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* [Bug tree-optimization/47673] New: Redundant NULL check
@ 2011-02-10 0:06 ian at airs dot com
2011-02-10 0:09 ` [Bug middle-end/47673] " pinskia at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: ian at airs dot com @ 2011-02-10 0:06 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47673
Summary: Redundant NULL check
Product: gcc
Version: 4.6.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: normal
Priority: P3
Component: tree-optimization
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: ian@airs.com
Consider this C code:
struct s1 { int x; };
struct s2 { struct s1 *p1; };
extern void f1(struct s1 *);
static inline void inline_func(struct s1 *p1) { if (p1) f1 (p1); }
void global_function(struct s2 *p2) {
if (p2->p1 != 0 && p2->p1 != (struct s1 *) -1)
inline_func(p2->p1);
}
When I compile this with -O2 with current mainline on x86_64, I get this:
movq (%rdi), %rdi
leaq -1(%rdi), %rax
cmpq $-3, %rax
ja .L1
testq %rdi, %rdi
je .L1
jmp f1
If %rdi is 0, %rax will be -1, and the ja branch will be taken. Therefore, the
je following the testq %rdi,%rdi will never be taken. The test and branch
should be eliminated.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug middle-end/47673] Redundant NULL check
2011-02-10 0:06 [Bug tree-optimization/47673] New: Redundant NULL check ian at airs dot com
@ 2011-02-10 0:09 ` pinskia at gcc dot gnu.org
2011-02-10 2:14 ` rguenth at gcc dot gnu.org
2021-07-26 9:49 ` pinskia at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu.org @ 2011-02-10 0:09 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47673
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2011.02.10 00:06:01
Component|tree-optimization |middle-end
Ever Confirmed|0 |1
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> 2011-02-10 00:06:01 UTC ---
if (p2->p1 + -1 <= -3B)
We should disable the optimization which converts
p2->p1 != 0 && p2->p1 != (struct s1 *) -1 into p2->p1 + -1 <= -3B for pointer
types.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug middle-end/47673] Redundant NULL check
2011-02-10 0:06 [Bug tree-optimization/47673] New: Redundant NULL check ian at airs dot com
2011-02-10 0:09 ` [Bug middle-end/47673] " pinskia at gcc dot gnu.org
@ 2011-02-10 2:14 ` rguenth at gcc dot gnu.org
2021-07-26 9:49 ` pinskia at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: rguenth at gcc dot gnu.org @ 2011-02-10 2:14 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47673
--- Comment #2 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-02-10 00:22:05 UTC ---
(In reply to comment #1)
> if (p2->p1 + -1 <= -3B)
>
> We should disable the optimization which converts
> p2->p1 != 0 && p2->p1 != (struct s1 *) -1 into p2->p1 + -1 <= -3B for pointer
> types.
No, VRP should simply work on pointers more properly.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug middle-end/47673] Redundant NULL check
2011-02-10 0:06 [Bug tree-optimization/47673] New: Redundant NULL check ian at airs dot com
2011-02-10 0:09 ` [Bug middle-end/47673] " pinskia at gcc dot gnu.org
2011-02-10 2:14 ` rguenth at gcc dot gnu.org
@ 2021-07-26 9:49 ` pinskia at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-07-26 9:49 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=47673
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|--- |11.0
Status|NEW |RESOLVED
Resolution|--- |FIXED
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Fixed in GCC 11.
I suspect r11-3685 but I am not 100%. It is definitely related to ranger
improvements to VRP.
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2021-07-26 9:49 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2011-02-10 0:06 [Bug tree-optimization/47673] New: Redundant NULL check ian at airs dot com
2011-02-10 0:09 ` [Bug middle-end/47673] " pinskia at gcc dot gnu.org
2011-02-10 2:14 ` rguenth at gcc dot gnu.org
2021-07-26 9:49 ` pinskia at gcc dot gnu.org
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