ST2 (single structure) -- A64

Store single 2-element structure from one lane of two registers. This instruction stores a 2-element structure to memory from corresponding elements of two SIMD&FP registers.

Depending on the settings in the CPACR_EL1, CPTR_EL2, and CPTR_EL3 registers, and the current Security state and Exception level, an attempt to execute the instruction might be trapped.

No offset

8-bit (opcode == 000)

ST2 { <Vt>.B, <Vt2>.B }[<index>], [<Xn|SP>] // (PSTATE.C64 == '0')

ST2 { <Vt>.B, <Vt2>.B }[<index>], [<Cn|CSP>] // (PSTATE.C64 == '1')

16-bit (opcode == 010 && size == x0)

ST2 { <Vt>.H, <Vt2>.H }[<index>], [<Xn|SP>] // (PSTATE.C64 == '0')

ST2 { <Vt>.H, <Vt2>.H }[<index>], [<Cn|CSP>] // (PSTATE.C64 == '1')

32-bit (opcode == 100 && size == 00)

ST2 { <Vt>.S, <Vt2>.S }[<index>], [<Xn|SP>] // (PSTATE.C64 == '0')

ST2 { <Vt>.S, <Vt2>.S }[<index>], [<Cn|CSP>] // (PSTATE.C64 == '1')

64-bit (opcode == 100 && S == 0 && size == 01)

ST2 { <Vt>.D, <Vt2>.D }[<index>], [<Xn|SP>] // (PSTATE.C64 == '0')

ST2 { <Vt>.D, <Vt2>.D }[<index>], [<Cn|CSP>] // (PSTATE.C64 == '1')

integer t = UInt(Rt); integer n = UInt(Rn); integer m = integer UNKNOWN; boolean wback = FALSE;

Post-index

8-bit, immediate offset (Rm == 11111 && opcode == 000)

ST2 { <Vt>.B, <Vt2>.B }[<index>], [<Xn|SP>], #2 // (PSTATE.C64 == '0')

ST2 { <Vt>.B, <Vt2>.B }[<index>], [<Cn|CSP>], #2 // (PSTATE.C64 == '1')

8-bit, register offset (Rm != 11111 && opcode == 000)

ST2 { <Vt>.B, <Vt2>.B }[<index>], [<Xn|SP>], <Xm> // (PSTATE.C64 == '0')

ST2 { <Vt>.B, <Vt2>.B }[<index>], [<Cn|CSP>], <Xm> // (PSTATE.C64 == '1')

16-bit, immediate offset (Rm == 11111 && opcode == 010 && size == x0)

ST2 { <Vt>.H, <Vt2>.H }[<index>], [<Xn|SP>], #4 // (PSTATE.C64 == '0')

ST2 { <Vt>.H, <Vt2>.H }[<index>], [<Cn|CSP>], #4 // (PSTATE.C64 == '1')

16-bit, register offset (Rm != 11111 && opcode == 010 && size == x0)

ST2 { <Vt>.H, <Vt2>.H }[<index>], [<Xn|SP>], <Xm> // (PSTATE.C64 == '0')

ST2 { <Vt>.H, <Vt2>.H }[<index>], [<Cn|CSP>], <Xm> // (PSTATE.C64 == '1')

32-bit, immediate offset (Rm == 11111 && opcode == 100 && size == 00)

ST2 { <Vt>.S, <Vt2>.S }[<index>], [<Xn|SP>], #8 // (PSTATE.C64 == '0')

ST2 { <Vt>.S, <Vt2>.S }[<index>], [<Cn|CSP>], #8 // (PSTATE.C64 == '1')

32-bit, register offset (Rm != 11111 && opcode == 100 && size == 00)

ST2 { <Vt>.S, <Vt2>.S }[<index>], [<Xn|SP>], <Xm> // (PSTATE.C64 == '0')

ST2 { <Vt>.S, <Vt2>.S }[<index>], [<Cn|CSP>], <Xm> // (PSTATE.C64 == '1')

64-bit, immediate offset (Rm == 11111 && opcode == 100 && S == 0 && size == 01)

