[vectorIntrinsics] C2 is fragile

[Vladimir Ivanov]

Hi Eugene,

Do you have a test case available so I can try to reproduce the problem 
myself?

The only idea I have right now is that profile pollution is in play here:

     private static final VectorSpecies<Integer> VIP = 
IntVector.SPECIES_256;
     private static final VectorSpecies<Integer> VI4 = 
IntVector.SPECIES_128;

     static void sumAbs(int[] sum, int count, int[] regionX, int[] dst) {
	...
        IntVector acc = IntVector.fromArray(VI4, sum, regionX[0] * 4);

vs

     // BAD
     IntVector off = IntVector.fromArray(VIP, rowOffset, i);


But considering VIP and VI4 are constants (static final), it's hard to 
see how it can be the case.

Best regards,
Vladimir Ivanov

On 15.03.2021 01:58, Eugene Kluchnikov wrote:
> private static final VectorSpecies<Float> VFP = FloatVector.SPECIES_256;
> private static final VectorSpecies<Integer> VIP = IntVector.SPECIES_256;
> private static final VectorSpecies<Integer> VI4 = IntVector.SPECIES_128;
> 
> static final int STEP = VFP.length();
> 
> static void sumAbs(int[] sum, int count, int[] regionX, int[] dst) {
> if (count > regionX.length) return;
> IntVector acc = IntVector.fromArray(VI4, sum, regionX[0] * 4);
> for (int i = 1; i < count; i++) {
> acc = acc.add(IntVector.fromArray(VI4, sum, regionX[i] * 4));
> }
> acc.intoArray(dst, 0);
> }
> 
> private static int MAX_INT = (1 << 23) - 1;
> private static IntVector INTEGER_MASK = IntVector.broadcast(VIP, MAX_INT);
> private static FloatVector IMPLICIT_ONE = FloatVector.broadcast(VFP,
> MAX_INT + 1);
> 
> // x >= (d - y * ny) / nx
> static void updateGeGeneric(int angle, int d, float[] regionY, float[]
> regionX0f,
> float[] regionX1f, int[] rowOffset, int[] regionX, int count, int kappa) {
> FloatVector mNyNx = FloatVector.broadcast(VFP, SinCos.MINUS_COT[angle]);
> FloatVector dNx = FloatVector.broadcast(VFP, (float)(d * SinCos.INV_SIN[
> angle]));
> FloatVector k = FloatVector.broadcast(VFP, kappa);
> for (int i = 0; i < count; i += STEP) {
> FloatVector y = FloatVector.fromArray(VFP, regionY, i);
> FloatVector x0 = FloatVector.fromArray(VFP, regionX0f, i);
> FloatVector x1 = FloatVector.fromArray(VFP, regionX1f, i);
> 
> // BAD
> IntVector off = IntVector.fromArray(VIP, rowOffset, i);
> FloatVector x = y.fma(mNyNx, dNx).max(x0).min(x1);
> IntVector xi = x.add(IMPLICIT_ONE).viewAsIntegralLanes().and(INTEGER_MASK);
> IntVector xOff = xi.add(off);
> xOff.intoArray(regionX, i);
> 
> // GOOD
> //FloatVector x = y.fma(mNyNx, dNx).max(x0).min(x1);
> //FloatVector xOff = y.fma(k, x);
> //xOff.add(IMPLICIT_ONE).viewAsIntegralLanes().and(INTEGER_MASK).intoArray(regionX,
> i);
> }
> }