* [Bug inline-asm/37562] [4.2] -funroll-loops destroys inline asm code von powerpc
2008-09-17 15:43 [Bug inline-asm/37562] New: [4.2] -funroll-loops destroys inline asm code von powerpc rbuergel at web dot de
@ 2008-09-17 15:45 ` rbuergel at web dot de
2008-09-17 16:52 ` [Bug inline-asm/37562] New: " Andrew Thomas Pinski
` (5 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: rbuergel at web dot de @ 2008-09-17 15:45 UTC (permalink / raw)
To: gcc-bugs
------- Comment #1 from rbuergel at web dot de 2008-09-17 15:44 -------
oops, i forgot to mention my command line to compile it:
powerpc-linux-g++ -O3 -funroll-loops -c -o GetBytes2.o GetBytes2.cpp
using -O3 is important for reproducing this error
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37562
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [Bug inline-asm/37562] New: [4.2] -funroll-loops destroys inline asm code von powerpc
2008-09-17 15:43 [Bug inline-asm/37562] New: [4.2] -funroll-loops destroys inline asm code von powerpc rbuergel at web dot de
2008-09-17 15:45 ` [Bug inline-asm/37562] " rbuergel at web dot de
@ 2008-09-17 16:52 ` Andrew Thomas Pinski
2008-09-17 16:53 ` [Bug inline-asm/37562] [4.2] -funroll-loops destroys inline asm code for powerpc pinskia at gmail dot com
` (4 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: Andrew Thomas Pinski @ 2008-09-17 16:52 UTC (permalink / raw)
To: gcc-bugzilla; +Cc: gcc-bugs
Sent from my iPhone
On Sep 17, 2008, at 8:42 AM, "rbuergel at web dot de" <gcc-bugzilla@gcc.gnu.org
> wrote:
> typedef unsigned int UInt32;
> typedef unsigned char UInt8;
>
> struct Data
> {
> UInt8 data[16];
>
> const UInt8* getData() const
> {
> return data + 4;
> }
> };
>
> struct Value {
> UInt32 value;
> static void update (Value& signal, const Data& source, UInt32
> startBit);
> };
>
> void Value::update(Value& signal, const Data& source, UInt32
> startByte)
> {
> UInt32& value = signal.value;
> const UInt8* data = source.getData();
> asm( "lwbrx %0,%1,%2;\n":"=r"(value): "r"(data), "r"(startByte),
> "m" (*(data
> + startByte)) );
> }
The second constraint should be using "b" instead of "r" as b says
don't use r0.
>
>
> generated for gcc-4.2.4 on powerpc:
> 00000000 <_ZN5Value6updateERS_RK4Dataj>:
> 0: 38 04 00 04 addi r0,r4,4
> 4: 7c 80 2c 2c lwbrx r4,0,r5
> 8: 90 83 00 00 stw r4,0(r3)
> c: 4e 80 00 20 blr
>
> the correct version without -funroll-loops reads:
> 00000000 <_ZN5Value6updateERS_RK4Dataj>:
> 0: 38 84 00 04 addi r4,r4,4
> 4: 7c 84 2c 2c lwbrx r4,r4,r5
> 8: 90 83 00 00 stw r4,0(r3)
> c: 4e 80 00 20 blr
>
>
> lwbrx sums the contents of r4 and r5 and accesses this address,
> swaps it's
> value and stores it again in r4. The incorrect version accesses an
> invalid
> address, which leads to a segmentation fault.
>
> this is corrected at least with gcc-4.3.1, there i couldn't
> reproduce the
> behaviour.
