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Re: [RFC] GCC aliasing bug PR optimization/9745
- From: <tm_gccmail at mail dot kloo dot net>
- To: David Edelsohn <dje at watson dot ibm dot com>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Thu, 6 Mar 2003 13:55:17 -0800 (PST)
- Subject: Re: [RFC] GCC aliasing bug PR optimization/9745
On Thu, 6 Mar 2003, David Edelsohn wrote:
> With some insight by Dale Johannesen, I have tracked down the
> cause of the miscompilation of libmcrypt by GCC 3.3 and the trunk, but the
> problem seems to be a fundamental bug in GCC's RTL aliasing design.
>
> The symptom is elicited by RTL which accesses an array both
> through the frame pointer and through a pseudo derived from the frame
> pointer. GCC alias analysis marks certain base registers (stack pointer,
> argument pointer, frame pointer, hard frame pointer) as special using
> ADDRESS. On some architectures, such as PowerPC, the frame pointer is not
> a fixed register and can be eliminated in terms of the stack pointer.
We have an alias analysis patch which handles pointer arithmetic.
Could this patch possibly solve this problem?
Toshi