CVTTSS2SI—Convert with Truncation Scalar Single-Precision FP Value to Dword Integer

Opcode/Instruction	Op/ En	64/32-bit Mode	CPUID Feature Flag	Description
F3 0F 2C /r CVTTSS2SI r32, xmm/m32	RM	V/V	SSE	Convert one single-precision floating-point value from xmm/m32 to one signed doubleword integer in r32 using truncation.
F3 REX.W 0F 2C /r CVTTSS2SI r64, xmm/m32	RM	V/N.E.	SSE	Convert one single-precision floating-point value from xmm/m32 to one signed quadword integer in r64 using truncation.
VEX.LIG.F3.0F.W0 2C /r VCVTTSS2SI r32, xmm1/m32	RM	V/V	AVX	Convert one single-precision floating-point value from xmm1/m32 to one signed doubleword integer in r32 using truncation.
VEX.LIG.F3.0F.W1 2C /r VCVTTSS2SI r64, xmm1/m32	RM	V/N.E.¹	AVX	Convert one single-precision floating-point value from xmm1/m32 to one signed quadword integer in r64 using truncation.

NOTES:

1. Encoding the VEX prefix with VEX.W=1 in non-64-bit mode is ignored.

Instruction Operand Encoding

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

Description

Converts a single-precision floating-point value in the source operand (second operand) to a signed doubleword integer (or signed quadword integer if operand size is 64 bits) in the destination operand (first operand). The source operand can be an XMM register or a 32-bit memory location. The destination operand is a general-purpose register. When the source operand is an XMM register, the single-precision floating-point value is contained in the low doubleword of the register.

When a conversion is inexact, a truncated (round toward zero) result is returned. If a converted result is larger than the maximum signed doubleword integer, the floating-point invalid exception is raised. If this exception is masked, the indefinite integer value (80000000H) is returned.

Legacy SSE instructions: In 64-bit mode, the instruction can access additional registers (XMM8-XMM15, R8-R15) when used with a REX.R prefix. Use of the REX.W prefix promotes the instruction to 64-bit operation. See the summary chart at the beginning of this section for encoding data and limits.

Note: In VEX-encoded versions, VEX.vvvv is reserved and must be 1111b, otherwise instructions will #UD.

Operation

IF 64-Bit Mode and OperandSize = 64
    THEN
         DEST[63:0] ← Convert_Single_Precision_Floating_Point_To_
                           Integer_Truncate(SRC[31:0]);
    ELSE
         DEST[31:0] ← Convert_Single_Precision_Floating_Point_To_
                          Integer_Truncate(SRC[31:0]);
FI;

Intel C/C++ Compiler Intrinsic Equivalent

int _mm_cvttss_si32(__m128d a)

__int64 _mm_cvttss_si64(__m128d a)

SIMD Floating-Point Exceptions

Invalid, Precision.

Other Exceptions

See Exceptions Type 3; additionally

#UD	If VEX.vvvv ≠ 1111B.