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VCVTTSH2SI

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Henk-Jan Lebbink edited this page Jun 4, 2026 · 1 revision

VCVTTSH2SI — Convert with Truncation Low FP16 Value to a Signed Integer

Opcode/ Instruction Op/ En 64/32 Bit Mode Support1 CPUID Feature Flag Description
EVEX.LLIG.F3.MAP5.W0 2C /r VCVTTSH2SI r32, xmm1/m16 {sae} AV/V 1 AVX512_FP16 OR AVX10.1 Convert FP16 value in the low element of xmm1/m16 to a signed doubleword integer and store the result in r32 using truncation.
EVEX.LLIG.F3.MAP5.W1 2C /r VCVTTSH2SI r64, xmm1/m16 {sae} A V/N.E. AVX512_FP16 OR AVX10.1 Convert FP16 value in the low element of xmm1/m16 to a signed quadword integer and store the result in r64 using truncation.

NOTES:

  1. Outside of 64b mode, the EVEX.W field is ignored. The instruction behaves as if W=0 was used.

Instruction Operand Encoding

Op/En Tuple Operand 1 Operand 2 Operand 3 Operand 4
A Scalar ModRM:reg (w) ModRM:r/m (r) N/A N/A

Description

This instruction converts the low FP16 element in the source operand to a signed integer in the destination general purpose register.

When a conversion is inexact, a truncated (round toward zero) value 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.

Operation

VCVTTSH2SI dest, src

IF 64-mode and OperandSize == 64:
    DEST.qword ← Convert_fp16_to_integer64_truncate(SRC.fp16[0])
ELSE:
    DEST.dword ← Convert_fp16_to_integer32_truncate(SRC.fp16[0])

Intel C/C++ Compiler Intrinsic Equivalent

VCVTTSH2SI int _mm_cvtt_roundsh_i32 (__m128h a, int sae);
VCVTTSH2SI __int64 _mm_cvtt_roundsh_i64 (__m128h a, int sae);
VCVTTSH2SI int _mm_cvttsh_i32 (__m128h a);
VCVTTSH2SI __int64 _mm_cvttsh_i64 (__m128h a);

SIMD Floating-Point Exceptions

Invalid, Precision.

Other Exceptions

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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