v_cmp_class_f16 GPU Native ISA AMD Vector

V CMP CLASS F16 Comparison

v_cmp_class_f16

Evaluate the IEEE numeric class function specified as a 10 bit mask in the second input on the first input, a half-precision float, and set the…

Encoding

Verified bit-level encoding data is not yet available for this instruction. The instruction-format classification below (VOPC) is well-documented and stable; exact per-target opcode/field bit positions have not yet been imported from a verified source.
Format VOPC
Execution Unit

Operands

Operand details have not yet been curated for this instruction.

GFX Target Compatibility

TargetSupport
gfx1100✅ Supported

Note that the S1 has a format of f16 since floating point literal constants are interpreted as 16 bit value for this opcode.

Related

More in Comparison

Reference

AMDGPU / GFX ISA

Description

Evaluate the IEEE numeric class function specified as a 10 bit mask in the second input on the first input, a half-precision float, and set the per-lane condition code to the result. Store the result into VCC or a scalar register. The function reports true if the floating point value is any of the numeric types selected in the 10 bit mask according to the following list: S1.u[0] value is a signaling NAN. S1.u[1] value is a quiet NAN. S1.u[2] value is negative infinity. S1.u[3] value is a negative normal value. S1.u[4] value is a negative denormal value. S1.u[5] value is negative zero. S1.u[6] value is positive zero. S1.u[7] value is a positive denormal value. S1.u[8] value is a positive normal value. S1.u[9] value is positive infinity.

Semantics

declare result : 1'U; if isSignalNAN(64'F(S0.f16)) then result = S1.u32[0] elsif isQuietNAN(64'F(S0.f16)) then result = S1.u32[1] elsif exponent(S0.f16) == 31 then // +-INF result = S1.u32[sign(S0.f16) ? 2 : 9] elsif exponent(S0.f16) > 0 then // +-normal value result = S1.u32[sign(S0.f16) ? 3 : 8] elsif 64'F(abs(S0.f16)) > 0.0 then // +-denormal value result = S1.u32[sign(S0.f16) ? 4 : 7] else // +-0.0 result = S1.u32[sign(S0.f16) ? 5 : 6] endif; D0.u64[laneId] = result; // D0 = VCC in VOPC encoding.

Example

v_cmp_class_f16 vcc, -1, v2

A real instruction accepted by the LLVM assembler, taken verbatim from LLVM's own AMDGPU MC test suite (gfx11). Not from an AMD document, and not authored here.

Sources