On Wed, Mar 18, 2015 at 12:12:17PM +0100, Richard Biener wrote:
> On Wed, Mar 18, 2015 at 5:22 AM, Alan Modra <amo...@gmail.com> wrote:
> > On Tue, Mar 17, 2015 at 01:28:41PM -0600, Jeff Law wrote:
> >> On 03/14/2015 07:02 AM, Alan Modra wrote:
> >> > PR target/65408
> >> > PR target/58744
> >> > PR middle-end/36043
> >> > * calls.c (load_register_parameters): Don't load past end of
> >> > mem unless suitably aligned.
> >> I think this is probably a stage1 item. Richi, Jakub, Joseph, do any of
> >> you
> >> think we should try to push this into gcc-5?
> >
> > Some (severity) background to PR65408. The bug came from SAP HANA
> > (en.wikipedia.org/wiki/SAP_HANA), a crash that happens on powerpc64
> > and powerpc64le. aarch64 would also be susceptible to the crash since
> > it also loads 16 bytes for the 12-byte struct. x86_64 only loads 12
> > bytes (i386.c:construct_container generates a parallel with a DImode
> > and SImode load). However the underlying bug is there and hits x86_64
> > too for the pr58744 and pr36043 testcases..
>
> It's a very very very old bug though. I'd be interested in any odd
> code-generation difference for compiling, say, the linux kernel
> (you _can_ get quite ugly code generated because of this fix).
Yes, all those byte loads.. As far as the kernel goes, x86_64 shows
some differences in calls to rgb_{fore,back}ground in
drivers/tty/vt/vt.c. Both before and after look ugly to me. :)
4d73: 8b 82 24 02 00 00 mov 0x224(%rdx),%eax
4d79: 48 89 df mov %rbx,%rdi
4d7c: 41 83 c4 04 add $0x4,%r12d
4d80: 88 45 b2 mov %al,-0x4e(%rbp)
4d83: 8b 82 28 02 00 00 mov 0x228(%rdx),%eax
4d89: 88 45 b3 mov %al,-0x4d(%rbp)
4d8c: 8b 82 2c 02 00 00 mov 0x22c(%rdx),%eax
4d92: 88 45 b4 mov %al,-0x4c(%rbp)
4d95: 48 8b 75 b2 mov -0x4e(%rbp),%rsi
4d99: e8 00 00 00 00 callq <rgb_background>
vs.
4d73: 8b 82 24 02 00 00 mov 0x224(%rdx),%eax
4d79: 0f b6 b2 2c 02 00 00 movzbl 0x22c(%rdx),%esi
4d80: 48 89 df mov %rbx,%rdi
4d83: 41 83 c4 04 add $0x4,%r12d
4d87: 88 45 b2 mov %al,-0x4e(%rbp)
4d8a: 8b 82 28 02 00 00 mov 0x228(%rdx),%eax
4d90: 48 c1 e6 10 shl $0x10,%rsi
4d94: 88 45 b3 mov %al,-0x4d(%rbp)
4d97: 0f b7 45 b2 movzwl -0x4e(%rbp),%eax
4d9b: 48 09 c6 or %rax,%rsi
4d9e: e8 00 00 00 00 callq <rgb_background>
Is the patch OK for stage1?
--
Alan Modra
Australia Development Lab, IBM
