vclzdm

Vector Count Leading Zeros Doubleword under bit Mask

vclzdm VRT, VRA, VRB

Counts the number of leading zeros in each doubleword element of a vector, considering a mask.

Details

Counts the number of leading zero bits in each doubleword element of the source vector, using a bit mask from a second source vector to selectively apply the count operation. The results are placed in the target vector as doubleword elements. This is a VMX (AltiVec) category instruction that does not affect condition register or status fields.

Pseudocode Operation

for i in 0 to 1 do
  if VRB[i*64:(i+1)*64] != 0 then
    VRT[i*64:(i+1)*64] ← LEADING_ZEROS(VRA[i*64:(i+1)*64])
  else
    VRT[i*64:(i+1)*64] ← 0
end for

Programming Note

Use vclzdm to efficiently count leading zeros in masked bit positions within doublewords. Ensure that VRB contains a valid mask where 1s indicate bits to be considered for zero counting. This instruction operates at user privilege level and does not generate exceptions under normal conditions.

Example

vclzdm v1, v2, v3

Encoding

Binary Layout

Format X-form

Opcode 0x10000784

Extension VMX (AltiVec)

Operands

VRT
Target Vector Register
VRA
Source Vector Register
VRB
Source Vector Register