
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Comments

H.J. Lu - July 30, 2010, 3:45 p.m.
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.
Xinliang David Li - July 30, 2010, 4:49 p.m.
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.
>
Xinliang David Li - July 30, 2010, 4:49 p.m.
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.
>
Xinliang David Li - July 30, 2010, 4:58 p.m.
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.

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. Lu - July 30, 2010, 5:27 p.m.
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.
>>>
>>
>
Xinliang David Li - July 30, 2010, 5:54 p.m.
Why is start offset not 1 to begin with? Let's assume it is correct,
there are a couple of problems in this patch:

1) when the precision of the HOST_WIDE_INT is the same as the bitsize
of the address_mode, max_offset = (HOST_WIDE_INT) 1 << width will
produce a negative number
2) last_off should be initialized to 0 to match the original behavior
3) The i&& guard will make sure the loop terminates, but the offset
compuation will be wrong -- i<<1 will first overflows to a negative
number, then gets truncated to zero,  that means when this happens,
the last_off will be negative when the loop terminates.

David

On Fri, Jul 30, 2010 at 10:27 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
> 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.
>

Patch

diff --git a/gcc/tree-ssa-loop-ivopts.c b/gcc/tree-ssa-loop-ivopts.c
index 1d65b4a..55aa10c 100644
--- a/gcc/tree-ssa-loop-ivopts.c
+++ b/gcc/tree-ssa-loop-ivopts.c
@@ -3243,7 +3243,7 @@  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;
+      int old_cse_not_expected, width;
       unsigned sym_p, var_p, off_p, rat_p, add_c;
       rtx seq, addr, base;
       rtx reg0, reg1;
@@ -3252,8 +3252,10 @@  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 - 2)
+          ? GET_MODE_BITSIZE (address_mode) : HOST_BITS_PER_WIDE_INT - 2;
       addr = gen_rtx_fmt_ee (PLUS, address_mode, reg1, NULL_RTX);
-      for (i = start; i <= 1 << 20; i <<= 1)
+      for (i = start; i && i <= (HOST_WIDE_INT) 1 << width; i <<= 1)
 	{
 	  XEXP (addr, 1) = gen_int_mode (i, address_mode);
 	  if (!memory_address_addr_space_p (mem_mode, addr, as))
@@ -3262,7 +3264,7 @@  get_address_cost (bool symbol_present, bool var_present,
       data->max_offset = i == start ? 0 : i >> 1;
       off = data->max_offset;
 
-      for (i = start; i <= 1 << 20; i <<= 1)
+      for (i = start; i && i <= (HOST_WIDE_INT) 1 << width; i <<= 1)
 	{
 	  XEXP (addr, 1) = gen_int_mode (-i, address_mode);
 	  if (!memory_address_addr_space_p (mem_mode, addr, as))
@@ -3273,12 +3275,12 @@  get_address_cost (bool symbol_present, bool var_present,
       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;