SQRDMLSH (by element)
Signed Saturating Rounding Doubling Multiply Subtract returning High Half (by element). This instruction multiplies the vector elements of the first source SIMD&FP register with the value of a vector element of the second source SIMD&FP register without saturating the multiply results, doubles the results, and subtracts the most significant half of the final results from the vector elements of the destination SIMD&FP register. The results are rounded.
If any of the results overflow, they are saturated. The cumulative saturation bit, FPSR.QC, is set if saturation occurs.
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.
It has encodings from 2 classes:
Scalar
and
Vector
Scalar
(FEAT_RDM)
| 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 |
| 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | size | L | M | Rm | 1 | 1 | 1 | 1 | H | 0 | Rn | Rd |
| | | | | | | | S | | | | | |
if !HaveQRDMLAHExt() then UNDEFINED;
integer idxdsize = if H == '1' then 128 else 64;
integer index;
bit Rmhi;
case size of
when '01' index = UInt(H:L:M); Rmhi = '0';
when '10' index = UInt(H:L); Rmhi = M;
otherwise UNDEFINED;
integer d = UInt(Rd);
integer n = UInt(Rn);
integer m = UInt(Rmhi:Rm);
integer esize = 8 << UInt(size);
integer datasize = esize;
integer elements = 1;
boolean rounding = TRUE;
boolean sub_op = (S == '1');
Vector
(FEAT_RDM)
| 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 |
| 0 | Q | 1 | 0 | 1 | 1 | 1 | 1 | size | L | M | Rm | 1 | 1 | 1 | 1 | H | 0 | Rn | Rd |
| | | | | | | | | S | | | | | |
if !HaveQRDMLAHExt() then UNDEFINED;
integer idxdsize = if H == '1' then 128 else 64;
integer index;
bit Rmhi;
case size of
when '01' index = UInt(H:L:M); Rmhi = '0';
when '10' index = UInt(H:L); Rmhi = M;
otherwise UNDEFINED;
integer d = UInt(Rd);
integer n = UInt(Rn);
integer m = UInt(Rmhi:Rm);
integer esize = 8 << UInt(size);
integer datasize = if Q == '1' then 128 else 64;
integer elements = datasize DIV esize;
boolean rounding = TRUE;
boolean sub_op = (S == '1');
Assembler Symbols
| <V> |
Is a width specifier,
encoded in
size :
| size |
<V> |
| 00 |
RESERVED |
| 01 |
H |
| 10 |
S |
| 11 |
RESERVED |
|
| <d> |
Is the number of the SIMD&FP destination register, encoded in the "Rd" field.
|
| <n> |
Is the number of the first SIMD&FP source register, encoded in the "Rn" field.
|
| <Vd> |
Is the name of the SIMD&FP destination register, encoded in the "Rd" field.
|
| <T> |
Is an arrangement specifier,
encoded in
size:Q :
| size |
Q |
<T> |
| 00 |
x |
RESERVED |
| 01 |
0 |
4H |
| 01 |
1 |
8H |
| 10 |
0 |
2S |
| 10 |
1 |
4S |
| 11 |
x |
RESERVED |
|
| <Vn> |
Is the name of the first SIMD&FP source register, encoded in the "Rn" field.
|
| <Vm> |
Is the name of the second SIMD&FP source register,
encoded in
size:M:Rm :
| size |
<Vm> |
| 00 |
RESERVED |
| 01 |
0:Rm |
| 10 |
M:Rm |
| 11 |
RESERVED |
Restricted to V0-V15 when element size <Ts> is H.
|
| <Ts> |
Is an element size specifier,
encoded in
size :
| size |
<Ts> |
| 00 |
RESERVED |
| 01 |
H |
| 10 |
S |
| 11 |
RESERVED |
|
| <index> |
Is the element index,
encoded in
size:L:H:M :
| size |
<index> |
| 00 |
RESERVED |
| 01 |
H:L:M |
| 10 |
H:L |
| 11 |
RESERVED |
|
Operation
CheckFPAdvSIMDEnabled64();
bits(datasize) operand1 = V[n];
bits(idxdsize) operand2 = V[m];
bits(datasize) operand3 = V[d];
bits(datasize) result;
integer rounding_const = if rounding then 1 << (esize - 1) else 0;
integer element1;
integer element2;
integer element3;
integer product;
boolean sat;
element2 = SInt(Elem[operand2, index, esize]);
for e = 0 to elements-1
element1 = SInt(Elem[operand1, e, esize]);
element3 = SInt(Elem[operand3, e, esize]);
if sub_op then
accum = ((element3 << esize) - 2 * (element1 * element2) + rounding_const);
else
accum = ((element3 << esize) + 2 * (element1 * element2) + rounding_const);
(Elem[result, e, esize], sat) = SignedSatQ(accum >> esize, esize);
if sat then FPSR.QC = '1';
V[d] = result;
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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