>
>
> --
> Summary: [4.2] -funroll-loops destroys inline asm code von
> powerpc
> Product: gcc
> Version: 4.2.4
> Status: UNCONFIRMED
> Severity: normal
> Priority: P3
> Component: inline-asm
> AssignedTo: unassigned at gcc dot gnu dot org
> ReportedBy: rbuergel at web dot de
>
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37562
>
^ permalink raw reply [flat|nested] 8+ messages in thread* [Bug inline-asm/37562] [4.2] -funroll-loops destroys inline asm code for powerpc
2008-09-17 15:43 [Bug inline-asm/37562] New: [4.2] -funroll-loops destroys inline asm code von powerpc rbuergel at web dot de
2008-09-17 15:45 ` [Bug inline-asm/37562] " rbuergel at web dot de
2008-09-17 16:52 ` [Bug inline-asm/37562] New: " Andrew Thomas Pinski
@ 2008-09-17 16:53 ` pinskia at gmail dot com
2008-09-17 18:47 ` rbuergel at web dot de
` (3 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: pinskia at gmail dot com @ 2008-09-17 16:53 UTC (permalink / raw)
To: gcc-bugs
------- Comment #2 from pinskia at gmail dot com 2008-09-17 16:52 -------
Subject: Re: New: [4.2] -funroll-loops destroys inline asm code von powerpc
Sent from my iPhone
On Sep 17, 2008, at 8:42 AM, "rbuergel at web dot de" <gcc-bugzilla@gcc.gnu.org
> wrote:
> typedef unsigned int UInt32;
> typedef unsigned char UInt8;
>
> struct Data
> {
> UInt8 data[16];
>
> const UInt8* getData() const
> {
> return data + 4;
> }
> };
>
> struct Value {
> UInt32 value;
> static void update (Value& signal, const Data& source, UInt32
> startBit);
> };
>
> void Value::update(Value& signal, const Data& source, UInt32
> startByte)
> {
> UInt32& value = signal.value;
> const UInt8* data = source.getData();
> asm( "lwbrx %0,%1,%2;\n":"=r"(value): "r"(data), "r"(startByte),
> "m" (*(data
> + startByte)) );
> }
The second constraint should be using "b" instead of "r" as b says
don't use r0.
>
>
> generated for gcc-4.2.4 on powerpc:
> 00000000 <_ZN5Value6updateERS_RK4Dataj>:
> 0: 38 04 00 04 addi r0,r4,4
> 4: 7c 80 2c 2c lwbrx r4,0,r5
> 8: 90 83 00 00 stw r4,0(r3)
> c: 4e 80 00 20 blr
>
> the correct version without -funroll-loops reads:
> 00000000 <_ZN5Value6updateERS_RK4Dataj>:
> 0: 38 84 00 04 addi r4,r4,4
> 4: 7c 84 2c 2c lwbrx r4,r4,r5
> 8: 90 83 00 00 stw r4,0(r3)
> c: 4e 80 00 20 blr
>
>
> lwbrx sums the contents of r4 and r5 and accesses this address,
> swaps it's
> value and stores it again in r4. The incorrect version accesses an
> invalid
> address, which leads to a segmentation fault.
>
> this is corrected at least with gcc-4.3.1, there i couldn't
> reproduce the
> behaviour.
>
>
> --
> Summary: [4.2] -funroll-loops destroys inline asm code von
> powerpc
> Product: gcc
> Version: 4.2.4
> Status: UNCONFIRMED
> Severity: normal
> Priority: P3
> Component: inline-asm
> AssignedTo: unassigned at gcc dot gnu dot org
> ReportedBy: rbuergel at web dot de
>
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37562
>
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37562
^ permalink raw reply [flat|nested] 8+ messages in thread* [Bug inline-asm/37562] [4.2] -funroll-loops destroys inline asm code for powerpc
2008-09-17 15:43 [Bug inline-asm/37562] New: [4.2] -funroll-loops destroys inline asm code von powerpc rbuergel at web dot de
` (2 preceding siblings ...)
