Re: [EXTERNAL] Re: [PATCH] [tree-optimization] Fix for PR97223
On 10/29/20 1:45 PM, Eugene Rozenfeld via Gcc-patches wrote:
> Thank you for the review Richard!
>
> I re-worked the patch based on your suggestions. I combined the two patterns.
> Neither one requires a signedness check as long as the type of the 'add' has
> overflow wrap semantics.
>
> I had to modify the regular expression in no-strict-overflow-4.c test. In
> that test the following function is compiled with -fno-strict-overflow :
>
> int
> foo (int i)
> {
> return i + 1 > i;
> }
>
> We now optimize this function so that the tree-optimized dump has
>
> ;; Function foo (foo, funcdef_no=0, decl_uid=1931, cgraph_uid=1,
> symbol_order=0)
>
> foo (int i)
> {
> _Bool _1;
> int _3;
>
>[local count: 1073741824]:
> _1 = i_2(D) != 2147483647;
> _3 = (int) _1;
> return _3;
> }
>
> This is a correct optimization since -fno-strict-overflow implies -fwrapv.
>
> Eugene
>
> -Original Message-
> From: Richard Biener
> Sent: Tuesday, October 27, 2020 2:23 AM
> To: Eugene Rozenfeld
> Cc: gcc-patches@gcc.gnu.org
> Subject: [EXTERNAL] Re: [PATCH] [tree-optimization] Fix for PR97223
>
> On Sat, Oct 24, 2020 at 2:20 AM Eugene Rozenfeld via Gcc-patches
> wrote:
>> This patch adds a pattern for folding
>> x < (short) ((unsigned short)x + const) to
>> x <= SHORT_MAX - const
>> (and similarly for other integral types) if const is not 0.
>> as described in PR97223.
>>
>> For example, without this patch the x86_64-pc-linux code generated for
>> this function
>>
>> bool f(char x)
>> {
>> return x < (char)(x + 12);
>> }
>>
>> is
>>
>> leaeax,[rdi+0xc]
>> cmpal,dil
>> setg al
>> ret
>>
>> With the patch the code is
>>
>> cmpdil,0x73
>> setle al
>> ret
>>
>> Tested on x86_64-pc-linux.
> +/* Similar to the previous pattern but with additional casts. */ (for
> +cmp (lt le ge gt)
> + out (gt gt le le)
> + (simplify
> + (cmp:c (convert@3 (plus@2 (convert@4 @0) INTEGER_CST@1)) @0)
> + (if (!TYPE_UNSIGNED (TREE_TYPE (@0))
> + && types_match (TREE_TYPE (@0), TREE_TYPE (@3))
> + && types_match (TREE_TYPE (@4), unsigned_type_for (TREE_TYPE (@0)))
> + && TYPE_OVERFLOW_WRAPS (TREE_TYPE (@4))
> + && wi::to_wide (@1) != 0
> + && single_use (@2))
> + (with { unsigned int prec = TYPE_PRECISION (TREE_TYPE (@0)); }
> +(out @0 { wide_int_to_tree (TREE_TYPE (@0),
> + wi::max_value (prec, SIGNED)
> + - wi::to_wide (@1)); })
>
> I think it's reasonable but the comment can be made more precise.
> In particular I wonder why we require a signed comparison here while the
> previous pattern requires an unsigned comparison. It might be an artifact
> and the restriction instead only applies to the plus?
>
> Note that
>
> + && types_match (TREE_TYPE (@4), unsigned_type_for (TREE_TYPE
> + (@0)))
>
> unsigned_type_for should be avoided since it's quite expensive. May I suggest
>
> && TYPE_UNSIGNED (TREE_TYPE (@4))
> && tree_nop_conversion_p (TREE_TYPE (@4), TREE_TYPE (@0))
>
> instead?
>
> I originally wondered if "but with additional casts" could be done in a
> single pattern via (convert? ...) uses but then I noticed the strange
> difference in the comparison signedness requirement ...
>
> Richard.
