[Bug target/43440] Overwriting neon quad register does not clobber all included single registers

[batuzovk at ispras dot ru]

--- Comment #3 from batuzovk at ispras dot ru  2010-03-20 12:35 ---
(In reply to comment #2)
  Does that look any better to you ? 
Yes, definitely better. Thank you for quick response.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43440

[Bug target/43440] New: Overwriting neon quad register does not clobber all included single registers

[batuzovk at ispras dot ru]

Function:
float y;
float foo(float x)
{
y = x * x + x;
asm volatile (vmov.i8 q0, #0 ::: q0);
asm volatile (vmov.i8 q1, #0 ::: q1);
asm volatile (vmov.i8 q2, #0 ::: q2);
asm volatile (vmov.i8 q3, #0 ::: q3);
asm volatile (vmov.i8 q4, #0 ::: q4);
asm volatile (vmov.i8 q5, #0 ::: q5);
asm volatile (vmov.i8 q6, #0 ::: q6);
asm volatile (vmov.i8 q7, #0 ::: q7);
return y;
}
being compiled with -O -Wall -mcpu=cortex-a8 -mfpu=neon -mfloat-abi=softfp
always returns 0.

The cause of incorrect behaviour is that in function foo y is allocated on s15
which is not considered clobbered by asm volatile (vmov.i8 q3, #0 :::
q3);. Mentioning in clobber lists s1 s2 and s3 alongside q0, s5 s6 and s7
alongside q1 and so on solves the problem: clobbered register got spilled.
Omitting any of them makes GCC allocate y on this register and do not spill it.

I also noticed that only d8, d10, d12 and d14 got saved at the beginning of the
function though all d8-d15 should be saved. This was mentioned in bug #42321
comment #1 also.

I tried this example on 4.4.3 and today's trunk.


-- 
   Summary: Overwriting neon quad register does not clobber all
included single registers
   Product: gcc
   Version: 4.5.0
Status: UNCONFIRMED
  Severity: normal
  Priority: P3
 Component: target
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: batuzovk at ispras dot ru
GCC target triplet: arm-unknown-linux-gnueabi


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43440