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Henk-Jan Lebbink edited this page Jun 4, 2026 · 13 revisions

CVTTSD2SI — Convert with Truncation Scalar Double Precision Floating-Point Value to Signed Integer

Opcode/ Instruction Op / En 64/32 bit Mode Support CPUID Feature Flag Description
F2 0F 2C /r CVTTSD2SI r32, xmm1/m64 A V/V SSE2 Convert one double precision floating-point value from xmm1/m64 to one signed doubleword integer in r32 using truncation.
F2 REX.W 0F 2C /r CVTTSD2SI r64, xmm1/m641 A V/N.E. SSE2 Convert one double precision floating-point value from xmm1/m64 to one signed quadword integer in r64 using truncation.
VEX.LIG.F2.0F.W0 2C /r VCVTTSD2SI r32, xmm1/m641 A V/V2 AVX Convert one double precision floating-point value from xmm1/m64 to one signed doubleword integer in r32 using truncation.
VEX.LIG.F2.0F.W1 2C /r VCVTTSD2SI r64, xmm1/m641 BV/N.E. 2 AVX Convert one double precision floating-point value from xmm1/m64 to one signed quadword integer in r64 using truncation.
EVEX.LLIG.F2.0F.W0 2C /r VCVTTSD2SI r32, xmm1/m64{sae} B V/V2 AVX512F OR AVX10.1 Convert one double precision floating-point value from xmm1/m64 to one signed doubleword integer in r32 using truncation.
EVEX.LLIG.F2.0F.W1 2C /r VCVTTSD2SI r64, xmm1/m64{sae} BV/N.E. 2 AVX512F OR AVX10.1 Convert one double precision floating-point value from xmm1/m64 to one signed quadword integer in r64 using truncation.

NOTES:

  1. Software should ensure VCVTTSD2SI is encoded with VEX.L=0. Encoding VCVTTSD2SI with VEX.L=1 may encounter unpredictable behavior across different processor generations.
  2. For this specific instruction, VEX.W/EVEX.W in non-64 bit is ignored; the instructions behaves as if the W0 version is used.

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 double 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 64-bit memory location. The destination operand is a general purpose register. When the source operand is an XMM register, the double precision floating-point value is contained in the low quadword 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. Note: VEX.vvvv and EVEX.vvvv are reserved and must be 1111b, otherwise instructions will #UD.

Software should ensure VCVTTSD2SI is encoded with VEX.L=0. Encoding VCVTTSD2SI with VEX.L=1 may encounter unpredictable behavior across different processor generations.

Operation

(V)CVTTSD2SI (All Versions)

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

Intel C/C++ Compiler Intrinsic Equivalent

VCVTTSD2SI int _mm_cvttsd_i32( __m128d a);
VCVTTSD2SI int _mm_cvtt_roundsd_i32( __m128d a, int sae);
VCVTTSD2SI __int64 _mm_cvttsd_i64( __m128d a);
VCVTTSD2SI __int64 _mm_cvtt_roundsd_i64( __m128d a, int sae);
CVTTSD2SI int _mm_cvttsd_si32( __m128d a);
CVTTSD2SI __int64 _mm_cvttsd_si64( __m128d a);

SIMD Floating-Point Exceptions

Invalid, Precision.

Other Exceptions

#UD If VEX.vvvv != 1111B.

Source: Intel® 64 and IA-32 Architectures Software Developer's Manual, Combined Volumes (Order Number 325462-091US, March 2026)
Generated: 7-6-2026

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