>
>> Eugene
>>
>>
>> 0001-Add-a-tree-optimization-described-in-PR97223.patch
>>
>> From 973942122522bbf2e9de54cff17de59de5955547 Mon Sep 17 00:00:00 2001
>> From: Eugene Rozenfeld
>> Date: Fri, 23 Oct 2020 16:47:01 -0700
>> Subject: [PATCH] Add a tree optimization described in PR97223.
>> MIME-Version: 1.0
>> Content-Type: text/plain; charset=UTF-8
>> Content-Transfer-Encoding: 8bit
>>
>> Convert
>> x < (short) ((unsigned short)x + const)
>> to
>> x <= SHORT_MAX – const
>> (and similarly for other integral types) if const is not 0.
>>
>> For example, without this patch the x86_64-pc-linux code generated for this
>> function
>>
>> bool f(char x)
>> {
>> return x < (char)(x + 12);
>> }
>>
>> is
>>
>> leaeax,[rdi+0xc]
>> cmpal,dil
>> setg al
>> ret
>>
>> With the patch the code is
>>
>> cmpdil,0x73
>> setle al
>> ret
>> ---
>> gcc/match.pd| 16 ++--
>> gcc/testsuite/gcc.dg/no-strict-overflow-4.c | 5 +++--
>> 2 files changed, 13 insertions(+), 8 deletions(-)
Committed to the trunk. Thanks.
jeff
Re: [EXTERNAL] Re: [PATCH] [tree-optimization] Fix for PR97223
On Thu, Oct 29, 2020 at 8:45 PM Eugene Rozenfeld
wrote:
>
> Thank you for the review Richard!
>
> I re-worked the patch based on your suggestions. I combined the two patterns.
> Neither one requires a signedness check as long as the type of the 'add' has
> overflow wrap semantics.
>
> I had to modify the regular expression in no-strict-overflow-4.c test. In
> that test the following function is compiled with -fno-strict-overflow :
>
> int
> foo (int i)
> {
> return i + 1 > i;
> }
>
> We now optimize this function so that the tree-optimized dump has
>
> ;; Function foo (foo, funcdef_no=0, decl_uid=1931, cgraph_uid=1,
> symbol_order=0)
>
> foo (int i)
> {
> _Bool _1;
> int _3;
>
>[local count: 1073741824]:
> _1 = i_2(D) != 2147483647;
> _3 = (int) _1;
> return _3;
> }
>
> This is a correct optimization since -fno-strict-overflow implies -fwrapv.
OK.
Thanks,
Richard.
> Eugene
>
> -Original Message-
> From: Richard Biener
> Sent: Tuesday, October 27, 2020 2:23 AM
> To: Eugene Rozenfeld
> Cc: gcc-patches@gcc.gnu.org
> Subject: [EXTERNAL] Re: [PATCH] [tree-optimization] Fix for PR97223
>
> On Sat, Oct 24, 2020 at 2:20 AM Eugene Rozenfeld via Gcc-patches
> wrote:
> >
> > This patch adds a pattern for folding
> > x < (short) ((unsigned short)x + const) to
> > x <= SHORT_MAX - const
> > (and similarly for other integral types) if const is not 0.
> > as described in PR97223.
> >
> > For example, without this patch the x86_64-pc-linux code generated for
> > this function
> >
> > bool f(char x)
> > {
> > return x < (char)(x + 12);
> > }
> >
> > is
> >
> > leaeax,[rdi+0xc]
> > cmpal,dil
> > setg al
> > ret
> >
> > With the patch the code is
> >
> > cmpdil,0x73
> > setle al
> > ret
> >
> > Tested on x86_64-pc-linux.
>
> +/* Similar to the previous pattern but with additional casts. */ (for
> +cmp (lt le ge gt)
> + out (gt gt le le)
> + (simplify
> + (cmp:c (convert@3 (plus@2 (convert@4 @0) INTEGER_CST@1)) @0)
> + (if (!TYPE_UNSIGNED (TREE_TYPE (@0))
> + && types_match (TREE_TYPE (@0), TREE_TYPE (@3))
> + && types_match (TREE_TYPE (@4), unsigned_type_for (TREE_TYPE (@0)))
> + && TYPE_OVERFLOW_WRAPS (TREE_TYPE (@4))
> + && wi::to_wide (@1) != 0
> + && single_use (@2))
> + (with { unsigned int prec = TYPE_PRECISION (TREE_TYPE (@0)); }
> +(out @0 { wide_int_to_tree (TREE_TYPE (@0),
> + wi::max_value (prec, SIGNED)
> + - wi::to_wide (@1)); })
>
> I think it's reasonable but the comment can be made more precise.
