cvttss2si

Convert with Truncation Scalar Single to Integer

CVTTSS2SI r32, xmm/m32

Converts float to 32-bit int (Truncate).

Details

Converts a 32-bit single-precision floating-point value to a 32-bit signed integer using truncation towards zero, regardless of the rounding mode in MXCSR. If a NaN or overflow occurs, the result is INT32_MIN (0x80000000) and no exception is raised by default.

Pseudocode Operation

dest32 ← (int32)truncate(src32_float); CF ← 0; OF ← 0; SF ← 0; ZF ← 0; AF ← 0; PF ← 0;

Example

CVTTSS2SI eax, xmm1

Encoding

Binary Layout

Format SSE

Opcode F3 0F 2C

Extension SSE

Operands

dest
32-bit general-purpose register (e.g. EAX)
src
128-bit XMM register or 32-bit memory

Reference (Intel® SDM)

Instruction Forms

Opcode	Instruction	Op/En	64/32-bit Mode	CPUID	Description
F3 0F 2C /r	CVTTSS2SI r32, xmm1/m32	A	V/V	SSE	Convert one single precision floating-point value from xmm1/m32 to one signed doubleword integer in r32 using truncation.
F3 REX.W 0F 2C /r	CVTTSS2SI r64, xmm1/m32	A	V/N.E.	SSE A AVX A AVX	Convert one single precision floating-point value from xmm1/m32 to one signed quadword integer in r64 using truncation. VEX.LIG.F3.0F.W0 2C /r 1 V/V Convert one single precision floating-point value from VCVTTSS2SI r32, xmm1/m32 xmm1/m32 to one signed doubleword integer in r32 using truncation. VEX.LIG.F3.0F.W1 2C /r 1 V/N.E.2 Convert one single precision floating-point value from VCVTTSS2SI r64, xmm1/m32 xmm1/m32 to one signed quadword integer in r64 using truncation.
EVEX.LLIG.F3.0F.W0 2C /r	VCVTTSS2SI r32, xmm1/m32{sae}	B	V/V	AVX512F OR AVX10.1	Convert one single precision floating-point value from xmm1/m32 to one signed doubleword integer in r32 using truncation.
EVEX.LLIG.F3.0F.W1 2C /r	VCVTTSS2SI r64, xmm1/m32{sae}	B	V/N.E.2	AVX512F OR AVX10.1	Convert one single precision floating-point value from xmm1/m32 to one signed quadword integer in r64 using truncation.

Instruction Operand Encoding

Op/En	Tuple Type	Operand 1	Operand 2	Operand 3	Operand 4
A	N/A	ModRM:reg (w)	ModRM:r/m (r)	N/A	N/A
B	Tuple1 Fixed	ModRM:reg (w)	ModRM:r/m (r)	N/A	N/A

Description

Converts a single precision floating-point value in the source operand (the second operand) to a signed doubleword integer (or signed quadword integer if operand size is 64 bits) in the destination operand (the 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 exceeds the range limits of signed doubleword integer (in non-64-bit modes or 64-bit mode with REX.W/VEX.W/EVEX.W=0), the floating-point invalid exception is raised, and if this exception is masked, the indefinite integer value 80000000H is returned. If a converted result exceeds the range limits of signed quadword integer (in 64-bit mode and REX.W/VEX.W/EVEX.W = 1), the floating-point invalid exception is raised, and if this exception is masked, the indefinite integer value 80000000_00000000H is returned. Legacy SSE instructions: In 64-bit mode, 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. VEX.W1 and EVEX.W1 versions: promotes the instruction to produce 64-bit data in 64-bit mode. CVTTSS2SI—Convert With Truncation Scalar Single Precision Floating-Point Value to Signed Integer Vol. 2A 3-255 Note: VEX.vvvv and EVEX.vvvv are reserved and must be 1111b, otherwise instructions will #UD. Software should ensure VCVTTSS2SI is encoded with VEX.L=0. Encoding VCVTTSS2SI with VEX.L=1 may encounter unpredictable behavior across different processor generations.

Operation

(V)CVTTSS2SI (All Versions)
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

VCVTTSS2SI int _mm_cvttss_i32( __m128 a);
VCVTTSS2SI int _mm_cvtt_roundss_i32( __m128 a, int sae);
VCVTTSS2SI __int64 _mm_cvttss_i64( __m128 a);
VCVTTSS2SI __int64 _mm_cvtt_roundss_i64( __m128 a, int sae);
CVTTSS2SI int _mm_cvttss_si32( __m128 a);
CVTTSS2SI __int64 _mm_cvttss_si64( __m128 a);

Exceptions

SIMD Floating-Point Exceptions

Invalid, Precision.

Other Exceptions

See Table 2-20, “Type 3 Class Exception Conditions,” additionally: #UD If VEX.vvvv != 1111B. EVEX-encoded instructions, see Table 2-50, “Type E3NF Class Exception Conditions.” CVTTSS2SI—Convert With Truncation Scalar Single Precision Floating-Point Value to Signed Integer Vol. 2A 3-256