[Bug c/53538] New: Compile error with ARM NEON intrinsics and certain compile flags

[Bug c/53538] New: Compile error with ARM NEON intrinsics and certain compile flags

[ahelm at gmx dot net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53538

             Bug #: 53538
           Summary: Compile error with ARM NEON intrinsics and certain
                    compile flags
    Classification: Unclassified
           Product: gcc
           Version: 4.5.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: ahelm@gmx.net


Created attachment 27529
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27529
test program

The attached test program fails to compile with the following command line
(cross compiling for ARM neon on Ubuntu):

gcc -c test_an_bug.c -o test_an_bug.o -O2 -g -Wall -march=armv7-a
-mlittle-endian -mfloat-abi=hard -mfpu=neon -mtp=cp15 -mthumb

Error message:

In file included from test_an_bug.c:2:0:
[...]/4.5/include/arm_neon.h: In function 'main':
[...]/4.5/include/arm_neon.h:4968:49: error: argument must be a constant
[...]/4.5/include/arm_neon.h:4968: confused by earlier errors, bailing out

However it builds without warning when either:
1) use -O3 instead of -O2 or
2) use -funroll-loops
3) if you move the intrinsic (vget_lane_u16) outside the for loop
4) if you use literals instead of the variable j

I haven't found any detailed documentation on the use of this intrinsic, but it
looks a bit odd if it only accepts literals as parameters. 
At what point did we give up pass-by-value for int?
And it certainly is odd that it compiles fine with different optimization
levels...

Note 1: This is not the original code, it is the minimum test program I derived
from it.

Note 2: It seems to fail on all compiler versions from 4.5 to 4.7 I've tried.

[Bug target/53538] Compile error with ARM NEON intrinsics and certain compile flags

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53538

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> 2012-05-31 16:24:43 UTC ---
They are defined by the ARM compiler which has them documented here:
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0491c/BABJFCGC.html

With either -funroll-loops or -O3 (which enables sometimes full unrolling), the
compiler is able to figure out the argument j is a constant as it duplicates it
4 times.

[Bug target/53538] Compile error with ARM NEON intrinsics and certain compile flags

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53538

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-05-31 16:28:32 UTC ---
Well, that confused by earlier errors, bailing out (i.e. ICE without release
checking) is still a compiler bug, bad error recovery.