UCOMISS (Intel x86/64 assembly instruction)

모두의 코드
UCOMISS (Intel x86/64 assembly instruction)

작성일 : 2020-09-01 이 글은 1374 번 읽혔습니다.

UCOMISS

Unordered Compare Scalar Single-Precision Floating-Point Values and Set EFLAGS

참고 사항

아래 표를 해석하는 방법은 x86-64 명령어 레퍼런스 읽는 법 글을 참조하시기 바랍니다.

Opcode/ Instruction	Op / En	64/32 bit Mode Support	CPUID Feature Flag	Description
`0F 2E /r` UCOMISS xmm1 xmm2/m32	RM	V/V	SSE	Compare low single-precision floating-point values in xmm1 and xmm2/mem32 and set the EFLAGS flags accordingly.
`VEX.128.0F.WIG 2E /r` VUCOMISS xmm1 xmm2/m32	RM	V/V	AVX	Compare low single-precision floating-point values in xmm1 and xmm2/mem32 and set the EFLAGS flags accordingly.
`EVEX.LIG.0F.W0 2E /r` VUCOMISS xmm1 xmm2/m32{sae}	T1S	V/V	AVX512F	Compare low single-precision floating-point values in xmm1 and xmm2/mem32 and set the EFLAGS flags accordingly.

Instruction Operand Encoding

Op/En	Operand 1	Operand 2	Operand 3	Operand 4
RM	ModRM:reg (r)	ModRM:r/m (r)	NA	NA
T1S	ModRM:reg (w)	ModRM:r/m (r)	NA	NA

Description

Compares the single-precision floating-point values in the low doublewords 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 (unor-dered, greater than, less than, or equal). The OF, SF and AF flags in the EFLAGS register are set to 0. The unor-dered 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 32 bit memory location.

The UCOMISS instruction differs from the COMISS instruction in that it signals a SIMD floating-point invalid opera-tion exception (#I) only if a source operand is an SNaN. The COMISS instruction signals an invalid numeric excep-tion 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.

Note: VEX.vvvv and EVEX.vvvv are reserved and must be 1111b, otherwise instructions will #UD.

Software should ensure VCOMISS is encoded with VEX.L=0. Encoding VCOMISS with VEX.L=1 may encounter unpredictable behavior across different processor generations.

Operation

(V)UCOMISS (all versions)

RESULT !=<- UnorderedCompare(DEST[31:0] <> SRC[31:0]) {
(* Set EFLAGS *) CASE (RESULT) OF
    UNORDERED: ZF,PF,CF <-  111;
    GREATER_THAN: ZF,PF,CF <-  000;
    LESS_THAN: ZF,PF,CF <-  001;
    EQUAL: ZF,PF,CF <-  100;
ESAC;
OF, AF, SF <-  0; }

Intel C/C++ Compiler Intrinsic Equivalent

VUCOMISS int _mm_comi_round_ss(__m128 a, __m128 b, int imm, int sae);
UCOMISS int _mm_ucomieq_ss(__m128 a, __m128 b);
UCOMISS int _mm_ucomilt_ss(__m128 a, __m128 b);
UCOMISS int _mm_ucomile_ss(__m128 a, __m128 b);
UCOMISS int _mm_ucomigt_ss(__m128 a, __m128 b);
UCOMISS int _mm_ucomige_ss(__m128 a, __m128 b);
UCOMISS int _mm_ucomineq_ss(__m128 a, __m128 b);

SIMD Floating-Point Exceptions

Invalid (if SNaN Operands), Denormal

Other Exceptions

VEX-encoded instructions, see Exceptions Type 3; additionally

#UD If VEX.vvvv != 1111B.

EVEX-encoded instructions, see Exceptions Type E3NF.

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모두의 코드 UCOMISS (Intel x86/64 assembly instruction)