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VUCOMISH

Unordered Compare Scalar FP16 Values and Set EFLAGS

stableVMJITAOTinstruction

Encodings

OpcodeInstructionOp/En64-bitCompat/LegacyDescription
EVEX.LLIG.NP.MAP5.W0 2E /rVUCOMISH xmm1, xmm2/m16 {sae}AValidValidCompare low FP16 values in xmm1 and OR AVX10.1 xmm2/m16 and set the EFLAGS flags accordingly.

Operand encoding

Each mode is a value of the Op/En column above. It says which field of the encoded instruction carries each operand, in the order they are written, and whether the instruction reads it, writes it or both.

A

  1. modrm.reg escrituraModRM byte, reg field (bits 5-3)
  2. modrm.rm lecturaModRM byte, r/m field (bits 2-0); with the SIB byte and the displacement when the mod field asks for them

Tupla: Scalar

Measured cost

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Description

This instruction compares the FP16 values in the low word of operand 1 (first operand) and operand 2 (second operand), and sets the ZF, PF, and CF flags in the EFLAGS register according to the result (unordered, greater than, less than, or equal). The OF, SF and AF flags in the EFLAGS register are set to 0. The unordered result is returned if either source operand is a NaN (QNaN or SNaN).

Operand 1 is an XMM register; operand 2 can be an XMM register or a 16-bit memory location.

The VUCOMISH instruction differs from the VCOMISH instruction in that it signals a SIMD floating-point invalid operation exception (#I) only if a source operand is an SNaN. The COMISS instruction signals an invalid numeric exception when a source operand is either a QNaN or SNaN.

The EFLAGS register is not updated if an unmasked SIMD floating-point exception is generated. EVEX.vvvv are reserved and must be 1111b, otherwise instructions will #UD.

Operation

VUCOMISH
RESULT := UnorderedCompare(SRC1.fp16[0],SRC2.fp16[0])
if RESULT is UNORDERED:

    ZF, PF, CF := 1, 1, 1
else if RESULT is GREATER_THAN:

    ZF, PF, CF := 0, 0, 0
else if RESULT is LESS_THAN:

    ZF, PF, CF := 0, 0, 1
else: // RESULT is EQUALS

    ZF, PF, CF := 1, 0, 0

OF, AF, SF := 0, 0, 0

Intel C/C++ compiler intrinsics

VUCOMISH int _mm_ucomieq_sh (__m128h a, __m128h b);
VUCOMISH int _mm_ucomige_sh (__m128h a, __m128h b);
VUCOMISH int _mm_ucomigt_sh (__m128h a, __m128h b);
VUCOMISH int _mm_ucomile_sh (__m128h a, __m128h b);
VUCOMISH int _mm_ucomilt_sh (__m128h a, __m128h b);
VUCOMISH int _mm_ucomineq_sh (__m128h a, __m128h b);

SIMD Floating-Point Exceptions

Invalid, Denormal.

Other Exceptions

EVEX-encoded instructions, see Table 2-50, "Type E3NF Class Exception Conditions."

Sources