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[Bug target/60925] [4.9/4.10 Regression] hppa: can't find a register in class 'R1_REGS' while reloading 'asm'
- From: "dave.anglin at bell dot net" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Sun, 25 May 2014 18:31:17 +0000
- Subject: [Bug target/60925] [4.9/4.10 Regression] hppa: can't find a register in class 'R1_REGS' while reloading 'asm'
- Auto-submitted: auto-generated
- References: <bug-60925-4 at http dot gcc dot gnu dot org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60925
--- Comment #7 from dave.anglin at bell dot net ---
On 25-May-14, at 7:11 AM, aaro.koskinen at iki dot fi wrote:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60925
>
> --- Comment #6 from Aaro Koskinen <aaro.koskinen at iki dot fi> ---
> Created attachment 32852
> --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=32852&action=edit
> Simplified reproducer.
>
> I tried to make a simpler reproducer.
Thanks for simplifying the test case. The problem is now clear.
>
> $ hppa-linux-gnu-gcc pr60925.c -c -O2 -Wall -g -fPIC
> pr60925.c: In function 'foo':
> pr60925.c:6:9: error: can't find a register in class 'R1_REGS' while
> reloading
> 'asm'
> asm volatile(
> ^
The problem is the argument "futex" used in the asm. When generating
PIC code, register
%r1 is needed for position independent loads and stores from memory.
In the test, both statements involving __lll_mutex_lock are needed to
trigger the
error. Essentially, reload fails to handle the reloads needed for
&lock because the
asm clobbers %r1 and %r1 is needed for the reload.
Possibly, reload should be able to do this because the reload insns
should be emitted
before %r1 is clobbered by the asm, but reload is complicated.
A better fix is to ensure that the futex argument is placed in a
general register
that is not clobbered by the asm. This has to happen anyway. For
example,
static inline int __attribute__((always_inline))
__lll_mutex_lock(int *futex, int private)
{
register int *f asm ("r5") = futex;
...
The other fix is to not inline __lll_mutex_lock. Then, one is sure
that futex will be
in %r26 on entry, and it can be copied to another general register
without %r1 being
needed.
Dave
--
John David Anglin dave.anglin@bell.net