Re: optimization/6673: gcc-3.1 produces wrong assembly code

[Nam SungHyun <namsh at wimo dot co dot kr>]

Richard Henderson wrote:
> On Fri, May 17, 2002 at 01:53:24PM +0900, Nam SungHyun wrote:
> > I saw the feed back message from the gnats web, but did not get a
> > mail. Did not know how I can reply for that feedback.
> 
> The gnats bug form has an originator email address that
> it cc's all status changes on.  Did you mistype it?

I typed namsh@kldp.org and it's valid. ???

> >     the 'a' in my example source is a 'global variable'.
> >     So, should the gcc treat it as a volatile by default?
> 
> No.
> 
> >     There are so many multi-threaded program. I didn't see
> >     any program which use volatile for the global variable.
> 
> Nor does any C compiler produce "thread aware" code by default.
> 
> You have to use cpu-specific thread synchronization primitives
> in order for that to work reliably.  Such a primitive would as
> a side effect tell the compiler that data must be committed to
> memory, which would cause 'a' to be written.
> 
> You did none of these.

You mean I should use '-fvolatile-global -fvolatile-static'?
Now I compiled the example source with:

    ppc-eabi-gcc -O1 -fvolatile-global -fvolatile-static -S ex.c

The result is same. What's wrong?

Regards,
namsh

	.file	"ex.c"
	.globl __eabi
	.section	".text"
	.align 2
	.globl main
	.type	main,@function
main:
	stwu 1,-8(1)
	mflr 0
	stw 0,12(1)
	bl __eabi
.L2:
	b .L2
.Lfe1:
	.size	main,.Lfe1-main
	.comm	a,4,4
	.ident	"GCC: (GNU) 3.1"