On 2 March 2016 at 10:49, Christophe Lyon <christophe.l...@linaro.org> wrote:
> On 2 March 2016 at 10:16, James Greenhalgh <james.greenha...@arm.com> wrote:
>> On Tue, Mar 01, 2016 at 05:56:30PM +0100, Christophe Lyon wrote:
>>> On 1 March 2016 at 10:51, James Greenhalgh <james.greenha...@arm.com> wrote:
>>> > On Tue, Mar 01, 2016 at 10:21:27AM +0100, Richard Biener wrote:
>>> >> On Mon, 29 Feb 2016, James Greenhalgh wrote:
>>> >>
>>> >> > On Fri, Feb 26, 2016 at 09:32:53AM +0100, Richard Biener wrote:
>>> >> > >
>>> >> > > The following fixes PR69951, hopefully the last case of decl alias
>>> >> > > issues with alias analysis. This time it's points-to and the
>>> >> > > DECL_UIDs
>>> >> > > used in points-to sets not being canonicalized.
>>> >> > >
>>> >> > > The simplest (and cheapest) fix is to make aliases refer to the
>>> >> > > ultimate alias target via their DECL_PT_UID which we conveniently
>>> >> > > have available.
>>> >> > >
>>> >> > > Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to
>>> >> > > trunk.
>>> >> > >
>>> >> > > Richard.
>>> >> > >
>>> >> > > 2016-02-26 Richard Biener <rguent...@suse.de>
>>> >> > >
>>> >> > > PR tree-optimization/69551
>>> >> > > * tree-ssa-structalias.c (get_constraint_for_ssa_var): When
>>> >> > > looking through aliases adjust DECL_PT_UID to refer to the
>>> >> > > ultimate alias target.
>>> >> > >
>>> >> > > * gcc.dg/torture/pr69951.c: New testcase.
>>> >> >
>>> >> > I see this new testcase failing on an ARM target as so:
>>> >> >
>>> >> > /tmp/ccChjoFc.s: Assembler messages:
>>> >> > /tmp/ccChjoFc.s:21: Warning: [-mwarn-syms]: Assignment makes a
>>> >> > symbol match an ARM instruction: b
>>> >> >
>>> >> > FAIL: gcc.dg/torture/pr69951.c -O0 (test for excess errors)
>>> >> >
>>> >> > But I haven't managed to reproduce it outside of the test environment.
>>> >> >
>>> >> > The fix looks trivial, rename b to anything else you fancy (well...
>>> >> > stay
>>> >> > clear of add and ldr). I'll put a fix in myself if I can manage to get
>>> >> > this to reproduce - though if anyone else wants to do it I won't be
>>> >> > offended :-).
>>> >>
>>> >> Huh, I wonder what's the use of such warning. After all 'ldr' is a valid
>>> >> C symbol name, too. In fact my cross arm as doesn't report this
>>> >> warning (binutils 2.25.0)
>>> >>
>>> >> > arm-suse-linux-gnueabi-as t.s -mwarn-syms
>>> >> Assembler messages:
>>> >> Error: unrecognized option -mwarn-syms
>>> >
>>> > Right, I've figured out the set of conditions... You need to be targeting
>>> > an arm-*-linux-* system to make sure that the ASM_OUTPUT_DEF definition
>>> > from config/arm/linux-elf.h is pulled in. This causes us to emit:
>>> >
>>> > b = a
>>> >
>>> > Rather than
>>> >
>>> > .set b,a
>>> >
>>> > Writing it as "b = a" causes the warning added to resolve binutils
>>> > PR18347 [1] to kick in, so you need binutils > 2.26 or to have backported
>>> > that patch).
>>> >
>>> James,
>>>
>>> What happens for you on arm-none-eabi configurations?
>>> I'm using binutils-2.25, so I can't see this warning whatever the target.
>>> However, I'm using qemu-arm and this test fails on arm-none-eabi,
>>> because argc is set to 0 during the startup-code.
>>>
>>> As I understand it, qemu-arm considers the code page as readonly,
>>> and thus the GetCmdLine semi hosting call cannot write argc/argv
>>> back to memory in the same code page (I'm using libgloss' crt0).
>>>
>>> I tried to play with qemu-system-arm, but then libgloss' crt0 does not
>>> set the reset vector and the simulation does random things, starting at
>>> address 0.
>>>
>>> Am I missing some newlib/libgloss configuration bits, or should I
>>> send a newlib patch to address this?
>>
>> Hi Christophe,
>>
>> I didn't get this running under arm-none-eabi. The testcase does have
>> undefined behaviour (too few arguments to main), but I'd be surprised if
>> that was the issue... I'm sure the testcase could be rewritten to avoid
>> the dependence on argc if this proves an issue for other bare-metal
>> testers running under an emulator.
>>
>
> Indeed, I'm wondering why the testcase depends on argc beeing non-zero?
>
To avoid modifying the testcase too much, I propose to replace
if (argc)
by
if (argc >= 0)
as in the attached patch.
This does make the trick on arm-non-eabi.
OK?
Christophe.
>> Thanks,
>> James
>>
>>> > Resolving it by hacking the testcase would be one fix, but I wonder why
>>> > the
>>> > ARM port prefers to emit "b = a" in a linux environment if .set does the
>>> > same thing and always avoids the warning? Maybe Ramana/Richard/Kyrill/Nick
>>> > remember? (AArch64 does the same thing, but the AArch64 gas port doesn't
>>> > have the PR18347 fix).
>>> >
>>> > Cheers,
>>> > James
>>> >
>>> > ---
>>> >
>>> > [1]: https://sourceware.org/bugzilla/show_bug.cgi?id=18347
>>> >
>>> >>
>>> >> Richard.
>>> >>
>>>
2016-03-04 Christophe Lyon <christophe.l...@linaro.org>
* gcc.dg/torture/pr69951.c: Accept argc==0.
diff --git a/gcc/testsuite/gcc.dg/torture/pr69951.c
b/gcc/testsuite/gcc.dg/torture/pr69951.c
index cb46fef..be9a027 100644
--- a/gcc/testsuite/gcc.dg/torture/pr69951.c
+++ b/gcc/testsuite/gcc.dg/torture/pr69951.c
@@ -9,7 +9,7 @@ extern int d __attribute__((alias("c")));
int main(int argc)
{
int *p, *q;
- if (argc)
+ if (argc >= 0)
p = &c, q = &d;
else
p = &b, q = &d;