> In particular I wonder why we require a signed comparison here while the
> previous pattern requires an unsigned comparison. It might be an artifact
> and the restriction instead only applies to the plus?
>
> Note that
>
> + && types_match (TREE_TYPE (@4), unsigned_type_for (TREE_TYPE
> + (@0)))
>
> unsigned_type_for should be avoided since it's quite expensive. May I suggest
>
> && TYPE_UNSIGNED (TREE_TYPE (@4))
> && tree_nop_conversion_p (TREE_TYPE (@4), TREE_TYPE (@0))
>
> instead?
>
> I originally wondered if "but with additional casts" could be done in a
> single pattern via (convert? ...) uses but then I noticed the strange
> difference in the comparison signedness requirement ...
>
> Richard.
>
> > Eugene
> >
RE: [EXTERNAL] Re: [PATCH] [tree-optimization] Fix for PR97223
Thank you for the review Richard!
I re-worked the patch based on your suggestions. I combined the two patterns.
Neither one requires a signedness check as long as the type of the 'add' has
overflow wrap semantics.
I had to modify the regular expression in no-strict-overflow-4.c test. In that
test the following function is compiled with -fno-strict-overflow :
int
foo (int i)
{
return i + 1 > i;
}
We now optimize this function so that the tree-optimized dump has
;; Function foo (foo, funcdef_no=0, decl_uid=1931, cgraph_uid=1, symbol_order=0)
foo (int i)
{
_Bool _1;
int _3;
[local count: 1073741824]:
_1 = i_2(D) != 2147483647;
_3 = (int) _1;
return _3;
}
This is a correct optimization since -fno-strict-overflow implies -fwrapv.
Eugene
-Original Message-
From: Richard Biener
Sent: Tuesday, October 27, 2020 2:23 AM
To: Eugene Rozenfeld
Cc: gcc-patches@gcc.gnu.org
Subject: [EXTERNAL] Re: [PATCH] [tree-optimization] Fix for PR97223
On Sat, Oct 24, 2020 at 2:20 AM Eugene Rozenfeld via Gcc-patches
wrote:
>
> This patch adds a pattern for folding
> x < (short) ((unsigned short)x + const) to
> x <= SHORT_MAX - const
> (and similarly for other integral types) if const is not 0.
> as described in PR97223.
>
> For example, without this patch the x86_64-pc-linux code generated for
> this function
>
> bool f(char x)
> {
> return x < (char)(x + 12);
> }
>
> is
>
> leaeax,[rdi+0xc]
> cmpal,dil
> setg al
> ret
>
> With the patch the code is
>
> cmpdil,0x73
> setle al
> ret
>
> Tested on x86_64-pc-linux.
+/* Similar to the previous pattern but with additional casts. */ (for
+cmp (lt le ge gt)
+ out (gt gt le le)
+ (simplify
+ (cmp:c (convert@3 (plus@2 (convert@4 @0) INTEGER_CST@1)) @0)
+ (if (!TYPE_UNSIGNED (TREE_TYPE (@0))
+ && types_match (TREE_TYPE (@0), TREE_TYPE (@3))
+ && types_match (TREE_TYPE (@4), unsigned_type_for (TREE_TYPE (@0)))
+ && TYPE_OVERFLOW_WRAPS (TREE_TYPE (@4))
+ && wi::to_wide (@1) != 0
+ && single_use (@2))
+ (with { unsigned int prec = TYPE_PRECISION (TREE_TYPE (@0)); }
+(out @0 { wide_int_to_tree (TREE_TYPE (@0),
+ wi::max_value (prec, SIGNED)
+ - wi::to_wide (@1)); })
I think it's reasonable but the comment can be made more precise.
