Arm® A64 Instruction Set Architecture: Future Architecture Technologies in the A architecture profile | LD1W (scalar plus immediate): Contiguous load unsigned words to vector (immediate index).

You copied the Doc URL to your clipboard.

LD1W (scalar plus immediate)

Contiguous load unsigned words to vector (immediate index).

Contiguous load of unsigned words to elements of a vector register from the memory address generated by a 64-bit scalar base and immediate index in the range -8 to 7 which is multiplied by the vector's in-memory size, irrespective of predication, and added to the base address. Inactive elements will not not cause a read from Device memory or signal a fault, and are set to zero in the destination vector.

It has encodings from 2 classes: 32-bit element and 64-bit element

32-bit element

31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
1	0	1	0	0	1	0	1	0	1	0	0	imm4				1	0	1	Pg			Rn					Zt
							dtype<3:1>			dtype<0>

LD1W { <Zt>.S }, <Pg>/Z, [<Xn|SP>{, #<imm>, MUL VL}]

if !HaveSVE() then UNDEFINED;
integer t = UInt(Zt);
integer n = UInt(Rn);
integer g = UInt(Pg);
integer esize = 32;
integer msize = 32;
boolean unsigned = TRUE;
integer offset = SInt(imm4);

64-bit element

31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
1	0	1	0	0	1	0	1	0	1	1	0	imm4				1	0	1	Pg			Rn					Zt
							dtype<3:1>			dtype<0>

LD1W { <Zt>.D }, <Pg>/Z, [<Xn|SP>{, #<imm>, MUL VL}]

if !HaveSVE() then UNDEFINED;
integer t = UInt(Zt);
integer n = UInt(Rn);
integer g = UInt(Pg);
integer esize = 64;
integer msize = 32;
boolean unsigned = TRUE;
integer offset = SInt(imm4);

Assembler Symbols

<Zt>	Is the name of the scalable vector register to be transferred, encoded in the "Zt" field.

<Pg>	Is the name of the governing scalable predicate register P0-P7, encoded in the "Pg" field.

<Xn|SP>

Is the 64-bit name of the general-purpose base register or stack pointer, encoded in the "Rn" field.

<imm>

Is the optional signed immediate vector offset, in the range -8 to 7, defaulting to 0, encoded in the "imm4" field.

Operation

CheckSVEEnabled();
integer elements = VL DIV esize;
bits(64) base;
bits(64) addr;
bits(PL) mask = P[g];
bits(VL) result;
bits(msize) data;
constant integer mbytes = msize DIV 8;

if n == 31 then
    if LastActiveElement(mask, esize) >= 0 || 
          ConstrainUnpredictableBool(Unpredictable_CHECKSPNONEACTIVE) then 
        CheckSPAlignment();
    if HaveMTEExt() then SetTagCheckedInstruction(FALSE);
    base = SP[];
else
    if HaveMTEExt() then SetTagCheckedInstruction(TRUE);
    base = X[n];

addr = base + offset * elements * mbytes;
for e = 0 to elements-1
    if ElemP[mask, e, esize] == '1' then
        data = Mem[addr, mbytes, AccType_NORMAL];
        Elem[result, e, esize] = Extend(data, esize, unsigned);
    else
        Elem[result, e, esize] = Zeros();
    addr = addr + mbytes;

Z[t] = result;

Previous Next