ST2 { <Vt>.D, <Vt2>.D }[<index>], [<Xn|SP>], #16 // (PSTATE.C64 == '0')

ST2 { <Vt>.D, <Vt2>.D }[<index>], [<Cn|CSP>], #16 // (PSTATE.C64 == '1')

64-bit, register offset (Rm != 11111 && opcode == 100 && S == 0 && size == 01)

ST2 { <Vt>.D, <Vt2>.D }[<index>], [<Xn|SP>], <Xm> // (PSTATE.C64 == '0')

ST2 { <Vt>.D, <Vt2>.D }[<index>], [<Cn|CSP>], <Xm> // (PSTATE.C64 == '1')

integer t = UInt(Rt); integer n = UInt(Rn); integer m = UInt(Rm); boolean wback = TRUE;

Assembler Symbols

<Vt>	Is the name of the first or only SIMD&FP register to be transferred, encoded in the "Rt" field.

<Vt2>

Is the name of the second SIMD&FP register to be transferred, encoded as "Rt" plus 1 modulo 32.

<index>	For the 8-bit variant: is the element index, encoded in "Q:S:size".
	For the 16-bit variant: is the element index, encoded in "Q:S:size<1>".
	For the 32-bit variant: is the element index, encoded in "Q:S".
	For the 64-bit variant: is the element index, encoded in "Q".

<Xn|SP>

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

<Cn|CSP>

Is the name of the capability register or capability stack pointer holding the base address, encoded in the "Rn" field.

<Xm>	Is the 64-bit name of the general-purpose post-index register, excluding XZR, encoded in the "Rm" field.

Shared Decode

integer scale = UInt(opcode<2:1>); integer selem = UInt(opcode<0>:R) + 1; boolean replicate = FALSE; integer index; case scale of when 3 // load and replicate if L == '0' || S == '1' then UNDEFINED; scale = UInt(size); replicate = TRUE; when 0 index = UInt(Q:S:size); // B[0-15] when 1 if size<0> == '1' then UNDEFINED; index = UInt(Q:S:size<1>); // H[0-7] when 2 if size<1> == '1' then UNDEFINED; if size<0> == '0' then index = UInt(Q:S); // S[0-3] else if S == '1' then UNDEFINED; index = UInt(Q); // D[0-1] scale = 3; MemOp memop = if L == '1' then MemOp_LOAD else MemOp_STORE; integer datasize = if Q == '1' then 128 else 64; integer esize = 8 << scale;

Operation

CheckFPAdvSIMDEnabled64(); bits(64) address; bits(64) offs; bits(128) rval; bits(esize) element; constant integer ebytes = esize DIV 8; VirtualAddress base = BaseReg[n]; address = VAddress(base); if replicate || memop == MemOp_LOAD then VACheckAddress(base, address, ebytes * selem, CAP_PERM_LOAD, AccType_VEC); else VACheckAddress(base, address, ebytes * selem, CAP_PERM_STORE, AccType_VEC); offs = Zeros(); if replicate then // load and replicate to all elements for s = 0 to selem-1 element = Mem[address + offs, ebytes, AccType_VEC]; // replicate to fill 128- or 64-bit register V[t] = Replicate(element, datasize DIV esize); offs = offs + ebytes; t = (t + 1) MOD 32; else // load/store one element per register for s = 0 to selem-1 rval = V[t]; if memop == MemOp_LOAD then // insert into one lane of 128-bit register Elem[rval, index, esize] = Mem[address + offs, ebytes, AccType_VEC]; V[t] = rval; else // memop == MemOp_STORE // extract from one lane of 128-bit register Mem[address + offs, ebytes, AccType_VEC] = Elem[rval, index, esize]; offs = offs + ebytes; t = (t + 1) MOD 32; if wback then if m != 31 then offs = X[m]; BaseReg[n] = VAAdd(base, offs);

Internal version only: isa v32.13, AdvSIMD v29.04, pseudocode morello-2022-01_rc2, capabilities morello-2022-01_rc2 ; Build timestamp: 2022-01-11T11:23

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0	Q	0	0	1	1	0	1	0	0	1	0	0	0	0	0	x	x	0	S	size		Rn					Rt
									L	R						opcode