In particular I wonder why we require a signed comparison here while the
previous pattern requires an unsigned comparison. It might be an artifact and
the restriction instead only applies to the plus?
Note that
+ && types_match (TREE_TYPE (@4), unsigned_type_for (TREE_TYPE
+ (@0)))
unsigned_type_for should be avoided since it's quite expensive. May I suggest
&& TYPE_UNSIGNED (TREE_TYPE (@4))
&& tree_nop_conversion_p (TREE_TYPE (@4), TREE_TYPE (@0))
instead?
I originally wondered if "but with additional casts" could be done in a single
pattern via (convert? ...) uses but then I noticed the strange difference in
the comparison signedness requirement ...
Richard.
> Eugene
>
0001-Add-a-tree-optimization-described-in-PR97223.patch
Description: 0001-Add-a-tree-optimization-described-in-PR97223.patch
Re: [PATCH] [tree-optimization] Fix for PR97223
On Sat, Oct 24, 2020 at 2:20 AM Eugene Rozenfeld via Gcc-patches
wrote:
>
> This patch adds a pattern for folding
> x < (short) ((unsigned short)x + const)
> to
> x <= SHORT_MAX - const
> (and similarly for other integral types) if const is not 0.
> as described in PR97223.
>
> For example, without this patch the x86_64-pc-linux code generated for this
> function
>
> bool f(char x)
> {
> return x < (char)(x + 12);
> }
>
> is
>
> leaeax,[rdi+0xc]
> cmpal,dil
> setg al
> ret
>
> With the patch the code is
>
> cmpdil,0x73
> setle al
> ret
>
> Tested on x86_64-pc-linux.
+/* Similar to the previous pattern but with additional casts. */
+(for cmp (lt le ge gt)
+ out (gt gt le le)
+ (simplify
+ (cmp:c (convert@3 (plus@2 (convert@4 @0) INTEGER_CST@1)) @0)
+ (if (!TYPE_UNSIGNED (TREE_TYPE (@0))
+ && types_match (TREE_TYPE (@0), TREE_TYPE (@3))
+ && types_match (TREE_TYPE (@4), unsigned_type_for (TREE_TYPE (@0)))
+ && TYPE_OVERFLOW_WRAPS (TREE_TYPE (@4))
+ && wi::to_wide (@1) != 0
+ && single_use (@2))
+ (with { unsigned int prec = TYPE_PRECISION (TREE_TYPE (@0)); }
+(out @0 { wide_int_to_tree (TREE_TYPE (@0),
+ wi::max_value (prec, SIGNED)
+ - wi::to_wide (@1)); })
I think it's reasonable but the comment can be made more precise.
In particular I wonder why we require a signed comparison here
while the previous pattern requires an unsigned comparison. It might
be an artifact and the restriction instead only applies to the plus?
Note that
+ && types_match (TREE_TYPE (@4), unsigned_type_for (TREE_TYPE (@0)))
unsigned_type_for should be avoided since it's quite expensive. May
I suggest
&& TYPE_UNSIGNED (TREE_TYPE (@4))
&& tree_nop_conversion_p (TREE_TYPE (@4), TREE_TYPE (@0))
instead?
I originally wondered if "but with additional casts" could be done in a single
pattern via (convert? ...) uses but then I noticed the strange difference in
the comparison signedness requirement ...
Richard.
> Eugene
>
[PATCH] [tree-optimization] Fix for PR97223
This patch adds a pattern for folding
x < (short) ((unsigned short)x + const)
to
x <= SHORT_MAX - const
(and similarly for other integral types) if const is not 0.
as described in PR97223.
For example, without this patch the x86_64-pc-linux code generated for this
function
bool f(char x)
{
return x < (char)(x + 12);
}
is
leaeax,[rdi+0xc]
cmpal,dil
setg al
ret
With the patch the code is
cmpdil,0x73
setle al
ret
Tested on x86_64-pc-linux.
Eugene
0001-Add-a-tree-optimization-described-in-PR97223.patch
Description: 0001-Add-a-tree-optimization-described-in-PR97223.patch
