[Bug c++/29106] New: sizeof(*var) in expression drops entire line of code out of compile

2006-09-16 Thread deb at pixar dot com 
#include 

int main()
{
int* const savepos = sizeof(*savepos) ? 0 : 0;

// code for the next line is left out!
printf("size of thingy is %d\n", sizeof(*savepos));
}

Any line of code containing sizeof(*savepos) gets stripped.   If you compile
and run this, nothing is printed.


-- 
   Summary: sizeof(*var) in expression drops entire line of code out
of compile
   Product: gcc
   Version: 4.0.3
Status: UNCONFIRMED
  Severity: normal
  Priority: P3
 Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: deb at pixar dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29106

[Bug c++/29106] sizeof(*var) in expression drops entire line of code out of compile

2006-09-16 Thread deb at pixar dot com 


--- Comment #1 from deb at pixar dot com  2006-09-16 14:18 ---
/*
Using built-in specs.
Target: x86_64-redhat-linux-gnu
Configured with: ../gcc-4.0.3/configure x86_64-redhat-linux-gnu
--prefix=/pixar/d2/sets/t\
ools-03 --exec-prefix=/pixar/d2/sets/tools-03
--bindir=/pixar/d2/sets/tools-03/bin --sbin\
dir=/pixar/d2/sets/tools-03/sbin --sysconfdir=/pixar/d2/sets/tools-03/etc
--datadir=/pixa\
r/d2/sets/tools-03/share --includedir=/pixar/d2/sets/tools-03/include
--libdir=/pixar/d2/\
sets/tools-03/lib --libexecdir=/pixar/d2/sets/tools-03/libexec
--localstatedir=/pixar/d2/\
sets/tools-03/var --sharedstatedir=/pixar/d2/sets/tools-03/com
--mandir=/pixar/d2/sets/to\
ols-03/man --infodir=/pixar/d2/sets/tools-03/info
--enable-version-specific-runtime-libs \
--enable-languages=c++,objc,f95 --enable-threads=posix --enable-shared
--enable-mudflap
Thread model: posix
gcc version 4.0.3

Compile as:
   g++ bug.cpp

Issue:
   Calll to printf left out.  (Indeed, any line of code that
   contains sizeof(*savepos) gets tossed on the floor.  I assume
   since sizeof() is a compile-time construct, something took this a bit
   too far?
*/


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29106

[Bug c++/29375] New: gcc4.0.3 produces code that copies a structure twice

2006-10-06 Thread deb at pixar dot com 
Using built-in specs.
Target: x86_64-redhat-linux-gnu
Configured with: ../gcc-4.0.3/configure x86_64-redhat-linux-gnu
--with-ld=/pixar/d2/sets/tools-03/bin/ld
--with-as=/pixar/d2/sets/tools-03/bin/as --prefix=/pixar/d2/sets/tools-03
--exec-prefix=/pixar/d2/sets/tools-03 --bindir=/pixar/d2/sets/tools-03/bin
--sbindir=/pixar/d2/sets/tools-03/sbin --sysconfdir=/pixar/d2/sets/tools-03/etc
--datadir=/pixar/d2/sets/tools-03/share
--includedir=/pixar/d2/sets/tools-03/include
--libdir=/pixar/d2/sets/tools-03/lib
--libexecdir=/pixar/d2/sets/tools-03/libexec
--localstatedir=/pixar/d2/sets/tools-03/var
--sharedstatedir=/pixar/d2/sets/tools-03/com
--mandir=/pixar/d2/sets/tools-03/man --infodir=/pixar/d2/sets/tools-03/info
--enable-version-specific-runtime-libs --enable-symvers
--enable-languages=c++,objc,f95 --enable-threads=posix --enable-shared
--enable-mudflap
Thread model: posix
gcc version 4.0.3


--code
struct Big {
char data[1024];
};

void ByValue(Big);

void MakeACopy() {
Big stuff;
ByValue(stuff);
}
---

The relevant assembly code, when compiled as:  g++ -O2 -S prog.cpp


.globl _Z9MakeACopyv
.type   _Z9MakeACopyv, @function
_Z9MakeACopyv:
.LFB2:
pushq   %rbx
.LCFI0:
movl$1024, %edx
subq$3072, %rsp
.LCFI1:
leaq2048(%rsp), %rbx
leaq1024(%rsp), %rsi
movq%rbx, %rdi
callmemcpy
movq%rbx, %rsi
movq%rsp, %rdi
movl$1024, %edx
callmemcpy
call_Z7ByValue3Big
addq$3072, %rsp
popq%rbx
ret
---

I'm far from an export, but it sure looks to me like memcpy is being called
twice to copy the data!
This is supported by the fact that gcc3.3.2 only emits code to copy it once,
and that code runs twice as fast.

Also, gcc3.3.2 inlines the memcpy, while gcc4.0.3 does not.  I assume that's a
regression as well?
If not, what's the best option to tell gcc4.0.3 to inline the copy?


-- 
   Summary: gcc4.0.3 produces code that copies a structure twice
   Product: gcc
   Version: 4.0.3
Status: UNCONFIRMED
  Severity: normal
  Priority: P3
 Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
    ReportedBy: deb at pixar dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29375

[Bug c++/29375] gcc4.0.3 produces code that copies a structure twice

2006-10-06 Thread deb at pixar dot com 


--- Comment #2 from deb at pixar dot com  2006-10-07 04:00 ---
(In reply to comment #1)
> I think this was fixed in 4.0.4 by the patch which fixed PR 23372.
> 

For various reasons, upgrading to 4.0.4 isn't an option at this time.
(a) How do I obtain the specific patch you are referring to and
(b) any idea if it would be safe to apply this patch to our current 4.0.3
source?

Also, are you saying that the fix for PR23372 also brings us back to avoiding
direct calls to memcpy?
That may be the bigger issue; the number of POD datastructures we're copying
around is probably very small.  I was really trying to uncover why we were
calling mempcy directly when I noticed the second copy.

Thanks.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29375

[Bug c++/29375] gcc4.0.3 produces code that copies a structure twice

2006-10-06 Thread deb at pixar dot com 


--- Comment #3 from deb at pixar dot com  2006-10-07 04:01 ---
Oops, I see how to get the patch.  Never mind that part of the question,
thanks.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29375