2008-09-17 16:53 ` [Bug inline-asm/37562] [4.2] -funroll-loops destroys inline asm code for powerpc pinskia at gmail dot com
@ 2008-09-17 18:47 ` rbuergel at web dot de
2008-09-17 18:51 ` pinskia at gcc dot gnu dot org
` (2 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: rbuergel at web dot de @ 2008-09-17 18:47 UTC (permalink / raw)
To: gcc-bugs
------- Comment #3 from rbuergel at web dot de 2008-09-17 18:46 -------
> The second constraint should be using "b" instead of "r" as b says
> don't use r0.
Is this documented anywhere? The gcc manual says "r" means "any general purpose
register" and "b" means "Address base register". Any Documentation (for example
http://developer.apple.com/documentation/DeveloperTools/Reference/Assembler/PPCInstructions/chapter_6_section_2.html
) i've found, lists r0-r31 as general purpose registers.
Anyway, ignoring this point, you seem to be right. I remember 4.3.1 using r6
instead of r0, probably that's why it works. Unfortunately, i can't check your
suggestion until monday, when i'm back at work.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37562
^ permalink raw reply [flat|nested] 8+ messages in thread* [Bug inline-asm/37562] [4.2] -funroll-loops destroys inline asm code for powerpc
2008-09-17 15:43 [Bug inline-asm/37562] New: [4.2] -funroll-loops destroys inline asm code von powerpc rbuergel at web dot de
` (3 preceding siblings ...)
2008-09-17 18:47 ` rbuergel at web dot de
@ 2008-09-17 18:51 ` pinskia at gcc dot gnu dot org
2008-09-17 18:58 ` rbuergel at web dot de
2008-09-17 19:08 ` pinskia at gcc dot gnu dot org
6 siblings, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2008-09-17 18:51 UTC (permalink / raw)
To: gcc-bugs
------- Comment #4 from pinskia at gcc dot gnu dot org 2008-09-17 18:50 -------
From:
http://gcc.gnu.org/onlinedocs/gcc-4.3.2/gcc/Machine-Constraints.html#Machine-Constraints
b
Address base register
Address base register is the standard saying rN or 0 (if r0 is used). This is
just the way PPC asm works.
--
pinskia at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution| |INVALID
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37562
^ permalink raw reply [flat|nested] 8+ messages in thread* [Bug inline-asm/37562] [4.2] -funroll-loops destroys inline asm code for powerpc
2008-09-17 15:43 [Bug inline-asm/37562] New: [4.2] -funroll-loops destroys inline asm code von powerpc rbuergel at web dot de
` (4 preceding siblings ...)
2008-09-17 18:51 ` pinskia at gcc dot gnu dot org
@ 2008-09-17 18:58 ` rbuergel at web dot de
2008-09-17 19:08 ` pinskia at gcc dot gnu dot org
6 siblings, 0 replies; 8+ messages in thread
From: rbuergel at web dot de @ 2008-09-17 18:58 UTC (permalink / raw)
To: gcc-bugs
------- Comment #5 from rbuergel at web dot de 2008-09-17 18:57 -------
Too bad for newbies to ppc asm. :)
But thank you for your explanations
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37562
^ permalink raw reply [flat|nested] 8+ messages in thread* [Bug inline-asm/37562] [4.2] -funroll-loops destroys inline asm code for powerpc
2008-09-17 15:43 [Bug inline-asm/37562] New: [4.2] -funroll-loops destroys inline asm code von powerpc rbuergel at web dot de
` (5 preceding siblings ...)
2008-09-17 18:58 ` rbuergel at web dot de
@ 2008-09-17 19:08 ` pinskia at gcc dot gnu dot org
6 siblings, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2008-09-17 19:08 UTC (permalink / raw)
To: gcc-bugs
------- Comment #6 from pinskia at gcc dot gnu dot org 2008-09-17 19:06 -------
You can also use __builtin_bswap32 in GCC 4.3 and above which gives you the
best code generation as it understands loading from memory and if the value is
in a register already.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37562
^ permalink raw reply [flat|nested] 8+ messages in thread