Im compiling the following ARM NEON intrinsics test code (in Eclipse with Android NDK):
void foo(uint64_t* Res)
{
uint64_t x = 0xff12aa8902acf78dULL;
uint64x1_t a,b;
a = vld1_u64 (&x);
b = vext_u64 (a, a, 3);
vst1_u64 (Res,b);
}
but I keep getting the following compiler error:
/home/developer/adt/ndk/ndk-build all
Install : libneon_test.so => libs/armeabi/libneon_test.so
Compile thumb : neon_test <= neon.c
jni/neon.c: In function 'foo':
jni/neon.c:17:1: error: constant out of range
make: *** [obj/local/armeabi-v7a/objs/neon_test/neon.o] Error 1`
Line 17 is the last }
brace of foo()
.
Does anyone have an idea what might be the cause of this strange error?
Problem is in this line
b = vext_u64 (a, a, 3);
You can't have 3
as shift for vext_u64
, it isn't allowed.
uint64x1_t vext_u64(uint64x1_t a, uint64x1_t b, __constrange(0,0) int c); // VEXT.64 d0,d0,d0,#0
It looks like gcc
's implementation (definition?) of neon intrinsics isn't as good as armcc
's in this aspect.
A trick to understand such behavior is to pass -S
to gcc
to convert code to assembly then try to compile that assembly file. That way gcc will tell you exactly which line is giving the problem.
$ ~/bin/android-ndk-r8d/toolchains/arm-linux-androideabi-4.7/prebuilt/linux-x86/bin/arm-linux-androideabi-gcc --sysroot=/home/auselen/bin/android-ndk-r8d/platforms/android-14/arch-arm -std=c99 -S neon.c -mfloat-abi=softfp -mfpu=neon -O2
neon.c: In function 'foo':
neon.c:11:1: error: constant out of range
$ ~/bin/android-ndk-r8d/toolchains/arm-linux-androideabi-4.7/prebuilt/linux-x86/bin/arm-linux-androideabi-gcc --sysroot=/home/auselen/bin/android-ndk-r8d/platforms/android-14/arch-arm -std=c99 -c neon.s -mfloat-abi=softfp -mfpu=neon -O2
neon.s: Assembler messages:
neon.s:28: Error: shift out of range -- `vext.64 d16,d16,d16,#3'
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