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Vol. 2A 3-147
INSTRUCTION SET REFERENCE, A-M
CMPSS—Compare Scalar Single-Precision Floating-Point Values
The greater-than relations not implemented in the processor require more than one
instruction to emulate in software and therefore should not be implemented as
pseudo-ops. (For these, the programmer should reverse the operands of the corre-
sponding less than relations and use move instructions to ensure that the mask is
moved to the correct destination register and that the source operand is left intact.)
In 64-bit mode, use of the REX.R prefix permits this instruction to access additional
registers (XMM8-XMM15).
Operation
CASE (COMPARISON PREDICATE) OF
0: OP ← EQ;
1: OP ← LT;
2: OP ← LE;
3: OP ← UNORD;
4: OP ← NEQ;
5: OP ← NLT;
6: OP ← NLE;
7: OP ← ORD;
DEFAULT: Reserved;
CMP0 ← DEST[31:0] OP SRC[31:0];
IF CMP0
= TRUE
THEN DEST[31:0] ← FFFFFFFFH;
ELSE DEST[31:0] ← 00000000H; FI;
(* DEST[127:32] unchanged *)
Intel C/C++ Compiler Intrinsic Equivalents
CMPSS for equality __m128 _mm_cmpeq_ss(__m128 a, __m128 b)
Table 3-11. Pseudo-Ops and CMPSS
Pseudo-Op CMPSS Implementation
CMPEQSS xmm1, xmm2 CMPSS xmm1, xmm2, 0
CMPLTSS xmm1, xmm2 CMPSS xmm1, xmm2, 1
CMPLESS xmm1, xmm2 CMPSS xmm1, xmm2, 2
CMPUNORDSS xmm1, xmm2 CMPSS xmm1, xmm2, 3
CMPNEQSS xmm1, xmm2 CMPSS xmm1, xmm2, 4
CMPNLTSS xmm1, xmm2 CMPSS xmm1, xmm2, 5
CMPNLESS xmm1, xmm2 CMPSS xmm1, xmm2, 6
CMPORDSS xmm1, xmm2 CMPSS xmm1, xmm2, 7