VCVTTSD2USIS instruction (AVX10.2)

VCVTTSD2USIS converts the low double of a register or eight bytes of memory to an unsigned integer in a general-purpose register, truncating toward zero and saturating: values beyond the range give FFFFFFFFh or all 64 bits set, values of -1 or less give 0, and a NaN gives 0. VCVTTSD2USI returns all ones, the unsigned indefinite, for every one of those, a negative input included. EVEX.W picks a 32-bit or, in 64-bit mode, a 64-bit result. It belongs to AVX10.2: opcode 6Ch in EVEX map 5 with an F2 prefix, beside the signed VCVTTSD2SIS’s 6Dh, with {sae}. NaNs, infinities and out-of-range values still set IE, and a lost fraction sets PE.

A corrected helper

Revision 7.0 of the AVX10.2 specification lists among its fixes that VCVTTSD2USIS’s operation called the signed conversion helper; it now names the unsigned one. Earlier revisions therefore described a signed result for this instruction.

In our builds

GCC 14 has no AVX10.2 option. Clang 23 with -mavx10.2 compiles _mm_cvtts_roundsd_u64(x, _MM_FROUND_CUR_DIRECTION) to vcvttsd2usis rax, xmm0, while (unsigned)x in C stays VCVTTSD2USI. No AVX10.2 processor appears in this site’s recorded cases.

Forms

Every encoding of VCVTTSD2USIS that Intel XED knows, one row per XED instruction form (iform). How to read the notation.

Instruction	Encoding	Requires
`VCVTTSD2USIS r32, xmm, {sae}` VCVTTSD2USIS_GPR32u32_XMMf64_AVX512	`EVEX.LIG.F2.MAP5.W0 6C /r`	AVX10.2
`VCVTTSD2USIS r32, m64` VCVTTSD2USIS_GPR32u32_MEMf64_AVX512	`EVEX.LIG.F2.MAP5.W0 6C /r`	AVX10.2
`VCVTTSD2USIS r64, xmm, {sae}` 64-bit mode only VCVTTSD2USIS_GPR64u64_XMMf64_AVX512	`EVEX.LIG.F2.MAP5.W1 6C /r`	AVX10.2
`VCVTTSD2USIS r64, m64` 64-bit mode only VCVTTSD2USIS_GPR64u64_MEMf64_AVX512	`EVEX.LIG.F2.MAP5.W1 6C /r`	AVX10.2

Data flow

Where the elements of the sources go, element 0 on the right; results that depend on a control value are drawn for an example. How to read.

The low double of xmm2 is converted, and the integer goes to r32.

r32 receives the conversion of double 0 of xmm2: r0.

Operation

What the forms do, in pseudocode that our tests run against results recorded on real processors. How to read.

a = src2.f64[0]
dest.write(cvtts_uint(a, dest.bits))  # r32: bits 63:32 cleared
# {sae}: no exception flags

Not run on a processor: none of these processors has AVX10.2.

Operands

What each form reads and writes, as Intel XED records it: the operands of its syntax, in order, and the implicit ones that the syntax does not name. How to read.

Operand	Kind	Action
`VCVTTSD2USIS r32, xmm/m64, {sae}` `VCVTTSD2USIS r64, xmm/m64, {sae}` 64-bit mode only
`r32/64`	explicit	write
`xmm/m64`	explicit	read

Flags

None: XED records no flag that the forms test or change.

Exceptions

The exception class is XED's name for the set of exception conditions that a form follows. How to read.

All forms: AVX512-E3NF

Attributes

What else XED records about the forms. How to read.

All forms: follows MXCSR

Intrinsics

The C intrinsics of Clang 23.1.2 that compile to VCVTTSD2USIS, each with the form it compiles to and the Clang options it needs. The forms come from compiling every intrinsic and decoding the result with Intel XED; all intrinsics A–Z explains the method.

Intrinsic	Compiles to
`_mm_cvtts_roundsd_u32` `unsigned int _mm_cvtts_roundsd_u32(__m128d __A, const int __R)`	`VCVTTSD2USIS r32, xmm, {sae}` EVEX.LIG -mavx10.2
`_mm_cvtts_roundsd_u64` `unsigned long long _mm_cvtts_roundsd_u64(__m128d __A, const int __R)`	`VCVTTSD2USIS r64, xmm, {sae}` EVEX.LIG -mavx10.2

CPUID and processors

Each form belongs to an XED ISA set. A form can be used when the processor reports every CPUID bit of one of its ISA set's alternatives.

CPUID requirements and processors of the XED ISA sets above. Alternatives are separated by “or”; processors follow XED’s chip model, whose AMD processors end with Zen 2, and the CPU data of this site for Zen 3 to Zen 6.

ISA set	CPUID	Processors
`AVX512_SAT_CVT_DS_SCALAR` AVX10.2	AVX10.2 `CPUID.(EAX=07H,ECX=1):EDX[19]` AVX10 `CPUID.(EAX=24H,ECX=0):EBX[7:0] ≥ 2` AVX10 version	Nova Lake, Diamond Rapids

More AVX10.2 instructions

All 96 AVX10.2 instructions

A corrected helper#

In our builds#