fjcvtzs
Floating-Point Javascript Convert
FJCVTZS <Wd>, <Dn>
Converts double to signed 32-bit integer with JS rounding semantics.
Details
Converts the 64-bit floating-point value in Dn to a signed 32-bit integer in Wd using JavaScript rounding semantics (round toward zero, with special handling for NaN and out-of-range values). AArch64-only; requires FEAT_JSCVT. Sets the C flag to 1 if the input is out of range or NaN, otherwise clears it. Other flags are not affected.
Pseudocode Operation
if IsNaN(Dn) or (Dn > 2^31 - 1) or (Dn < -2^31) then Wd ← 0; C ← 1; else Wd ← SignedSaturate(RoundTowardZero(Dn), 32); C ← 0;Example
FJCVTZS w0, d1
Encoding
Binary Layout
0
0
0
11110
01
1
11
110
000000
Rn
Rd
Operands
-
Wd
Destination 32-bit integer register -
Dn
First source 64-bit SIMD/FP register
Reference (Arm A64 ISA)
Instruction Forms
| Encoding | Instruction | ISA | Bit pattern | ||
|---|---|---|---|---|---|
| 0x1E7E0000 | FJCVTZS <Wd>, <Dn> | A64 | 0 | 0 | 0 | 11110 | 01 | 1 | 11 | 110 | 000000 | Rn | Rd |
Description
Floating-point Javascript Convert to Signed fixed-point, rounding toward Zero. This instruction converts the double-precision floating-point value in the SIMD&FP source register to a 32-bit signed integer using the Round towards Zero rounding mode, and writes the result to the general-purpose destination register. If the result is too large to be represented as a signed 32-bit integer, then the result is the integer modulo 232, as held in a 32-bit signed integer.
This instruction can generate a floating-point exception. Depending on the settings in FPCR, the exception results in either a flag being set in FPSR or a synchronous exception being generated. For more information, see Floating-point exception traps.
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.
Operation
CheckFPAdvSIMDEnabled64(); bits(64) fltval; bits(32) intval; bit z; fltval = V[n, 64]; (intval, z) = FPToFixedJS(fltval, FPCR, 32); PSTATE.<N,Z,C,V> = '0':z:'00'; X[d, 32] = intval;