Add vblend vector operation

[gita-omr]

• similar to vbitselect but works on lanes and under control of the mask (third child)
• if lane is not set in the mask the value from the first vector is chosen
• the lane from the second vector is chosen otherwise

[gita-omr]

@0xdaryl @jdmpapin @mstoodle @vijaysun-omr @hzongaro : fyi

[gita-omr]

Jenkins build all

[gita-omr]

Fixed build errors.

[gita-omr]

Jenkins build all

[gita-omr]

RISC build failed due to unrelated reasons (machine is offline).

[0xdaryl]

What is the type and semantics of the "mask" child? i.e., how does it describe how the the first and second children are blended?

[gita-omr]

All three arguments have the same number of elements. Mask element is a boolean value. If it's true, corresponding element of the first vector is chosen. If it's false, element from the second argument is chosen.

[gita-omr]

Actually, it's a good question. Let me think what the exact semantic should be.

[hzongaro]

vblend is similar to vselect

What is vselect? Or did you mean select?

All three arguments have the same number of elements. Mask element is a boolean value. If it's true, corresponding element of the first vector is chosen. If it's false, element from the second argument is chosen.

If this is meant to be analogous to select, should the first argument be the mask, rather than the third?

[gita-omr]

Updated with expected semantics.

@BradleyWood

[gita-omr]

If this is meant to be analogous to select, should the first argument be the mask, rather than the third?

We have vbitselect vector operation. It selects bits from the second vector if corresponding bit in the third vector is set. Otherwise, the bit from the first vector is selected.

[hzongaro]

We have vbitselect vector operation. It selects bits from the second vector if corresponding bit in the third vector is set. Otherwise, the bit from the first vector is selected.

I see. It's unfortunate that the order of the operands differs from those of iselect, et al.

[BradleyWood]

Thanks for doing this @gita-omr. Did you find out the reason that the vbitselect opcode had a strange extra operand?

[gita-omr]

We have vbitselect vector operation. It selects bits from the second vector if corresponding bit in the third vector is set. Otherwise, the bit from the first vector is selected.

I see. It's unfortunate that the order of the operands differs from those of iselect, et al.

This is a common meaning for vector blend operations and that's how corresponding instructions work at least on Intel ans Power. Essentially, we blend second vector into the first one based on the third vector or mask.