v_rcp_f32 GPU Native ISA AMD Vector

Vector Arithmetic

v_rcp_f32

Calculate the reciprocal of the single-precision float input using IEEE rules and store the result into a vector register.

Encoding

Binary Layout (AMD CDNA 5)
0111111
31:25
VDST
24:17
unassigned
16
0101010
15:9
SRC0
8:0
 

The ENC_VOP1 layout from AMD's machine-readable ISA specification (AMD CDNA 5). Opcode 42 in OP rebuilds 0x7E005400, an identifier AMD lists for this encoding. Bits marked unassigned have no field in the specification. Not the same in every generation: AMD CDNA 4 (opcode 34, field layout), AMD CDNA 3 (opcode 34, field layout), AMD CDNA 2 (opcode 34, field layout), AMD CDNA 1 (opcode 34, field layout), AMD RDNA 3.5 (field layout), AMD RDNA 3 (field layout), AMD RDNA 2 (field layout), AMD RDNA 1 (field layout). The same in AMD RDNA 4.

Format VOP1
Width 32 bits
Opcode 42
Identifier 0x7E005400

Operands

  • VDST
    Written. Operand must be a vector GPR. Uses an 8-bit operand field. Data format: 32-bit single-precision floating point value. (OPR_VGPR, FMT_NUM_F32)
  • SRC0
    Read. All operands. Covers all operands that are allowed as scalar or vector sources. Data format: 32-bit single-precision floating point value. (OPR_SRC, FMT_NUM_F32)

In AMD's order, as its machine-readable ISA specification lists them for the ENC_VOP1 encoding (AMD CDNA 5).

GFX Target Compatibility

TargetSupport
gfx1100✅ Supported

1ULP accuracy. Accuracy converges to < 0.5ULP when using the Newton-Raphson method and 2 FMA operations. Denormals are flushed.

Related PTX Concepts

Special-Function Approximation ↗
equivalent with restrictions
rsqrt (PTX)
sin (PTX)
lg2 (PTX)
sqrt (PTX)
rcp (PTX)

Related

More in Vector Arithmetic

Reference

AMDGPU / GFX ISA

Semantics

D0.f32 = 1.0F / S0.f32

Example

V_RCP_F32(0xff800000) => 0x80000000     // rcp(-INF) = -0
V_RCP_F32(0xc0000000) => 0xbf000000     // rcp(-2.0) = -0.5
V_RCP_F32(0x80000000) => 0xff800000     // rcp(-0.0) = -INF
V_RCP_F32(0x00000000) => 0x7f800000     // rcp(+0.0) = +INF

Reproduced from AMD's official "AMD Instinct MI300" ISA Reference Guide for technical accuracy.

Sources